Abstract
Aluminium (Al) stress was imposed on 285 lentil genotypes at seedling stage under hydroponics to study its effects on morpho-physiological traits where resistant cultigens and wilds showed minimum reduction in root and shoot length and maximum root re-growth (RRG) after staining. Molecular assortment based on 46 simple sequence repeat (SSR) markers clustered the genotypes into 11 groups, where wilds were separated from the cultigens. Genetic diversity and polymorphism information content (PIC) varied between 0.148–0.775 and 0.140–0.739, respectively. Breeding lines which were found to be most resistant (L-7903, L-4602); sensitive cultivars (BM-4, L-4147) and wilds ILWL-185 (resistant), ILWL-436 (sensitive) were grouped into different clusters. These genotypes were also separated on the basis of population structure and Jaccard’s similarity index and analysed to study Al resistance mechanism through determination of different attributes like localization of Al and callose, lipid peroxidation, secretion of organic acids and production of antioxidant enzymes. In contrast to sensitive genotypes, in resistant ones most of the Al was localized in the epidermal cells, where its movement to apoplastic region was restricted due to release of citrate and malate. Under acidic field conditions, resistant genotypes produced maximum seed yield/plant as compared to sensitive genotypes at two different locations i.e. Imphal, Manipur, India and Basar, Arunanchal Pradesh, India during 2012–13, 2013–14 and 2014–15. These findings suggest that Al stress adaptation in lentil is through exclusion mechanism and hybridization between the contrasting genotypes from distinct clusters can help in development of resistant varieties.
Highlights
Lentil is cultivated on 4.5 million ha with a production of 4.9 million tons [1]
root re-growth (RRG) after haematoxylin staining in resistant cultigens was from 1.20–1.60 cm, while in sensitive cultigens it ranged from 0–0.47 cm
The important acquisition in this study could be applied to lentil breeding programs for improving Al resistance
Summary
Lentil is cultivated on 4.5 million ha with a production of 4.9 million tons [1]. The major lentil-growing countries include India, Canada, Turkey, Syria, Australia, Nepal and United States These countries have large acreage under acidic soils with a problem of aluminium (Al) toxicity [2]. Among various Al toxicity symptoms, the first visible symptom is rapid inhibition of root growth which can occur within hours or even minutes of exposure to Al3+ [5] This trait has been used as a biomarker to estimate Al sensitivity in crop plants. Two most reliable screening parameters are root re-growth (RRG) after staining and callose accumulation in roots under hydroponic assay [2, 6, 7] This assay has unconditional advantages over field screening, as Al concentration in soil may not always be uniform and other environmental factors may interact with soil Al to mask the expression of Al resistance [8]. Screening for Al resistance under hydroponics in combination with field evaluation for Al resistance would be the best approach for characterization of whole plant resistance in terms of seed yield and its contributing traits
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