Diversity, richness and degree of colonization of arbuscular mycorrhizal fungi in coconut cultivated along with intercrops in high productive zone of Kerala, India

Degree of arbuscular mycorrhizal (AM) association and its diversity were investigated in the coconut palm (Cocos nucifera L.) cultivated in crop mixed system under rain-fed condition in a highly productive humid tropical zone in Malappuram district of Kerala, India. Forty AM species belonging to ten genera viz. Acaulospora, Claroideoglomus, Dentiscutata, Diversispora, Funneliformis, Gigaspora, Glomus, Redeckera, Scutellospora and Septoglomus were recorded indicating high level of AM richness in coconut rhizosphere. Of these, eighteen AM fungal species are being reported for first time from this palm. Claroideoglomus, Glomus and Gigaspora were the most commonly present genera and Claroideoglomus etunicatum and Glomus aggregatum the common species. The diversity indices (Shannon indices values) of AM fungi associated with coconut palm in a crop mixed system and mono crop varied significantly. The Shannon index, Simpson's index and evenness ranged from 1.40 +/- 0.10 to 2.70 +/- 0.01, 0.65 +/- 0.033 to 0.90 +/- 0.004, 0.51 +/- 0.01 to 0.82 +/- 0.01, respectively. Correlation between soil physio chemical characters and mycorrhizal parameters were worked out. Soil pH had negative correlation with spore count, root colonization, species richness, Shannon H and Simpson indices but had positive correlation with species evenness. Electrical conductivity showed positive correlation with root mycorrhizal colonization which indicated active AMF mediated uptake of nutrients.