Sources of wheat powdery mildew resistance from wheat-rye and wheat-Leymus hybrids

Introgression of germplasm from rye and Leymus mollis has been used in the objective of broadening mildew resistance in wheat. The mildew resistant wheat lines were isolated from crosses of three hexaploid triticale lines, a mildew resistant double wheat-rye substitution line and a mildew resistant hexaploid wheat-L. mollis hybrid with three mildew susceptible breadwheats. Three different mildew isolates with a broad virulence have been used and lines with different resistance patterns, including resistance to all three mildew isolates, were selected. From a total of about 13,000 lines, eight lines from the triticale crosses, 58 from the double wheat-rye substitution line crosses and six from the L. mollis-hybrid crosses showed homozygous resistance to all three isolates. A differential tester set of wheat lines with known mildew resistance genes including earlier known resistance genes from rye showed a similarity between IRS-cultivars and the largest category in the triticale populations, indicating a higher frequency of IR chromosomes. The results are discussed in relation to the differential tester set and in relation to broadening the genetic base of resistance in wheat by interspecific hybridization.