Antagonizing Impact of Endophytic Fungal Isolates against Potato Black Scurf (Rhizoctonia solani)

Abstract

Four endophytic fungal isolates, naturally associated with Solanum tuberosum L., were evaluated for their antagonistic activity against Rhizoctonia solani and their ability to suppress black scurf disease of potato tubers. To identify the potential implication of antifungal compounds in their inhibitory activity, cell-free culture filtrates were produced and tested for their antifungal potential against R. solani mycelial growth and for their protective effect against development of on potato tuber slices.  Results showed that percent inhibition of R. solani mycelial growth, based on in vitro antibiosis tests, ranged between 16 to 59%. Hyphal damage and lysis were the most frequent stress responses exhibited by the target pathogen during its in vitro interactions with the potato-associated fungi tested. All Cell-free culture filtrates of tested fungi had significantly inhibited the radial growth of Rhizoctonia solani Rs20. The cell-free culture filtrates of Penicillium chrysogenum and Aspergillus niger had decreased pathogen growth by more than 60% over control. These two filtrates (P. chrysogenum and A. niger) were found to be the most effective in decreasing the decay incidence in potato slices by 36 and 40%, respectively, as compared to pathogen-inoculated and untreated control. Thus, the present study clearly demonstrated that fungal isolates, occurring ubiquitously within potato plants, may be explored as potent biocontrol agents against potato-associated fungal pathogens and as source of bioactive metabolites for R. solani suppression.