INHERITANCE OF RESISTANCE TO HESSIAN FLY IN RYE AND IN WHEAT RYE TRANSLOCATION LINES

Rye, Secale cereale L., is an important genetic resource for resistanc e to Hessian fly, Mayetiola destructor (Say). Resistance genes have be en transferred from 'Chaupon' rye chromosome arm 2RL and 'Balbo' rye c hromosome arm 6RL to common wheat (Triticum aestivum L.) via wheat-rye chromosomal translocations. Our objectives were to determine (i) the number of resistance genes in Chaupon and Balbo and their allelic rela tionships, and (ii) the mode of inheritance of resistance in the wheat -rye translocation lines. Several crosses were tested in a greenhouse for reaction to Biotype L of Hessian fly. Analyses of F2 populations s howed that Chaupon and Balbo each segregated for two independent domin ant genes exhibiting duplicate epistasis. All genes conditioned antibi osis to first-instar larvae. One of the genes in Chaupon expressed a c hlorotic lesion reaction in response to larval feeding and was differe nt from the genes in Balbo. When this gene occurred together with gene s that did not cause expression of chlorotic lesions, F2 plants segreg ated in modified ratios of 12 resistant plants without lesions: 3 resi stant plants with lesions: 1 susceptible plant. Crosses of T2BS.2RL tr anslocation line with susceptible wheat 'Karl' showed that resistance from Chaupon chromosome arm 2RL was inherited as a single dominant fac tor and that 2RL carries the gene that expresses chlorotic lesions. Cr osses of Ti4AS-4AL-6RL-4AL translocation lines with susceptible wheat 'TAM106' showed that resistance from the Balbo 6RL segment was inherit ed as a single dominant factor. These results demonstrate that the whe at-rye translocations can be utilized efficiently for incorporating He ssian fly resistance into wheat.