Utilization of Malondialdehyde Content for Drought Stress Tolerance in Rice Screening

Abstract

Rice (Oryza sativa L.) is a crop that requires a lot of water to grow. However, heat and drought stresses caused by global climate change can adversely affect reproductive organ establishment, seedling morphogenesis, yield, and the quality of rice. Breeding for a drought-tolerant variety, a vital strategy in coping with drought stress, requires multiple tools and indices in the selection of drought-tolerant varieties, as drought tolerance is a complex phenomenon. In this study, we measured malondialdehyde (MDA) content in conjunction with the degree of leaf rolling in rice plants as an indicator of drought tolerance under two water regimes, i.e., well-watered and drought-stress conditions. The total number of 228 rice lines/varieties, which 224 recombinant inbred lines (RILs) population derived from a single cross of IR57514 and Khao Dawk Mali 105 (KDML105), and the other four standard check varieties, i.e., IR57514 (tolerant standard check), IR1552, KDML105 and Khao Pahk Maw 148, was investigated for leaf rolling score and malondialdehyde (MDA) content at Ubon Ratchathani Rice Research Center and Thailand Rice Science Institute during October 2012 to September 2013. The MDA content and leaf rolling score of the rice plants were examined in both wellwatered conditions and subjected to drought stress for 20 days during the vegetative stage. The results showed that, under well-watered conditions, the leaf rolling score of all tested rice was at level 1 with the MDA content ranging from 3.56 to 7.00 μmol/g FW and increased up to 8.85 - 30.35 μmol/g FW under drought stress. In addition, under drought stress, the leaf rolling score of most of the rice population was 5, and only seven lines exhibited the rolling score at level 1. These seven lines were PSL99094-350-9-5R-21, PSL99093-108-3-5R-40, PSL99094-72-8-5R-2, PSL99093-108-4-5R-38, PSL99094-13-5R-25, PSL99094-32-1-5R-21, and PSL99094-159-7-5R-21 which not only showed the lowest leaf rolling score of 1 but also contained the lowest MDA content ranged from 8.86 to 11.07 μmol/g FW. The line PSL99094-350-9-5R-21 had superior drought tolerance as it contained the lowest MDA content. It is noted that the MDA content of IR57514, the drought tolerant standard check, was 12.10 μmol/g FW with a leaf rolling score of 2. However, some rice lines which exhibited a low degree of leaf rolling contained MDA content as high as those with a high degree of leaf rolling. This could suggest that the leaf rolling score is not a precise parameter in selecting rice for drought tolerance. While MDA content is closely related to the antioxidant enzyme activity and lipid oxidation which are important mechanisms that enable rice to tolerate drought. Furthermore, the strong correlation between the leaf rolling score and the MDA content is highlighted here, MDA content could be effectively used as a selection parameter in rice breeding for drought tolerance.