Expression of phosphate solubilizing genes in rhizobium transconjugants

Rhizobium as a Gram-negative bacteria play a significant role in phosphate solubilization. This study was designed to identify phosphate-solubilizing ability of Rhizobium transconjugants. About 10 of Rhizobium wild types were isolated from fenugreek and lentil hosts. The strains are genetically marking based on their resistance or sensitivity to different antibiotics. Conjugation was done between both strains nodulating the opposite hosts that harboring the opposite genetic markers. Eight conjugations were done, from each, eight recombinant transconjugants were evaluated for phosphorus solubilizing abilityon medium supported with tri-calcium phosphate as insoluble source of phosphate. Most transconjugants derived from the conjugations between P2 x P6 and P5 x P7 revealed high capacity in P solubilization after six days of incubation time and then auto consumption at nine days. All transconjugants derived from the conjugations between P3 x P7, P3 x P9, P4 x P6 and P4 x P7 appeared gradually increase in P solubilization till reached the maximum at nine days. High heritability estimates coupled with high genetic advance as a percent of mean were obtained in P solubilization at all time intervals, indicating the main impact of genetic effects on the gene expression of P solubilization. All Rhizobium transconjugants having a broad host range among fenugreek and lentil with better nodulation ability on both hosts. All transconjugants improved plant growth parameters in relation to both controls and their mid-parents. The results position Rhizobium recombinants as an excellent biofertilizer in sustainable agriculture to establish an effective nitrogen-fixing root nodule symbiosis with a broad host range.