Correlations of Vegetative and Reproductive Characters with Root Traits of Upland Rice under Imposed Soil Moisture Stress

An understanding of the relationship between traits related to plant performance is advantageous in rice breeding for tolerance to drought and increase in grain yield. Correlations studies involving root, vegetative and reproductive traits were carried out with sixteen rice genotypes under differing soil moisture through a combination of three amounts of moisture and two periods of application. Data from root, vegetative and grain yield traits were used to compute phenotypic and genotypic coefficients of variation (CV), correlations and heritability. Phenotypic and genotypic CV were generally low, with the exception of root branching and grain weight per plant. Heritability estimates were also low. Among the root traits, the highest heritability value of 36.6 and 30.5 was recorded by root thickness and root branching respectively while the estimate for 100-grain weight (48.7), days to flowering (47.8) and primary branching (45.9) were moderate. Genetic advance was highest for root thickness, root branching and grain weight per plant. Root volume showed significant negative correlation with root thickness at phenotypic and genotypic levels (-0.124, -0.286), but had positive correlation with fresh root weight (0.340, 0.917) and dry root weight (0.338, 0.910). Root volume and root thickness exhibited counteracting relationships with primary branching, secondary branching, spikelets number per panicle and spikelet fertility. Root branching was significantly correlated with grain weight per plant at genotypic level. The diffused relationships of root traits with the vegetative and reproductive traits underscore their intricate nature and require consideration in trait selection for direct and indirect increase in grain production.Keywords: Root volume, root thickness, root dry weight, drought, grain yield.