Quantitative genetics of net blotch resistance in barley

A half diallel was made amongst 5 barley ( Hordeum vulgare L.) genotypes (Zephyr, Hassan, Mata, Kaniere, and Manchuria) which varied in resistance to net blotch disease, caused by the fungus Drechslera teres (Sacc.) Shoem. The 5 parents and 10 F 1 progeny were grown to physiological maturity in a controlled environment. All genotypes were inoculated first at 14 days after sowing and thereafter 10 times at about weekly intervals. The procedures of Mather and Jinks were used to analyse the half diallel 89 days after sowing. Net blotch infection was measured on top canopy, bottom canopy, flag leaf (leaf number = 1) and second leaf. Infection of detached leaf segments in petri dishes was also analysed. This test provides a simple and rapid technique for net blotch assessment. All analyses showed that average effects of alleles were of much greater importance than dominance in controlling resistance. Epistasis and/or correlated gene distributions were trivial. Resistance was conditioned by a partially dominant, single effective‐factor. Heritability levels were moderate (mostly 40‐60%).