AM are ubiquitous and most plants are colonized by AMF in nature, i.e., mycorrhizosphere is the rule, not the exception. Thus if we are to understand the rhizosphere reactions and interactions, we must understand the mycorrhizosphere. Mycorrhization helper bacteria (MHB) might be exploited to improve mycorrhization, and AMF to improve nodulation and stimulate PGPR. It is anticipated that future commercial biofertilizers would contain PGPR, MHB, and AMF. Requena et al.(1997) found that AM fungus Glomus coronatum, native in the desertified semi-arid ecosystems in the southeast of Spain, was more effective than the exotic G. intraradices in AM/PGPR co-inoculum treatments. The indigenous isolates must be involved. This area merits greater attention. More extensive field investigations on this multi-agent biofertilizer will make this a popular technology among field workers in agriculture, forestry and horticulture. Manipulation of microorganisms in the mycorrhizosphere for the benefit of plant growth requires research at the field level (Khan, 1975; 2002b). In order to exploit microbes as biofertilizers, biostimulants and bioprotectants against pathogens and heavy metals, ecological complexity of microbes in the mycorrhizosphere needs to be taken into consideration and optimization of rhizosphere/mycorrhizosphere systems need to be tailored. Smith (2002) stressed the need to better integrate information on root and soil microbe distribution dynamics and activities with known spatial and physiochemical properties of soil. This, as pointed out by Smith (2002), should be achieved through greater collaborative efforts between biologists, soil chemists and physicists.
*A Keynote Lecture of the “1st International Symposium on Phytoremediation and Ecosystem Health” Held at Hangzhou, China