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Introgression and Characterization of Black Rot Resistance Derived from Brassica carinata in Cole Crops 2000

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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.