Abstract
Acid soils encompass nearly one-third of the available terrestrial land surface worldwide. Acidic soil is one of the major abiotic constraints for agricultural practices by potentially creating aluminum (Al) toxicity and/or phosphorous (P) deficiency. Assam, being an agricultural state of India, has the majority of its area covered by acidic soils due to the varied terrain in the region. Soil acidification increases the solubility of Al present in the soil from its nontoxic silicate or oxide forms into highly phytotoxic ionic Al (mainly the trivalent cation Al<sup>3+</sup>). Ionic Al can form complexes with the available phosphorous leading to plant nutrient deficiency. In the present investigation, screening of traditional rice varieties from Assam was conducted for tolerance to combined Al toxicity and P deficiency. Seedlings of 41 rice landraces from various agro-climatic locations were subjected to three different concentrations of Al (0, 50, 100 µM) for 24, 48, and 72 h under P deficiency in static nutrient culture to identify the extent of their resistance to these stressed conditions. Different morpho-physiological parameters (root and shoot lengths, fresh and dry weight yields, chlorophyll and relative water content) were evaluated after stress treatment. All the experiments were conducted in a randomized block design with three replicates. Based on the overall morphological characters, total stress response index (TSRI) was calculated which showed a variation ranging from 18 to 23. Accordingly, the varieties were classified into different groups of resistance. Varieties ‘Moti’ and ‘Baismuthi’ were found to be the least resistant, whereas ‘Holpuna’, ‘Beto’, and ‘Soria Sali’ were identified as most tolerant varieties to Al toxicity under P deficiency. The findings of the present investigation could be exploited for developing promising varieties in future rice breeding programs.
Highlights
Aluminum (Al) is one of the most abundant metals comprising approximately 7% in the Earth’s crust
Forty-eight h of stress resulted in a range of shoot lengths between 15.0 and 40.8 cm at 50 μM Al and between 15.8 and 25.1 cm in the 100 μM Al treatment
There arises a relative ranking of Al tolerance in plants and the probable cause is due to P and Al interactions which exist in acidic soils
Summary
Aluminum (Al) is one of the most abundant metals comprising approximately 7% in the Earth’s crust. The chemical stability of Al depends upon the pH of the soil. At a neutral pH, Al minerals exist in an almost insoluble state. In acidic conditions Al is oxidized to Al3+, which is toxic to most of the conventional crops including rice [1,2,3]. Al3+ binds to soluble phosphorous (P) limiting the plant-available P. The adverse effect of an acidic soil on plant growth is strongly related to both the toxicity of Al3+ and P deficiency
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