Physiological and molecular characterization of rice germplasm tolearnt to multiple abiotic stress

Abstract

Rice is susceptible to salt-stress especially at seedling stage. Yet, rice is grown newlinewhere very frequently it encounters salt attack. Most successful rice cultivars survive newlinethe salt-stress mainly through the restriction of transport of Na+ to young leaves as well newlineas greater transport of K+. Besides this mechanism, partitioning of more Na+ into old newlinetissues and tissue tolerance also impart survival under salinity. Diverse cultivars newlinepossessing more than one tolerance mechanisms are highly valuable in crop newlineimprovement. The objectives of the present study were to check the existence of newlinedifferent salt tolerance mechanisms among 24 contrasting genotypes, using their newlinediversity analysis and characterization of physiological parameters. Using hydroponic newlinemethod twenty four rice cultivars were tested for their tolerance to salinity. Standard newlineprocedures were followed to determine several physiological parameters. UPGMA newlinemethod was used for cluster analysis. Taking Na+ data of old and new leaves, Na newlinecompartmentation was calculated. The Na+ content corresponding with 50% loss of newlinechlorophyll content was the tissue tolerance of a cultivar. Both root and shoot length newlinedecreased significantly due to salt stress and the percent reduction was greater in newlinesusceptible cultivars compared to tolerant cultivars. Dry matter accumulation in root newlineunder salt was less in tolerant cultivars compared to susceptible cultivars whereas dry newlinematter accumulation in shoot was greater in tolerant cultivars. Shoot growth, however, newlinewas greater in salt tolerant rice plant. Salt-stress decreased the green leafy part and newlineultimately plant died out. Salt tolerant cultivars maintained greater leafy part compared newlineto other types of plant. It was due to lower uptake of Na+ and greater uptake of K+ by newlinetolerant cultivars compared to susceptible cultivars. Thus tolerant cultivars maintained newlinelower ratio of Na+ and K+. Correlation studies revealed that absorption of greater newlinecontent of K+ was beneficial whereas greater absorption of Na+ was harmf