Rice: The Monocot Plant Oryza Sativa (PGPR)

Rice is the seed of the monocot plants Oryza sativa (Asian rice). As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies (Sharif et al., 2014). It is the grain with the third-highest worldwide production, after maize (corn) and wheat, according to 2012 FAOSTAT data (Data of FAOSTAT). Since a large portion of maize crops are grown for purposes other than human consumption, rice is the most important grain with regard to human nutrition and caloric intake, providing more than one fifth of the calories consumed worldwide by the human species (Smith & Bruce, 1998).

However, due to the use of chemical fertilizers,

PGPR have been applied to various crops to enhance growth, seed emergence, crop yield and few have been commercialized (Joseph et al., 2012;Khalid et al., 2004;Leinhos, 1994). PGPR are a heterogeneous group of bacteria that can be found in the rhizosphere, at root surfaces and in association with roots. They can improve the extent or quality of plant growth by direct and/or indirect methods. In last few decades, a large array of bacteria including species of Pseudomonas, Azospirillum, Azotobacter, Klebsiella, Enterobacter, Alcaligens, Arthobacter, Burkholderia, Bacillus and Serratia have been isolated and reported to enhance plant growth (Glick, 1995). The direct plant growth promotion by PGPR entails either providing the plant with a plant growth promoting substances that are synthesized by the bacterium or facilitate the uptake of certain plant nutrients from the environment (Beneduzi et al., 2012). The indirect promotion of plant growth occurs when PGPR minimize or prevent the deleterious effect of one or more phytopathogenic micro-organisms and help plants to fight against the environmental stresses (Okon and Labandera-Gonzalez,

The total production of rice in the State is about 0.9-1.1 million tons with a productivity of 1500 to 1800 kg/ha. The productivity of irrigated rice is nearly 2 tons/ha whereas that of unirrigated rice is nearly 1 ton/ha (Mehta et al., 2010). In Gujarat, rice is grown in 14 districts. Out of which the productivity of 5 districts each is low and very low and three districts are under medium-low productivity group. Surat district is under medium-low productivity group (1500-2000 kg/ha) comprising of three districts was 0.25 million hectares, which was 39.8% of triennium average area (0.64 million hectares) under rice in the state. Triennium average production was 0.45 million tonnes, which was 51.8% of triennium average production (0.87 million tonnes) of rice in the state. Triennium average productivity of medium low productivity group comprising of three districts was 1,765 kg/ha as against 1,356 kg/ha triennium average productivity of the state (Vashi et al., 2010). Surat is a rice producing district of Gujarat, but screening of rhizobacteria for the search of efficient PGPR have not been done. Keeping this objective in mind the present investigation was performed and their plant growth promoting abilities were evaluated after screening and isolation of plant growth promoting rhizobacteria (PGPR) from the rhizosphere of rice plants of Surat districts of Gujarat,