Genetic variation of Meloidogyne spp. of brinjal reveals their difference in pathogenicity and hatching

Brinjal (Solanum melongena L.) is an important vegetable worldwide and its production is hampered by the infestation of root-knot nematodes (Meloidogyne spp.). In an attempt to identify the Meloidogyne species involved in causing root-knot disease of brinjal by using molecular tools, plants showing knots/galls were collected from 22 brinjal growing locations that belong to different agro-ecological zones in Bangladesh. Nematode populations were maintained in a susceptible brinjal variety by inoculating with egg-masses developed on different varieties of brinjal roots collected from different locations. For molecular identification, DNA was extracted directly from galls developed in the roots of the inoculated plants. Randomly selected three galls from each location were crushed together in order to get DNA from mixed species of root-knot nematodes. Sequence Specific Amplified Region (SCAR) primers specific for Meloidogyne incognita, M. javanica or M. arenaria were used for PCR amplification. For 18 of the 22 locations, M. javanica was identified. At two locations M. incognita was found as a mixed population with M. javanica. M. arenaria was not found. PCR products were sequenced bi-directionally and their analysis revealed genetic variation among the populations. M. javanica was the predominant root-knot nematode species of brinjal in Bangladesh. Intra-specific variation of the SCAR suggested six phylogenetic groups of M. javanica. They showed significant differences in reproduction on brinjal and in their effect on root and shoot weight, while differences in hatching dynamics over five weeks were not significant. This population-dependent aggressiveness of the dominant root-knot nematode M. javanica on brinjal in Bangladesh should be considered for a more efficient management.