Inheritance of puccinia sorghi schw. lesion length in maize

The inheritance of Puccinia sorghi rust pustule lesion length in maize(Zea. mays) was studied in a set of 9×9 diallel crosses. Highly significant variations for rust lesion length were found among nine parental inbreds and their 36 F₁ hybrids. Resistant inbreds at the adult stage usually had shorter lesion lengths than did the susceptible inbreds. However, a inbred, CI21E, had relatively long lesions and showed resistance at the adult plant stage. Average heterotic effects for rust lesion lengths in the 36 F₁ hybrids were extremely high, dominant effects accounting for 35.5% of the heterotic variation while over-dominant effects accounted for 8.2% of the heterotic variation. General combining ability(GCA) was the major variance component, accounting for 73.7% of total phenotypic variance, while specific combining ability (SCA) was a minor component (24.5%). A highly general resistant inbred, Oh545, showed exceptionally low GCA effect for increasing rust lesion length, while the moderate resistant inbred, CI21E, showed an exceptionally high GCA effect. From these data we conclude that resistant maize inbreds having long lesions should be excluded from selections for Puccinia sorghi rust resistance. Because inbreds with long lesions could contribute to rust susceptibility in hybrid combination, due to their high GCA effects.