Study the effect of Rhizobium phaseoli and plant growth promoting rhizobacteria (PGPR) on nitrogen fixation and nodulation of bean (Phaseolus vulgaris)

In order to evaluate nitrogen fixation and nodulation ratio in bean (Phaseolus vulgaris L.) Iranian cultivars with different strains of Rhizobium leguminosarum biovar phaseoli with Plant Growth Promoting Bacteria to determine the best bacteria×cultivar’s combination، a spilt plot experiment in randomized complete block design was conducted in the field at Shahrekord، Iran in 2006 and 2007. The factors were six bacterial strains Rb-133، Rb-133×Azospirillum، Rb-133×Pseudomonas، Rb-136، Rb-136×Azospirillum، Rb-136×Pseudomonas and non-inoculated controls including application of nitrogen fertilizer treatment (100 kg N ha-1) and without application of nitrogen fertilizer in main plots. Three bean cultivars Sayad، Akhtar and Goli were assigned as factor B to subplots. The results revealed that there were significant differences among levels of factor A in shoot nitrogen content، nitrogen fixation، number nod، dry weight and fresh weight of nod at early flowering (45-50 days after emergence). Treatment of inoculated seeds with strain bacteria×Pseudomonas and non-inoculated control (without N–fertilizer application) demonstrated the highest and lowest nitrogen fixation and nodulation، respectively. The results showed that all treatments of bacteria are capable of nodulation; however، strains Rb-133 gave highest nodule dry weight، N total (shoot) and percent of fixed N2.