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Project Leader: Phillip D. Griffiths, Department of Horticultural Sciences,
Cornell University NYSAES, 302 Hedrick Hall, Geneva NY 14456
Abstract: Black rot (Xanthomonas campestris pv. campestris)
is one of the most serious diseases of cole crops in NY State, particularly
during warm damp seasons. Resistance to black rot from Ethiopian mustard has
been introgressed into broccoli lines using protoplast fusion and hybrid crosses
with cabbage and cauliflower have been made. This resistance source has been
studied by comparing molecular polymorphisms with disease severity segregations
following greenhouse inoculations of plants. Disease severity ratings at the
juvenile and mature plants stages indicated that complete resistance to black
rot was being recovered in F2 populations derived from the broccoli
lines 11 and 11B crossed with cauliflower. Plants exhibiting intermediate resistance
to black rot were also observed in the juvenile and mature plant inoculation
trials. The segregation results suggested that more than one gene may control
the resistance. However, closer studies with molecular markers suggested that
the source of resistance may indeed be a single dominant gene. The resistance
may not be fully stabilized resulting in low recovery of resistant plants in
the F2 populations derived from 11 and 11B. Markers may be important
in pyramiding resistance genes to other pests simultaneously even if seedling
disease screening is possible. Other black rot resistant material was evaluated,
in total 124 lines were field screened and inoculated with black rot during
summer 2000, and significant screening of black rot material derived from B.
carinata was made in greenhouse trials. Selections of resistant material
have been made, and these selections are being crossed to the major vegetable
cole crops.
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