Antagonistic and growth enhancement activities of native Pseudomonas spp. against soil and tuber-borne diseases of potato (Solanum tuberosum L.).

Background: Soil and tuber-borne diseases are serious threat for potato cultivation worldwide which causes severe economical losses in terms of yield, quantity and quality. Generally, these diseases managed by chemical pesticide, are a major concern for human health and environment. Therefore, finding an eco-friendly alternative management strategies are necessary. The native bacterial isolates collected from different crops rhizosphere soil were evaluated against Rhizoctonia solani, Sclerotinia sclerotiorum, Sclerotium rolfsii and Fusarium spp and were also tested for their growth enhancement attributes on potato crop and phosphate solubilising efficiency. Results: Based on the morphological and phenotypic characters, most of the isolates were identified as Pseudomonas spp (18 isolates). A total of twenty-two bacterial isolates were screened for bio-control activity in dual culture assay. Isolate Pf14 showed the highest mycelial inhibitory potential (ranged from 62.2 to 59.3%) against R. solani, S. sclerotiorum, S. rolfsii and Fusarium spp. In sealed plate assay, Pf14 produced antifungal volatile compounds that significantly inhibited mycelial growth (ranged from > 80 to > 50%). Maximum reduction in fungal biomass (ranged from > 80%) was observed in King's broth in shake liquid culture in all the pathogens. Cell-free culture filtrate of the selected isolate inhibited mycelial growth ranged from 68.9 to 42.6% of the tested pathogens with 48-h old culture filtrate. Additionally, the isolates exhibited higher phosphorus solubilizing efficiency on PVK media. Under field conditions, talc based formulation of Pf14 showed enhanced agronomical characters and inhibits black scurf severity up to 67.59%. This treatment also recorded a highest tuber yield (21.90 t/ha) with increase of 15.38% in comparison to untreated control. Conclusion: Overall, antagonistic bacterium Pf14 can be recommended as bio fertilizers for eco-friendly management of major potato fungal diseases as well as increasing marketable yield and used as an alternative to the pesticides and chemical fertilizers. [ABSTRACT FROM AUTHOR]