Phylosphere is the surface of the aerial parts of plants and a place for micro-organisms to live. Simple sugars such as glucose, fructose and sucrose are the predominant carbonaceous substances on leaves and stem that pass out of wound areas or secretory pores. In these areas, can be seen the largest population bacteria of phylosphere (Mercier and Lindow 2000). The microbial inhabitants of the phylosphere include different genera of bacteria, filamentous fungi, yeasts, algae, protozoa and nematodes. The bacteria are the most abundant inhabitants of the phylosphere (Andrews and Harris 2000). Plant species and leaf type have a beneficial effect on the number of bacteria of phylosphere. For example, the number of bacteria in the phylosphere of broadleaf plants such as cucumbers and beans is significantly higher than that of broadleaf plants with waxy leaves and grasses. On the other hand, the surface of the aerial parts of the plant is subject to rapid and continuous changes in temperature, humidity, ultraviolet rays, relative humidity and the concentration gradient of nutrients (Brencic and Winans 2005).
The rhizosphere is an area of the root that soil microorganisms are very interested in, using root secretions as carbon and energy sources and competing for food and trritory. Bacteria such as Bacillus, Pseudomonas, Azospirillium, Azotobacter, Arthrobacter, Entrobacter and Serratia are among the growth-promoting bacteria (Podile and Kishore 2006). Plant growth-promoting bacteria are part of the integrated disease management program and reduce chemical consumption (Shivalingaiah et al. 2013). These bacteria can stimulate the induction resistance system against a wide range of plant pathogens (Pieterse et al. 2003). The induction of diseases resistance in various crops such as banana, beans, rice, and cucumbers has been reported by Pseudomonas and Bacillus (Harish et al. 2008; Hasan et al. 2010). Most Pseudomonas spp. significantly increases plant length, root length, and dry matter, leading to the production of plant buds and roots. Most plant growth-promoting bacteria are able to settle in the roots, especially if inoculated before sowing. The use of plant growth promoting bacteria as a biological control agent is an alternative to the use of chemical fertilizers that have led to environmental pollution (Ali et al. 2010). Pseudomonads are the major group of the plant growth-promoting bacteria, which act by strategies such as the production of plant hormones, stimulating nutrient uptake, and controlling plant pathogens (Minaxi 2010).
Bacillus species were reported as endophytes within different plant tissues. B. megaterium was the most abundant species in the rhizosphere and B. pumilus and B. subtilis were the most abundant species in the soybean phylosphere (Arias et al. 1999). B. endophyticus from the inner tissue of cotton fibers (Reva et al, 2002), Erwinia sp., Bacillus sp., B. pumilus, B. brevis, Clavibacter sp. and Xanthomonas sp. isolated as endophytes from roots, stems, buds and bolls (Misaghi and Donndelinger 1990). Enterobacter asburiae was isolated as an endophyte and from the cotton rhizosphere, which showed that this bacterium is able to spread systemically in the plant (Hallmann et al. 1998). P. fluorescens caused a significant increase in germination and dry weight of cotton in greenhouse conditions (Salaheddin et al. 2010). P. fluorescens stimulated seedling growth and increased yield with reduced disease (Safyazov et al. 1995).