Selection of Indicator Plants for the estimation of Root-knot Nematode Population Density in soil

Abstract

Selection of potential indicator plants for estimation of soil population density of root-knot nematode(Meloidogyne spp.) was initially made in a greenhouse. After germination, a single plant from 40 different plantspecies grown in a 350-ml plastic cup filled with sterilized soil was inoculated with 5,000 eggs of M. incognita andkept for 30 days, 10-20 plants of each species were tested. Each washed root system was rated for galling percentage(GP). Okra (Abelmoschus esculentus) var. PJ 005, jute (Cochorus olitorius), tomato (Lycopersicon esculentum),garden basam (Impatiens balsamina), and mungbean (Vigna radiata) were five plant species selected for a furthertest, based on the following criteria: GP greater than slightly high level (>51%), consistent galling, strong rootsystem, and upright stem. Twenty plants of each 5 plant species germinated singly as in the earlier test were inocu-lated with 12 different density levels of nematode eggs and kept for 30 days in the greenhouse. At the results, all 5species showed positive correlation between GP and initial population density (Pi) (r=0.891** to 0.896**). Con-cerning about having non-dormant seed and high percent germination rates, garden balsam and mungbean wereselected for microplot test. The two plant species were broadcast seeded in microplot artificially infested with variedpopulation densities of the nematode. After 30 days, data were available only for garden balsam with non-uniformgermination, and showed no correlation between GP and Pi. A repeated test of mungbean with 2 rates of seed useshowed positive correlation between GP and Pi, especially in the low seed rate plot, and the correlation coefficientswere lower than those in the greenhouse. The results could not finalize the suitability of mungbean as the indicatorplant for the estimation of soil population of root-knot nematode. Further studies are still needed. However, among40 plant species tested, mungbean seemed to be a good choice for this purpose.