VARIED REACTIONS OF FCV TOBACCO GERMPLASM AGAINST ROOT-KNOT NEMATODES, MELOIDOGYNE SP .

Abstract

Flue-cured Virginia (FCV) tobacco is an important commercial crop grown worldwide. It is highly susceptible to plant parasitic nematodes especially root-knot nematodes. Root-knot nematodes are a serious limiting factor for tobacco production in both nursery and main field. Planting of root-knot infected seedlings in main field causes stunted growth and death of plant resulting in poor plant stand. Yield reduction due to root-knot nematodes in FCV tobacco in both nursery and field crop in Karnataka was estimated to the tune of 59.4 and 52.9%, respectively (Hussaini, 1983). Losses caused by these nematodes are very high, particularly when they cause disease complex with other pathogenic organisms in soil. Nematicides of chemical origin are being successfully used against root-knot nematodes in tobacco crop both nursery and field (Hussaini, 1985; Ramakrishnan et al., 1998b). But, such use of synthethic nematicides against nematode pests is neither desirable nor economical due to the residue problems posed by them. Hence, use of resistant/tolerant crop varieties is the desirable, eco-friendly and economical way of nematode management. To have root-knot resistant FCV tobacco varieties through breeding programmes, it is essential to have identified resistant sources. To identify rootknot nematode resistant sources, FCV tobacco germplasm accessions being maintained at the research station were screened against root-knot nematodes under root-knot nematode sick field conditions.