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Breeding high-yielding drought-tolerant rice: genetic variations and conventional and molecular approaches.

ABSTRACT: The increased occurrence and severity of drought stress have led to a high yield decline in rice in recent years in drought-affected areas. Drought research at the International Rice Research Institute (IRRI) over the past decade has concentrated on direct selection for grain yield under drought. This approach has led to the successful development and release of 17 high-yielding drought-tolerant rice varieties in South Asia, Southeast Asia, and Africa. In addition to this, 14 quantitative trait loci (QTLs) showing a large effect against high-yielding drought-susceptible popular varieties were identified using grain yield as a selection criterion. Six of these (qDTY 1.1 , qDTY 2.2 , qDTY 3.1 , qDTY 3.2 , qDTY 6.1 , and qDTY 12.1 ) showed an effect against two or more high-yielding genetic backgrounds in both the lowland and upland ecosystem, indicating their usefulness in increasing the grain yield of rice under drought. The yield of popular rice varieties IR64 and Vandana has been successfully improved through a well-planned marker-assisted backcross breeding approach, and QTL introgression in several other popular varieties is in progress. The identification of large-effect QTLs for grain yield under drought and the higher yield increase under drought obtained through the use of these QTLs (which has not been reported in other cereals) indicate that rice, because of its continuous cultivation in two diverse ecosystems (upland, drought tolerant, and lowland, drought susceptible), has benefited from the existence of larger genetic variability than in other cereals. This can be successfully exploited using marker-assisted breeding.

SUBMITTER: Kumar A

PROVIDER: S-EPMC4223988 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The present work makes an effort to assess and standardize some redox metabolic and molecular parameters for screening drought tolerant indigenous aromatic rice cultivars of West Bengal, India. PEG-induced dehydration stress during early germination caused disruption of redox-homeostasis and oxidative damage in four IARVs (Jamainadu, Tulaipanji, Sitabhog and Badshabhog) by enhancing the accumulation of pro-oxidants [assessed in terms of oxidation of 2',7'-dichlorofluorescindiacetate (DCFDA), accumulation of [Formula: see text] and H2O2 and in situ staining of reactive oxygen species (ROS) in germinating tissue], significant reduction of antioxidative defence (total antioxidant and radical scavenging capacity, total thiol content and activities of antioxidative defence enzymes) and aggravating protein oxidation and lipid peroxidation (assessed in terms of free carbonyl content and accumulation of thiobarbituric acid reactive substances). When compared between the indigenous aromatic rice cultivars, a clear trend in differential redox regulatory properties in which ROS-antioxidant interaction acts at metabolic interface for redox homeostasis was observed in the order Badshabhog > Tulaipanji > Sitabhog > Jamainadu. Moreover, when the efficacy of ascorbate-glutathione cycle for scavenging H2O2 generated during dehydration stress was assessed and compared between the landraces exposed to PEG-induced dehydration stress in germinating tissue, it also exhibited almost the same trend with the landrace Tulaipanji and Badsabhog exhibiting maximum and Jamainadu the minimum efficiencies of the redox cycle. The indigenous aromatic rice cultivars Tulaipanji and Badsabhog resist dehydration stress better than the other two landraces due to its early preparedness to combat oxidative stress by up-regulating expression of genes of some enzymes of ascorbate-glutathione cycle along with some other antioxidative enzymes. A model of redox homeostasis in which ROS-antioxidant (ascorbate-glutathione system) acts at metabolic interface for up-regulation of antioxidative gene expression necessary for differential drought stress tolerance among the indigenous aromatic rice varieties is suggested.

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Breeding high-yielding drought-tolerant rice: genetic variations and conventional and molecular approaches.

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