Pot and field assessment of the symbiotic performance of new identified rhizobium strains nodulating common bean (Phaseolus vulgaris L.) in Egypt under nitrogen and phosphorus fertilization

Two strains (EBRI 2 and EBRI 26) belong to Rhizobium etli species and one strain (EBRI 32) belong to Rhizobium gallicum were identified among 12 Rhizobium isolates isolated from nodulated roots of common bean (Phaseolus vulgaris L.). Pot experiments were carried out to select the high efficient nitrogen fixing Rhizobium strains and these results revealed that there is a high degree of strain-cultivar compatibility whereas strain CIAT 899 and TAL 1367 were the best forming nodules with Giza 3, strains EBRI 2 and EBRI 32 were the superior nodule forming with Giza 6 and strain EBRI 32 gave the highest nodule record with Giza xbB 201. The addition of nitrogen fertilizer was associated with reduction in nodule numbers with the examined strains especially at high levels of N (60 kg N fed-¹) while the low dosage (15 kg N fed-¹) promoted nodule formation with cultivar Giza 6. On the contrary, the application of phosphorus fertilization was markedly increased nodule numbers and dry weight with higher dose of Phosphorus. A field trial was applied in a clay soil characterized by high pH at El-Shohada, in El Menoufia governorate in the middle of Delta Nile Valley as a major productive site for common bean as dry seeds or green vegetables. Under field conditions, there was a response to inoculation with Rhizobium strains and the native Egyptian strains were equal in its effect for forming nodules except strain EBRI 2, gave the highest record while these native strains produced seed yield higher than those obtained by reference strains.