Sorghum grain hardness and its relationship to mold susceptibility and mold resistance

Sorghum [Sorghum bicolor (L.) Moench] cultivars exhibiting contrasting reactions to the gram mold complex were grown at Patancheru, India, in one postrainy (1988-1989) and two consecutive rainy seasons (1989 and 1990). Sorghum grain hardness was measured by four methods: grinding time required to obtain a fixed volume of flour from grains in a Stenvert hardness tester, force required to break the grains using Kiya and Instron food testers, and density grading in sodium nitrate solution measured as percentage of floating grains. Ergosterol concentration was determined in grains to assess the extent of mold damage. The Stenvert method was convenient and rapid and was significantly correlated with the other three methods but negatively and significantly correlated with the ergosterol concentration. Grains grown in the postrainy season exhibited higher hardness than those grown in the rainy seasons. Mold-resistant cultivars exhibited significantly greater hardness than mold-susceptible cultivars. Ergosterol concentration indicating the extent of mold attack was negatively and significantly( P < 0.01) correlated with Stenvert hardness values in mold-resistant phenotypically white sorghum grains (without testa) in both the rainy seasons