Qualitative morphological diversity and eco-geographical structuring of curry leaf (Murraya koenigii (L.) Spreng.) germplasm in India

Curry leaf ( Murraya koenigii (L.) Spreng) is an economically and medicinally important perennial spice crop of India, yet systematic characterization of its qualitative morphological diversity remains limited. In this study, a diverse germplasm collection of 155 accessions from Tamil Nadu, Karnataka, the Western Ghats, Central India, and the Himalayan region was evaluated ex situ at ICAR–IIHR, Bengaluru using 20 standardized qualitative descriptors covering plant growth habit, leaflet morphology, pigmentation, pubescence, and fruit traits. Phenotypic diversity was assessed using the Shannon–Weaver diversity index (H'), and relationships among accessions were examined through Multiple Correspondence Analysis (MCA) and hierarchical clustering. Considerable variation was recorded for most traits, particularly leaflet shape, margin, waxiness, pubescence, mature leaflet colour, and fruit shape, which showed high diversity (H' > 0.60). Accessions from Central India and the Western Ghats exhibited the highest overall qualitative diversity, whereas the Himalayan region contributed several rare trait states and unique morphotypes. Multivariate analyses grouped the germplasm into four major phenotypic clusters representing a cultivated–wild continuum. Cultivated accessions were characterized by uniform tree growth habit, horizontal leaflet orientation, and strong fragrance, while wild and semi-wild accessions displayed greater heterogeneity with distinctive leaflet and fruit morphotypes and dense pubescence. Rare morphotypes, including heart- and egg-shaped fruits, cuspidate leaflet tips, and pendant leaflet orientation, were mainly identified from the Himalayan and Western Ghats regions. This study establishes a comprehensive morphological baseline for curry leaf germplasm, supporting conservation planning and the identification of elite and unique morphotypes for future breeding and genetic improvement programs.