Response of selected banana varieties to root knot nematode meloidogyne incognita (Kofoid and white)

Abstract

Banana, a dessert fruit for millions, otherwise known as “Apple of Paradise” is botanically Musa spp. It is one of the most popular fruits in the world in terms of per capita consumption as well as the most widely traded fruit in the world. Among the various pests and diseases of banana, plant parasitic nematodes constitute one of the major limiting factors to banana production causing extensive root damage and serious economic loss throughout the world. The root knot nematode, Meloidogyne incognita (Kofoid and White) alone causes 31 per cent yield reduction in India (Jonathan and Rajendran, 2000b).Management of this nematode relies mainly on the repeated use of chemical nematicides which has adverse side effect on environment. One of the most effective and economical ways to control plant parasitic nematodes is exploiting host plant resistance. In this context a study entitled “Response of selected banana varieties to root knot nematode, Meloidogyne incognita (Kofoid and White)” was carried out in the Department of Agricultural Entomology, College of Horticulture, Vellanikkara and Banana Research Station (BRS), Kannara during 2014-2015 with the objective of screening selected banana varieties hybrids against M. incognita and to elucidate the biochemical basis of resistance. Twenty five banana varieties from the germplasm collection of BRS, Kannara, comprising of nine exotic hybrids, six Indian varieties, nine exotic varieties and a highly susceptible check (Robusta) were screened for their reaction to M. incognita. Pot culture experiment was conducted at BRS, Kannara in Completely Randomized Design with three replications. Nematodes were inoculated @ one second stage juvenile per gram of soil at forty five days after planting. Monthly observations on the biometric characters viz., plant height, pseudostem girth and number of leaves were recorded from the date of inoculation till uprooting (six months after inoculation). At the time of uprooting, root knot number and nematode population in soil and roots were recorded. Based on the number of galls, indexing was done on 1-5 scale and the banana varieties/hybrids were respectively categorized as highly resistant, resistant, moderately resistant, susceptible and highly susceptible (Gitanjalidevi et al., 2014). None of the varieties were highly resistant whereas, SH–3640 (AAAB) and SH–3436-6 (AAAA) with mean root knot index of 2 were classified as resistant. Nine varieties viz., FHIA-1 (AAB), FHIA-3 (AABB), SH–3436-9 (AAAA), TMB × 5295-1 (AAAB), Udayam (ABB), Dudhsagar (AAB), Manjeri Nendran II (AAB), Big Ebanga (AAB) and Pisang Nangka (AAB) with root knot index of 3 rated as moderately resistant. Seven varieties viz., TMP 2829 (AB), Mysore Ethan (AAB), Sugandhi (AAB), Yangambi Km5 (AAA), Bangrier (ABB), Popoulu (AAB) and Pisang Madu (AA) with root knot index of 4 found to be susceptible and rest of the seven varieties viz., FHIA -17 (AAAA), FHIA -18 (AAAB), Karpooravally Dwarf (ABB), Pisang Ceylan (AAB), Pisang Jari Buaya (AA), Pisang Buntal (AA) and Robusta (AAA) with root knot index of 5 were classified as highly susceptible. To study the biochemical basis of resistance, biochemical components like total phenol content, peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) activity were estimated three months after inoculation based on standard procedures. Biochemical analysis revealed a higher total phenol content and enzymes like polyphenol oxidase, peroxidase, and phenylalanine ammonia lyase in resistant varieties. A significant negative correlation was observed between the biochemical parameters and number of root knots, root knot index and population of M. incognita in root and soil.