Host suitability of Mediterranean olive ( Olea europaea L.) varieties to two root‐knot nematode species ( Meloidogyne javanica and M. incognita ) under greenhouse conditions

Abstract Root‐knot nematodes ( Meloidogyne spp.) are major constraints on olive ( Olea europaea L.) production in Morocco, with Meloidogyne javanica and Meloidogyne incognita causing substantial yield losses through root damage and nutrient disruption. This study evaluated the resistance of seven olive varieties, including Moroccan autochthonous native varieties (Picholine Marocaine, Menara, and Haouzia) and Mediterranean introductions (Koroneiki, Arbequina, Arbosana, and Picholine Languedoc), to both nematode species under controlled greenhouse conditions. At 9 months after inoculation with 1500 second‐stage juveniles (J2s) per pot (70 J2s per 100 cm 3 of soil), nematode reproduction, plant growth, and biochemical defense responses were assessed. The results revealed variation in host suitability, with Koroneiki and Picholine Marocaine exhibiting strong resistance, maintaining plant biomass, and showing elevated activities of defense enzymes (peroxidase, polyphenol oxidase, and catalase), whereas Arbequina and Picholine Languedoc were highly susceptible, showing severe growth reduction and oxidative stress. M. javanica demonstrated 27%–40% higher reproductive efficiency than M. incognita across all varieties, inducing greater chlorophyll degradation and lipid peroxidation. Multivariate correlation network analysis revealed that chlorophyll retention could be explored as an auxiliary resistance biomarker, whereas the integrated assessment of defense enzymes, flavonoid content, and malondialdehyde levels provided a comprehensive resistance profile. Fourier transform infrared spectroscopic fingerprinting provided exploratory discrimination between resistant and susceptible responses based on differential phenolic and carbohydrate signatures, although these findings warrant further validation. These findings establish Koroneiki and Picholine Marocaine as promising resistance sources for Moroccan olive breeding programs pending field validation, and identify multiparameter indices for resistance screening that merit evaluation in nursery production systems.