Volume 30 Number 1 Article 6 Pages: 10-10
Year 1976 Month 1
Title: Screening Apple Seedlings for Disease Resistance
Author: E.B. Williams
Citation
Abstract:
The following criteria should be
applied for screening apple seedlings
for disease resistance: (1) seedling
and mature stages must exhibit same
response; (2) leaf and fruit stages
should have same level of resistance;
(3) must have access to quantities of
inoculum; (4) must be able to control
environment; (5) must have reproducible
reactions test after test.
Resistance to the following diseases
is easily determined by screening
young seedlings in the greenhouse:
apple scab, cedar-apple and hawthorn
rusts, and collar rot.
Other diseases
(i.e., fireblight, powdery mildew, fruit
rots, and summer diseases) are less
easily screened for in the young seedling
stage and one may have to depend
on nursery or field response to
select for resistance.
Due to the genetic diversity of the
apple and as many of the characters
are quantitatively controlled, one must
screen large numbers of seedlings to
recover the desired level of resistance
as well as desired pomological characters.
In our Purdue-Rutgers-Illinois
program where we screen only for
scab resistance in the young seedling
stage and depend on field selection
for acceptable levels of resistance to
other diseases, we average one selection
per 100 scab resistant seedlings
planted in the field.
During the
past 29 years we have screened over
350,000 controlled pollinated seedlings
for scab resistance.
Over 100,000 have
been planted in the field for evaluation
of resistance to other diseases and
for pomological characters.
Four varieties,
'Prima', 'Priscilla', 'Priam', and
'Sir Prize', have been named.
With the large numbers of seedlings
required, we believe that it may be
more practical to screen for resistance
to one or possibly two of the most
important diseases and depend on the
judicious use of a limited number of
fungicide applications to control other,
diseases.
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