Comparative growth rates of western white pine varieties resistant to blister rust

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April 1980

COMPARATIVE GROWTH RATES OF WESTERN WHITE PINE VARIETIES
RESISTANT TO BLISTER RUST

R. J. Hoff and R. J. Steinhoff!

ABSTRACT

Compared was the growth of seedlings of western white pine
that displayed specific mechanisms of resistance in response
to white pine blister rust. These growth statistics were then
compared to those of seedlings that had blister rust cankers.
No difference was detected among these categories.

KEYWORDS: Resistance, white pine blister rust, western white pine.

Breeding for resistance in western white pine (Pinus monticola) to white pine
blister rust (caused by Cronartium ribicola) started in 1950. By 1974, a grafted
seed orchard, three seedling seed orchards, and a breeding arboretum were established.

Mechanisms of resistance to blister rust were of several types (Bingham and
others 1973; Hoff and McDonald, in press). One question frequently asked was: What
is the impact of these various mechanisms on other traits, mainly growth? This
paper compares the growth rates of young white pines in a natural forest that contain
various mechanisms of resistance.

1principal plant geneticist and plant geneticist, respectively, located at the
Intermountain Station's Forestry Sciences Laboratory, Moscow, Idaho.

MATERIALS AND METHODS

The trees used in this study were grown from seed planted in the nursery at
Moscow, Idaho, in 1964, 1965, and 1966. Seedlings were from phenotypically blister
rust resistant parents growing in natural stands. The seedlings were the first
generation (F,) produced after selection by blister rust. The second generation
seedlings (F2) were produced from the F, seedlings that survived intense artificial
inoculation with blister rust. This inoculation took place when the seedlings were
two years old, using methods described by Bingham (1972). To determine presence or
absence of blister rust fungus, and to identify any resistance mechanisms, inspections
were conducted using procedures described by Hoff and McDonald (in press).

In 1971, the surviving seedlings were labeled, lifted, and outplanted in the
Canyon Creek drainage of the Priest River Experimental Forest in north Idaho. The
site, a gently sloping stream bottom aluvial plain, supports the Hemlock-Pachistima
type vegetation. The seedlings were planted 8 feet apart in a random design.

The trees were measured in 1976 and 1977. Data are presented for 1976 height,
and 1977 growth adjusted for 1976 height. The adjustment was made because trees
when planted were of various heights due to rust resistance testing methods, because
trees broke out of transplanting shock at different times, and because cankered
trees were about 10 percent shorter than noncankered ones.

The data are grouped by the year seedlings were sown in the nursery (1964,
1965, 1966) progeny type (F,, Fo, self), and by the following mechanisms of resistance:

Ig No needle spots and no cankers: fungus did not infect the tree in any
manner.
(be Needle spots only: fungus infected needles but was killed or eliminated

before it could enter the stem.

Bs Stem symptoms: fungus infected needles and grew into stem but was killed
soon after entering stem, leaving a readily noticeable reddish-brown dead
patch of stem tissue.

4. Canker death: fungus developed extensively but was then killed.

No Cankered: fungus fully progressed from needle spots to typical stem
canker; however, slowing of fungus growth or tolerance for the rust
allowed tree to survive.

RESULTS AND DISCUSSION
Total 1976 height and adjusted 1977 growth are tabulated in tables 1, 2, and 3.

Trees that were cankered (category 5) were 10-15 percent shorter than those
noncankered. There was little difference, however, between cankered and noncankered
in the adusted 1977 growth. For some reason cankers affected the early growth of
these trees but not later growth. Bingham and others (1973) report that cankers did
not affect the growth of young trees. In fact, the infected trees were slightly
taller. Transplanting the fairly large stock (trees 6, 5, and 4 years old) may have
had more adverse affects on the cankered trees.

Table 1.--Mean adjusted 1977 growth and total 1976 height of western white pine F , trees
infected with blister rust or not infected because of several mechanisms of resistance

Mechanism of 1964 PT* Total height 965 eR Ts Total height

resistance Trees 77 growth 1976 Trees 77 growth 1976
No. cm cm No. cm cm

No spots,

no cankers 671 29 100 141 32 119

Needle

spots only 641 29 104 70 51 ILL

Stem symptoms 770 29 99 Sy 32 114

Canker death 440 28 104 65 33 116

Cankered : 48 2H), 85 - - -

Total 2570 pe. 29 101 333 oe si2 iy

*1964 PT (progeny test), 1965 PT seed were sown in autumn 1964 and 1965, respectively.

Table 2.--Mean adjusted 1977 growth and total 1976 height of western white pine Fy) trees
infected with blister rust or not infected because of several mechanisms of resistance

Mechanism of L96S5aeis Total height 1966 PT* Total height
resistance Trees 77 growth 1976 Trees 77 growth 1976
No. cm cm No. cm cm
No spots,
no cankers 98 S58) 1S 184 27 94
Needle
spots only
60 33 116 761 27 92
Stem symptoms 29 29 121 63 By 93
Canker death 50 31 103 55 25 92
Cankered - - - 47 27 84
Total Deen a SD 114 1088 a2) 92

*1965 PT and 1966 PT seed were sown in autumn 1965 and 1966, respectively.

Table 3.--Mean adjusted 1977 growth and total 1976 height of western white pine selfed
trees infected with blister rust or not infected because of several mechanisms

Mechanism of
resistance

No spots,
no cankers

Needle
spots only

Stem symptoms
Canker death
Cankered

Total

+1964) Pi, L965

of resistance

1964 PT* Total height WEXOS WE Total height
Trees 77 growth 1976 Trees 77 growth 1976
No. cm cm No. cm cm
109 20 67 22 20 80
82 19 70 - - -
85 Zi vel - - -
34 20 81 11 24 82
4 18 60 - = =
Md 5g AO 70 MA 5 DE 81

PT seed were sown in fall of 1964 and 1965, respectively.

Among the noncankered categories no consistent pattern emerged in the variation
of total height. And after adjustment of 1977 growth on 1976 total height, differences
among all categories were insignificant.

For the F, progenies in the 1964 test, correlations between traits were as
follows:

0.003 N.S.

is Resistance types and 1976 height r
Dr Resistance types and 1977 growth r = 0.015 N.S.

So Resistance types and 1977 adjusted growth r = 0.021 N.S.
4. 1976 height and 1977 growth r = 0.65 signif. 0.001.

One weakness in this test is that there were no truly susceptible control
plants. They all died from blister rust in the nursery or soon after outplanting.
The trees most closely approximating a control group were those with living cankers,
but even these are probably still alive because of some resistance or tolerance to
the fungus. Nevertheless, it seems unlikely that if blister rust resistance were
negatively related to growth that it would occur uniformly over all resistance
types. Further, Bingham and others (1973) found no difference in young seedling
growth among controls and F, and F» blister rust resistant stock. The controls were
standard nursery stock with little or no resistance. Thus, we conclude (within the
limits of the data presented) that growth rate and resistance to blister rust are
independently inherited characteristics.

In addition, we have not noticed any association between resistance types and
other traits such as tree form or the occurrence of other pests.

We intend to measure the trees in the plantation every 5 years and to continue
looking for associations between resistance types and other traits.

PUBLICATIONS CITED

Bingham, R. T.
1972. Artificial inoculation of large numbers of Pinus monticola seedlings with
Cronartium: ribicolal.) Enzi BlOlOgys OF USED GeSiStance: an proresit trees spi) S5i/—
S125 USDA FOr Serviq Misc buble. 221 isle pr.
Binghams, Rot Re Jia chor. and=Ge. i Mebonailid
1973. Breeding blister rust resistant western white pine. VI. First results
from field testing of resistant planting stock. USDA For. Serv. Res. Note INT-
L/S) i 70s
Hotty Reds cand Geel MeDonailide
In press. Improving rust-resistant strains of inland western white pine. USDA
ones Sore MOS, WPehos JUNI 5 0),

W U.S. GOVERNMENT PRINTING OFFICE: 1979-0-677-121/121

The Intermountain Station, headquartered in Ogden,
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