The inheritance of resistance to Rhynchosporium secalis in some European spring barley cultivars

The inheritance of partial resistance to Rhynchosporium secalis, which appears to be race non-specific, was studied in a diverse range of European spring barley cultivars. Data from the F₂ generation of a 6 × 6 diallel cross and the F₃ generation of three crosses selected from this diallel set suggested that resistance was complex in inheritance, the results being incompatible with any hypothesis involving less than four genes. The F₂ studies indicated that both dominant and recessive genes were active in conferring resistance, and that there were significant additive gene effects. Transgressive segregation occurred in all cross combinations in the F₃ material. Consequently the alleles conferring resistance were not completely concentrated in the most resistant cultivar studied (cv. Proctor). Heritability estimates obtained from F₂ and F₃ material suggested that field selection was of limited reliability, even when spreader drills were incorporated amongst the segregates. Single-plant selection (in F₂) was considered to be of little value, and the results of F_a head-row tests would require confirmation by replicated tests in subsequent generations.