Growth and water use response of doubled-haploid rice lines to drought and rewatering during the vegetative stage

We examined the responses of doubled-haploid lines (DHLs) of rice (Oryza sativa L.) to drought and rewatering in controlled rainfed lowland conditions, to test the the hypothesis that the DHLs would permit trait comparisons with less confounding by unrelated traits than had been reported previously. IR62266 and four DHLs derived from the cross between IR62266 and CT9993 (DHL-32, 51, 54 and 79) were grown in pot experiments in the greenhouse at the IRRI, Los Baños, Philippines. Genotypic variation in leaf and tiller development, transpiration, water use efficiency, osmotic adjustment and leaf water potential was examined in relation to dry matter production. Results revealed that greater seedling vigor through continued leaf expansion in early drought was associated with greater dry matter production after rewatering. A higher water use efficiency was related to a greater increase in dry matter production during drought. Leaf water potential was correlated strongly with dry weight, not only during drought, but especially on rewatering. Therefore, we found that the ability to continue leaf expansion, higher water use efficiency, and a greater osmotic adjustment for maintenance of leaf water potential as drought progressed were desirable traits for improved performance under drought and improved ability to recover on rewatering. These relationships could be analyzed precisely using such genetically-related materials as DHLs, with less confounding effects of plant size and genetic background.