Bacterial spot of tomato is a disease complex caused by at least four species of Xanthomonas and leads to severe yield and quality losses in humid growing conditions in the world. Five physiological species (T1-T5) have been defined by their virulence on tomato varieties. These races are associated with three species: X. euvesicatoria (T1), X. vesicatoria (T2), and X. perforans (T3-T5). Recent epidemics of X. gardneri has occurred in the Midwest United States. In this study, we developed germplasm with resistance to multiple species of bacterial spot. Six advanced breeding lines with at least three different source of resistance were crossed and their F1 hybrids were inter-mated to produce a complex breeding population consisting over 1,100 progeny. Three lines (OH7663, OH7667 and 2k7-6117-S2) were selected by field evaluations of the population against T1, T2, T3, and X. gardneri. Graphical genotypes demonstrated that these breeding lines contain a QTL and Rx-4/Xv3 in coupling phase on chromosome 11 as well as Rx-3 on chromosome 5. In order to test the combining ability of the lines, we developed hybrids from multiple crosses and conducted replicated field trials to evaluate bacterial spot resistance and yield. As a male parent, OH7663 showed acceptable combining ability for yield and for resistance against multiple species of Xanthomonas. Several hybrids produced yields that were not significantly different from yields of commercial varieties.

• Sung-Chur Sim(Sejong University, Dept. of Bioresources Engineering)
• David M. Francis(The Ohio State University, Ohio Agricultural Research and Development Center, Dept. of Horticulture and Crop Science, USA)