Association of Deep Rooting Trait with Yield under Water Stress in Rice (Oryza sativa L)

Deeper rooting ability with high water use efficiency appears to be an efficient strategy for avoiding drought stress. A deeper root system has been shown to allow upland rice to extract more water from the soil, resulting in a higher yield potential under drought. The extent of variation for water stress indicators, physio-morphological and yield components were assessed by evaluating 35 rice genotypes collected from R.A.R.S., Pattambi under water stress and irrigated conditions in the rainout shelter. The rice accessions were grown in polythene tubes of one meter height were exposed to water stress at panicle initiation for a period of 15 days along with irrigated control. Significant variation was observed for physio-morphological, biochemical and yield components among rice genotypes under stress period. Correlation study revealed that grain yield per plant under water stress was positively correlated with parameters such as relative water content, membrane stability index, proline content, stomatal conductance, photosynthetic rate, transpiration rate, root length, root shoot ratio, spikelet fertility percentage and 1000 grain weight where as negatively correlated with leaf temperature, leaf rolling score, days to 50% flowering and panicle length. Genotypes having higher root length and root shoot ratio were found to be tolerant to drought. They are Ptb-29, Ptb-30, Ptb-15, Ptb-1 and Ptb-55. Ptb-29 and Ptb-30 showed no leaf rolling score of one. Highest RWC was recorded by Ptb-4. Membrane stability index was highest in Ptb-29 and Ptb-10. Minimum leaf temperature was recorded by Ptb-7. Highest stomatal conductance and photosynthetic rate was recorded by Ptb-30.Highest root length was recorded by Ptb-15 but root-shoot ratio was highest for Ptb-29. These genotypes can be used in breeding programmes to improve drought tolerance in rice. Root anatomical traits also influences the water uptake mechanism in rice. Hence the anatomical difference between drought tolerant and susceptible varieties under water stress is in progress.