Characterization of grain mold resistance in sorghum [Sorghum bicolor (L.) Moench]

Abstract

Sorghum grain lots with various levels of resistance to sorghum grain mold (SGM) were evaluated for several loss parameters: kernel weight, kernel density, electrolyte leachate level, percentage germination, vigor, and visual quality appraisal; and two indirect measures of disease intensity, ergosterol level and colony-forming units (CFU) of Fusarium moniliforme. Ergosterol level was significantly correlated with CFU (r= +0.94), visual rating (r= +0.92), leachate level (r= +0.90), and percentage germination (r= -0.86). Leachate level was highly correlated with germination (r= -0.98). In all cases, correlation coefficients for the standard deviation of kernel weight were higher than for the mean. Fitting variables to a theoretical linear model resulted in a highly significant cultivar x treatment (treatment = inoculated vs. noninoculated) interaction for kernel weight. Two greenhouse inoculation procedures, vacuum infiltration and panicle spraying differented among resistant and susceptible cultivars and caused symptoms similar to those resulting from natural infection or inoculation in the field. On susceptible cultivar TX2536, reduction in kernel weight due to inoculation by the vacuum and panicle spray methods were 31 and 41%, respectively, and reductions in percentage germination were 93 and 94%, respectively. On resistant cultivar SC0170-6, kernel weight reductions for vacuum and spray inoculations wer 10 and 22%, respectively.