Volume 30 Number 1 Article 15 Pages: 16-16
Year 1976 Month 1
Title: Inoculation Technique for Evaluating Valsa Canker Resistance in Stone Fruits
Author: H.L. Keil
Citation
Abstract:
A simple inoculation technique for
evaluating Valsa canker (Valsa leucostoma)
resistance in stone fruit trees
is reported here.
The trees are grown
in pots in the greenhouse until the
trunks have increased in diameter
from 3/8 to 6/8 inches about 3 inches
above ground level or above the graft
union.
A sharp knife is used to make
a crosscut 0.5 inch long and the bark
folded back.
A piece of Valsa mycelium
about l/4 inch square from a 2-
week old culture growing on potato
dextrose agar is placed next to the
xylem and the bark returned to its
original position.
The bark is held
tight over the mycelium by wrapping
once with "Time Tape" or any other
adhesive tape.
Inoculated plants are
kept on the greenhouse bench for 1.5-
2 months when the tape is removed
and the plants inspected for infection.
Both seedling and budded trees have
been successfully inoculated by this
method.
Results thus far indicate that
of 2 isolates, V-1 is less virulent than
V-c.
The latter produced both gumming
and cankering in all tested peach
cultivars ('Earlired', 'Elberta', 'Fairhaven',
'Golden Jubilee', 'Harbrite',
'Jefferson', 'Loring', 'Madison', 'Ranger',
'Raritan Rose' x 'Ranger', 'Richhaven'
and 'Sunhigh'). Isolate V-1
usually produced gumming without
visible cankers.
Check plants in the same peach cultivars when cut without introduction of the mycelium rapidly
healed with no visible gum formation
or canker production.
In addition
about 200 inoculated apricot seedlings
are presently under study.
In
apricots, V-c produced both gumming
with variable cankering while isolate
V-1 produced more gum and cankers.
than it did in peaches.
These plants
will be observed over a period of
months to see if any have the ability
to overcome infection.
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