Arbuscular mycorrhizal fungi: Significance of the diversity and its importance in plant growth promotion

All ecosystem processes are the combined activities of variety of organisms and main component of the soil micro biota in most ecosystems are Arbuscular mycorrhizal fungi (AMF), an obligatory symbiotic fungi which colonizes the roots of the majority of plants including crop plants. It forms an effective link between the plants and ecosystems through symbiotic interaction. All mycorrhiza (ecto-, endo- and ect- endo mycorrhiza) have in common a fungal connection between the soil and roots. Some host species may have more than one kind of mycorrhiza, but most form only one. Amongst all binds, AMF are the most widespread type of mycorrhiza. These fungi form branched hyphal structure, termed as arbuscules which are formed inside the cortical cells of plant roots. Arbuscules are the main characteristic feature of all AM fungi, however, vesicles are produced by only Glomus, Entrophospora, Acaulospora and Sclerocystis which are terminal, globose and lipid rich structure in intracellular areas of root cortex (Strullu et al., 1983). Hence in this article we will be using the term AMF to cover all kinds of fungi having endomycorrhizal association. The AM symbiosis is typically mutualistic. As obligate symbionts, AMF are believed to be dependent upon the host plant for fixed carbon and in return plant receives a variety of benefits such as nutrient uptake, stress tolerance and resistance from pathogens, etc. The most important of these benefits is increased nutrient uptake notably of immobile nutrients such as P and Zn. Though there is no as such host specificity in AMF but still the responses vary from genus, species and strain level. Hence, it is important to know the diversity of these unique fungi under different ecosystems. This article is framed to understand this issue and also to understand the significance of AMF in plant sustenance.