New Sources of Resistance to Southern Corn Leaf Blight from Tropical Hybrid Maize Derivatives. R. N. Holley, Former Research Associate, Department of Crop Science, North Carolina State University, Raleigh 27695-7620. M. M. Goodman, Professor, Department of Crop Science, North Carolina State University, Raleigh 27695-7620. Plant Dis. 73:562-564. Accepted for publication 12 January 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0562.

This study documents several new sources of resistance to Bipolaris maydis (= Helminthosporium maydis, Cochliobolus heterostrophus) in tropical maize (Zea mays L.) germ plasm and presents preliminary data on their mode of inheritance. Three selected inbred lines were intercrossed and were also topcrossed to a known resistant (NC250) and a known susceptible (B73) inbred. Early-generation progenies from these crosses were evaluated in greenhouse and field tests using a mixture of race O isolates as the initial inoculum source. In field studies, natural inoculum levels were high and artificial inoculum was applied once, about 6 wk after planting. Several sources of resistance roughly equivalent to the high level of resistance available from NC250 were identified. Inheritance studies suggest that different genetic systems are involved, with a range of additive and recessive types of gene action. Resistance in these sources appears to be controlled by relatively few genes that combine in a positive epistatic fashion with the resistance genes in NC250.

Keyword(s): exotic germ plasm.