A diallel cross of seven inbreds and one synthetic line of maize were
analyzed in 1994 and 1995 for their reaction to Diplodia ear rot. An a
dditional inbred line was included in the 1995 analysis. Plants were i
noculated by placing a pycnidiospore suspension (5 x 10(3) spores per
mi) of Stenocarpella maydis in the whorl at the V14 to V15 growth stag
e. Crosses were evaluated for disease incidence of Diplodia ear rot at
harvest, and the percentage of plants with Diplodia ear rot in a plot
was used for analysis. In both years, general combining ability (GCA)
effects were significant. In 1995, specific combining ability effects
were also significant. There were no reciprocal effects. There was no
significant interaction between year and genotypes, indicating that c
rosses reacted the same in both years. Inbred lines B37, H111, B68, an
d MS had negative GCA effects that contributed toward resistance in bo
th years. VA26, with intermediate resistance to Diplodia ear rot, cont
ributed toward susceptibility. Only inbred lines with a high degree of
resistance should be used as parents.