PHYTOPHTHORA-SOJAE AVIRULENCE GENES, RAPD, AND RFLP MARKERS USED TO CONSTRUCT A DETAILED GENETIC-LINKAGE MAP

Two crosses between different races of Phytophthora sojae were establi shed using one race as a common parent in both crosses. F-2 population s comprising over 200 individuals were generated for each cross. A sub set of 53 F-2 individuals from each cross was selected at random for g enetic analysis of virulence/avirulence and molecular markers, and fin ally the construction of a detailed genetic linkage map. The linkage m ap developed for P. sojae is based on a total of 257 markers (22 RFLP, 228 RAPD, and 7 avirulence genes). The linkage map comprises 10 major and 12 minor linkage groups covering a total of 830.5 cM. Close linka ge was observed between Avr4 and Avr6 (0.0 cM), Avr1b and Avr1k (0.0 c M), and Avr3a and Avr5 (4.6 cM). Coupling phase linkage of RFLP and RA PD markers to all seven avirulence genes was identified at the minimum and maximum distances of 0.0 and 14.7 cM, respectively.