Penicillium pinophilum has the Potential to Reduce Damping-off Caused by Rhizoctonia solani in Sugar Beet

Rhizoctonia solani is an economically important pathogen of sugar beet (Beta vulgaris L.) causing seedling damping-off, and root and crown rot. Cultural practices, partially resistant cultivars, and fungicides are among the methods most used to manage R. solani. Penicillium pinophilum, a potential biocontrol agent for Rhizoctonia damping-off, was isolated from sugar beet. Our objective was to evaluate the biocontrol potential of P. pinophilum against R. solani AG 2-2 under laboratory and greenhouse conditions. In vitro co-culture of both fungi showed that R. solani growth was inhibited by P. pinophilum. A greenhouse inoculation study was done using sclerotia of R. solani and a conidia suspension of P. pinophilum to evaluate the response of a Rhizoctonia susceptible cultivar. Treatments included R. solani sclerotia, P. pinophilum conidia suspension, a combination of R. solani sclerotia with P. pinophilum conidia suspension, and a mock inoculation with water (control). One 2-cm deep furrow was made in the middle of peat filled trays into which 10 seeds were planted. Each treatment was applied adjacent to each seed and covered with peat. There were four replicates per treatment arranged in a completely randomized design. The sole sclerotia treatment caused 75% damping-off and severe root rot on surviving plants whereas the combination of sclerotia with P. pinophilum conidia suspension reduced damping-off by 50%. No damping-off incidences were observed with the P. pinophilum conidia suspension or the mock-inoculated control. It was concluded that P. pinophilum has the potential to reduce damping-off caused by R. solani but use of the most appropriate P. pinophilum concentration and its mitigation mechanisms need further studies.