Plus Tree selection for improvement of Neem (Azadirachta indica A. Juss): A heuristic approach through Exploratory Factor and CRITIC analysis

Indigenous to the Indian subcontinent, Neem (A. indica) is a perennial tree belonging to Meliaceae family. The species has been recognized as the “Tree of 21st Century” by the United Nations due to its diverse applications in medicine, bio-pesticide, and cosmetic sectors. Nonetheless, its habitat faces considerable pressures from anthropogenic activities and climate change. Therefore, in this study we proposed a robust mechanism for selection of Plus Trees (PTs) of Neem from natural population to aid improvement of this important Forest Genetic Resource (FGR). Data of 14 traits including phenotypic parameters, fruit – seed morphological characters and biochemical parameters like kernel oil content and azadirachtin concentration were recorded from 197 Candidate Plus Trees (CPTs) identified from three agro-climatic zones (ACZs) of India, viz., III, IV and VII. Exploratory Factor Analysis was carried out to identify three factors namely ‘sink stoutness’, ‘tree stature’ and ‘tree outspread and oil content’ significantly contributing in the selection explaining a cumulative variance of 61.024 %. To develop a unified scoring matrix for selecting PTs, CRiteria Importance Through Intercriteria Correlation (CRITIC) analysis was performed providing appropriate weightage to each selection criteria with statistical basis. The CPTs were scored against their performance under each observed parameter according to the developed scoring matrix and 50 PTs were identified across the three ACZs. The current study offers valuable insights into the selection procedure of PTs demonstrating excellent qualitative and quantitative characteristics in comparison to the population mean, which can readily be utilized in future tree improvement programs of Neem.