Morphological, morphometric, and biochemical characterisation of four root-knot nematode (Meloidogyne sp.) populations infecting various crops in India

Abstract Root-knot nematodes, RKNs (Meloidogyne sp.) are polyphagous pests that threaten numerous economically important crops worldwide. Identifying RKN species remains a major challenge for nematologists serving advisory services to crop growers. To date, nematologists use the perineal pattern of mature females for species identification of RKNs despite its variability among populations, particularly in regions where molecular facilities are limited due to cost. In our study, notable variability was detected among four RKN populations: those infecting okra and Indian spinach (Basella) in Odisha, fennel in Rajasthan, and carnation in Karnataka, underscoring the importance of an integrative approach. Therefore, this study employed an integrative approach combining morphological, morphometric and biochemical methods to identify four RKN populations. Morphology and esterase phenotypes confirmed the presence of M. javanica (infecting okra in Odisha and carnation in Karnataka) and M. incognita (infecting Basella in Odisha and fennel in Rajasthan). To further resolve the population-level variations, linear discriminant analysis (LDA) was performed on morphometric variables from different life stages, which effectively distinguished between species. This study underscores the importance of using a multifaceted approach for accurate RKN species identification, which is crucial for developing targeted nematode management strategies.