Abstracts |
The common mycorrhizal association in most of the plants is the arbuscular type occurring in majority of agricultural crops, most shrubs, most tropical tree species and some temperate tree species. Arbuscular mycorrhizae (AM) are formed by non-septate Glomeromycetous fungi. They belong to the phylum Glomeromycota, which has three classes (Glomeromycetes, Archaeosporomycetes and Paraglomeromycetes) with 5 orders (Glomerales, Diversisporales, Gigasporales, Paraglomerales and Archaeosporales), 14 families and 26 genera. Commonly occurring genera of AM fungi are Glomus, Gigaspora, Scutellospora, Acaulospora and Entrophospora. These fungi are obligate symbionts and have not been cultured on nutrient media. These endophytes are not host specific, although evidence is growing that certain endophytes may form preferential association with certain host plants. Several investigations indicated that even in unsterile soils, plants respond to inoculation with efficient strains of arbuscular mycorrhizae. The mechanism of improved plant growth caused by mycorrhizal inoculation has been investigated by many workers. Greater soil exploration by mycorrhizal roots as a means of increasing phosphate uptake is well established. They also improve the uptake of other diffusion-limited elements like Zn, Cu, etc. Other beneficial effects include their role in the biological control of root pathogens, biological nitrogen fixation, hormone production and greater ability to withstand water stress. Co-inoculation of AM fungi with other beneficial soil microorganisms is more useful in improving plant growth, thus suggesting the development of suitable "microbial consortia" for inoculating different crop plants. The current day emphasis is on sustainable agriculture, which uses less of chemical inputs having adverse effect on soil health, and environment. Thus, microbial inoculants play an important role in sustainable agriculture. |