Re-established desiccation tolerance as a mechanism of stress tolerance in wheat
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
Re-established desiccation tolerance (Re-DT) is a mechanism of extreme level of tolerance for almost complete water loss. It was found higher in wheat cultivar PBW 644 (drought tolerant) than PBW 343 (drought susceptible). Higher level of Re-DT in PBW 644 was related to higher reduction of water level so to arrest metabolic activity to avoid increases of ROS and oxidative toxicity, induction of special antioxidants like aldehyde dehydrogenase for detoxification and effective recycling of ascorbate under desiccation. This type of response in PBW 644 helped this plant to revive with higher survival upon rehydration. Contrary to it, PBW 343 showed higher water content, metabolic activity, ROS and oxidative toxicity under desiccation, though it induced antioxidant enzymes but failed to induce effective detoxification system (aldehyde dehydrogenase) and ascorbate recycling, therefore produced poor survival upon rehydration. Re-DT was ABA-regulated mechanism of cross tolerance. It involved ABA/ROS/NO-pathways for induction of antioxidant activity under desiccation and subsequent rehydration. It was improved by ABA and stress factors like water deficit stress, salt stress and heat stress. Ten wheat cultivars were screened for Re-DT and other related features. Four cultivars (HD 3086, PBW 725, PBW 658, PBW 677) showed a clear difference from six cultivars (gladius, kirchauff, HD 2967, BWL 5200, BWL 5202, PBW 723) for having higher level of Re-DT. Seeds of these four cultivars also showed higher dormancy, ABA sensitivity, less level of ROS/nitric oxides in embryos at 0 and 90 days of after-ripening. Laboratory testing of abiotic (osmotic, salt and heat) stress tolerance at seedlings stage found higher increase of root length and root to shoot length ratios by these four cultivars compared to other six. Therefore, this study indicated the presence of relatively higher level of vegetative stress tolerance in HD 3086, PBW 725, PBW 658, PBW 677compared to other six cultivars.
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