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.
