Effect of plant growth promoting rhizobacteria (PGPR) on yield and yield components of rice varieties

In year 2010, two isolates of PGPR from rice field were identified as potential PGPR by Malaysian Agricultural Research and Development Institute (MARDI) (Saad et al., 2010). These PGPR were successfully identified using Biolog GP2 MicroPlate as Burkholderia glumea (BCA29) and Burkholderia vietnamiensis (2A1). The genus of Burkholderia has just been known for only the last fourteen years. Its species composition, distribution and ecological importance are still largely unknown. All Burkholderia species have heterotrophic style of metabolism making them capable of thriving on plant exudates. They can be found in most rhizospheres (Balandreau and Mavingui, 2007) and in all reported cases Burkholderia, the population density is much higher (up to 4000 folds) in the rhizosphere than in bulk soil (Hebbar et al., 1994). In rice, ?-proteobacteria of the genus Burkholderia, for example, Burkholderia brasilensis, B. vietnamiensis (Gillis et al., 1995) and Burkholderia spp. (Muthukumarasamy et al., 2007) have been reported in high numbers. Recently, public health and safety concerns about the environmental impact of chemical fertilizers and pesticides have led to PGPR being considered as a natural approach to maintaining crop health and yield enhancement. Biofertilizers are becoming increasingly popular in many countries and for many crops. They are defined as products containing active or latent strains of soil microorganisms, either bacteria alone or in combination with algae or fungi that increase the plant availability and uptake of mineral nutrients. In general, they contain free-living organisms associated with root surfaces but they may also include endophytes, microorganisms that are able to colonize the intercellular or even intracellular spaces of plant tissues without causing apparent damage to the host plant. The concept of biofertilizers was developed based on the observation that these microorganisms can have a beneficial effect on plant and crop growth (Davidson, 1988). Consequently, a range of plant growth-promoting rhizobacteria (PGPR) has been identified and well characterized. Direct beneficial effects can occur when the microorganisms provide the plants with useful products. Thus, the main objectives of these experiments are to assess and determine the effect of PGPR on yield and yield components of rice varieties. (Copied from article)