HERITABILITY OF COMMON ROOT-ROT AND SPOT BLOTCH RESISTANCE IN BARLEY

Heritability of resistance to common root rot and spot blotch [Cochlio bolus sativus] was investigated in two resistant-by-susceptible barley crosses. Parental cultivars, F(1)s and progeny lines were evaluated f or common root rot reaction in a field disease nursery in four experim ents and for spot blotch reaction in two growth chamber experiments. T he heritability of common root rot resistance of cross Fr926-77 x Deuc e ranged from 56 to 85%. Heritability for spot blotch resistance in th is cross was 43 and 61%. For the cross Virden x Ellice, heritability f or common root rot resistance ranged from 53 to 78%, and heritability for spot blotch resistance was 73 and 78%. Common root rot resistance appeared to be conditioned by dominant genes in Virden X Ellice, but t he genetic basis of the resistance could not be determined for Fr926-7 7 x Deuce. The continuous nature of the distributions of mean disease reactions of progeny lines and estimation of the number of genes condi tioning resistance indicated that inheritance of resistance for both d iseases was quantitative in nature. No association between common root rot reaction and spot blotch reaction was detected.