In this root-soil interaction there is four distinct ecological niches: the root surface (mainly plant material) is known as the rhizoplane. Some microorganisms can colonize the interior of the roots (endosphere) and are considered endophytes. The rhizosphere is the soil under the influence of roots. Root exudates are energy rich photosynthates supporting important microbial activities. Therefore the number of microorganisms in the rhizoplane and the rhizosphere are several times more important than their number in the bulk soil, which is the soil distant from the roots. Since most agricultural crops are mycorrhizal (form a symbiotic association with mycorrhizas), the concept of the mycorrhizosphere replaced that of rhizosphere to include the zone under the influence of plant roots and the symbiotic fungi, and it includes the hyphosphere which is the zone surrounding mycelia. Efficient phosphate solubilizing microorganisms should therefore be able to colonize the mycorrhizosphere and have beneficial interactions with plant roots and with mycorrhizas, to support high yields in sustainable agriculture systems while using less input in fertilizers and pesticides or in organic agriculture by using direct application of phosphate rock or other sources of organic Phosphorus.