INFLUENCE OF EDAPHIC AND CLIMATIC FACTORS AN DYNAMICS OF ROOT COLONIZATION AND SPORE DENSITY OF VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGI IN ACACIA-FARNESIANA WILLD, AND A-PLANIFRONS W-ET-A

A study was conducted to assess the dynamics of vesicular-arbuscular m ycorrhizal (VAM) fungi associated with Acacia farnesiana and A. planif rons in moderately fertile alkaline soils. The intensity of root colon ization by VAM fungi and the distribution of VAM fungal structures var ied with host species over a period of time. The occurrence of vesicle s with varied morphology in the mycorrhizal roots indicates infection by different VAM fungal species. This was further confirmed from the p resence of spores belonging to different VAM fungal species in the rhi zosphere soils. Root colonization and spore number ranged from 56%-72% and 5-14 g(-1) soil in A. farnesiana and from 60%-73% and 5-15 g(-1) soil in A. planifrons. Per cent root colonization and VAM spore number in the rhizosphere soil were inversely related to each other in both the Acacia species. However, patterns of the occurrence of VAM fungal structures were erratic. Spores of Acaulospora foveata, Gigaspora albi da, Glomus fasciculatum, G. geosporum and Sclerocystis sinuosa were is olated from the rhizosphere of A. farnesiana whereas A. scrobiculata, G. pustulatum, G. fasciculatum, G. geosporum and G. microcarpum were i solated from that of A. planifrons. The response of VAM status to fluc tuating edaphic factors varied with host species. In A. farnesiana tho ugh soil nitrogen (N) was positively correlated with root colonization , soil moisture, potassium and air temperature were negatively correla ted to both root colonization and spore number. Per cent root coloniza tion and spore number in A. planifrons were negatively related to each other. Further, in A. planifrons as the soil phosphorus and N were ne gatively correlated with the density of VAM fungal spores, the same ed aphic factors along with soil moisture negatively influenced root colo nization.