Selection of pigeonpea genotypes for tolerance to aluminium toxicity

Aluminium toxicity is a major growth limiting factor for pigeonpea [Cajanus cajan (L.) Millspaugh] production in acid soils. Thus, screening and selection of pigeonpea genotypes for aluminium tolerance is important. The effects of five aluminium concentrations (0, 10, 20, 30 and 50 ppm Al) on 32 genotypes of pigeonpea were studied in hydroponic and sand assays (growth response methods). Ratings of genotypes were similar for the two screening methods, suggesting that either of the two could be used for evaluation of genotypes for aluminium tolerance. Root and shoot aluminium contents were significantly lower in the tolerant ('IPA 7-10' and 'T 7') than sensitive genotypes ('Bahar' and 'Pusa 9'), indicating that aluminium tolerance mechanism per se in the tolerant genotypes involved aluminium exclusion. Genotypes 'IPA 7-10' and 'T 7' will be useful in breeding programmes to improve aluminium tolerance in pigeonpea.