Abstract/Summary

Water scarcity is a major concern for agricultural production worldwide. The staple crop, rice, is one of the most inefficient crops in its consumption of water using 30% of the world’s freshwater resources. Therefore, research for appropriate solutions to overcome this problem is necessary. Plant growth regulators (PGRs) could be one of these solutions, stimulating cell division and elongation in the root system during early plant growth, which can help seedlings to establish a strong root system. Increasing the root length of plants can allow them to access water at depth for a longer period and increase their tolerance to drought conditions. Seedling growth assays were conducted to investigate the effect of soaking seeds for 24 hours in different PGRs. Rice genotype IR64 was used to investigate the optimal time for seedling growth assays and to quantify the effects of soaking seeds in six PGRs at four different concentrations on seedling growth. Subsequently, twenty rice genotypes were investigated with one selected concentration and four PGRs compared with water (control) to highlight the variation in root and shoot trait responses. Genotype GHRAIBA was selected to investigate the effect of 1000 µM gibberellin (GA3) seed treatment on growth and development under drought stress. Results confirmed there was a significant response to GA3 treatment during the early growth stages. Although, this effect was not observed 40 days after sowing (DAS), at maturity (139 DAS) plants whose seeds were treated with 1000 µM GA3 had significantly (P<0.001) increased root fresh and dry weight. The transcriptional analysis of seedlings treated with GA3 showed only Os04g0612500 was upregulated. This gene is similar to a proline-rich protein which is involved in protein protection under stress. These results could be used to develop practical approaches to improve drought tolerance in rice crops.