The inheritance of resistance to grey leaf spot of maize (Zea maysL.), caused byCercospora zeae-maydis, was studied using a 12 #xD7; 12 diallel cross. Information on the heterotic performance of the inbred lines enabled identification of patterns of transmission of resistance to susceptible genotypes. The study confirmed that an accurate evaluation of heterotic patterns for grey leaf spot requires an assessment of both the inbred lines and all the single crosses among them. Resistance of the tested maize genotypes to grey leaf spot can be expressed in terms of an additive-dominance model, with dominance almost complete. As the incidence of this fungus reached epidemic proportions only after physiological maturity, yield was not adversely affected by grey leaf spot. Genotypic correlations between grey leaf spot ratings, yield and kernel quality traits suggested that certain of the tested genotypes displayed sink-induced susceptibility to the disease. Hayman's (1954) variance-covariance graphical technique confirmed several findings of the heterotic pattern analysis and it provided additional information that will be used in the development of resistant genotypes.
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