Genetic correlation between test environments and genotype ranking for moisture stress tolerance in sorghum (Sorghum bicolor L.)

Abstract

Sorghum is cultivated both in rainy (kharif) and post rainy (rabi) seasons predominantly under rainfed conditions in India. The rabi sorghum (Sorghum bicolor L.) sown in the months of September/October completes its life cycle with residual soil moisture condition under normal growing season. Due to erratic rainfall the timing and duration of occurrence of moisture stress vary from year to year. If the environmental conditions experienced in the test environment are different from those in normal season, the assessment of plant physiological response to soil water deficits would be incorrect leading to wrong selection [1]. To determine the degree of similarity among the test environments Type-B genetic correlations [2, 3] are used for genotype ranking. Also the model of correlated selection [4] can be used to determine the relative merits of selecting for specific versus broad adaptation. In test environment, the field sowing is postponed by one or two months (rain-out dry season), so that the genotypes are exposed to severe moisture stress condition from seedling to maturity. Based on the superior yield performance in test environment (rain-out dry season) the drought tolerant genotypes are selected and recommended for normal growing season. Although, the test and growing environments are rabi season, the change in microenvironment due to late sowing may influence the genotypic performance. The genotypes x microenvironment interaction, is hitherto, not considered. Therefore, in the present study we analyzed the effect of moisture stress treatment vis-a-vis test environment on the performance of sorghum genotypes.