Inhibition of the development of Rhizoctonia solani by plant secondary metabolites – a laboratory study

Summary in the original language of the document

Black scurf and stem canker on potatoes, caused by the destructive soil-borne pathogen Rhizoctonia solani Kühn are a major problem for potato growers worldwide. Biological control agents such as plant leaf extracts can influence
the severity of R. solani infection and help to reduce the risks to human health and the environment associated with the use of chemical fungicides. In this study, the inhibitory effect of the secondary plant metabolites aucubin, catalpol (iridoid glucosides) and acteoside (phenylethanoid glycoside) from methanolic extracts of Plantago lanceolata (Ribwort plantain (en), Smalkjempe (no)), a native plant in the Nordic countries, on the growth of R. solani mycelium on potato dextrose agar growth medium will be tested for the first time. Plant extracts will
be obtained from plants of different age classes and metabolic profiling will be performed with LC-(HR)MS analyses and the concentrations of identified metabolites will be determined. To analyse whether the inhibitory interactions on fungal growth originate from the known secondary metabolites or are caused by the bulk
plant extract, we will first expose the fungus to different concentrations of extracts, redissolved in aqueous solution and added to the growth medium, and in a further step we will carry out the same approach with the isolated secondary
metabolites as pure substances. The fugus will be incubated for 5 days and the mycelium growth radius will be measured every 24 hours during incubation. Thereafter a suppression index will be calculated and compared to the untreated
control. The results are pending at the time of submission of the abstract but will provide a good initial understanding to determine whether extracts of P. lanceolata can be used as a natural biological control agent as an additional component of a more sustainable strategy
to manage the risk of infection of potato with R.solani and to reduce the severity of the disease caused by this pathogen.