5.2.26
BIOCONTROL OF THE ROOT-KNOT NEMATODE MELOIDOGYNE INCOGNITA USING THE NEMATODE-TRAPPING FUNGUS ARTHROBOTRYS SUPERBA AND THE VAM FUNGUS GLOMUS MACROCARPUM IN NICOTIANA TABACUM

G SAXENA, N MITTAL, M SHARMA, R RAWAT and KG MUKERJI

Applied Mycology Laboratory, Botany Department, University of Delhi, Delhi-110 00, India

Background and objectives
The root-knot or gall nematodes are economically the most important nematode pests of tobacco. Problems arising due to intensive use of nematicides have triggered the use of biocontrol methods for integrated management of plant-parasitic nematodes. Most experiments with the nematode-trapping fungi have involved the use of large quantitites of organic amendments. VAM fungi have the potential to serve both as biological fertilizers and biocontrol agents [1]. Chitin amendments are also known to stimulate growth of nematophagous fungi thereby providing effective control of nematodes [2]. The objective of the present study was to evaluate the combined effect of two biocontrol agents, i.e. a nematode-trapping fungus Arthrobotrys superba and a VAM fungus Glomus macrocarpum in combination with chitin in controlling Meloidogyne incognita causing root-knot disease of tobacco.

Materials and methods
Treatments in sterilized soil consisted of (i) control (sterilized soil only); (ii) nematodes only (N); (iii) nematodes+VAM (N+V); (iv) nematodes+A. superba (N+F); (v) nematodes+chitin (N+C); (vi) nematodes+VAM+A. superba (N+V+F); (vii) nematodes+chitin+VAM (N+C+V); (viii) nematodes+chitin+A. superba (N+C+F); (ix) nematodes+chitin+VAM+A superba (N+C+V+F). The growth was assessed in terms of shoot/root length, fresh and dry weight and number of galls per g fresh root wt. Statistical analysis was also done.

Results and conclusions
Plants inoculated with A. superba and G. macrocarpum in chitin-amended pots achieved maximum height and shoot weight in comparison to inoculation with each biocontrol fungus separately. Lowest plant weight and height was observed in plants inoculated with nematodes. Maximum galling in N-treated plants was observed and there was no galling in N+C+V+F treatments. It can be concluded that both VAM and nematode-trapping fungi were acting synergistically along with the effectiveness of chitin in controlling M. incognita in tobacco plants.

References
1. Carling DE, Roncadori RW, Hussey RS, 1996. Mycorrhiza 6, 9-13.
2. Mittal N, Saxena G, Mukerji KG, 1995. Crop Protection 14, 647-51.