MORPHO-PHYSIOLOGICAL RESPONSE OF RICE (ORYZA SATIVA L.) VARIETIES TO SALINITY STRESS

Morpho-physiological response of 7 rice (Oryza sativa L.) varieties viz., Moroberekan, Co39, Azucena, Bala, IR64, Kalinga-III and Nipponbare was assessed under control and 100 mol m(-3) NaCl + 5 mol m(-3) CaCl2 stress in a flood bench system in greenhouse. Physiological and growth parameters were recorded after 21 or 42 days of salt stress. The statistical analysis revealed significant differences among varieties for various traits associated with salt tolerance under salinity stress. Regarding physiological parameters significant higher accumulation of Na+ was in Moroberekan (52.9 mol m(-3)), whereas lowest (14.1 mol m(-3)) in IR64, followed by Co39 (14.6 mol m(-3)) and Azucena (14.7 mol m(-3)). There was a significant negative correlation between leaf Na+ and K/Na ratio in varieties under salt stress; however salinity and salinityxvariety interaction had nonsignificant effect on leaf K+ concentration in this study. Growth parameters were also negatively correlated with salinity stress. Among varieties the lowest reduction in shoot fresh (58%) and dry weight (36.5%) was in Co39, indicating its tolerance to salt stress, whereas, the most sensitive genotype was Azucena with highest reductions in shoot fresh (82%) and dry weights (77%). The use of salinity damage scores as assessment criteria in the appraisal of salt tolerance is discussed. A contrasting response of Co39 and Moroberekan to salt stress suggests the use of available recombinant inbred lines (RILs) population from Co39xMoroberekan, for mapping of QTLs associated with salinity tolerance.