MYCOFLORA OF SUNFLOWER RHIZOSPHERE IN RELATION TO SOIL FUMIGATION

SUMMARY The present investigation was aimed at analyzing the role of fumigants, i.e., different concentrations of carbon disulphide (CS2) and formalin, on soil mycoflora including mycorrhizal fungi in the sunflower rhizosphere. Fungi were greatly reduced immediately after fumigant application but with the passage of time these started to reappear. In qualitative analyses of mycoflora, Aspergillus niger, Aspergillus terreus and Penicillium nigricans reappeared only after 20 days at all CS2 concentrations. The quantitative study showed the boosting up of the population of Trichoderma viride with increasing concentrations of formalin and CS2 after 20 days. High concentrations of both fumigants initially decreased mycorrhizal spore number. However, the mycorrhizal spore number increased later on. Mycorrhizal root colonization reached maximum after 40 days in treated soils. Glomus mosseae was resistant to CS2 application but Glomus geosporum and Acaulospora laevis were inhibited by high concentrations of the fumigant.