Genotypic variation for root growth orientation in rice (Oryza sativa L.) under aerobic and well-watered condition

Deep root system study is an important component of drought resistant rice (Oryza sativa L.) variety. Root morphology is a complex trait combining various components. Drought acts as major limitation for growing rice in rainfed ecosystems. Therefore, there is a need to screen and breeding rice genotypes for drought resistance. The objective of this study is to elucidate the genotypic variation among rice genotypes in root distribution and root angle including deep-root development. The experiment was conducted with eight genotypes using basket method in aerobic and well-watered conditions. The results from genotype × year interactions for the S-R (Shoot-root) ratio, with Devamallige, AM65, and BJ21 responded more to water stress as compared to other genotypes. Genotypes azucena had highest root diameter (1.5 mm) followed by devamallige (1.4 mm) and AM65 (1.4 mm) under both aerobic and well-watered conditions. IR20 showed lowest root diameter/thickness (0.7 mm) in both the conditions. Increase in number of roots at 00-450 under aerobic condition indirectly measures the increase in deep root length. Correlation coefficients between total root diameter and deep root length were also high in both aerobic (r = 0.724 and r = 0.924) and well- watered (r = 0.605 and r = 0.842) conditions which subsequently evolved into greater deep root length.