Diversity of Potassium Solubilizing Microorganisms and Their Interactions with Plants
Potassium is, together with nitrogen and phosphorus, an essential element for plant nutrition, being the third element in the classical chemical fertilizers NPK. Deficiencies in K results in plants with poorly developed roots, small seeds and lower yields, and therefore the availability of this element is crucial for plant growth and development. The plants take this element from soil, but high amounts of K present in soils correspond to insoluble forms from rocks and silicate minerals. The solubilization of K by microorganisms is then a reliable alternative to make available this element for plants. In this chapter, we review the microorganisms reported as K solubilizers and their phylogenetic diversity, including filamentous fungi such as Penicillium or Aspergillus, yeasts such as Torulaspora and bacteria of many different genera from phyla Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. Some of these potassium solubilizing microorganisms (KSMs) play a positive role in the growth of different plants, which is relevant to sustainable agriculture schemes, and therefore this is a promising field of study in the 'greening' era.