Selection for Resistance to Macrophomina phaseolina and Fusarium moniliforme in Sorghum

Lodging of grain sorghum, Sorghum bicolor (L.) Moench, can be a serious problem under certain environmental conditions. Lodging at either the base of the panicle or stalk is often attributed to a complex of stalk-rotting organisms. The two most prevalent are Macrophomina phaseolina (Tassi) G. Goid, the causal agent of charcoal rot, and Fusarium moniliforme Sheldon, the causal agent of fusarium root and stalk rots. The field study reported here evaluated the predicted gain from selection in a random-mated population of grain sorghum for resistance to these two stalk-rotting organisms. The experiment consisted of 150 random half-sib families from a random-mated population, KP8B, which were evaluated in a 2-yr study at McCune, KS. The families were artificially inoculated with both organisms using a toothpick inoculation technique and were rated for stalk disintegration on a scale of 1 (resistant) to 6 (very susceptible). The families differed significantly for M. phaseolina and F. moniliforme resistance in each year, but the effect of years and the interaction with years were significant. The predicted gain from selection indicated that improvement could be made in this population for resistance to these organisms either directly or indirectly with selection for green leaf retention, but the level of postflowering stress would need to be severe enough to ensure the development of the disease.