Functional aspect of phosphate-solubilizing bacteria: Importance in crop production

Abstract

Phosphorus (P) is one of the major plant nutrients whose deficiency results in severe losses to crop yields. To achieve optimum crop production, P is, therefore, consistently required. The use of chemical fertilizers in contrast is discouraged for two basic reasons: one, the repeated and injudicious application may alter soil fertility by adversely affecting microbial composition and functions and, second, it is expensive. To address these problems, scientists have identified soil-borne microorganisms belonging to a specific functional group generally referred to as phosphate-solubilizing microorganisms (PSM) which play many ecophysiological roles, especially in providing plants with P. They can be found in any environment from conventional to contaminated ones and are able to express their activity both in vitro and under field conditions. The solubilization of P by bacteria including even some of the strict nitrogen fixers, for example, rhizobia (symbiotic) or Azotobacter (asymbiotic), is a multifactor process. The ability to release bound P from both organic (enzymatic) and inorganic (acidification) sources by this functionally diverse group of organisms and to provide growth regulators (phytohormones) to plants or protecting plants from various diseases through other mechanisms (such as synthesizing antibiotics, siderophores, cyanogenic compounds, etc.) is indeed some of the most fascinating biological traits that have resulted in increased crop yields. Here, we highlight the functional aspects of PS bacteria especially their role in crop improvement particularly legumes and cereals grown in varied agro-ecological regions. The discussion attempted here is likely to serve as a low-cost prospective option for sustainable agriculture and also to solve economic constraint to considerable extent faced by the farming communities.