Seedling emergence and of growth of sorghum genotypes under variable soil moisture deficit

Abstract

A greenhouse experiment was conducted to understand the seedling germination behaviour and growth of sorghum genotypes, to investigate genotypic differences between sorghum genotypes and to identify a selection method for seedling drought resistance studies in sorghum under variable soil moisture deficit conditions. The experimental design used was a split plot design with four soil moisture deficit treatments (25%, 45%, 65% and 85% of field capacity) as main plot treatments and five sorghum genotypes (76 T1 #23, (148xE-35-1)-1-4-1xcs 3541 drive-5-3-2, M36121, 12x34/F4/3/E/1 and IS2284) as subplot treatments. Sorghum genotypes differed significantly in response to variable soil moisture deficit for percentage germination, seedling shoot dry weight, specific root length and seedling leaf area. The percentage germination of all genotypes was markedly reduced by increasing the levels of soil moisture deficits. Among the genotypes 76 T1 #23, M36121 and IS2284 had a satisfactory percentage germination at 25% of field capacity (F.C.), ranging from 55–57% germination based on arc sin transformed data. The seedling shoot dry weight of all genotypes was also significantly (p<0.05) reduced at all levels of soil moisture deficits, except in IS2284 where there was an increase of 3.6% at 65% of F.C. relative to the control. Although the interaction effects for seedling shoot and root lengths were not significant, IS2284 had the longest seedling shoot and root lengths and this is a desirable trait related to drought resistance. It has been observed that the reduction in seedling shoot length was greater than that of seedling root length at all levels of soil moisture deficit treatments, indicating that extensive root growth under drought conditions is a major avoidance mechanism in sorghum. Genotypes were also found to have differential responses to variable soil moisture deficits for their specific root length and leaf area. Based on the results of this study, percentage germination, seedling shoot dry weight, specific root length and seedling leaf area may be used as potential selection criteria for seedling drought resistance studies in sorghum and further studies are required to confirm this result under field conditions.