Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. EPARTMENT OF AGRICULTURE In cooperation with the ELLERY Pennsylvania Agricultural Experiment Station and the Pennsylvania Department of Agriculture DEPARTMENT BULLETIN No. 1156 Washington, D. C. May, 1923 INVESTIGATIONS OF POTATO WART.’ By Freeman Wess, Pathologist, Office of Cotton, Truck, and Forage Crop Disease Investigations, Bureau of Plant Industry; C. R. Orton, Pathologist, Pennsylvania Agricultural Experiment Station; and R. E. Hartman, Pathologist for Potatoes, Pennsylvania Department of Agriculture. CONTENTS. . age. I—The varietal and species hosts of Synchytrium endobioticum. By Freeman Weiss and C. R. (a. 23S S See 202 ee ee ee ees oe Seen ae ae eee _ I1.—The adaptability and use of wart-immune varieties of the potato in the quarantined areas of : Pennsylvania. By R. E. Hartman............. eS Se SOY WS NG A RS ve 17 o—thestability of wart immunity. By. Freeman’ WeiSS. <..... .- on nnccewere ence ccc cceeecnceee 20 i I.—THE VARIETAL AND SPECIES HOSTS OF SYNCHYTRIUM 7 ENDOBIOTICUM. By Freeman Wetss and C. R. Orton. TESTS WITH POTATO VARIETIES AND SEEDLINGS. ' When the diseasé of the Irish potato known as wart was discovered in the United States in 1918 * the question of the reaction of American _ potato varieties to the newly introduced parasite assumed a posi- _ tion of first importance. The fact that certain potato varieties remained entirely free from infection even: when grown in soils thoroughly infested by the pathogen, as shown by the behavior of _other varieties, had been known in Europe for a number of years, and the cultivation of such resistant varieties was even then regarded as the only means of avoiding the severe crop losses occasioned by this disease. Variety tests conducted in ir alee had included several American sorts, and these were reported upon in 1919 & but aside from this, no information was Swailuble as to the reaction _ of American varieties to this disease. However, the severity of _ infection on the heterogeneous stocks commonly grown in the wart- 4 1 This report is based upon cooperative investigations carried on by the Bureau of Plant Industry and _ the Federal Horticultural Board of the United States Department of Agriculture, the Pennsylvania A gri- cultural Experiment Station, and the Pennsylvania Department of Agriculture. __7Sanders, James G. The discovery of European potato wart disease in Pennsylvania. Jn Jour. Econ. Ent., v. 12 P. 85-90, pl. 3. 1919. 3 Snell, John. Ormskirk potato trials. Annual report, 1918. Jn Jour. Bd. Agr. [Gt. Brit.], Sup. 18, ¥ p. 68-102, fig. 20-33 on Spl. 1919. Od 33570—23—B ull. 1156-——1 2 BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE. infested area showed that susceptible potatoes predominated. Subsequent tests of a large number of tuber selections among the diverse types grown in this area confirmed the fact of the general culture of susceptible types. The bearing of this upon the restricted — distribution of potato wart in the United States, as brought to — light by the disease survey (Fig. 1), is of particular importance, | for it is believed that shipments of potatoes equally capable of — introducing the parasite as those eee found their way into the — mining towns of Pennsylvania may have reached diverse sections — of the country, but failed to introduce the disease ‘because of the prevalent culture of immune varieties in many sections. vee Oho PENNSYLVANIA » i poe A. OSE TER H Fia. 1.—Outline map of Maryland, Pennsylvania, and West Virginia, showing the geographical distribu- tion of potato wart on September 1, 1922. Localities of findings: 1, Originaleastern Pennsylvania area; 2, Nanty Glo; 3, Whitmer; 4, Thomas; 5, Lilly; 6, Llanfair; 7, Vintondale; 8, Osceola Mills; 9, Clarence; 10, Woodvale; 11, Robertsdale; 12, Smithmill; 13, Mount Savage, Eckhart Mines, and Lord; 14, Midland; Charles Town, and Detmold; 15, Yatesboro; 16, Beaverdale; 17, Onnalinda. (Prepared by the Office of Plant-Disease Survey, Bureau of Plant Industry.) It became necessary, therefore, to prohibit at once the cultiva- tion of potatoes in ali gardens which were known to be infested, but it was thought desirable to permit the continued use of sus- ceptible varieties in the general area, in order to determine the ultimate extent of infestation; meantime, the rest of the country was protected against extension of the disease by a quarantine on the movement of potatoes and materials capable of transporting the parasite from the infested area as then known. The lateness of the season when wart was discovered prevented making tests of varietal susceptibility in 1918, but during the winter it was determined that the Triumph variety was susceptible. The ees ME INVESTIGATIONS OF POTATO WART., 3 following season a systematic test of all obtainable American varieties was begun. In addition, investigations of a number of immune English varieties were made to determine their commercial value as well as their reaction to wart in the United States. A preliminary report ‘of these investigations was issued in 1920, covering the results of the trials of the first season. These tests established the fact that the wart pathogen was consistent in its behavior in Ameri- ca and Kurope in that the immune varieties of Europe remained free from infection also in this country. It was furthermore shown that although most American varieties were susceptible, including some of the particularly valuable commercial types, 10 varieties, including the well-known Irish Cobbler, Green Mountain, and Spauld- ing Rose, could with reasonable assurance be classed as immune. As a result of these tests it became possible to modify the quarantine regulations in the Pennsylvania areas so as to permit the culture of the immune sorts, Edzell Blue and Spaulding Rose, in infested gardens, and the supplying of approved immune seed potatoes became a function of the quarantine administration. The general effect on potato culture of changing over from the mixed stocks of predomi- nantly susceptible potatoes to selected seed of immune varieties is described in a later section of this bulletin. A similar modification of quarantine procedure has been found advisable in the infested areas in West Virginia and Maryland, and it is now well established that potato culture need nowhere be abandoned on account of this disease so long as suitable immune varieties are available. The project of determining the wart reaction of all American potatoes and also their adaptability for commercial culture in the regions infested by wart and areas adjacent thereto has been con- _ tinued on a more extensive scale for three additional years. In general, methods of planting and culture similar to those described in the earlier report have been followed. The site of most of the _ trial plats has been the vicinity of Freeland, Pa., where gardens which are heavily infested naturally and are in favorable tilth for potato culture are already at hand. Since the same gardens, for the most part, have been employed again and again, accurate information as to the thoroughness and density of infestation is now available, a factor of great importance in analyzing the results. Additional tests have been carried on at Thomas, W. Va., and in the greenhouses of the United States Department of Agriculture at Washington, D. C. Single rows of a given variety or seedling, crossing the garden transversely and averaging 30 feet in length, have been the standard form of plat, but larger test plantings have been made in some cases. Grdinkily only a single plat of each variety has been grown each year; that is, no attempt has been made to duplicate plats sys- tematically, but in a number of cases certain varieties have been repeated m other gardens either in the same or a different region. At regular intervals of nine rows a susceptible variety has been _ planted as an indicator of the presence of the pathogen in a virulent state. As check varieties, Triumph and various stocks of Rural New Yorker and Up-to-Date have been employed; the last two named are very readily susceptible and react to infection by the * Lyman, G. R., Kunkel, L. O., and Orton, C. R. Potato wart. U.S. Dept. Agr., Dept. Cire. 111, 19 p.,4fig. 1920. _ eae mr 4 BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE. production of very striking overgrowths, so that check rows commonly exhibit practically 100 per cent infection. Any variety with 20 per cent or more of tuber infection was classed as susceptible and forthwith discarded, but stocks which were infested to a lesser degree were grown another year before discarding. _ Where no infection occurred, the entire stock was saved for successive planting year by year until immunity was considered definitely established. Where a single hill or only two or three tubers showed wart- formation, as occurred in but very few instances, the infected hill was discarded and the test repeated with the remainder of the stock. | _ It is to be noted that, owing to the limited occurrence of areas infested by wart our tests have not been carried on with the same degree of attention to large size and systematic duplication of plats, repeated through several years or in a number of localities, that has been characteristic of similar tests in England and Germany.*. Nevertheless, it is felt that a very high degree of reliability attaches to the results here reported. This question was discussed briefly in the preliminary report® to which reference has been made. The following considerations derived from more extensive experience may be cited in addition: Purity of stocks —The material which has been available for these tests has been of exceptional quality as regards uniformity and trueness to type. For the most part - these stocks have been grown by the Office of Horticu!tural and Pomological Investi- gations of the Bureau of Plant Industry for a number of years at the potato-breeding farm of the United States Department of Agriculture in Aroostook County, Me., and mixtures have been entirely or practically eliminated. This has avoided at the outset most of the difficulty due to errors in variety names and to mixed types nearly always inherent in lots obtained from commercial seedsmen. Likewise, the seedlings upon which these tests have been made do not have the heterogeneous and uncertain element that prevails in material obtained from amateur plant breeders, but are s2lected lines derived from the controlled crossing of known parents. Consistent results from trials.—All varieties for which a definite report of immunity is here made have been carried through two or more years, surviving tests conducted in at least three gardens, for the most part located in different regions. A few others indicated as probably immune by the tests of the past season are entered in the tables as immune, but with a question mark. These variety tests were begun in 1919 under a cooperative agree- ment between the Bureau of Plant Industry and the Federal Horti- cultural Board of the United States Department of Agriculture and the Pennsylvania Agricultural Experiment Station. The same ar- rangement was continued in 1920 and 1921. A similar test was carried out in cooperation with the Agricultural Experiment Station of West Virginia. In 1920, feeling the need for further information as to the adaptability of some of the immune varieties as compared with that of the standard susceptible varieties grown in the wart- infested areas, the Pennsylvania State Department of Agriculture began tests of local varieties collected in the quarantined areas as compared with a number of immune stocks, the introduction of which it was thought would be desirable for purposes of regulated planting. These trials led to the collection of considerable data on. the relative value of immune and susceptible varieties in districts situated climatically like those infested with the disease and furnished Appel, O. Uber die Anfilligkeit und Widerstandsfihigkeit!verschiedener Kartofielsorten gegen Krebs. Arb. Gesell. Férd. Baues and Verwend. Kartoffeln, Heft 15, 19 p., fold diagr. 1918. . Lyman, G. R.,and others. Op. cit. INVESTIGATIONS OF POTATO WART, 5 also a demonstration of the practicability of changing over to new » varieties in localities threatened by the introduction of the wart para- "site. This cooperative report is issued to bring together all available j information regarding the reaction to wart and the suitability of Ameri- . ean potato varieties for purposes of potato-wart quarantine. Further- | more, in order to present the studies upon additional host range which were carried on by the United States Department of Agriculture, in their proper relation to the varietal investigations with potatoes, a summary of all planting tests with miscellaneous solanaceous species in wart- infested soil has been appended. The susceptibility of tomato varie- ties to wart was discovered in 19197 and extensively confirmed in 1920. The need for further information as to the importance of this host from the standpoint of quarantine administration led to the adoption in 1921 of a cooperative agreement between the Federal Horticultural Board and the Pennsylvania State Department of Agriculture for testing on a large scale all obtainable tomato varieties. _As already stated, most of the named varieties of potatoes and all the seedlings employed in these tests were furnished by the Office of Horticultural and Pomological Investigations of the Bureau of Plant Industry. One collection was received from the Agricultura! Experiment Station of Prince Edward Island, and a number of local varieties have been obtained from growers. In the first year of the _ tests 29 immune varieties were received from England through the courtesy of Sir Lawrence Weaver, of the Board of Agriculture and Fisheries. Duplicates of some of these, together with a number of additional stocks, were imported in 1920 by J. G. Sanders, of the Pennsylvania State Department of Agriculture. By an arrangement _ between the Federal Horticultural Board and William Stuart, of the _ Office of Horticultural and Pomological Investigations, new varieties received by that office from abroad are grown for one year in quar- antine before being tested in Maine or elsewhere. This arrange- _ ment has resulted in including several varieties received from Scot- land and Holland in the wart-reaction trials at Freeland, Pa. Finally, a collection of German varieties was received from I. Schaffnit, of Poppelsdorf, Bonn, in 1921 and carried through two years, and a collection of eight French varieties, furnished by E. Foéx, of the Station de Pathologie Végétale, France, was available for testing in 1922. The results of the trials covering four years are assembled and summarized in Table 1. The American varieties are placed in groups according to Stuart’s classification. It should be noted, however, that in material of so diverse a germinal complexion as the potato the varietal similarities which constitute the basis of a horticultural classification can not afford an index to genetic relationships adequate in all cases to Sia in advance oi actual testing the wart reaction of a variety rom the known behavior of horticulturally similar types. This is well illustrated by the behavior of the varieties of the Early Michigan _ and the Green Mountain groups. In the former group, Marly Har- vest, Hhnola, Extra Early Sunlight, and White Albino are regarded _ as unmune, while Karly Sunrise and Early White Albino are suscep- tible (Pl. I). Among the varieties belonging to section 2 of the Green Mountain group, which have faintly colored sprouts, Charles 7 Lyman, G. R., and others. Op. cit. ss § Stuart, William. Group classification and varietal descriptions of some American potatoes. U.S. i Dept. Agr. Bul. 176,59 p.,19 pl. 1915. = 4 6 BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE, Downing (Ormskirk, England, trials, 1919), and Idaho Rural, are immune, whereas American Giant and Empire State are readily sus- ceptible. In the white-sprout section Carman No. 1, Clyde, Gold Coin, Delaware, Dreer Standard, Green Mountain Junior, Norcross, Snow, State of Maine, Uncle Sam, and Wee MacGregor are regarded © by many commercial growers as identical,® yet strains grown under — these names in the tests here described have reacted diversely to this — disease (Table 1). Similar diversity of reaction is exhibited in the — Burbank and Early Rose groups. Only extensive testing of numer- ous stocks of a given variety obtained from different sources and a careful checking of varietal characters to detect differences can — eliminate such confusion. On the other hand, the Karly Ohio, Rural New Yorker, and Triumph groups comprise only susceptible — varieties, while the Cobbler and Peachblow groups are composed | entirely of immunes. TaBLE 1.—Reaction of American and European potato varieties to potato wart. { ExpLANATION.—Column 1: The test data for varieties marked with a star (*) were furnished by R. E. Hartman. Column 2: The data given were furnished by William Stuart. The Field Laboratory of § Plant Pathology, Charlottetown, Prince Edward Island, is abbreviated to Field Laboratory, Prince Edward Island. Column 4: >=Numerous. Column 5: The following symbols are used to indicate — varying degrees of susceptibility or resistance: 0=immune (every plant free from infection in repeated trials); +=slightly susceptible (less than 20 per cent of individual plants in any test infected, weak — development of warts); +=moderately susceptible (usually less than 50 per cent of plants infected, — weak to strong development of warts, depending upon which part of the plant is attacked and the stage of growth at infection); ++ —=very susceptible (all or most of the plants in a test infected, copious develop- ment of overgrowths on all susceptible parts, Pls. lto 1V). The question mark (?) implies not that the — conclusion is doubtful in this instance, but that it has not been confirmed by repeated tests.] . Years Tests | Wart re- Group and variety. Source of seed. tested «fs tua de: ieee 1 2 3 » 4 is) Group I.—Cobbler: Cordon’s Early Snowflake....} Cordon Bros., Rockford, Ill....,...... 2 2 | 0 Ary SUTEK Ec ahc.cs occ coer s W.H. Maule, Philadelphia, Pa....... 2 2) 0 Barly Petoskey J. .-..2c2:5.. Darling & Beaham, Petoskey, Mich. ..! 3 3 0 First Early....-..------+---- S. M. Isbel & Co., Jackson, Mich...... | 2 2 0 Irish Cobbler. Jsa¢ {222 32 2.22 H, ExGero;-Rutland, Vite. 22-2. 22s 0e 3 3 0 15 10 Sens S peek ee ee I. B. Bradford, Goldenridge, Me....-. 3 3 0 dD Xo pe aie Race a 4 eon Wilfrid Boulter, Prince Edward Island 1 1 0 Dass 23 2 segs aries. J. Bolgiano, Baltimore, Md........... 1 1 0 New Early Standard......... Henry A. Dreer (Inc.), Philadelphia, 3 3 0 a. Group II.—Triumph: Bliss, Trrumiph. 2: so cease =a. F. S. Campbell & Sons, Three Lakes, 3 = Wis., and others. Barly Prospect... ..- sks. Smith Bros., Auburn,.N. Y.....24..5. 1 1 + White Bliss Triumph. ....... T. W. Wood & Sons, Richmond, Va. -| 1 | 1 + Group III.—Early Michigan: Brown Beauty (known lo- | C. F. Clark, Greeley, Colo..........-... i 1 ‘ +4- cally in Colorado as Bark- ley’s Prolific). Warly Harvest =<]. vc .s- Jee C. D. Woods, Orono, Me.........-.---.- 2 2 0 Harky, Sunnise 979s eguess'< doz Robert Buist Co., Philadelphia, Pa... 1 1 ++ Early White Albino!........ '! Johnson Seed Co., Leominster, Mass... 1 1 4 Ehnola..... PER EOE rf aed Tek E. F. Corey, Presque Isle, Me...----... 4 4 0 Extra Early Sunlight ........ | T. W. Wood & Sons, Richmond, Va.. 3 3 0 Wihite-Allbino >: = 22. 5 fe. | Johnson Seed Potato Co., Richmond, 2 2 0 z | Me. Group IV.—Rose: Barhyi Rosemsts fat ec Eee Several Sonreds 232i 5928. - 322.2 ees. 3 3 + Miverereen 2 2 30" ek i tae 1 a Hardenburg, Ithaca, N. Y...... 1 1 + BlOrivers Wingo. oi: soon. ee Iowa Seed Co., Des Moines, lowa.....- 2 | 2 0 Seneca Beauty (greenhouse | Gurney Seed & Nursery Co., Yankton, 1 | 1 + test). : S. Dak. Spaudling Rose .22522%.,222-8 Several sourees: j-205222 ie. 2s 4 | > 0 WihbitevRoseits. 33. sess e Wesco Seed Co., Rochester, N. Y....- 3 3 0 Woodbury’s White Rose..... Vaughan’s Seed Store, New York City. 1 | 1 | + 1 A variety received under this name from Beckert’s Seed Store, Pittsburgh, Pa., in 1922 proved to be . Irish Cobbler and was immune. 4 5 - 2 Doubtfully referable to Rose group on account of its very late growing habit. ’ The stock grown under this name is not White Rose, but probably Burbank. 4 ®[Ontario. Potato Council.] {Potato varieties decided to be identical.] In Potato Mag., v. 1, no. 7. : p.15. 1918. | INVESTIGATIONS OF POTATO WART. 7 TaBLe 1.—Reaction of American and European potato varieties to potato wart—Contd. a =e = a Pe ce xy Years Tests Wart re- z Group and variety. Source of seed. | tested: | andlariaeuetioc: 1 2 3 4/8 5 | Grour V.—Early Ohio: | . pry TCS eee See | ©. F. Clark, Greeley, Colo......-----.: 2 2 > -. SRS Eee Joseph Harris, Coldwater, N. Y....... | 1 1 1p ECU ee C. F. Clark, Greeley, Colo.--.......-..) 1 1 - EIS ES SS ae ee 1 ph SB eee eames An ee 1 1) ++ Group Vi.—Hebron: ; Aroostook Pride 4....-....... Selden McGlauflin, Presque Isle, Me.. 1 | 1 + Beauty of Hebron............ BELA E EL MOS ot a th | 1 1 + Country Gentleman *........ Beckert’s Seed Store, Pittsburgh, Pa.| 2 | 2 = Early Beauty of Hebron..... Robert Buist Co., Philadelphia, Pa-.-.! 2 | 2 + MarlyeHOVveel-. 3s 54-5... -005- Beckert’s Seed Store, Pittsburgh, Pa... 1 1 = , BeeWr GTOOR +o... 4-5522+055-2-5 Pennsylvania Department of Agricul- | 1 | 1 3e5= me ’ ture. | Group VII.—Burbank: Se eae L. A. Hawkins, Middle River, Calif... 2 | 2 0 California Russet...........-- Low S. Darling, Petoskey, Mich......., 1 1 ~ Imperial Burbank*.........| Pennsylvania Department of Agricul- | 1 1 20 ture. MeuvedY Gent s-.e- 6.2.5 2.2t William Wagner, Jerome, Idaho....... 1 1 + - Russet Burbank............- Colorado Seed Co., Denver, Colo....... 1 | 1 0 Monite Burbank: Os -- <2... 20). Pr Sa Seed Co., San Francisco, | ] 1 aod alif. Group VIli.—Green Mountain: “American Giant 7... 3.00.52 J. Bolgiano, Baltimore, Md............ 1 1 + American Giant 8...........- H. F. Michel, Philadelphia, Pa........ 2 2 0 _ US eS Cordon Bros. Seed Co., Rockford, Il. .' 1 1 20 Peete? oe oo. 2 eo August Mongrain, St. Luce, Province | 1 1 aa of Quebec. RUPIAMW ANE. eo 8. oats SSeS Central Maine Potato Co.............. 2 3 0 MERIGE SEAL: 5.225 23 5522 Ks pe eat ee Prince Edward | 2 2 ++ sland. | Saad Seah ee Be ee I. D. Adams, South Royalton, Vt... ..! 2 3 0 Green Mountain -... ....-....- Several saarees. 5) Y. . s3 sheen nanges > | 4 > 0 Green Mountain Junior....... A ghegon. Seed Potato Co., Richmond, | 3 3 0 e. | Green Mountain ( @ero strain ):|- 2-2 o3- 2 ie se eo ate oe (eae 2 2 + Gurney’s White Harvest..... ered bases & Nursery Co., Yankton, | 1 1 + . Dak. Idaho ural ® > S9s< oo. s 52. - Pennsylvania Department of Agricul- 2 2 0 ture. | Dao) ea Sees Inland Seed Co., Spokane, Wash......, 2 2 0 MOCISIIOY, pon 522 te 5208 Sf W. W. Barnard Co., Chicago, Il...... 3 3 0 ee Ee pe Farmers’ Seed & Nursery Co., Fari- | 1 1 a | bault, Minn. 3k Bee gee a C.O. Hoose, Duane, N. Y., and others.) 3 > 0 State of Maine. ..-....:...25.. Jean Carton Gray, Van Buren, Me. ...' 1 2 + LCS ae eee Robert Buist, Philadelphia, Pa....... 1 1 0 | Li Ss ae 2 ie Pennsylvania Department of Agricul- 1 1 0 é ture. Vermont Gold Coin.......... Beckert’s Seed Store, Pittsburgh, Pa.. 1 1 0 Group 1X.—Rural: OE AOR a ee Pe@asyiyanis Department of Agricul- 1 1 ++ ure. Barnes Seedling.............-}..... Om se ee Ae oe ee os Sa Eo 1 1 ++ PeetianNG. So y--..:..>---| A. N. Newman, Phelps, N.. Y......... 2 2 ++ Early Surprise *............. Pennsylvania Department of Agricul- 1 1 aa ure. Fairbault Mammoth Prize...| Farmers’ Seed & Nursery Co., Fari- 1 1 ++ bault, Minn. Golden Rule ¥...... Pewee setae A.J, Derlith, Lincoln Park, N. Y..... 2 2 ++ Guilder ural 2s 3.52 2..2<2222 Joseph Harris, Coldwater, N. Y....-.. 1 1 ++ Golden Russet *... .......... | Pennsylvania Department of Agricul- 1 1 coe ture. Heath’s Late Surprise *......'....- Oe ee ee a. ee ae LS Soe id 1 + ‘ This is the local name for a stock that is in all respects Beauty of Hebron. It is not the Aroostook Prize belonging to section 2 of Group VIII, which is practically identical with American Giant and Jersey Giant; nor 1s it referable to Aroostook Pride, which is a true Green Mountain type. 5 In the previous report (Lyman, G. R., and others. Op. cit.) this variety was referred to the Hebron group and is therefore so retained, but it is likely that Country Gentleman more properly belongs 1n sec- tion 2 of the Green Mountain group. 8 Infected tubers somewhat off type and probably American Giant. 7 American Giant is a type of the colored-sprout section of the Green Mountain group. Belonging to this same section are Jersey Giant and Aroostook Prize, identical with the first named, !daho Rural, Charles Downing, and probably Cordner. 8 This variety is now considered to be Burbank, which often occurs as a mixture with American Giant. Schafinit (Versuche zur Bekiimpfung des Kartoffelkrebses im Jahr 1918-19. Jn Ztschr. Pflanzenkrank., Bd. 30, p. 59-67. 1920) reports ‘“‘ Amerikanische Riesen” as immune. ® Rural type with heavy vines and late-growing habit. a e 4s 8 TaBLeE 1.—Reaction of American and European potato varieties to potato wart—Oontd BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE. - Group and variety. Source of seed. Reed 1 2 3 a [== — = esoort —— ed Group IX.—Rural—Continued. | Heavy weights.os. 2. 2 25.28 T.-C: Gibbs, Fillmore, N.:Y2.5-2 5: £232) 2 wohn Peolin 102 jc5, cst wclekon Lawrence Bros., Byron, N. Y......... 1 Kasoae Russet (Same as "RUS= |occcocec samc oces tenccc tease os cetice shee i set Rural). | Knowle’s Big Cropper *...... Penney type Department of Agricul- 1 ure. Late Petoskey 2.2.22. science eose (0 Lae Neat sabre tebd er ene be it 1 ASO se. cece sapece eee o et Pennsylvania Agricultural Experi- | 1 ment Station. H Million Dollars: 22-2. ee Pennsylvania Department of Agricul- 1 ture. INEX ONE Stier se sas ot des | Pennsylvania Agricultural Experi- 1 ment Station. Nonbltehts:.2 ss es2 hao Ford’s Seed Co., Ravenna, Ohio.......' 2 Pan-American (not certainly | Jos. Harris Co., Coldwater, N. Y...... 1 referable to this group). Pearl of Canaan Valley....... | Farmers’ Seed & Nursery Co., Fari- 1 bault, Minn. Prince Henry. vs oes. eee Fred G. Smith, Scottsville, N. Y...... 1 Rural New Yorker No. 2..... Je es Milliman, Naples, N. Y., and 4 others. HUSSCD RUPAl ete eee gees cess E. F. Dibble, Honeoye Falls, N. Y., 4 and others. BaNSAOH eases ieee Went Boyce Seed Co., Seattle, 1 ash. Sir Walter Raleigh........... Harold Hubbs, Kirkville, N. Y....... 2 Ui Mage 22 0 eo epi ena en eS Pennsylvania Agricultural Experi- 1 ment Station. Group X.—Pearl: BlugwVietores snce ence os eee West Virginia Agricultural Experi- 1 ment Station. Dearborn Hs. 3 eee Vaughan’s Seed Store, New York City. 1 GBaPl Ba> ce Mase slots ccceucee Colorado Seed Co., Denver, Colo...... 1 BeopleSs stan en coe ato | William Wagner, Jerome, Idaho....... 1 SNOWHAKO ie. tooo nooo cnn ou | Farmers’ Seed & Nursery Co., Fari- 1 bault, Minn. Group XT.—Peachblow: McCormick: o2..ssc0.s..cceess aS Hattie Girder, Bowling Green, 2 ON ee ee oicantee tee ts Bolgian6. BalpimMore, Masses: es. 5s 1 Hed: McWlures.. bas cecee nes Colorado Seed Co., Denver, Colo...... 1 Round Pinkeye. > 2... 6cs8e- H. J. Presley, Port Huron, Mich...... 3 White McCormick............ Richard Wellington, College Park, Md. 1 he SEN en Rae i J. Bolgiano, Baltimore, Md...:........ 1 Group XII.—Up-to-Date: American Wonder........... } Salona Seed Co., San Francisco, 1 alif. British Queen. 2 a... canes eae ats pie dy Sapp i kc eS 1 Cummiing’s Prides... 222.2222 | P. A. Murphy, Charlottetown, Prince 1 Edward Island. Davies Warrior #:2. 5.2222. Pennsylvania Department of Agricul- 1 | tire: Pindley se. eee ee Ree | H. J: Presley, Perry; Ohio-.-:..052.:: 1 PlOduUCer. eee hee ome eka Portland Seed Co., Portland, Oreg...- 1 HCOLCh Ural ee cel ee } Louis Rase. Frostburg, Md...-2....... 2 Wp-tosWate en eee eos | EK. F. Dibble, Honeoye Falls, N. Y.... 2 ellinetone asses oekee Roy Harrington, Patten, Me.......... 2 Whiteomb 7.20500 .5.25625¢ Pansy Au Department of Agricul- 1 | ture. AMERICAN VARIETIES (unclassed):| Hlack Christie "2.15 ooh Eucinicolm: nOx bees see nen eee = 2 Dakota Red #i2 22... c.0. 422 | Hie Poesy: Prince Edward | 2 | Siand. ’ | Deposit. Wonder. +: . - axle Deon Seed Co., Deposit, N. Y-..... Gamet Chilii 2.4 2o:2k fee. Me ie Lahorsiory, Prince Edward | sland. Jersey Redskin............... Henry ¥. Michel, Philadelphia, Pa.... Keeper... ichowcccus wean sae}, Bs A. j\Corbett, Colebrook, No i -.-<. 3. AICI yTO Ne oe Ss eee eens AINOVE SCOUGEE <5 os ccsaGmncacrenatenet act 3 lo A potato identical with this is known under the name Dooley also; the variety Dooley used in these trials is an Up-to-Date type. 1 The original Dearborn was a Rural type. group 12 The original Snowflake is probably not now in existence; the variety under consideration is a renamed Pearl. 18 This variety is widely and successfully grown as an immune potato in Newfoundland. 4 A light and a dark strain of this variety exist, but the types are not wholly fixed. j | The present variety undoubtedly belongs to the Pearl | Tests | Wart re- made. | action. © | 4 Sa 2 hat ee 1} ++ 1 pe | ee 1| + 1) 44 1] ++ 1 | ++. 1) +4 1 | + Ly att 1} ++ >] ++ >! ++ 1} ++ >| ++ 1] ++ 1 + 1 + i om 1 + 1 | + 3 0 1 : 0 1 0 3 0 1 0 1 A) 1} .++ 1} ++ 1|) +4 sasdbants. ++ 1] 44+ 1} 44 3) 44 2} ++ 2) ++ Gee | | % pu Dige i teal 4 ro ere ; 3 | sr q Lol adit ' eae 4 51 ++ i A INVESTIGATIONS OF POTATO WART, 9 Years Tests Wart re- Group and variety. Source of seed. | featea oh rahese) dation: 1 2 | 3 4 5 AMERICAN VARIETIES (un-| el classed )—Continued. 0 ee ee pues Laboratory, Prince Edward 1 1 + slan 7 LS ee eee Pee ee biesiusired. bs. be Sree 1 1 | 20 P UF Se | Highland, PA OGAN oe ese 2 eS £} 1 a é, maenown 114... ......... |W. G. Utterback, Sigourney, Iowa.. 1, 1 | 2} 4 peemen VARIETIES (miscellan- | % us): } | 4 ae Pete Se). ~ 2 nn op Agricultural Experiment Station, 2} 3) ++ z Sitka, Alaska. ee Sone. oc oct oe | Stat. Path. Veg., France...........--- 1 | Ld. 3 PCT Se ee eee ee H. M. Quanjer, Groeningen, Holland.. 1 14 == : INGE Se et Bee cc | H. Dolkowsk & Sons, Galicia, Austria. 1 | 1); ++ Cacha Negra }..............- ad eg RS ete Sie Ne a os pone 5 Sie ieee 2 | 2 | 0 , Casaker Salathornschen...... [ Genmtann as Soe on 22 oe ete iad eI 1 | i) < Clifden Seedling.............. ae a ShOTaLOr ys Prince Edward 2 | 2 0 slan | SS eee Le OU ai foe Se | 1 | Ul mee. 2 Commandant. .............--. | Joha. Westerdijk, Holland............. 1 | 1 + = Concordia........ Ms ho vite | E. Schaffnit, Germany..............-- 1 1 - i no aa eee | Stat. Path. Veg., Hranee = $26 <8 5 1 | 1 20 ; 2 LLP ETT Ti be eS a ee ae =&E. H. Grubb, Carbondale, Cale... ss: 1 | 1 +4. we) PE ae ee ee A ee eee ee 1 | 1 -- lo "Donald Reddick, Ithaca, N. Y.....-..- 1 1 + Eigenheimer...............-.| —<&«@. M. Quanjer, Groeningen, Holland.. 1 1 20 Sromerpen Kron... ...-.......,-<-=- Ee Ce eg 5. ee sees ae 2 | 2 t+ 3 LEDS Ty a a aie | E. S. Schultz, Presaue Isle, Me........ 1 | 1 + Institut de Beauvais......... | Stat. Path. Veg., Miamp 265225. - 22. - | 1 | 1 ++ ; ee ee eee Pee | Se ee Eas ae 1 | 1 ao r oe es = ek ee | i. Schaffnit, Germany..........-...-- 1 | 1 a 3 SS SOs a ee iS pea ae air SP Se ee Sore 1 1 = s Northern Invincible........-.! Miett Laboratory, Prince Edward | 1 | 1 _ | slan 2 irs: | E. Schafinit, Germany..........-.---- 1 | 1 20 : 0 nS ee Ee eae tas al 1) 1 + < Quarantaine de I la Halle...... I" Stat: Path. Veg., France... : 1 | if 20 6 Rheingold | E. Sehaffnit, Germany..............-. 1 | 1 20 7 Roode Star 16_.... | H. M. Quanjer, Groeningen, Holland..| 1 | 1 20 % Russian Blue. ... Be agen e it takai mf $2 prem os ole 1 | 1 + 7 Saxony. ....... , W. W. Rawson & Co., Boston, Mass... 1 1 ++ i Saucisse...... Stat. Path Veg., France............... 1| 1 woe < oe Joha. Westerdijk, Holland............ 1 | 1 20 3 oo ee eee vad Laboreory, Prince Edward | 1 | 1 — } slan a pbsicters Somes ees ee | E. Schaffnit, Germany............-.... 2 2 + ] Cpe es oa ee ! H. Dolkowski & Sons, Galicia, Austria. 2 2 + = DT Mine i en de SS he eal E. Schafinit. Germany............2.-- z 2 ~ Violette d’Auvergne.......... Stat. Pat.Veg., France: :):-:.....-.-< 1 1 =—+ _ One Alford. Lincolnshire, England......... 1 1 _ ie eee oc eecik. | Joha. Westerdijk, Holland............ 2 2 + 6 SS ee | H. Dolkowski & Sons, Galicia, Austria- 1 1 ao it. fas Pe os eee Stat. Path. Veg., France: --.- 2... se 1 1 ++ _ ENGLISH AND SCOTCH VARIETIES: OT SS rae | Board of Agriculture and Fisheries, 2 2 0 | London, England. f pL See ee | pope CE SERS SS See ars See ae ee 3 3 0 wo Se eee ite ge pepnnras Sheds SETS lial 1 1 0 sc |b CAS See ae eee Fine Laboratory, Prince Edward 1 1 oo Z | Tslan 2 Arran Comrade............-. | Board of Agriculture and Fisheries, 3 3 0 | London, ngland. 3 We Se ee ee ee Ae ae ek eee 3 3 0 = Te Di Ga a 1.63 ga 2 Be. eb de = er ee eis. Nace. 1 1 0 Le Se as ae, ipa aree i pair 1 1 0 Se EI ate BOOM Enel bbe bus bosGess ues tieecndaacd 1 1 ++ : SS ee ae ae Board of Agriculture and Fisheries, 1 1 0 4 London, England. 2 Burnhouse Beauty.........-..|....- Ee by fe ee ee ee ee gee a 1 1 0 % 05 ae Sader eet gir aie See pais 2 2 0 - na a re eae ye ees Be RES Lees eee bey ae 2 2 0 € OE Ne) 8 acs cee owe ae oR RE Sart ie DS Sear ae ted 3 3 0 ’ 2 Dai = yet Bey ce iia aaa al teh Sipe Th en fd Ra Ret ad SESS F 3 2 2 + 3 1 Golden Wonder.............. | Board of Agriculture and Fisheries, 3 3 0 _| London, England. + St eee Bee | EGET Seo Vie raed SPECT ERS ae 3 3 0 é & A primitive type of Solanum tuberosum from Chile. 16 Reported to be resistant but not immune in Germany. 33570—23—Bull. 1156——2 10 BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE. TaBLE 1.—Reaction of American and European potato varieties to potato wart—Contd. — | { : Years Tests | Wart re- Group and variety. Source of seed. | tested. | made: | ncaa = be Se eae | | er 1 2 3 | 4 5 | ENGLISH AND SCOTCH VARIE- | TIES—Continued. ' t Erish Chieftain. 222. 2.5. 208 a tae a Prince Edward | 2| 2 | 0 sland. | irish: Queen 5. oss ere Board of Agriculture and Fisheries, | 3 | | 0 London, England. | | | Kerr’s: New Pinker. 252 othe aes See PO aes eae eee ee ses 2 | 2 | 0 Kerr's Pink. 252254 sc22eesc08 Board of Agriculture and Fisheries, } 3 | 3 | 0 London, England. { Kine Georpe:.. 325.26 ee do. 23h oss ete SER ree a Bish 3 0 aneworthyy = fas cause ccealemeecs (0 (s SES rc eee ee Pao 1 | 1 0 Leinster Wonder.........-... mele Taber, Prince Edward ; its 1 0 sland. | Rapehie 2565 Anes ot aoe Board of Agriculture and Fisheries, | 2 2 0 London, England. } Brajestic ore aes. ey Poe GOzs < 2 txts icant Se ta we i 2| 2 0 Manve.Queen i222) s22-. fees GO: Pee oe Saeed eee cor) 1 1 0 Mity Queen. = a ass Fo oe CO Se ie Sse ee Pe | 2 | 2 0 Midlothian Early. ..........- | eae vs Cas, Nc Pees Wee SP ee ee Se 2 | 2 + INGeHSdalo. ooo eae veces | eek do. 2a ee eA, a A 2 | 2 0 Propane ir B6xs 1 SARE? Or od, 1 2 | 2 0 RUCCLORSt ogee ee cet eee ats aaee Gt i RAE ES RS FS OE eee oo 2 2 0 Resistant Snowdrop. ........|....- GO. tee ERAS CSR ood ae se } 1 1 0 Bhaderick Dhue. 2... 2. eebocoe vi IN ES aE eRe AB ln Sate Se AE 1 1 0 Dit Malo Midney- =... ..6--se} ewes OGIh. MEE eee ss Ie eas oS: { 2 2 0 Scottish Triumph. ........... see Laboratory, Prince Edward | 1 1 20 sland. SHANIEOCH. 3... S2ies as coe n ceee Board of Agriculture and Fisheries, | 3 3 0 | London, England. Sharpe's Hx press. 22; 3... 822% bars SRE: anteater moet meats eae stataaet 1 1 SNOWALOPIs - cease see eaes | Board of Agriculture and Fisheries, ; 1 i 6 | London, England. WEIMpPIAR Soe as Cee (6 oes 5 Os Aig thee te 2 2 0 Pinwald Perfection... -...f22-)s522- GO ee ens a6 cena ste } 2 5 0 WihiteiGitye. 22s. oo. es Bae GOs baa eas Sete ie apeeeee j 3 3 0 Witch Hille: co asso}: hee booced OS Dea ota aw ot ohio ssa eee 3 3 0 17 One warted hill was found of this variety in 1920; it was saved separately from the uninfected hills, and both were planted in 1921. The progeny of the warted hill showed 40 per cent infection; the progeny of the wart free hills were not infected: the former are therefore believed to have been rogues. In plats of ey marley grown by the State Department of Agriculture of Pennsylvania no infection has ever been observed. In addition to the varieties included in Table 1, tests have been made of an extensive collection of seedlings bred by William Stuart, of the Bureau of Plant Industry. Two principal ends have been sought in these seedling trials: (1) The immediate attaiment of new types of immune potatoes which might show superior adaptation to the climate and soil of the wart-infested areas and hence might be introduced into general culture and (2) the development of infor- mation upon the inheritance of susceptibility and immunity in the progeny of crosses which combine in various ways immune and sus- ceptible parents. Two preliminary reports upon the results of these studies have appeared.*° | To date, 194 seedlings, practically all of known pee have been grown on the wart hats at Freeland, Pa. Of these seedlings 12 appear to be certainly immune and 48 have resisted or escaped infection in a single test. Of the 12 immunes, 7 have been under observation for four years and 5 have been tested for three years. In stability of the immune character and in commercial value, these seedlings are comparable with the named varieties; and further tests may demonstrate that superior-yielding immune types are already at 10 Lyman, G. R., and others. Op. cit. Orton, C. R., and Weiss, Freeman. The reaction of first-generation hybrid potatoes to the wart disease. In Phytopathology, vol. 11, pp. 306-310. 1921. 4 ad 2%. bt * INVESTIGATIONS OF POTATO WART. 11 hand and may be introduced into general culture. In particular, a _| potato is desired which shall combine immunity with the drought | and heat resisting qualities and other desirable characters of the Rural New Yorker. As the details of this study are of technical interest only and as a report has been issued which embodies the results attained to date " reference to the seedling tests is here limited to the statement that immune seedlings having as one parent a Rural type are already at hand, but the testing of their commercial value as compared with standard varieties will be the work of several years. _ Meantime, new hybrids of similar origin will be sought, and all wart- immune seedlings will be subjected to careful tests of yielding capacity, general adaptability, and disease resistance, to the end that should any of them be brought into general culture their introduction will be a distinct gain over existing varieties. TESTS WITH MISCELLANEOUS SOLANACEOUS SPECIES. One of the favored theories to account for the origm of the wart, or at least its sudden appearance and rise to economic importance in Europe, has been that the pathogen has spread to the potato from - some other host, which is believed to have been some native plant upon which it produced only inconspicuous malformations and hence was overlooked. In support of this hypothesis it has been shown that this disease appeared rather suddenly in England during the last decade of the nineteenth century. Although some earlier accounts antedating this by 20 years may have actually referred to the same mal- ady, nearly 150 years elapsed after the introduction of the potato into general aaligite in Europe before any mention of this disease is found. Its slow extension during the next 10 or 15 years may have been due to the gradual adaptation of the parasite to a new host, upon which it ultimately came to have its present marked pathological effect, leading to its recognition. The rapid spread in the British Isles within recent years can be accounted for, as Taylor * has shown, by the introduction into general cultivation of susceptible potatoes, to- gether with the moyement of seed stock, particularly from Scotland after the disease had become well established there. It seems un- likely that the wart pathogen was introduced into Europe along with the original potato, since some of the endemic species of Solanum of South America most closely related to Solanum tuberosum resist in- fection * (see note 15, Table 1), although if such immunity could have developed through long association with the pathogen this evi- dence is not significant. The comparatively recent appearance of this striking malady is better evidence against such early introduc- tion. On the other hand, Cotton ™ has found that the common gar- den weeds, Solanum nigrum L. and S. dulcamara L., are susceptible to infection by Synchyirium endobioticum (Schilb.) Pere., although they have never been found warted in nature. Although the biological validity of the theory which assumes that this parasite within recent times has passed over to a more congenial host may be open to serious objections, the importance from the i! Orton, C. R., and Weiss, Freeman. Op. cit. 1 Taylor, H. V. The distribution of wart disease. Jn Jour. Min. Agr. (Gt. Brit.), vol. 27, pp. 733-738, 863-867, 946-953. 1920-21. % Cotton, A.D. Host plants of Synchytrium endobioticum. Jn Roy. Gard. Kew, Bul. Misc. Inform., 1916, pp. 272-275. 1916. . 12 BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE. standpoint of quarantine administration of determining the host range in America requires the testing of all obtainable botanical relatives of the potato. Such tests have been carried on during four years both in the open at Freeland, Pa., and in the greenhouse at Wash- ington, D.C. The possibility of the wart pathogen attacking nonsola- naceous plants which occur in infested gardens, either native or cultivated, has been investigated, as previously reported" and also by the present writers, but no indication has been found that such — extension of host range takes place. The species listed in Tables 2 and 3 have not been infected by wart when grown in infested soil. In both the greenhouse and garden tests susceptible potatoes were grown under similar conditions as controls, and in all cases these developed wart infections. | The solanaceous species listed in Table 2 have been grown in wart-infested soil in the greenhouse at Washington, D. C., under favorable conditions for wart infection, as shown by the results with controls. Infection of these species failed. On the other hand, infection of the black nightshade (Solanum nigrum L.) and bitter- sweet (S. dulcamara L.) has followed experimental inoculation. TABLE 2.—Solanaceous specics of plants tested for susceptibility to potato wart in pots in the greenhouse at Washington, D. C.} {Infection of all these species failed.]} Number and name of species. a iis i Number and name of species. pert | No. 1. Solanum atropurpureum Schrank 5 || No. 8 Datura humilis flava............- 3 No. 2. Solanum gilo Radii....:........- a0 || Nios % Daturanretel Ib. sc 2. oo so.4 see, oe x No. 3. Solanum lobelii Lenore (=integ- || No. 10. Datura stramonium L.......... 2 rifohitmm (Poirs)-s: oe 42 ee 4 \,Nos11. Datnratatulaii se. 2 bass 2 No. 4. Solanum pseudocapsicum L...... 5 || No. 12. Cyphomandra betacea Sendt.... 3 No. 5. Nierembergia gracilis Hook. ...... 5. |} No-13.;Physahs sp... 0. A Ae 10 No. 6. Datura atroviolacea Hill. ........ 1 | No. 14. Solanum aculeatissimum Jacq... No. 7. Datura bertolonii Parl. ex Guss. | || No. 15. Solanum marginatum L......... 6 CDPTorox Ty... -. Awe oe eae 1} _} The writers are indebted to J. B. Hill, of Pennsylvania State College, for furnishing seed of all spe- cies tested except Nos. 4, 10, 11, and 12. The solanaceous species listed in Table 3 have been grown in wart-infested gardens at Freeland and Upper Lehigh, Pa., under very favorable conditions for the infection of susceptible potato varieties. Certain of these species have been tested for two years in different plats, but wart infection has not occurred. To the knowledge of the writers Solanum nigrum has not been found as a weed in any wart-infested garden, either in Pennsylvania or West Virginia, nor has it been observed in the quarantined area in eastern Pennsylvania. Similarly, Solanum dulcamara has been collected only occasionally within this district, growing cultivated in nonin- fested gardens. None of the solanaceous annuals, such as Solanum integrifolium, Datura tatula, and others, which have been grown possess underground parts which ordinarily would prove susceptible to infection by a parasite of the nature of Synchytrium. The stem is usually single below ground, without lateral shoots or buds, and the firm epidermis and tough cortex of the crown and taproot would 4 Lyman, G. R., and others. Op. cit. ‘ounurutT “Vystjung Apes eaiyxop fopqidoosns AoA ‘astiung Ayieq founururl ‘vpouysy 17481104 We] Wor = “dnoas [wIMyMoTWAOY BV UIYIIA UOTJOVOI OSVOSTP UT AJISIOATP OY OFVAYSNI][T SOMOMCA 99144 VSO, “dNOYS) NVOIHOIW ATYVS AHL AO SAILAIYVA OLVLOd PLATE |. Bul. 1156, U. S. Dept. of Agriculture. PLATE II. Bul. 1156, U. S. Dept. of Agriculture. “AVOMIVA OUIVS OYJ UT UOTOOJUT U0[OJS SUIMOYS ‘TIT OV[q JO vAUyY PUBY-IoT oy} YITM orvdt0D ~“yaed que[d & ul souRystsod [eTqaed Jo ofdurexo ue st AoA STYI UO “SYHSENL OLVLOd HdWNIYL Ssiig » UMOYS UOTJOJUT JOGNY JYSI[S oy, PLATE Bul. 1156, U. S. Dept. of Agriculture. "U9') POTION ‘GYSTI 7B fosvastp oy} UIA] dad] JSOWTV S19qNy INQ ‘UOTIIIJUT UOTOIS SUTMOYsS ‘(JJoeT Ve) YduINtAy, ss_ "LYVMA OL AIGILdSOSNS ATSLVYSGOW SAILSIYVA OLVLOd Bul. 1156, U. S. Dept. of Agriculture. PLATE IV. ROOTS AND TUBERS OF UP-TO-DATE POTATO. A variety very susceptible to wart. INVESTIGATIONS OF POTATO WART, 13 seem to be an unfavorable tissue for the entry of zoospores or to show a marked growth response resulting from infection. In the tomato and eggplant, adventitious shoots arise from the underground portion of the stem, usually late in the season. Infection of these buds or of the shoots occurs in the tomato, but fails through the operation of an unknown factor in the eggplant. | = TABLE 3.—Solanaceous species of plants tested for susceptibility to potato wart in gardens at Freeland and Upper Lehigh, Pa., in 1920 and 1921. {Infection of all these species and varieties failed.] ao Number of Number of plants. . plants. Species. Species. soso? 1920 | 1921 1920 | 1921 ED Pe CE Sdlanum melongena L. var. esculen- | || Datura stramonium L. (stramonium).}...... 20 3 tum Ness. (eggplant): || Datura tatula L. (purpletatula).......|...... 20 Beramseseewy WILE. 212. 8. [oss 9e5c To oes 7 || Solanum integrifolium Poir. (=S. | ‘ A a ees eee 30 Tobe Lenore) a. 350 ee aoe ne LEE ete a! 9 % Wew York - Improved -~.---..:...<.|.2e-.- 13 || Nicotiana rustica L. (wild tobacco)?.. tg 4 Capsicum annuum L. (peppers): Nicotiana tabacum L.: ; ey IORI os cnc wacla dee aocc 2 ig Dera Pennsylvania Seedleaf...........- 6 23 bone Red Cayenne: .i2......-...|..:..- 15 | Connecticut Havana...........--. Oy esi . Shell’s New Quality.............- Kean | White Burley... as. 02 ra: ocd) ascaes 10:}_ Wess BeetrCn pores. 202 AM siete rt Pete e Pennsylvania Broadleaf.......... ot yaa Mend Beater: 1. <2. = feet cin He wowc 6 | cea Maniniotlt.<... bis: .eceek oaelae = Si bees Bae REM Sesion a= aS aon of = mnie 6 | 20 || Nicandra_ physalodes (L.) Pers. | Physalis pubescens L. (Burpee husk (apple of Pert) tet S268 2: eee | (2) (2) UT tS a Se Sean See 14 || Petunia violacea Lindl. (petunia).....) 18 12 Solanum carolinense L.(horsenettle)..)...... 12 || Nicotiana paniculata L............... | (hg eS Solanum dulcamara L. (bittersweet). . 8 ep es | | 1 These species occur as weeds in one of the gardens most heavily infested with wart. 2 Numerous. While the testing of potential hosts will be continued, particularly with the aim of including all temperate-climate species of Solanum, it is believed that the failure to find new hosts among the several cul- tivated and most common indigenous solanaceous plants of this region (with the exceptions mentioned) makes it improbable that the athogen is able to maintain itself in this region on unsuspected osts, which therefore require particular quarantine action. VARIETAL TESTS WITH TOMATOES. _. . The susceptibility of the tomato to infection by Synchytrium en- _ dobioticum (Schilb.) Perc. was shown by Kunkel and Orton in 1919.* Tests with tomatoes have been carried on each year since then, but not all factors entering into the tests have been amenable to satisfac- tory control so it is not yet considered that complete and entirely - reliable data as to the susceptibility of tomato varieties are at hand. The present state of information in this respect is shown in Table 4, _ in which are listed only the varieties that have been proved to be susceptible. 3 The tomato is much less readily susceptible to wart infection than the potato, and the development of the overgrowths is always less ‘ marked. Infection usually occurs in buds or adventitious shoots _ on the main stalk below the soil surface. It therefore appears % Lyman, G. R.,and others. Op. cit. 14 BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE. ordinarily late in the season, usually not until September, but by © setting out tomato seedlings in a wart-infested garden in August — infection has been brought about on very young plants. Salsa : infection has been produced on young plants grown in water c tures. The readiness with which infection may occur is influenced — to a considerable extent by hilling up the soil about the plants, thus inducing growth activity in the buds of the covered part of the — stem. Under these conditions tumors which are evidently mal- formed stems or leaves and sometimes reach 2 centimeters in diameter are produced. Kunkel and Orton* reported root infections also, a noteworthy case, since potato roots apparently never become infected. While an examination of Kunkel’s preparations shows indubitable resting spores -of the wart pathogen in a considerably disorganized tissue, which is nevertheless of.root topography, sub- sequent observations have not brought to light wart infections on tomato roots. In 1920 many of the tomatoes under test developed very striking lesions in the nature of fusiform swellings or pulvinate outgrowths of the cortex of the larger feeding roots at the base of the stalk. The smaller “brace roots” springing from near the crown were not observed to be so infected. These lesions were at first regarded as being due to Synchytrium, but a microscopic examina- tion of them in the fresh state consistently failed to show recognizable stages in the life cycle of this pathogen. Fixed and embedded mate- rial disclosed the presence of extensive areas of infected host cells, resembling the figures given by Melhus” for infection of tomato and potato roots by powdery scab (Spongospora subterranea (Wallr.) Johnson). Veritable ‘‘krankheitsherde’’ were commonly present, involving from a few to several hundred host cells in which each host nucleus was surrounded by a plasmodium or an aggregation of amcebe containing numerous minute nuclei. The host nucleus was greatly enlarged, but appeared otherwise normal. The parasitic nuclei agreed in size with the figures of Melhus representing Spongo- spora; they possessed a definite nuclear membrane, a central nucleolus, and usually a few delicate chromatin strands. No division stages have as yet been made out in these nuclei, but there was clear evidence of giant host cells showing mitotic nuclear division which was not immediately followed by cell division. Neither have any stages suggesting spore ball formation in Spongospora as de- scribed by Osborn!® been observed. A complete cytological inves- tigation of these galls is in progress; meantime, they are provisionally | referred to Spongospora subterranea. It is noteworthy, however, that powdery scab affecting potatoes had not been reported from any part of Pennsylvania up to this time, but a careful search for its presence, made subsequent to finding these tomato-root infec- tions, disclosed its limited occurrence on certain English varieties growing in a different garden.” 16 Lyman, G. R., and others. Op. cit. 11 Melhus, I. E., Rosenbaum, J., and Schultz, E. S. Spongospora subterranea and Phoma tuberosa on a Irish potato. Jn Jour. Agr. Research, v.7, pp. 213-254, 1 fig., pl. A (col.), 7-14. Literature cited, p. . 1916 18 Osborn, T. G. B. Spongospora subterranea (Wallroth) Johnson. Jn Ann. Bot., vol. 25, pp. 327-341, 1.27. Bibliography, p. 340. 1911. 19 Shapovalov, Michael. ‘Skin spot:’’ a stage of powdery scab. (Abstract.) In Phytopathology, vol. 12, pp. 37-38. 1922. ee es INVESTIGATIONS OF POTATO WART, : 15 | Taste 4.—Varieties of tomatoes found to be susceptible by planting in infested soil as tn the field. [EXPLANATION.—The plus mark (+) indicates susceptibility; a blank (—) indicates no test.] Number of plants. - Number of plants. 1920 1921 1922 1920 1921 1922 Variety. 1919] = Variety. 1919 d/B)a/Bl/¢|z d/B/d\B\a/3 e/2/8\8/2| 2 sj/2i/s\2\sis a (=P A a OR i Se ar =| SiA/o/4A|o\4 BD Bearpank. 22.2... 4's +})/—);-|— |} —|— | — || Matehless.......2.- —| 4); 2;—;/—}|—|] — _ Carter’s Sunrise....; + | 6) 6;—j/—/— Michigan Early.....— | 6) 1};/—|)/—|—]| — _ Early Detroit ..-... +/ 4] 4;—/;—/15 2 || Ponderosa. ........ ad ae ct Ca Fees Landreth’s Red Redhead..........- SE se ee bet bre UNO ae ee +;—|/—/|— > —|—| — || San Jose Canner.....—| 3); 3;—j,;—|—| — MAGNUS 252 5.2.5..- -- | 5} 1}/—{/—]—] — || Stone..........2... —/} 6} 6/—j|—|] 6 0 Maule’s New Im- lege | | Trucker’s Favorite-.;— | 5); 4)/—;}—/—/| — (og Ses Sie op) — LP | 1 Crackerjack.-- -2 2. —{—|—] 4) 2);—)] — puecess. 2222-252... +)/—|/—!}/—}—| 7] 0] Comet.............. —|—|—|]—|—] 18) 11 __ eee Seen eee ah hy low Ore TROP ye ec. ce hss - - Ba) Agena) gpg CP aE cc) emeareenampion..)—2) 6) }<1 ) —.| — | — |*—») Aeme.............- Se | eg) et 1 Duke of York...... Beal oGebete| 1 — | a -—| | Lorillard... -.-. ae te ee a Leauihn) — | 12 | 4;—/}—/|14 2, i|-bOntly- Best... -.-.- —{j;—;—;—|—!} 5!/ 1 John Baer.......... sedi LOA AAS 20) Red Cherry . ae2. . — fp te fe a MGs ci sses ac _ | Sri aay — | Yellow Cherry... —|—|—|j—j—} 3 | 1 a ae i! | 1 Test with seedlings only. In 1921 about 85 varieties of tomatoes were grown, but owing to the early maturity of the vines brought about by hot weather and Septoria leaf-spot and also owing to very light infestation of the soil, only afew plants developed wart infection. In 1922 certain varieties, including some not hitherto tested, were grown in well-infested soil or were subjected to experimental inoculation. The observation that tomatoes may become infected at an early stage of growth was confirmed, and additional evidence was obtained that plants nearing maturity are in general more susceptible. It appears from the results of field tests during four years that the precise conditions requisite for the infection of tomatoes can be elucidated only by experimental inoculation in the greenhouse with all factors subject to control. All the trials with tomatoes to date have not given a definite answer to the question whether immune varieties comparable to immune potatoes really exist. This is a point of much scientific interest. The statement may be ventured, however, that the tomato has not been found to possess such significance as a host plant in the Freeland area as to require special consideration in the potato-wart quarantine. SUMMARY. A number of American varieties of potatoes have been shown to be immune to wart caused by Synchytriwm endobioticum (Schilb.) Perc. This conclusion is based upon tests extending from one to four years in which such varieties remained free from wart infection when grown in heavily infested soil in which susceptible varieties were generally and severely infected. The varieties which have thus proved to be immune are: Early Kureka, Early Petoskey, First Early, Cordon’s Early Snowflake, Flourball and Irish Cobbler, belonging to the Cobbler group; Early ee > 16 BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE. Harvest, Ehnola, Extra Early Sunlight, and White Albino, of the Early Michigan group; Spaulding Rose, of the Rose group; Burbank, of the Burbank group; Bountiful, Delaware, Gold Coin, Green Mountain, Green Mountain Junior, Idaho Rufal, McGregor, McKinley, and Norcross, of the Green Mountain group; McCormick, Round Pinkeye, and White McCormick, of the Peachblow group; and — Dakota Red and Keeper, unclassified as to group. Most of the varieties of tomatoes tested have proved to be suscep- | tible to wart, but some of the tests have been inconclusive, and it is not yet certain whether different degrees of susceptibility and resistance exist in the tomato. In general, the tomato becomes infected less readily than the potato, requiring particularly favorable environ- mental conditions and appropriate stages of host development. A number of solanaceous plants, including the native solanaceous weeds of Pennsylvania, and the eggplant, tobacco, petunia, and pepper, which are in common cultivation, have been tested for sus- ceptibility to the wart pathogen, but infection has thus far failed. 4 a ~IL.—THE ADAPTABILITY AND USE OF WART-IMMUNE VARIE- TIES OF THE POTATO IN THE QUARANTINED AREAS OF PENNSYLVANIA. By R. E. Hartman. The results of experiments to determine the adaptability of the common commercial wart-immune varieties of potatoes, Green Mountain, Irish Cobbler, Spaulding Rose, and McCormick, have shown that these varieties are all well adapted to the present quaran- tined areas. This is perhaps accounted for by the fact that the quar- antined areas of Pennsylvania are all at altitudes ranging from 1,200 = AREAS COVERED BY FEDERAL akD STATE SUAYZY FROM 1918 YO 1921. FESS incatiou oF AREaS WHIRE WART HAS 3528 FOURS fy = Lita. te e ok ; o ar ee. = ae 2. se: See Fig. 2.—Outline map of Pennsylvania, showing the distribfition of potato wart as determined by suryeNs completed in 1921. All infested areas are in coal-mining localities and are generally at hig altitudes. - to°2,000 feet, where the climatic conditions of temperature and rain- fall are favorable for potato production. (Fig. 2.) “The use of wart-immune varieties of potatoes was adopted as a quarantine policy in 1920. As a preliminary step in this direction all owners of gardens and fields actually infested with potato wart were permitted to grow only wart-immune varieties. The particular variety selected for this purpose was Spaulding Rose, which is a potato _ of good commercial quality and in addition possesses such outstand- _ ing varietal characteristics that the detection of mixtures is compara- _ tively easy during the whole season of summer inspection. During the first season approximately 800 bushels of Spaulding Rose potatoes were used with very pronounced success in 300 fields and gardens, and in 1921 it was decided to extend the use of this immune variety to all the areas under quarantine. 17 18 BULLETIN 1156, U. S. DEPARTMENT OF AGRICULTURE. The production of this wart-immune seed is very carefully regu- lated by the Pennsylvania Department of Agriculture in order to be certain that each variety is free from mixtures. For the season of 1921 approximately 10,000 bushels of Spaulding Rose potatoes were. grown in Potter County, Pa., and distributed to growers in the quar- antined areas thrbads the ordinary commercial channels. The results of the first season of the general use of immune varieties have roved very successful, as the newly introduced immune varieties are ar superior to the varieties formerly grown in general appearance, stand, and yield. As a further means of preventing the spread of potato wart, it was decided in 1921 to establish a safety zone, surrounding the quaran- timed area. (Fig. 3.) This area is largely agricultural, comprising 2,000 farms and a few scattered rural villages, and since it comprises and includes all the culti- vated land for several : miles on every side of the LUZERNE wart-infested region the | value of this zone in pre- venting the spread of the disease is obvious. Within this area after April 1, 1922, only wart- immune varieties could be grown. The varieties selected for the safety zone are Irish Cobbler and Green COLUMBIA ve JS Mountain, the former an we" SCHUYLEILL | y | early and the latter a late Fig. 3.—Outli i CAT ai EP variety. To furnish the 1G. 3.—Outline map of Luzerne and Carbon Counties and por- = tions of Columbia and Schuylkill Counties, Pa., showing the large supply of seed pota- area heavily infested by potato wait (marked by cross hatch- toes nee de d in 1922 the ing) which is under rigid quarantine and the surrounding safety zone (marked by small dots) in which a limited quar- potato growers of the antine is maintained. A safety zone organized potato associations and brought in and grew during the season of 1921 under State inspection and supervision 50,000 bushels of Green Mountain and Irish Cobbler potatoes. To obtain experimental data as to the adaptability of these varieties to the safety zone, these potatoes were grown on 42 different farms in the three portions of the counties comprising the safety zone, where they produced an average yield of 360 bushels per acre, as compared with an average of 225 bushels per acre for local varieties. The experience gained in connection with the supervision of the seed production of wart-immune varieties for the quarantined area has emphasized the absolute necessity of careful inspection and regu- lation. The loose application of a multitude of names to various strains of our commercial varieties has resulted in such uncertainty in regard to the identity of any individual stock that it has been found necessary to test every prospective seed stock for wart im- INVESTIGATIONS OF POTATO WART. 19 - munity and then carefully supervise the propagation of seed from it *| before it can be certified for use in quarantined areas. The results of the adaptability tests of the selected wart-immune -| varieties would seem to indicate that these can be profitably used in ‘| the quarantined areas of Pennsylvania. HoweVer, should the use of _wart-immune varieties become necessary in other sections of the State where less favorable temperature and moisture conditions obtain, it will be necessary to provide wart-immune varieties better adapted to such conditions. Since the possibility of the spread of the wart into other sections of the State is a threatening factor, con- _ tinued efforts should be made to develop immune varieties of such _ diverse types that one or more of these varieties will be available for the commercial or home potato grower in every part of the State. Il._THE STABILITY OF WART IMMUNITY. By FreEMAN WEIss. Since the use of immune varieties continues to be the most effec- tive means known of dealing with potato wart, both as to avoiding the loss of the potato crop in infested districts and as to restricting the extension of the pathogen beyond its present range, the question of the permanence of immunity is of great concern to growers and quarantine officials alike. Fortunately, the information which has been adduced in England and in Germany from immunity tests, which have extended over a much longer period than the similar line of investigation in the United States, furnishes a satisfactory answer — to this question. In Leaflet 105,?° issued in 1918 by the British Board of Agriculture and Fisheries, the following statement appears: The trials carried out at Ormskirk . . . demonstrate beyond all doubt the absolute immunity . . . of certain varieties. Disappointment in the past as to resistant varieties has been due either (a) to wrongly named seed, or (b) to the presence of ‘‘rogues,’’ or (c) to the use of varieties which, though formerly supposed to be immune, had not been properly tested on badly and uniformly infected soil. As far as known the immunity of no variety which has been thoroughly tested has as yet broken down. Subsequent evidence has not yet appeared from the English tests which in any way requires the modification of this conclusion, and the experience of three years with immune varieties in the United States is wholly confirmatory. It is significant that the list of immune varieties which was published” as a result of the first year’s trials has not required amendment except to add new varieties. Schaffnit,2? however, holds that immiunity is not absolute, but only relative; that varieties showing immunity under normal con- ditions may lose this faculty as soon as the plant no longer exhibits its normal form of development or is weakened as a result of tuber- transmissible pathological conditions expressed in leaf-roll and mosaic mottling. The opinion has been expressed by Gough,”? however, that the loss of immunity reported by Schaffnit is probably the result of using originally impure seed stocks or the occurrence of mixtures during the test. Some data in this connection have been derived from the tests at Freeland, Pa. - The immune varieties which were imported from England in 1919 exhibited in their first year a considerable propor- tion of leaf-roll and mosaic mottling. The seed for 1920 was saved from these same stocks and increased percentages of leaf-roll and mosaic, in some cases affecting the entire crop, were noted in the 1920 plats. Both diseases appeared to a greater or less extent among 20 Anonymous. Wart disease (black scab) of potatoes (Synchytrium endobioticum Percival). Leaf- let Bd. Agr. and Fish. [Gt. Brit.], No. 105, 6 p., 4 fig. (Issued 1904, rev. 1918). 21 Lyman, G. R., and others. Op. cit. 22 Schafinit, E. Versuche zur Bekiimpfung des Kartoffelkrebses in Jahr 1918-19. In Ztschr. Pflanzen- krank, Ba. 30, p. 59-67. 1920. % Gough, G. C. [Discussion on immunity from wart disease.] In Rpt. Internat. Potato Conf., 1921, p. 103. [1922] 20 } INVESTIGATIONS OF POTATO WART. yA the American variety and seedling collections also. Individual plants showing particularly marked symptoms were selected that ear, and tubers were saved from these for planting a mosaic and leaf-roll pathologium in 1921. The immune stocks so selected were grown in the most heavily infested garden available, where sus- ceptible sorts regularly showed total infection. The results of this experiment appear in Table 5. n 1922 a further planting was made of stocks of certain English immune varieties imported in 1919, which had since become thor- oughly degenerate and exhibited pronounced symptoms of crinkle, mosaic necrosis, streak, and leaf-drop, combined in some cases with extreme dwarfing. It is Baievorthy that not a single instance of deterioration of im- munity was observed, although all plants and tubers were examined minutely, and susceptible sorts, interplanted, were generally infected. TABLE 5.—Tests of the stability of wart immunity in degenerate stocks of potato varieties at Freeland, Pa., in 1919, 1920, and 1921. 1919 1920 | 1921 Variety. ta ar a eT = eat — Foliage. Wart. | Foliage. Wart. Foliage. Wart | —— i* geaeneaane ree] CSS Le Ee Eee eee Abundance.\. . cis 4220 Healthy...... O) AWeat-roll see ence cae 0 | Leaf-roll and mosaic. 0 Ue ees eee Goss Opt as sees GO Neco caacn ake Orie ROO te eee eoeee 0 Wareill Barly: 207225233 Mosaic. ....... 0 | Mosaic --.2 25.505 25022 UNO! SMOSRIOUS SUS 0 Haze Blue oo ..--+.--.-': Healthy...... Q') Leat-rolls yet com caroe 0 | Leaf-roll and Mosaic 0 MSC oe scatinncnecs}-0-0 0 GOSs os sass Once (i (ewe eee bee O locate (3 Ko tei tae es 0 miny Queen. sejseks bs. . 5.155 Ss cb = 3s do oe sk. MOSAIC ee eee a 52 0 j;Mosaiosso oes) ta. iG 0 Early Petoskey......... Healthy...... 0) Leaf-rolle 4. ses see 0 | Leaf-roll and mosaic. 0 Extra Early Sunlight...)..... Got. eset 0 | Curly dwarf......... 0 | Curly dwarf. -....... 0 Green Mountain Junior.)..... OO nerve hsicis Olt Mosaicici sc Saco 5e%< OF |'Saaes GOP jase saakoshe 0 LETR1G O70) 0) 0) (2) haan en (ea (0.0 yale aero | 0 | Leaf-roll and mosaic. 0 | Leaf-roll and mosaic. 0 PSGOPCr. <2. <== 4s ee ee Curly dwarf... 0} Curly dwart:. 02... .- 0 |. Curly dwarf......... ) Round Pinkeye......... MOSSIC. osc. Q | Leaf-roll and mosaic. 0 | Leaf-roll and mosaic. 0 Seedling No. 3615....... | a S20 G02 2.4% 23 0}! Curly dwarf... ..<..2. Osos (5 (Oe Se a 0 Seedling No. 37662...... eee PRE Cece 0: Mosaic... .#..-...+ Q)) Mosaics: ou. 3 0 Seedling No. 38899....../..... GOetcitwesic Oe es GOS oe een ee 1s fae GO caccaniouasser 0 _ Seedling No. 39304......| Healthy...... Ouleeee. Const es tee sse Olks. -3 GO) Sth. 0 ECT Te eee eee Fe 2 ein daw clos cosllioe = asave ivealthiycc cc staess is (2) | Mosaicand leaf-roll..| (8) mairal Now Yorkerioit.|.cf2bici Alle. | seaweed ov aces cose cee et eres | saree Moves ws (4) 3 One warted stolon. 4 Wart 50 per cent. During an experience covering three years in the culture of the immune varieties, Kdzell Blue, Spaulding Rose, Irish Cobbler, and Green Mountain, in the quarantined area of eastern Pennsylvania, many cases of mosaic and leaf-roll infection have been observed, but in no case has immunity to wart been affected. Particularly during 1921 were the potatoes grown in this district subjected to very adverse conditions brought about by drought, warm weather, severe om and flea-beetle injury, and competition with weeds. Although plantings of susceptible potatoes continued to develop wart under even these conditions, no immune variety has yet broken down. Similarly, injuries to the tuber caused by common scab or by milli- pedes and burrowing insect larve have never been observed to pre- dispose the affected part to wart infection, although such injuries must expose the cortical and meristematic tissues beneath the pro- tective periderm. 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