PHYSIOLOGICAL, BIOCHEMICAL AND MOLECULAR STUDIES ON EFFECT OF SALT STRESS IN CLUSTER BEAN

Abstract

Clusterbean or guar is an industrially important crop because of galactomannan gum present in its seed endosperm. The productivity of guar is reduced under saline conditions which often occur in areas under guar cultivation. Despite the commercial importance of this crop, there is no report on response of guar plants to salt stress at molecular level. To understand the molecular mechanism of salt tolerance in guar we selected a salt sensitive landrace IC-116824 and a salt tolerant landrace PLG-15 by subjecting 11commercial varieties and 59 landraces of guar to various concentrations of NaCl. ICP-MS analysis revealed that the Na+ accumulation and K+ loss from roots and leaves of salt tolerant landrace PLG-15 were less than those from the salt sensitive landrace IC-116824. The two selected landraces were also tested for their differences in salt tolerance behavior at biochemical levels. By designing primers from 12 ion-transporter genes of soybean, we searched, by PCR amplification, the presence of ion-transporter genes in guar. The PCR results showed the presence of six ion-transporter genes in guar, out of which four (v-atpase, nhx1, kup and kea3) were found to express in roots and leaves. Upregulation of the four expressed genes was found in roots and leaves of salt tolerant plants under salt stress. Fluorescence microscopy analysis using Na+-specific cell permeant fluorescent probe Coro-Na Red showed Na+ accumulation in the vacuoles of root cortical cells and leaf mesophyll cells of salt tolerant plants under high salt stress (150 mM and 200 mM NaCl). On the basis of above findings, a molecular mechanism of salt tolerance in guar has been proposed.