Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: MOLECULAR MAPPING OF RESISTANCE GENES INVOLVING
HYPERSENSITIVITY TO THE TOMATO BACTERIAL SPOT (Xanthomonas
campestris pv. vesicatoria)
MOLECULAR MAPPING OF RESISTANCE GENES INVOLVING
HYPERSENSITIVITY TO THE TOMATO BACTERIAL SPOT (Xanthomonas
campestris pv. vesicatoria).
Z. H. Yu 1,3, J. F. Wang 2, R. E. Stall 2, and C. E.
Vallejos1,3, Department of Horticultural Sciences 1, Department
of Plant Pathology 2, and Plant Molecular and Cellular Biology
Group 3, University of Florida, Gainesville, FL 32611
Bacterial spot is one of the most destructive diseases in
tomato production. 'Hawaii 7998' has been the only available
source of resistance to this disease. Resistance of the 'Hawaii
7998' line is associated with a hypersensitive response (HR).
Inheritance of such resistance is polygenic. Recently, we have
been using both RFLP and isozyme markers to identify this
polygenic resistance complex in the tomato genome. HR reactions
to the X. camp. pv vesicatoria wild strain '90-14' were monitored
by observing the development of necrosis in the inoculated area
at eight-hour intervals after inoculation in an F2 ('Hawaii 7998'
X L. pennellii) and the BC, to 'Hawaii 7998'. The association
between the phenotypic innoculation responses and 72 molecular
marker loci (16 isozyme and 56 RFLPs) were analyzed by two-way
contingency tables. These markers probed about 66% of the tomato
genome. Significant deviations from random distribution were
assumed to be the result of linkage between a marker locus and
the gene involved in the HR reaction. Results indicated that
there are at least two major chromosome segments associated with
hypersensitivity (TG24, TG184, TG236, Prx-1, and Skdh-1 clustered
on chromosome 1; and TG23 on chromosome 5). Moreover, three HR
modifiers present in the susceptible genotype L. pennellii were
detected near Pgm-2 on chromosome 4, TG94 on chromosome 3, and
TG223 on chromosome 9. We are now using additional markers to
cover the rest of the tomato genome.
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