Phenotyping of tomato germplasm for root knot nematode resistance

Abstract

The present study entitled “Phenotyping of tomato germplasm for root knot nematode resistance” was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during 2018-2020, with the objective to screen tomato germplasm including released varieties of KAU for root knot nematode resistance through artificial screening.

The study comprised of two experiments. In the first experiment, collection, identification and multiplication of Meloidogyne incognita (Kofoid and White, 1919) Chitwood culture for artificial inoculation was performed. Root knot nematode infested root and soil samples were collected from tomato plants in the Department of Nematology, College of Agriculture, Vellayani. Root knot nematode females, egg masses and juveniles were extracted from the samples and identified. The collected soil samples upon identification are then inoculated to healthy seedlings for multiplication and maintained as pure source of inoculum.

The second experiment was screening of tomato germplasm for root knot nematode resistance using thirty seven tomato genotypes (including released varieties of KAU) which were evaluated in Completely Randomized Design with three replications. Fifteen days after transplanting the seedlings, hatched juveniles were inoculated @ 2000 juveniles plant-1. Observations were recorded for number of larvae in 5 g root, root-knot count in 5 g root, number of females in 5 g root, number of egg masses in 5 g root, average number of eggs in egg mass and nematode population in 200 cc soil. Reproductive potential was assessed by calculating reproduction factor. Weight of root and shoot were recorded. Analysis of variance was found to be significant for all the parameters observed.

PNR – 7 recorded lower for number of larvae and egg masses in 5 g root. EC – 165700 recorded higher for root knot count and number of females 5 g root-1. IIHR – 2868 recorded lower and EC – 165700 recorded higher for number of nematodes in 200 cc soil as well as reproduction factor. Root knot indexing was done using the method given by Heald et al. (1989). The genotypes were categorized on a root knot index scale of 0-5 using total root knots in root system (0 – highly resistant, 1 – resistant, 2 – moderately resistant, 3 – moderately susceptible, 4 – susceptible and 5 – highly susceptible).

The study revealed the lack of resistance in all the genotypes. No genotype was found to be highly resistant, resistant or moderately resistant. Vellayani Vijai was found to be moderately susceptible with a root knot index of 3 and EC – 160855 was susceptible with a root knot index value of 4, while all other genotypes in the study were highly susceptible. Vellayani Vijai can be forwarded further for fruit yields under nematode infected fields. Genotyping can also be performed to check for the presence of gene Mi conferring resistance to M. incognita.