SASHIDHAR, V RSUSHMA M, AWAJI2017-06-302017-06-302009-07-10TH-9354http://krishikosh.egranth.ac.in/handle/1/5810023768Salinity is one of the major environmental factors limiting plant growth and its productivity worldwide. To maintain growth and productivity plants must adapt to stress conditions and exercise specific tolerance mechanisms. In plants Na+/H+ antiporters which catalyze the exchange of Na+ for H+ are localized on both plasma and vacuolar membranes, removing Na+ from cytosol or compartmentalizing it in vacuoles for maintenance of a low Na+ concentration. In the present study, analysis of T1 transgenic rice plants overexpressing NHX1 to select putative transformants was done. To screen putative T1 plants for salt tolerance, a Stringent Salt Screening Test (SSST) was followed at two levels. At seed level, root and shoot growth of T1 putative transformants was used as a selection criterion. At plant level, extent of chlorosis was used at selection criteria. Some of the transgenics showed significantly higher root and shoot growth and lesser or no chlorotic symptoms compared to wild type. To confirm the presence of gene in putative T1 transgenic plants, PCR, Southern analysis and RT-PCR analysis were followed using genomic DNA. The results showed that all the selected seedlings from the SSST were PCR positives. And four selected lines were positive for southern and RT-PCR analysis. Physiological studies such as chlorophyll estimation and membrane permeability tests were also conducted to assess their levels of tolerance at T1 generation. Some of the T1 transformants showed lower percent reduction in chlorophyll content and less membrane leakage after NaCl treatment compared to wild type. These results clearly demonstrate that transgenic rice plants overexpressing PgNHX1, a vacuolar antiporter have better salt-tolerance. This could have been mediated by compartmentation of excess Na+ from cytosol into the vacuole and there by reducing the toxic effects of Na+ in the cell.ennullThesis