Influence of different maize genotypes and cytoplasms on resistance to Drechslera maydis race T on the north coast of New South Wales

Abstract

Sixteen Australian and two United States maize (Zea mays) inbred genotypes, and six single and double-cross hybrids, were evaluated for reaction to natural infection by Drechslera maydis (race T) Zea (Maydis Leaf Blight) in the field at Grafton, New South Wales, in 1973. Each genotype was evaluated in Texas male-sterile (T) cytoplasm and normal (N) cytoplasm. All lines with T cytoplasm were susceptible to the disease, but those with N cytoplasm were resistant. However, the progress of the disease was significantly slower on inbred NNI 8 and, to a lesser extent, on inbred 25. Variation in degree of resistance among genotypes in N cytoplasm was also observed. Although D. maydis (race T) was virulent on plants with T cytoplasm, another form of male-sterile cytoplasm, designated C, did not predispose plants of one hybrid and two inbred genotypes to the disease. Comparisons were also made between each of six Australian inbred genotypes in T cytoplasm and their respective backcross recoveries having male-fertility restoring genes. The presence of these genes had no effect on plant reaction to D. maydis (race T) infection.