Screening of Chilli ( Capsicum annuum L.) Germplasm for Response to Root-Knot Nematode ( Meloidogyne incognita ) under Glasshouse Conditions

Abstract Root-knot nematodes (RKN), genus Meloidogyne , are important plant-parasitic nematodes that infect roots and induce gall formation, thereby impairing nutrient and water uptake and reducing crop productivity. Chilli ( Capsicum annuum L.) is an economically important vegetable and spice crop, and identification of germplasm with reduced susceptibility to Meloidogyne incognita is a key step toward integrated nematode management. The present study screened eleven chilli lines, OHP-35 to OHP-45, for root-galling response to M. incognita under glasshouse conditions at the Plant Pathology Research Institute, Ayub Agricultural Research Institute (AARI), Faisalabad, Pakistan, in 2021. Two-week-old chilli seedlings were transplanted into 6-inch earthen pots containing sterilized silt–sand soil. Soil sterilization was carried out using a 5% formalin solution prepared at a formalin:water ratio of 5:95, followed by covering the treated soil with polyethylene for 48 h and airing for 24 h. Fifteen days after transplanting, plants were inoculated with 2,000 second-stage juveniles (J2) of M. incognita per pot. The nematode species was confirmed morphologically using female perineal patterns and juvenile characters. Plants were harvested 60 days after transplanting, roots were washed, and the number of galls per root system was recorded. Each chilli line was represented by five independent pot replicates. Mean root-gall counts varied significantly among genotypes, ranging from 1.4 in OHP-42 to 207.8 in OHP-36. OHP-45 also showed a low mean count of 4.2 galls per root system. Based on the Bridge and Page galling scale, OHP-42 was classified as resistant, OHP-45 as moderately resistant, OHP-40 as moderately susceptible, OHP-39, OHP-41 and OHP-43 as susceptible, and OHP-35, OHP-36, OHP-37, OHP-38 and OHP-44 as highly susceptible. Statistical analysis revealed highly significant differences among lines (one-way ANOVA: F 10,44 = 60.51, p < 0.001; Kruskal–Wallis: H = 50.21, df = 10, p < 0.001). These results identify OHP-42 and OHP-45 as promising candidates for confirmatory resistance evaluation. However, because the study was conducted under a single glasshouse screening and did not include nematode reproduction parameters such as egg masses, final population density, or reproduction factor, the findings should be interpreted as preliminary evidence of reduced susceptibility rather than proof of durable field-level resistance.