Arbuscular Mycorrhizal Fungi in Roots and Rhizosphere of Black Rice in Terrace Fields of North-East India

Morphological assessment of arbuscular mycorrhizal (AM) fungal diversity in rhizosphere soils may not reflect the AM fungal species colonizing the roots. Recently, DNA-based molecular approaches offer a wide range of advantages in understanding the AM fungal abundance both in soil and root systems. In this study, the community composition of native AM fungi in the soil and roots of aromatic black rice (Oryza sativa L. cv. Chakhao amubi) during the flowering stage in the terrace farming system was evaluated. AM fungal spore density ranged between 72 and 110 spores per 100 g shade-dried soil and varied significantly with rice terraces. All examined root fragments were colonized by AM fungi. However, the root length containing different AM fungal structures did not vary significantly compared to total root length colonization. The genomic DNA from rice roots was amplified with AM fungal specific primers using nested PCR and sequenced thereafter. Results of 18S rDNA partial region sequences revealed the presence of seven AM fungal species in roots, whereas in rhizosphere soils ten AM fungal spore morphotypes were recorded. Such dissimilarity in species richness of AMF between rhizosphere soil and the roots implied that some indigenous AMF species were adapted to specific soil environments that could colonize the paddy crop roots and suggests that the conditions can be suitable for some AMF species which have an important function in traditional terrace rice cultivation of hilly tracts in North-East India. © 2021, The National Academy of Sciences, India.