Comparative Salinity Responses among Pigeonpea Genotypes and Their Wild Relatives

Abstract

Soil salinity can be a major constraint to pigeonpea (Cajanus cajan (L.) Millsp.) in the regions where it is predominantly grown. This study was conducted to assess the extent of genetic variation for salinity tolerance in the germplasm of pigeonpea and its wild relatives. Solution culture experiments in a greenhouse and controlled environment chamber were conducted to screen a range of cultivated pigeonpea genotypes for ability to germinate and grow up to 60 d under saline conditions. Several wild relatives of pigeonpea were screened for salinity response in a sand culture system in a greenhouse. Among cultivated pigeonpea genotypes, ICPL 227 was one of the most tolerant and HY 3C one of the most sensitive genotypes tested. None of the pigeonpea genotypes tested were able to survive beyond 30 d at 8 dS m−1 or higher salinity levels. The extent of variation in salinity response among cultivated pigeonpea genotypes appeared too limited to warrant genetic enhancement of salinity tolerance. Among the wild relatives of pigeonpea, various species of Atylosia, Rynchosia, and Dunbaria showed a wide range of variation in their salinity tolerance (critical levels from 4 to 12 dS m−1): A. albicans (W. & A.) Benth., and A. platycarpa could grow in a sand culture system at 12 dS m−1 and Rynchosia albiflora could not tolerate salinity levels above 4 dS m−1. These results suggest that using wild relatives for genetic improvement may increase salinity tolerance of pigeonpea.