Tools Towards Managing Mycorrhiza for Sustainable Agriculture

The arbuscular mycorrhizal (AM) fungi, in concert with other soil dwelling microorganisms such as the so-called “plant growth promoting rhizobacteria”, play a pivotal role for natural soil fertility and stability, hence, for sustainable crop production. Appropriate management of the AM fungal community is crucial, especially in the tropics where the cultivated soils are notoriously fragile and prone to degradation. The discovery of the multiple benefi ts of the AM symbiosis provided to the crops induced a global mushrooming of enterprises commercializing AM fungal inoculants to be used as “bio-fertilizers”. A serious drawback of these endeavors was that the AM fungal inoculants could not be identifi ed at the strain level, precluding a scientifi cally rigorous test of the origin and persistent quality of such inoculants. Furthermore, after fi eld application the inoculated AM fungal strains could not be traced precluding verifi cation of root colonization by the strains in target crops and studies on the strain competitiveness and persistence in the fi eld amidst the native AM fungal community. The “holy grail” for researchers on AM fungal ecology and application was therefore to obtain tools allowing specifi c tracing of AM fungi at the strain level in soil and roots sampled from fi eld sites. We are happy to report that two of our approaches to attain this goal were successful. We also accomplished our additional tasks, namely to assess the native AM fungal communities present at the various experimental fi eld sites in India prior to the application of the AM fungal “bio-fertilizers” and, furthermore, to develop experimental test systems at the laboratory scale for screening important functional traits of isolated AM fungal strains.