Root colonization of mandarin plants grown in orchards of Darjeeling hills and plains with arbuscular mycorrhizal fungi and their effects on plant growth

Citrus reticulata is an ancient commercial crop being cultivated in Darjeeling-Sikkim hills. Many diseases are prevalent in mandarin plants, out of them, bacterial & fungal diseases are mostly dangerous. Arbuscular Mycorrhizal Fungi were screened from rhizosphere of mandarin plants from the four different regions using wet sieving and decanting method. Microscopical observation revealed the presence of different genus of AM fungi present in the root as hyphae, spores and sporocarp. Glomus mosseae, G. fasciculatum, G. aggregatum, G. badium. G. constrictum, G. versiforme, Gigaspora gigantea, G. margarita, Acaulospora capsicula, A. bireticulata, Sclerocystis and Scutellospora rubra were found to be dominant in all the soil samples of mandarin. Species of Glomus were found to be high in both hilly and foothill regions. Glomus mosseae and G. fasciculatum were selected for mass multiplication in maize plant in pots. Histopathological study of root showed the presence of vesicles and arbuscules. AMF infection and total number of spores per 100 gram of soil were recorded. Scanning Electron Microscopy (SEM) of AMF spores of mandarin revealed clear morphology, spore wall characters and hyphal attachment of spores. Total phosphate content of the soil, soil analysis and enzyme activities in roots and leaves of mandarin plant from the different regions were studied. Three major defense enzymes peroxidase, chitinase and β- 1,3- glucanase showed enhanced activities and the total phosphate content also decreased in soil with respect to control. Present study evaluates the effect of AMF in plant growth and phosphate solubilization.