44 AJCS 5(1):44-48 (2011) ISSN:1835-2707 Nutrient uptake and yield of chickpea (Cicer arietinum L.) inoculated with plant growth- promoting rhizobacteria Asad Rokhzadi 1* , Vafa Toashih 2 1 Department of Agronomy & Plant Breeding, Faculty of Agriculture & Natural Resources, Islamic Azad University-Sanandaj Branch, Iran 2 Soil & Water Research Institute, Agricultural & Natural Resources Research Center of Kurdistan, Iran * Corresponding author: asadrokh@yahoo.com Abstract This research was carried out to evaluate the effects of single and combined inoculation with plant growth-promoting rhizobacteria from four genera including Azospirillum, Azotobacter, Mesorhizobium and Pseudomonas on nutrient uptake, growth and yield of chickpea plants under field conditions. Nodulation and nutrient concentration in shoots were significantly affected by the treatments at the beginning of flowering stage. The maximum dry weight of root nodules was recorded by applying the combined inoculation with Azospirillum spp. + Azotobacter chroococcum 5 + Mesorhizobium ciceri SWRI7 + Pseudomonas fluorescens P21. All inoculants were statistically superior over uninoculated control with respect to nitrogen concentration of shoots. The treatments containing Azospirillum + Azotobacter significantly improved phosphorus concentration in shoots. Grain yield, biomass dry weight and nitrogen & phosphorus uptake of grains were statistically improved by applying every inoculation treatment in comparison with control plants. Group comparisons between treatments showed that the occurance of Azospirillum or Azotobacter inoculants in the treatment composition caused an expressive improvement in grain yield and plant biomass. In conclusion, application of every inoculation treatment studied here, especially treatments which contained Azospirillum or Azotobacter may stimulate growth and yield of chickpea as compared with uninoculated plants. Keywords: Azospirillum; Azotobacter; Cicer arietinum L.; Mesorhizobium; Plant growth-promoting rhizobacteria; Pseudomonas. Abbreviations: CFU- colony forming units; DAS- days after sowing; PGPR- plant growth promoting rhizobacteria. Introduction Plant growth promoting rhizobacteria (PGPR) represent a wide variety of soil bacteria which, when grown in association with a host plant, result in stimulation of growth of their host plant (Vessey, 2003). Several mechanisms have been suggested by which PGPR can promote plant growth, including phytohormone production, N 2 fixation, stimulation of nutrient uptake and biocontrol of pathogenic microorganisms (Kloepper et al., 1981; Rodriguez and Fraga, 1999; Sindhu et al., 1999; Benizri et al., 2001; Persello- Cartieaux et al., 2003; Somers et al., 2004). Many different genera of plant growth promoting rhizobacteria such as Azospirillum, Azotobacter, Bacillus, Enterobacter and Pseudomonas have been used as biofertilizers for economically important crops. Seed inoculation with a combination of beneficial microorganisms including rhizobia, PGPR and PSB (Phosphate Solubilizing Bacteria) have been shown to increase crop growth and productivity (Dashti et al., 1998; Rodelas et al., 1999; Chebotar et al., 2001; Sindhu et al., 2002; Zaidi et al., 2003; Rudresh et al., 2005). However little is known about the response of chickpea to combined inoculation with rhizobium and plant growth promoting rhizobacteria under field conditions. Chickpea (Cicer arietinum L.) is one of the major pulse crops in the world and provides high quality protein for the people in South, West and East Asia and North Africa. It is also used as feed for livestock and has a significant role in farming systems (Singh, 1997). In Iran chickpea is the most important grain legume and improving it’s productivity is a necessity. Hence the present study was conducted to evaluate the effects of single and combined inoculations with strains of bacteria from genera Mesorhizobium, Azospirillum, Azotobacter and Pseudomonas on nutrient uptake, growth and yield of chickpea under field conditions. Materials and methods Experimental site This experiment was carried out at the agricultural research station of Saral (35˚ 43′ N and 47˚ 8′ E with an altitude of 2100 m) in Kurdistan, Iran, during the cropping season of 2005-2006 in rainfed conditions. The long-term rates of average temperature and annual precipitation in the region are 7.9˚C and 393.6 mm respectively. The total precipitation during 2005-2006 was 305.8 mm. Some of the soil properties were: sand 35.3%, silt 38.7%, clay 26%, pH 7.5, OC 0.89%, total N 0.076%, available P and K, 8.7 & 409.3 ppm respectively. All plots of experimental field treated with 30 kg nitrogen ha -1 in urea form according to soil tests before sowing. Bacterial strains The bacterial cultures used in this study were obtained from the soil biology department, Soil & Water Research Institute (SWRI), ministry of agriculture , Tehran, Iran. The strains