Inheritance of Resistance to <i>Macrophomina phaseolina</i> (Tassi) Goid. and <i>Fusarium moniliforme</i> Sheldom in Sorghum

Abstract

Lodging of grain sorghum [ Sorghum bicolor ] a serious problem under certain environmental conditions such as water stress or heat stress. Lodging at the base of the stalk or the base of the panicle has been attributed to a complex of stalk rotting organisms, which includes Macrophomina phaseolina (Tassi) Goid and Fusarium moniliforme Sheldon. The field study reported here evaluated the use of a toothpick inoculation technique to artificially infect plants with these two organisms and determined inheritance of resistance. The experimental material consisted of the 45 F 1 's from a 10‐parent diallel with no reciprocals, the 10 parents, and five hybrid checks grown in 2 yr under two water regimes. The inoculated and noninoculated plants in a plot were rated for stalk disintegration on a scale of 1 (resistant) to 6 (susceptible). Hybrids differed nificantly and consistently across environments for the two inoculation treatments but not for the noninoculated. General combining ability was significant in both dryland environments for both inoculation treatments; specific combining ability was significant for F. moniliforme in both years but only in 1984 for M. phaseolina . The expression of resistance seems to depend upon the environment, especially for F. moniliforme .