QUALITATIVE INHERITANCE OF TAN SPOT RESISTANCE IN HEXAPLOID, TETRAPLOID, AND DIPLOID WHEAT

The inheritance of resistance to the ASC1 isolate of Pyrenophora tritici-repentis was investigated in some lines of hexaploid, tetraploid, and diploid wheat in growth room studies. Plants were inoculated at the 4-to 6-leaf growth stage and resistance susceptibility was assessed on the basis of lesion type. Qualitative inheritance of tan spot resistance was detected within all ploidy levels. In the six crosses and reciprocals of the hexaploid inheritance study, F2 results of the resistant X susceptible crosses suggested the involvement of two recessive genes conditioning resistance to tan spot. The lack of segregation in crosses between the cultivars Salamouni, Carifen 12, and Erik indicated that they have the same gene(s) for resistance. Reactions of progeny from the backcross of F1 plants from the cross of Salamouni and Carifen 12 to the parents confirmed that the parents share the same gene(s) for resistance. In the six tetraploid crosses and reciprocals, F2 data for both the 2-leaf and 4-to 6-leaf growth stages revealed that the moderately resistant parent 4B175 possesses one recessive gene for resistance. F2 intercross data suggested that the moderately resistant parents 4B233 and 4B242 share the resistance gene(s) of 4B175. F2 data for the two resistant X susceptible and two resistant X resistant diploid crosses revealed that the resistant parents 2B27 and 2B53 each carries one recessive gene for resistance, which may or may not be common to both. F2 data also indicated that the resistant parents 2B27, 2B26, and 2B7 possess the same resistance gene or genes.