Antagonistic effect of Pseudomonas spp. on pathogenic fungi and enhancement of growth of green gram (Vigna radiata)

Pseudomonas species were isolated from the rhizosphere of green gram [Vigna radiata (L,) Wilczek] and some of the rhizobacterial isolates were found t o have a wide: range of antifungal activity inhibiting growth of the phytop athogenic fungi Aspergillus sp., Curvularia sp.. Fusarium oxysporum and Rhi zoctonia solani in culture. These isolates also showed slight inhibition of the growth of a Bradyrhizobium strain (Vigna) in a spot test which was mai nly a result of nutrient competition as culture supernatants of the Pseudom onas isolates did nor inhibit the growth of bradyrhizobia but inhibited the growth of fungi. The rhizobacterial isolates produced siderophores in Fe-d eficient succinate medium. However, the inhibition of fungal growth by diff erent Pseudomonas isolates in Luria Bertani and King's medium B which were not limiting in Fe3+ ions suggested that, besides siderophores, other antif ungal compounds (antibiotics) produced by these rhizobacteria were involved in antagonism On coinoculation of green gram with Pseudomonas strains MRS1 3 and MRS16 and Bradyrhizobium sp. (Vigna) strain S24, there was a signific ant increase in nodule weight, plant dry weight and total plant N as compar ed to inoculation with Bradyrhizobium strain S24 alone, suggesting that the nodule-promoting effects of Pseudomonas sp. lead to an increase in symbiot ic N fixation and plant growth.