MICROMYCETES DIVERSITY IN THE RHIZOSPHERE OF RICE FIELDS

The rice (Oryza sativa L.) rhizosphere is a dynamic biological niche hosting a diverse community of micromycetes that play crucial roles in soil processes and plant health. This chapter reviews the diversity and distribution of micromycetes associated with rice rhizospheric soil, roots, seeds, and plant tissues, integrating findings from both culture-dependent and molecular studies. Fungal communities are predominantly composed of Aspergillus, Penicillium, Fusarium, Trichoderma, Alternaria, Curvularia, Rhizoctonia, and Magnaporthe species. Culture-based analyses revealed significant variation in colony-forming units and occurrence frequencies across wetland and dryland rice soils, with Aspergillus terreus, Fusarium spp., Penicillium spp., Trichoderma spp., and dematiaceous fungi being particularly prevalent. Seed-borne and endophytic studies demonstrated high fungal incidence in seeds, leaves, stems, and roots, with Fusarium and Aspergillus exhibiting the highest isolation rates. Arbuscular mycorrhizal fungi, mainly from Glomus, Acaulospora, and Gigaspora, were consistently detected in rice roots, though colonization intensity declined under continuous flooding. Morphological identification combined with ITS and LSU rDNA-based molecular analyses enhanced species resolution and phylogenetic understanding of rice-associated micromycetes. Collectively, the data highlight the roles of micromycetes in organic matter decomposition, nutrient cycling, plant growth, and disease dynamics within rice ecosystems. The chapter underscores the importance of integrated morphological and molecular approaches for elucidating micromycete diversity and informing sustainable rice cultivation strategies.