Soil sodicity is one of the major constraints for the success of afforestation worldwide. High sodicity causes poor soil physical conditions and thus adversely affect tree growth and biomass production. However, considerable intraspecific variation for sodicity tolerance exists in most of the trees species. Presently, no information is available on sodicity tolerance in the genotypes of the industrially important Melia dubia tree. Therefore, we examined twenty-five genotypes of M. dubia, that has evolved in different parts of India, to elucidate mechanisms and identify traits imparting sodicity tolerance in these genotypes. The experimental evidence showed the significant genetic variability and relationships in genotypes for various morphological and physiological traits in response to the sodicity stress. On an average, sodicity stress reduced plant height, collar diameter, and shoot biomass by 15%, 18%, and 60%, respectively. The shoots Na⁺ concentration had negative correlation with the growth traits. Shoot Na⁺ ions exclusion was found to increase sodicity tolerance and conferred salt tolerance mechanism in M. dubia. Path analysis revealed that the plant height, collar diameter, number of leaves, and branches were major determinants of shoot biomass production. Cluster analysis validated the genotypes response to sodicity and classified the germplasm into sensitive, moderately tolerant, and tolerant category each consisting of nine, eleven, and five genotypes, respectively. Among genotypes, the MDSS06, MDSS13, and MDSS21 produced greater growth and biomass under sodic stress and indicated good growth potential in such soil. The results showed the presence of a high genetic diversity for salt tolerance in Melia, and the identified genotypes can be considered for strengthening the breeding programs aiming at improving the sodicity tolerance of the species. Our result concluded that genetic variation and breeding approaches using the MDSS06, 13, and 21 genotypes have tremendous potential to improve the growth, biomass, and overall productivity of M. dubia under sodic soil conditions.

中文翻译：

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探索在印度条件下进化的 Melia dubia 耐碱度的遗传变异

土壤碱度是全球造林成功的主要制约因素之一。高碱度导致土壤物理条件差，从而对树木生长和生物量生产产生不利影响。然而，在大多数树种中存在相当大的耐碱度的种内变异。目前，没有关于工业上重要的苦楝树基因型耐碱度的信息。因此，我们检测了杜比亚 M. dubia 的25 个基因型，已在印度不同地区发展，以阐明机制并确定赋予这些基因型耐碱度的性状。实验证据表明，响应碱度胁迫的各种形态和生理特征的基因型存在显着的遗传变异性和相关性。平均而言，碱度胁迫使植物高度、领径和地上部生物量分别降低了 15%、18% 和 60%。枝条Na ⁺浓度与生长性状呈负相关。茎Na ⁺离子排斥，发现增加在碱度耐受性和赋予的耐盐性机制M.鳖. 通径分析表明，株高、领径、叶数和枝条是地上部生物量产生的主要决定因素。聚类分析验证了对碱度的基因型反应，并将种质分为敏感、中度耐受和耐受类别，每个类别分别由 9、11 和 5 个基因型组成。在基因型中，MDSS06、MDSS13 和 MDSS21 在钠胁迫下产生更大的生长和生物量，并在此类土壤中显示出良好的生长潜力。结果表明，楝树耐盐性高的遗传多样性，并且可以考虑将鉴定的基因型用于加强旨在提高物种耐碱度的育种计划。我们的结果得出的结论是遗传变异和育种使用MDSS06，接近13和21个基因型有巨大的潜力，提高生长，生物量，以及整体生产力M.鳖盐碱土壤条件下。