The inheritance of specific virulence in Bremia lactucae (downy mildew) to match resistance factors 1, 2, 4, 6 and 11 in Lactuca sativa (lettuce)

Publisher Website
Google Scholar
Abstract
The inheritance of specific virulence in Bremia lactucae was studied by hybridizing two isolates which differed in their virulence on host cultivars carrying the resistance factors R1, R2, R4, R6 and R11. Avirulence on R1, R2, R4 and R11 was dominant to virulence and the segregation conformed to that expected for alleles at single loci, although reactions on R4 were not always dearly defined. The loci conditioning avirulence on R2 and R11 were probably linked. It was difficult to classify the reactions of isolates on R6 and the ratios obtained could not readily be interpreted in Mendelian terms. Since no segregation was observed for reaction on R3, R5, R7, R8, R9 and R10 it was concluded that the genes determining virulence on these factors occurred at the same loci in both isolates, Sexual compatibility type (B1 and B2) segregated with a ratio of 1:1.