Genetics of nonsenescence and charcoal rot resistance in sorghum
1992
Tenkouano, A. (Texas A and M Univ., College Station (USA). Dept. of Soil and Crop Sciences) | Miller, F.R. | Frederiksen, R.A. | Rosenow, D.T.
Nonsenescence is a delayed leaf and plant death resistance mechanism in sorghum that circumvents the detrimental effects of reduced soil moisture combined with high temperatures during post-anthesis growth. This drought-tolerance mechanism is often equated with charcoal rot resistance, a widespread root and stalk disease of great destructive potential. Therefore, the inheritance of charcoal rot resistance was investigated directly, by exposure of sorghum to Macrophomina phaseolina, the causal organism, and indirectly, by determination of the inheritance of nonsenescence. Sorghum families derived from diallel crosses between two nonsenescent, resistant inbreds (B35, SC599-11E) and two senescent, susceptible inbreds (BTx378, BTx623) were evaluated in 1989 at College Station and at Lubbock, Texas, under controlled and field conditions. Nonsenescence was regulated by dominant and recessive epistatic interactions between two nonsenescence-inducing loci and a third locus with modifying effects. The same conclusion was reached for charcoal rot resistance. The presence of different gentic mechanisms within SC599-11E for nonsenescence and charcoal rot resistance verifies that these two forms of resistance are not different manifestations of a single trait, i.e., they are not to be equated with each other. Nonsenescence alone cannot account for, and should not be used as the sole breeding criterion for, resistance to charchoal rot in sorghum.
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