Effect of Corn Genotypes on Ear Rot Infection byGibberella zeae

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Abstract
In a disease screening of 58 inbred corn lines, 10 lines with varying degrees of susceptibility to G. zeae ear rot were selected for diallel analysis. The parental inbreds were rated resistant (PA347, MS74, and A509), susceptible (A669, ND100, and A637), and highly susceptible (B73HT, Mo17HT, B79 and A670). The F1 progeny of all possible crosses between the 10 inbred lines were inoculated through the husks with toothpicks infested with G. zeae isolate W-8 and rated for percentage of rotted kernels on the ears. Differences among genotypes in their reaction to inoculation by G. zeae were significant (P = 0.05). General combining ability (GCA) effects were significant (P = 0.01) but specific combining ability (SCA) effects were not. Therefore, the reaction of single-cross hybrids to infection by G. zeae could be predicted on the basis of the parental inbred reaction to G. zeae. Analysis of infected grain from the inbred lines indicated a positive but low correlation (r = 0.47) between the concentration of the mycotoxin deoxynivalenol and disease ratings. The concentration of deoxynivalenol was low at lower disease ratings but varied considerably at higher disease ratings. Zearalenone concentrations varied and no trends were observed.