Screening of pigeonpea genotypes for nutrient uptake efficiency under aluminium toxicity.

For increasing pigeonpea production in India, it is necessary to expand its area in non-traditional areas such as north-eastern states, which have considerable area under acidic soils. In such soils, aluminium toxicity, which is a major yield limiting factor, interferes with nutrient uptake efficiency of crop plants. 32 genotypes of pigeonpea [Cajanus cajan (L.) Millsp.] were screened for tolerance to aluminium toxicity at four different aluminium concentrations (41, 82, 123 and 205 μM Al) by hematoxylin staining and root re-growth methods. The results of the two screening methods were consistent, suggesting that either of the two methods could be used for screening purpose. The most tolerant (IPA 7-10, T 7, 67 B and GT 101E) and sensitive (Bahar, Pusa 9 and Pusa 2002-2) genotypes were assessed for root and shoot aluminium contents in hydroponic assay at 0, 41, 82, 123 and 205 μM aluminium concentrations. Root and shoot aluminium contents were significantly lower in the tolerant than sensitive genotypes, indicating that aluminium tolerance mechanism involved aluminium exclusion and perhaps internal detoxification. Tolerant and sensitive genotypes were further assessed for phosphorus, potassium, calcium and magnesium contents in their root and shoot. Tolerant genotypes (IPA 7-10, T 7, 67 B and GT 101E) accumulated significantly high amounts of these nutrients (>1.5 times) compared to the sensitive ones. Better performance of tolerant genotypes could be ascribed to better nutrient uptake efficiency and distribution within the plants.