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Resistance

Diallel Analysis of Resistance of Eight Maize Inbred Lines to Sphacelotheca reiliana. I. V. Whythe, Senior agricultural researcher, Summer Grain Sub-Centre, c/o University of Natal, P.O. Box 375, Pietermaritzburg, Natal, Republic of South Africa; H. O. Gevers, Assistant director, Summer Grain Sub-Centre, c/o University of Natal, P.O. Box 375, Pietermaritzburg, Natal, Republic of South Africa. Phytopathology 78:65-68. Accepted for publication 20 February 1987. Copyright 1988 Department of Agriculture. Government of Canada. DOI: 10.1094/Phyto-78-65.

A diallel set of hybrids (excluding reciprocals) involving eight maize inbred lines was used to analyze the genetic basis of resistance to Sphacelotheca reiliana. Inoculum was applied at planting, and the incidence of disease, yield, and plant height measured. Correlations among these three characters were highly significant. The most resistant crosses involved Mo17 or U267Y as a parent. Estimates of combining ability indicated that general combining ability effects were an important source of genetic variance for ear and tassel smut resistance. The V_r, W_r graphic analysis indicated that resistance to S. reiliana was additive and partially dominant. The relative position on the regression line of Mo17 and U267Y to the other inbreds suggested that these lines had the most dominant genes. Recurrent selection is therefore suggested for the development of maize resistant to S. reiliana.