Heterosis Analysis for Physio-Morphological Traits in Relation to Drought Tolerance in Rice (Oryza sativa L.)

Rice (Oryza sativa L.) is the most important food crop of the world; but drought stress is a serious limiting factor to rice production and yield stability in rainfed areas. Breeding for drought tolerance is a challenging task because of the complexicity of the component traits, screening technique, environmental factors and their interaction. The major setback in drought tolerance breeding is the poor understanding of genetics and inheritance of drought tolerance traits and complete ignorance about the physiological drought tolerance attributes. Alternatively, yield improvements in water-limited environments can be achieved by selecting for secondary traits contributing to drought resistance in breeding programs. Hence, the present investigation was undertaken to study the heterosis manifested by the 40 hybrids derived from eight lines and five testers for physio-morphological traits by line x tester analysis. Results revealed that, maximum desirable heterosis over mid parent was observed for root: shoot ratio (100.00%), leaf drying (-66.10%), followed by root length (60.58%), root dry weight (60.00%), days to 70% RWC (51.87) and chlorophyll stability index (44.19). Similar trend of desirable heterosis over better parent was observed for root: shoot ratio (71.43%) and leaf drying (-62.96%) followed by leaf rolling (-47.50%), root length (42.42%) and root dry weight (39.22%). Among 40 hybrids, CPMB ACM 03 017 x MDU 5 had considerably higher desirable heterosis over mid parent and better parents for physiological traits whereas CT 9993 x IR 50, CT 9993 x ASD 18, CPMB ACM 03 015 x ASD 18 and Moroberekan x ASD 16 exhibited positive and significant favorable heterosis over mid parent and better parents for root traits.