Quantification of resistance to Meloidogyne incognita in okra cultivars using linear and nonlinear analyses of growth parameters and nematode infestations

ABSTRACT

One of the most effective and cost-efficient methods to manage plant parasitic nematodes is to use resistant cultivars. However, little information on the resistance of commercial okra cultivars grown in the country was available. Therefore, nine okra cultivars were evaluated for their comparative resistance against Meloidogyne incognita, the most damaging root-knot nematode. None of the tested okra cultivars showed high level of resistance. However, three cultivars viz. Pusa Swami, PB Selection and Green Star appeared as moderately resistant. Sabz Pari, Neelum and Tulsi were found moderately susceptible to the nematode. Two cultivars i.e. Ikra-1 and Ikra-2 were susceptible and Arka Anamika was highly susceptible. The okra cultivars differed significantly in their growth parameters depending on their response to M. incognita. Moderately resistant cultivars sustained little damage as compared to moderately susceptible or susceptible cultivars while the highly susceptible cultivar suffered the maximum damage by the nematode. Significant differences in the numbers of galls, eggmasses and reproductive factors of M. incognita on the nine okra cultivars were also observed. The highest numbers were found on Arka Anamika, followed by Ikra-1 and Ikra-2. The lowest numbers were found on the moderately resistant cultivars, followed by the moderately susceptible ones. High and positive correlations between the number of galls and eggmasses and the decreases in growth metrics were found using linear and non-linear regression analysis.

KEY WORDS
Abelmoschus esculentus ; root-knot nematodes; reproductive factor; resistance; growth metrics