Volume 30 Number 1 Article 27 Pages: 25-26
Year 1976 Month 1
Title: Mass Screening of Young Strawberry Seedlings for Resistance to Pytophtora fragariae
Authors: D.H. Scott and A.D. Draper
Citation
Abstract:
Feasibility of screening young strawberry
seedlings for resistance to Phytophthora fragariae was determined.
Use of a red stele mycelium-agarwater
mixture as a root dip at time
of planting into greenhouse seedling
beds eliminated young strawberry
seedlings susceptible to red stele.
When seedlings from 111 progenies
containing 79,060 seedlings that were
segregating for resistance were screened
by this method, 49.5 to 81.5 percent
of the seedlings were eliminated
as susceptible.
The percent of susceptible
seedlings differed within progenies,
depending upon parentage,
and varied somewhat from year to
year over the 4-year period, 1972-1975.
As a comparison, when 1736 seedlings
of Midland x self, a susceptible progeny,
were inoculated to determine
uniformity of infection and grown in
102 plots during a 4-year period all
were completely susceptible.
Inoculum
was prepared by growing mycelium
of five races of the fungus on
kidney bean meal agar and mixing
them in a food blender with some
water.
Seedlings 6 to 8 weeks old,
grown in milled sphagnum, were
dipped in the inoculum and planted
immediataely with a spacing of 5 x 5
cms in sterile sand in greenhouse
benches, in mid-October to mid-November.
The sand was irrigated 3 to
4 times daily.
Susceptible seedlings
began to collapse in 3 to 4 weeks after
inoculation.
All surviving seedlings
were examined in February or March
and partially resistant ones discarded,
retaining only the highly resistant
ones.
A preliminary effort to screen seedlings
for resistance to red stele in seed
flats containing four different germination
media (Jiffy mix, potting soil,
sand, and milled sphagnum) eliminated
71.0, 68.4, 65.7, and 64.6% of
the seedlings, respectively.
Seeds were
planted in rows in the seed flats Nov.
13, 1974, and inoculated Jan. 28, 1975.
The seedlings were inoculated in place
by opening 2.5 cm deep trenches on
each side of the row and pouring inoculum
into the trenches.
After inoculation, the flats were irrigated by
flooding daily.
The method appears
promising.
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