Screening sorghum germplasm for biotic and abiotic stress tolerance and potential use of selected physiological traits as disease severity predictors
A. Y. BANDARA (1), R. Perumal (2), M. H. Kapanigowda (2), C. R. Little (1). (1) Kansas State University, Manhattan, KS, U.S.A.; (2) Agricultural Research Center, Kansas State University, Hays, KS, U.S.A.
Stalk rots are major biotic stresses of sorghum [<i>Sorghum bicolor</i> (L) Moench], while drought is the most important abiotic stress. The objectives of this study were to screen 46 ‘minicore’ accessions to identify sources of resistance/tolerance for both stressors and to analyze the potential of using selected physiological traits in predicting resistance to stalk rot diseases. Plants were inoculated with <i>Macrophomina phaseolina</i> (MP) and <i>Fusarium thapsinum</i> (FT) at 14 days after flowering. At harvest, plants were screened for disease severity using lesion length (LL), number of diseased nodes (NC) and 100-seed weight (SW). Three physiological traits: chlorophyll fluorescence, chlorophyll content and canopy temperature were measured at 74, 84 and 94 days after planting (DAP). No accession exhibited significantly decreased LL or NC compared to the resistant control ‘SC599R’, against both pathogens. However, one genotype exhibited significantly higher SW than SC599R in FT-inoculated treatment while there were four such genotypes for MP, indicating their potential use as sources of tolerance. Chlorophyll content at 74 DAP was significantly correlated with LL in both MP and FT inoculated treatments revealing its potential use in forecasting disease severity. There was no statistical evidence for the potential use of canopy temperature and chlorophyll fluorescence as predictors of disease severity though they could be used in screening sorghum germplasm for drought tolerance.
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