Genotypic variability for tolerance to salinity of N-2-fixing common bean (Phaseolus vulgaris)

The common bean (Phaseolus vulgaris L.) is often subject to various environ mental constraints in the soil. One of these constraints is salinity which is a major limitation for grain legumes yield, especially when the plant gr owth depends upon N-2 fixation. In order to confirm the variability of the response to moderate salinity, and identify the morphological and physiolog ical criteria associated with tolerance, 9 common bean lines (BAT477, Coco blanc, DOR585, ABA16, NAG310, Flamingo, BRB17, Candide and Striker) were in oculated with Rhizobium tropici CIAT899, and grown in a glasshouse with or without 25 mM NaCl on sterilized sand. A genotypic variation in tolerance t o salt was found: ABA16 and BRB17 were the most sensitive lines whereas BAT 477 and Flamingo were the most tolerant. The estimated parameters of growth and symbiotic nitrogen fixation showed that (i) some lines which exhibited vigorous growth under the control treatment were greatly affected by salt treatment, (ii) the relative tolerance of some lines to salt seems to depen d on the ability to maintain an adequate leaf area and to develop an abunda nt and efficient nodular system.