Salinity effects over growth and yield of IR8 rice and its mutant

Abstract

IRm6, an improved useful, EMS induced mutant of IR8 rice exhibits higher salt tolerance than the parent variety at all the growth stages. High salinity levels reduced germination per cent, early seedling growth and mature plant height in both the genotypes. Roots were more sensitive to salinity than shoots. Within seven days from germination, IRm6 accumulated three times more proline than IR8. Toxicity of individual salt concentrations was in order of NaCl>Na₂SO₄>CaCl₂. At germination and early seedling stages, dry weight of the seedling increased while fresh weight decreased with the rise in salinity unlike later growth stages when both fresh and dry weights of mature plants decreased under salt stress. All the yield components were adversely affected by varying degrees of saline treatments. The order of their contributions in final grain yield reduction was, productive tiller number>fertile grain number>grain specific density>1,000 grain weight. Tillering stage was most sensitive to salinity. Grain yield losses between 27-43% in IR8 and 14-30% in IRm6 occurred after salt treatments at flowering and tillering stages, respectively.