UNDERSTANDING THE PHENOLOGICAL, PHYSIOBIOCHEMICAL AND MOLECULAR ASPECTS OF DROUGHT STRESS RESPONSES IN RICE (Oryza sativa L.)
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Date
2020
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Indira Gandhi Krishi Vishwavidyalaya, Raipur
Abstract
Among the abiotic stresses, drought (water stress) is considered as a complex axiom for rice yield under rainfed ecosystem. Repeated efforts have been taken to improve rice productivity but comprehensive approach is still needed to identify suitable donors for development of drought resilient high yielding rice.The present investigation was carried out at Institute Research Farm and Stress Physiology Laboratory of ICAR-National Rice Research Institute, Cuttack, Odisha in the year 2017 and 2018. Aset of twenty one rice genotypes including one tolerant check (Sahabhagidhan) and one susceptible check (IR20) was studied based on phenological, physio-biochemical and molecular aspects with the objective to identify an appropriate donor parents for further incorporation as a source of drought tolerance.
Rice genotypes were grown under well-watered (WW) and water stress (WS) conditions in PVC pipes in a completely randomized design with three replications to fulfill the objective ofphenotyping of different root traits responsible for drought tolerance. It is very interesting to note that root and shoot traits showed greater plasticity under WS as compared to WW condition. The study of nine important root and shoot traits revealed maximum root length (MRL), shoot length (SL), root volume (RV), root dry weight (RDW), shoot dry weight (SDW),total dry weight (TDW) were reduced by 6.10%, 20.65%, 11.86%, 40.07%, 41.34% and 41.26% while, root to shoot dry weight ratio (RDW/SDW), root to total dry weight ratio (RDW/TDW),maximum root length to shoot length ratio (MRL/SL) increased by 6.05%, 3.17% and 18.06%respectively under WS over WW condition. The root and shoot phenotyping study confirmed superiority ofMahamaya, Safri 17, Sahabahagidhan, N22, Vanaprabha, Poornima, Satyabhama, Khandagiri, Anjali,Vandana and Danteshwariunder drought condition.
To fullfill the objectiveof understanding the mechanism of drought tolerance based on photosynthesis and water related traits, genotypes were grown in pots under WW and WS conditions. Stress was imposed at flowering stage and important physiological and biochemical traits were measured to elucidate tolerant and susceptible genotypes. Overall, WS caused reduction in chlorophyll concentration (soil plant analysis development, normalized difference vegetative index), chlorophyll fluorescence parameters except initial fluorescence (maximum, variable, ratio of variable to maximum, ratio of variable to initial chlorophyll fluorescence, performance index), gas exchange parameters except intrinsic water use efficiency (photosynthetic rate, stomatal conductance, transpiration rate, ratio of internal to ambient CO2), water related traits (relative water content, leaf water potential) while, canopy temperature and biochemical parameters (proline, protein content, total soluble sugar and antioxidant enzymes superoxide dismutase, peroxidase, catalase) were increased as compared to WW condition. Mahamaya, Sahabhagidhan, Safri 17, IBD-1 and Kalinga III showed relatively better performance while IR20 exhibited poor performance among the studied genotypes under water stress condition in terms of studied physiological and biochemical traits.
The field experiment was design to evaluate the yield and yield attributesunder drought stress, during two dry seasons 2017 and 2018 in randomized block design with three replications under both WW and WS conditions. Water stress was imposed at vegetative (withheld irrigation for 30 days) and reproductive stages (maintained 17% soil moisture content). Seven genotypes (Mahamaya, Samleshwari, Poornima, IBD-1, Safri 17, Sahabhagidhan and N22) indicated their tolerance at vegetative stage through improved leaf rolling (LR), drought score (DS), drought recovery score (DRS) for both the seasons while, at reproductive stage nine genotypes (Mahamaya, Sahabahagidhan, Poornima, Samleshwari, Vandana, IBD 1, Satyabhama, Danteshwari and N22) exhibited superior performance in accordance to grain yield and yield attributes obtained from pooled data of both the seasons.
Assessment of genetic diversity among the rice varieties using trait specific molecular markers was accomplishedwith 91 root trait specific SSR markers for the same set of genotypes. The results revealed 199 reproducible alleles from 91 SSR markers with 2 to 5 alleles per locus with an average of 2.19. RM336 detected the highest number(5) of alleles per locus. Major allele frequency (MAF) was ranged from 0.38 (RM336) to 0.95(RM223, RM438, RM576, RM 530and RM 1385) with a mean of 0.73. The mean PIC value was 0.30, with a minimum value of 0.09 (RM1385, RM530, RM576, RM438, and RM223) and a maximum value 0.64 (RM336). The gene diversity or expected heterozygosity (He) was varied from 0.09 (RM1385, RM530, RM576, RM438, RM223) to 0.69 (RM336) with an average of 0.37. The UPGMA dendrogram clustered the 21 rice genotypes into two major clusters, 1st group includes four genotypes viz., Virendra, Hazaridhan, Vanaprabha and N22 and 2nd group with 17 genotypes. The highest level of genetic dissimilarity (0.66) was found between Mahamaya and Virendra, followed by Danteshwari and Virendra (0.65), MTU 1010 and Virendra (0.63), IBD 1 and Virendra, and Samleshwari and Virendra (0.60).
Since, Mahamaya, Sahabahagidhan,Safri 17, N22,Poornima, Samleshwari and Vandana have promising root traits and have performed superior at physiological and biochemical level. Under WS condition,higher MRL, RV, RDW, RWC, LWP, Fv/Fm, PI, Pn, gs, proline, protein, total soluble sugar and antioxidative enzyme activities suggested that these parameters have strong influence on higher grain yield under stress condition. As Mahamaya, Danteshwari, MTU 1010, IBD 1, Samleshwari had maximum genetic dissimilarity with Virendra, they can be used in breeding programme to develop drought tolerant varieties.
Description
UNDERSTANDING THE PHENOLOGICAL, PHYSIOBIOCHEMICAL AND MOLECULAR ASPECTS OF DROUGHT STRESS RESPONSES IN RICE (Oryza sativa L.)
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