Mechanism of sodicity tolerance and genetic variability in wild and cultivated genotypes of pigeonpea

Eight genotypes of Cajanus cajan and two of its close wild relatives-Atylosia platycarpa and A. albicans, were screened for their sodicity tolerance. Experiment was conducted using four levels of pH/sodicity. i.e., pH 8.4, 9.0, 9.2 and 9.5 having corresponding ESP values of 14, 22, 30 and 40, respectively. ICPL 94009, CSPP 89401 and CSPP 89314 suffered maximum in terms of reduction in plant growth parameters, namely number of leaves, shoot height, fresh and dry weight. Out of these genotypes, only A. platycarpa and A. albicans were able to survive and complete their life cycles at pH 9.5 and ESP 40, while all other genotypes failed to survive and complete their life cycle. Reduction in plant growth caused by sodie stress was accompanied by increase in Na⁺ and decrease in K⁺ concentrations in the cultivated genotypes. Wild relatives, A. platycarpa and A. albicans, on the other hand, did not show any change in Na⁺ concentration, and also maintained K⁺ concentration and water content up to pH 9.2. Moderate degree of sodicity tolerance shown by the wild genotypes can be attributed to regulation of uptake, and distribution of Na⁺ and K⁺ ions. This suggests the possibility of using these species for improving sodicity tolerance of cultivated species.