Damage effects of root knot nematodes (melodiogyn javanica) on chia (salvia hispanica)

Abstract

Tobacco (Nicotiana tabacum), a key cash crop in Zimbabwe, is highly susceptible to root knot nematode infestations leading to huge yield losses. Traditionally, nematodes are controlled by crop rotation with grass fallows, meaning reduced income for farmers in those seasons when the land is fallow. The aim of this research was to determine the capacity of one chia variety (Jalisco) to suppress the root knot nematode (Meloidogyne javanica) populations when incorporated in tobacco rotations. An experiment was carried out at the Tobacco Research Board (Kutsaga) in the 2025 - 2026 rainy season. It was arranged in a Completely Randomized Design (CRD) with six treatments replicated five times. The treatments were based on Meloidogyne javanica inoculum concentrations applied to plants as follows: untreated control, 5000, 10000, 15000, 20000 and 25000 eggs per plant. The chia was planted in a greenhouse, inoculated with nematodes and observed for reaction over 10 weeks. The results demonstrated that, Meloidogyne javanica infection caused no significant effect (p > 0.05) on plant height and stalk dry weight in the early stages of growth that was at 4 weeks after inoculation for plant height and at 6 and 8 weeks after inoculation for stalk dry weight. Significant reduction in plant height and stalk dry weight were observed at 6, 8 and 10 weeks after inoculation for plant height and at 10 weeks after inoculation for stalk dry weight. Minimal nematode root galling damage scores ranging from 0 to 2 on a scale of 0 to 8 were observed across all the rates of inoculation. The weight of seeds produced per plant were not significantly different (p >0.05) between the treatments. Based on the results of this trial, it is recommended that farmers incorporate chia into tobacco rotation cycles to keep Meloidogyne javanica populations low