conn s 43 Connecticut Scantic, A New Fusarium-Wilt Resistant Broadleaf Tobacco Cultivar BY JAMES A. LAMONDIA Digitized by the Internet Archive in 2011 with funding from LYRASIS members and Sloan Foundation http://www.archive.org/details/scanticnewfusariOOIamo Scantic, A New Fusarium-Wilt Resistant Broadleaf Tobacco Cultivar BY JAMES A. LAMONDIA A new cultivar of Connecticut broadleaf cigar wrapper tobacco (Nicotiana tabacum L.) resistant to Fusarium wilt, caused by the fungus Fusarium oxysporum Schlechtend.:Fr. f. sp. nicotianae (J. Johnson) W.C. Snyder & H.N. Hans., has been developed at The Connecticut Agricultural Experiment Station's Valley Laboratory. This cultivar, 'Scantic', allows broadleaf tobacco production in soils infested with the Fusarium wilt pathogen. Yields and sorting quality of Scantic are equal to or better than the current standard wilt-resistant cultivar 'C9' or similar wilt- susceptible cultivars. Limited quantities of seed are available to growers and scientists. Fusarium wilt has been the most persistent and important disease of broadleaf tobacco in the Connecticut River Valley over the last two decades. The most effective control of Fusarium wilt has been achieved through the development and use of wilt-resistant broadleaf tobacco cultivars (LaMondia and Taylor, 1991; Lucas, 1975). One wilt-resistant cultivar, C9, was released in 1991 and has been widely grown (up to 80% of the total acreage annually) throughout the Valley. Wilt-resistant cultivars are not immune to Fusarium infection and will develop wilt symptoms under high inoculum potential (LaMondia and Taylor, 1987). Resistance to F. oxysporum is conferred by an unknown number of small-effect genes (quantitatively inherited) (Gritton et al., 1965). Continuous growth of a single cultivar such as C9 over a number of years may eventually select for isolates able to cause disease on that cultivar. The development and production of additional wilt-resistant cultivars, likely with different numbers or types of resistance genes, is desirable as it may prolong the effective use of plant resistance over time. BREEDING AND SELECTION Scantic is an inbred derived from a bulk system of modified single seed descent. In this breeding system, the best individuals (approximately two percent in this case) are allowed to self-pollinate (inbreed) and resulting progeny are mixed together in equal proportions (bulked) prior to seeding for the next generation. Selection for traits such as disease resistance and agronomic type are made from the second (F2) generation on until plants are inbred for six to eight generations (F6-F8). The greatest variation occurs in the F2 generation and selection reduces variation and increases the frequency of desirable traits over time. After the F6-F8 generations, each plant represents a genetically uniform homozygous inbred line and a potential new cultivar. The F2 generation of a composite of three crosses between wilt-susceptible Connecticut broadleaf tobacco lines and the wilt-resistant cultivar 'C2' (C2 x 'Winn'; C2 x 'Gogulski'; and C2 x 'Gradowski') was selected for resistance under greenhouse conditions. One thousand seedlings of the F2 composite were each inoculated with 1.0 x 107 microconidia of F. oxysporum per plant in greenhouse trays. Twenty-five of the most resistant and vigorous seedlings were selected and selfed. Each year, an additional 1,200 F3 to F8 progeny were planted annually into Merrimac fine sandy loam field soil (71.8% sand, 23.0% silt, 5.2% clay and 2.2% organic matter, pH 6.2) naturally infested with high levels of/7, oxysporum. Transplants were placed in rows 1 m apart and 0.3 m apart within rows. Twenty-five superior wilt-resistant plants out of the approximately 1,200 individuals planted were selected, selfed, and seed was bulked each year from 1988 (F3) to 1993 (F8). Plants were also selected for growth habit, traits, and reduced sensitivity to weather fleck caused by ozone. Twenty superior F8 inbred lines were self pollinated in 1993 (given the designations A-l to A-20) and evaluated as inbred lines in 1994 and thereafter. EVALUATION AND PERFORMANCE Scantic (evaluated as line A-7 in commercial field trials) was selected as a superior advanced inbred. Agronomic Connecticut Agricultural Experiment Station Bulletin 974 characteristics and cured leaf quality were evaluated in both experimental plots and under commercial conditions with cooperating farmers. Yields and sorting characteristics of Scantic were compared to the wilt-resistant standard C9 on a commercial farm in South Windsor, CT in 1995, 1997, and 1998. Cured leaves were commercially graded into one of six grades representing wrapper, binder, or filler quality. The percent of the total yield in each grade was determined and value per acre calculated (Table 1). Economic return per acre for Scantic was significantly higher than for C9 in 1995 and 1997 and similar to C9 in 1998. Cured leaf weight per acre was higher in each year and percent wrapper grades were higher in two of the three years. In 1999, an additional commercial field trial in Whately, MA concluded that Scantic had 14.5% higher weight per acre than C9 and that 64.6% of the cured leaves of Scantic were wrapper quality, while 25% were binder and 10.4% were filler. Leaf yields, wilt incidence and wilt severity were determined in field plots at the Valley Laboratory in 1996. Scantic, C9 and the wilt-susceptible cultivar Gogulski were compared in soils either infested or uninfested with the wilt pathogen F. oxysporum. Each cultivar was transplanted to six replicate two-row plots of 20 plants per plot in each F. oxysporum-'infested or uninfested field. Plants were rated for disease incidence (number of 20 plants symptomatic) and severity (rated on a scale of 0 - 4 where 0 = healthy, 1 = stunted or off-color, 2 = one leaf symptomatic, 3 = more than one leaf symptomatic, and 4 = plant dead) on August 5, 1996. Ten plants per plot were harvested on August 16, 1996 and weighed. Wilt incidence and severity were low for both Scantic and C9 (Table 2). Scantic resulted in over 20% fresh weight yield increases in comparison to C9, regardless of whether soils were infested with the pathogen or not. Yield increases over the susceptible cultivar were approximately 5% in the absence of disease and dramatically different in F. oxysporum-infested soil. Resistance to F. oxysporum is quantitatively inherited (Gritton et al., 1965). Previous observations in field and greenhouse experiments as well as in commercial production have shown that wilt expression on wilt-resistant plants is often mild and that plants often outgrow early symptoms (LaMondia and Taylor, 1987; LaMondia and Taylor, 1991). Differences in wilt severity between Scantic and C9 were not significantly different. Fusarium wilt severity, as determined by ratings of visible symptoms, was much greater for the wilt-susceptible Gogulski than wilt- resistant Scantic or C9 tobacco. Wilt-resistant tobacco is not immune to Fusarium oxysporum infection. F. oxysporum has been isolated repeatedly from wilt-resistant broadleaf tobacco (LaMondia and Taylor, 1987). Resistance to F. oxysporum in other crops has been correlated with a lack of infection, or with reduced infection, of vascular tissues above the soil line (Elgersma, et al., 1972; Gordon et al., 1990; LaMondia and Taylor, 1987). Wilt-resistant broadleaf tobacco cultivars appear to minimize increases in F. oxysporum population densities in soil (LaMondia, 1995). These results are similar to the effects of wilt-resistant watermelon, pea or tomato on densities of pathogenic F. oxysporum in soil (Larkin et al., 1993; Reyes and Mitchell, 1962). Wilt-resistant tobacco, while not providing a means of eliminating the pathogen from soil, continues to allow the successful production of broadleaf tobacco in fields infested with F. oxysporum (LaMondia and Taylor, 1991). The wilt- resistant cultivar C9 has been widely grown in F. oxysporum -infested soils. Scantic is an additional Fusarium wilt-resistant cultivar available for commercial production with a similar level of resistance and the advantage of increased cured weight yield per acre compared to C9. ACKNOWLEDGMENTS The author wishes to thank S. Waldron. W. Dunn, and Fairview Farm for excellent cooperation in commercial scale field trials and cured leaf quality analysis, and J. Canepa-Morrison, S. Lamoureux, and R. Horvath for technical assistance. REFERENCES Elgersma, D.M., MacHardy, W.E., and Beckman, C.H. 1972. Growth and distribution of Fusarium oxysporum fsp. lycopersica in near-isogenic lines of tomato resistant or susceptible to wilt. Phytopathology 62: 1232-1237. Gordon, T.R., Jacobson, D.J., May D.M., Tyler, K.B., and Zink, F.W. 1990. Fruit yield, disease incidence, and root colonization of hybrid muskmelons resistant to Fusarium wilt. Plant Dis. 74:778-781. Gritton, E.T., Jones, G.L., Powell, N.T., and Matzinger, D.F. 1965. Inheritance of resistance to Fusarium wilt in flue-cured tobacco. Crop Sci. 5:547-550. LaMondia, J.A. 1995. Influence of resistant tobacco and tobacco cyst nematodes on root infection and secondary inoculum of Fusarium oxysporum fsp. nicotianae. Plant Disease 79:337-340. LaMondia, J.A., and Taylor, G.S. 1987. Influence of the tobacco cyst nematode (Globodera tabacum) on Fusarium wilt of Connecticut broadleaf tobacco. Plant Dis. 71:1 129- 1132. Scantic. A New Fusarium-Wilt Resistant Broadleaf Tobacco Cultivar LaMondia. J. A., and Taylor. G.S. 1991. New Fusarium wilt-resistant Connecticut broadleaf tobacco varieties. Conn. Agricultural Experiment Station Bull. 891. Larkin. R.P.. Hopkins. D.L., and Martin. F.N. 1993. Effect of successive watermelon plantings on Fusarium oxysporum and other microorganisms in soils suppressive and conducive to Fusarium wilt of watermelon. Phytopathology 83:1097-1105. Lucas. G.B. 1975. Diseases of Tobacco. 3rd ed. H.E. Parker and Sons. Fuquay-Varina, N.C. Reyes. A. A., and Mitchell, J.E. 1962. Growth response of several isolates of Fusarium in rhizospheres of host and nonhost plants. Phytopathology 52:1 196-1200. Connecticut Agricultural Experiment Station Bulletin (>74 Table 1. Percent leaf grades, cured leaf yields and value per acre of Semitic and C9 broadlcaf tobacco over three sears under commercial production conditions (South Windsor. CT). 1995 1997 1998 Leaf Scantic C9 Scantic C9 Scantic C9 Grade (%) (%) (%) (%) (%) ("■») Wrapper 65.6 57.9 59.0 23.0 44.0 50.0 Binder 21.9 25.4 28.0 51.0 30.0 39.0 Filler 12.5 14.8 13.0 26.0 26.0 11.0 Yield and value Yield and v alue Yield and value Pounds/acre* 2304 2016 2486 2373 2232 2000 Value/acre+ $13,202 $10,231 $13,171 $8,130 $9,812 $10,032 * Cured weight leaf yield per acre. + Weight in each grade multiplied by price per pound for each grade. Table 2. Fusarium wilt incidence, severity, and shoot fresh weight of wilt-resistant C9 and Scantic and wilt-susceptible Gogulski broadleaf tobacco in wilt-infested or uninfested fields. Cultivar Wilt Status Field Wilt Incidence* Wilt Severity+ Yield' Scantic resistant Infested 0.7 1.0 29.5 Scantic resistant Uninfested 0.0 0.0 34.0 C9 resistant Infested 0.2 0.2 24.3 C9 resistant Uninfested 0.0 0.0 27.8 Gogulski susceptible Infested 17.0 3.6 4.0 Gogulski susceptible Uninfested 0.5 1.0 32.4 * Number of 20 plants per plot with wilt symptoms evident. + Disease rating (0=healthy, 4=dead) of plants. A Fresh weight (lb) per 10 plants. The Connecticut Agricultural Experiment Station (CAES) prohibits discrimination in all its programs and activities on the basis of race, color, ancestry, national origin, sex, religious creed, age, political beliefs, sexual orientation, criminal conviction record, genetic information, learning disability, present or past history of mental disorder, mental retardation or physical disability including but not limited to blindness, or marital or family status. 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