High levels of resistance to common bacterial blight caused by Xanthomonas campestris pv. phaseoli (Smith) Dye (Xcp) have been observed for tepary bean (Phaseolus acutifolius A. Gray var. latifolius Freeman). However, the inheritance of resistance from this source is unknown for many lines. The inheritance of common bacterial blight resistance was studied in four tepary bean lines crossed with the susceptible tepary bean MEX-114. Progenies were inoculated with a single Xcp strain 484a. Segregation ratios in the F2 generation suggested that resistance in Neb-T-6-s and PI 321637-s was governed by one dominant gene, and Neb T-8a-s had two dominant genes with complementary effects. These hypotheses for inheritance of resistance were supported by various combinations of F1, F3, BC1Pn segregation data in all lines except PI 321637-s where an additional minor-effect gene with recessive inheritance was indicated. Generation means analyses corroborated that multiple resistance genes were present in PI 321638-s. Lack of segregation for susceptibility among testcrosses for allelism between Neb-T-6-s/PI 321637-s, Neb-T-6-s/Neb-T-8a-s, PI 321637-s/Neb-T-8a-s, and PI 321637-s/PI 321638-s, suggested that one or more loci conditioning resistance to common bacterial blight were in common across the four tepary lines.
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