Effectiveness of Co-inoculation with Pseudomonas koreensis and Rhizobia on Growth, Nodulation and Yield of Common Bean (Phaseolus vulgaris L.)

The establishment of nodulation, nitrogen fixation and productivity in legumes is affected by specificity of inoculant’s strain and effectiveness as well as interactions with rhizosphere microorganisms. This study aimed to isolate and identify Pseudomonas isolates and investigates the effect of Rhizobium - Pseudomonas co-inoculation on growth, nodulation and yield of common bean (Phaseolus vulgaris L.) cv. Nebraska under greenhouse and lyzemeter conditions. In total, 7 Pseudomonas isolates were isolated from clay soil and evaluated as co-inoculation by measuring the symbiotic N2-fixation parameters under greenhouse. The nine treatments consisted of (seven Pseudomonas isolates (PS1-PS7) combinations with R. leguminosarium sembiovar phaseoli (TAL-3612), one inoculated with R. leguminosarium sembiovar phaseoli (TAL-3612), and one control). One isolate (PS7) exhibited the highest values of growth, symbiosis, photosynthetic and nitrogen content. Based on 16S rRNA sequence, this strain was shown to belong to Pseudomonas koreensis.

Lyzemeter experiment was carried out as complete randomized block designed which consisted of four treatments; T1= Control, T2= Inoculation with R. leguminosarium sembiovar phaseoli (TAL-3612), T3= Inoculation with P. koreensis, and T4= T2+T3 with 5 replicates. Co-inoculation treatment significantly enhanced plant height, nodulation, dry biomass and increased macroelements content (N, P and K) and microelements content (Zn, Mn, Fe and Cu) over single inoculation and control at 30 and 60 days of sowing. The treatments T4 and T3 recorded the highest values at all growth stages, they recorded 241.00 and 225.66 μg TPF g-1 soil day-1 at 30 days and 249.33 and 235.00 μg TPF g-1 soil day-1 at 60 days and 203.66 and 179.66 μg TPF g-1 soil day-1 at harvest for dehydrogenase activity. Also, phosphatase activity in soil generally reduced with the aging of the plant. Similar trend are showed for seed yield and quality assessment.

Therefore, co-inoculation with R. leguminosarium sembiovar phaseoli and P. koreensis could be an effective biofertilization for common bean plant production.