Genetic Relationship and Structural Variation of Root Growth Angle for Deep Rooting in Rice (Oryza sativa L.)

Breeding for drought tolerance revolves around selection of genotypes with desirable root characters. Root pattern studies in rice have shown significant relationship with drought tolerance. In order to understand the effects of deep rooting pattern and root growth angle in relation to water stress was assessed following basket method. The Backcross inbred lines (BILs) of ADT (R) 45*1/Apo and ADT (R) 45*1/Wayrarem with drought QTLs viz., qDTY1.1, qDTY3.1, qDTY4.1 and qDTY12.1 were evaluated for various root traits. Out of 20 BILs and three parental lines studied four BILs showed high values for root growth at deep angle 65-90 °and yield under drought stress. Based on association studies among the root traits positive and significant correlation was observed between yield and root traits viz., root dry weight, root growth at deep angle 65-90° (RA4), ratio of deep rooting and root length. Clustering of BILs and parents have grouped deep rooting BILs and drought tolerant donors into one cluster and drought susceptible ADT (R) 45 into a separate cluster II which clearly indicates, the importance of deep rooting and yield under drought stress. Strong association of root traits and drought tolerance clearly shows the importance in utilization of these traits as selection criteria for drought tolerance in rice.