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Paddy has been the staple food in India since generations. India being one of the densely populated countries has an ever ending demand for the food requirement. The only way to achieve its needs is to increase the production of the staple crop or develop the quality of the current crops in terms of disease and drought resistance. The study includes recording the occurrence of three different drought resistance genes among 19 varieties of Oryza sativa grown in south India. All the 19 varieties were sown under lab conditions and the leaf material was collected for DNA extractions. The target specific primers were designed and band pattern was recorded upon amplification. The successfully amplified samples were sequenced to confirm the presence of these genes.
Cultivars, Drought Tolarance, Abiotic Stress,OsDHODH1, DREB, LEA, Amplification, RFLP
Rice, (Oryza sativa L.) is the most important food crop for nearly half of the world’s population (Sellamuthu et al., 2011). Worldwide, rice is cultivated on an area of 154 million hectors with an annual production of 700 million tonnes (FAO, 2011). Globally, India ranks first in cultivable area under rice and second in production, producing 131 million tonnes. Water is the critical and most important factor in rice production. The 70% of the world’s food-growing areas turn increasingly parched (IRRI, 2009), so that main challenge for rice producers is to develop a strategy to raise yields of the water intensive crop. Drought is a major abiotic stress that limits rice productivity in rainfed and upland ecosystems (Bimpong et al., 2011) and worldwide, drought affects approximately 27 million ha of rainfed (IRRI, 2011) crop fields. In India, area under rice cultivation remained stagnant and even declined in the recent years due to water unavailability. Drought reduces yield by 15–50% depending on the stress intensity and crop growth period at which the stress occurs in rice (Srividhya et al., 2011). Eastern India, comprising Jharkhand, Orissa, and Chhattisgarh alone accounts loss of about 40% of the total rice production due to severe drought (Pandey and Bhandari, 2009). Developing high yielding and drought resistant varieties for rainfed area is priority for improving rainfed rice production. Plants’ response to drought stress is one of the most complex biological processes, and it involves numerous changes at the physiological, cellular, and molecular levels. Many genes have been identified to be involved in the response of drought stress in plants (Zhang et al., 2012). The effect of drought on rice plants considerably varies with genotypes, developmental stages, and degree and duration of drought stress (Wang et al., 2011). A better understanding of the complex physiological mechanisms underlying drought response is important to improve rice yields under water-limited environments. Roots, the hidden half of a plant, are important for numerous functions including water and nutrient uptake that make it difficult to overlook their importance to plant productivity (MacMillan et al., 2006). DREB, LEA and OsDHODH1 genes are known for their association with Drought resistance in plants. . DREB (Dehydration responsive element binding factor) play key roles in plant stress signalling transduction pathway, they can specifically bind to DRE/CRT element (G/ACCGAC) and activate the expression of many stress inducible genes. LEA proteins are late embryonic proteins abundant in higher plant embryos. It has been found that LEA genes are a gene family and play important roles in the protection of water stress. In a study conducted by Liu et al the overexpression of the OsDHODH1 gene in rice increased the DHODH activity and enhanced plant tolerance to salt and drought stresses as compared with wild type and OsDHODH1- antisense transgenic plants. Their findings revealed that the cytosolic dihydroorotate dehydrogenase is involved in plant stress response and that OsDHODH1 could be used in engineering crop plants with enhanced tolerance to salt and drought.
The current research was undertaken to detect/identify the presence of three of the drought resistant genes DREB, LEA and OsDHODH1 among 19 varieties of paddy. The results of amplification showed that DREB was present in all the varieties except Rajshree, Kala namak-3, Gotra Bidhan and NDR-97 while LEA could not be detected in Malviya Dhan-2, PNR-301, Lalat and NDR-97. OsDHODH1 was comparatively much rare than these two genes and was not identified in Pusa-1612, Rajshree, Annada, Lalat and Gotra Bidhan.The samples in which all these three genes were identified were Pratikshaa, Rajendra Mehsuri, Komal-1, NDR-2064, MTU-Swarna/7029, Prabhat, Pusa sugandha-5 and Sarju-52.
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