Arbuscular mycorrhizal fungi benefit mango (Mangifera indica L.) plant growth in the field

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The rhizospheres of three year old-mango (Mangifera indica L.) rootstocks namely, Vellakulamban, Bappakai, Olour, Chandrakaran, Necker, Peach, Totapuri and Vellakulamban were studied for the spore load of arbuscular mycorrhizal (AM) fungi and root colonization at 15cm, and 30cm depths. Mycorrhizal spores were highest in Totapuri followed by Bappakai, Olour and Peach and Vellakulamban at 15cm depth. Spores belonged to the genera Glomus and Acaulospora and few other genera, the predominant ones being Glomus fasciculatum and Glomus mosseae as identified by their morphology. The colonization of the root was higher in Vellakullamban and Totapuri rootstocks. Frequently occurring AM species were initially multiplied on finger millet (Eleucine coracona L.) in paper cups filled with soilrite and then in 12in. pots that contained 1:1 sand soil mixture. The rootstock cultivars predominantly used for grafting mango scions in southern India were screened for their response to AM inoculation in pot culture. All the rootstock seedlings responded to mycorrhizal inoculations showed varied intensity of root colonization and improved plant height, growth and nutrient content compared to non-mycorrhizal in pot culture. Under field conditions, rootstock cv Totapuri inoculated with AM fungi and scions of mango hybrids Arka Aruna and Arka Puneeth grafted on them produced shoots earlier compared to non-mycorrhizal plants. Within two years of application of AM fungi yearly, clear difference in growth performance of mycorrhizal and nonmycorrhizal plants was observed. Plant growth studied in terms of number of branches, available soil P, leaf P, Zn and Cu improved significantly in AM colonized plants compared to uninoculated plants. This trend continued in the 8th year of sampling. The root acid and alkaline phosphatase activity was higher in six month old Arka Puneeth grafted on AM colonized Totapuri rootstock. Mycorrhizal inoculums can be easily multiplied on-farm on finger millet and applied yearly for desired results.