Bioactivity of an extract from the endophyte Diaporthe infecunda on soybean seeds inoculated with Colletotrichum truncatum and Sclerotinia sclerotiorum

Colletotrichum truncatum and Sclerotinia sclerotiorum are fungal pathogens that can be disseminated by soybean seed, and they are usually controlled by seed treatment with fungicides. However, due to the harmful effects of pesticides on the environment and human health, the search for alternative methods to control seed-borne pathogens is necessary. Thus, this study evaluated whether the extract of Diaporthe infecunda , an endophyte from Schinus terebinthifolius leaves, inhibits the growth of C. truncatum and S. sclerotiorum, and improves the sanitary quality of soybean seeds. Initially, diffusion in agar assays with a D. infecunda extract were carried out. It was shown that the extract results in an inhibition of 94.4% and 83.8% of mycelial growth of C. truncatum and S. sclerotiorum , respectively . In a second study, soybean seeds were artificial inoculated with C. truncatum and S. sclerotiorum separately for each pathogen species with a water restriction technique using mannitol. The treatments consisted of: T1 = synthetic fungicide (thiophanate-methyl + fluazinam); T2 = D. infecunda extract (10 mg mL −1 ); T3 = solvent only (methanol:water); T4 = D. infecunda extract + fungicide; T5 = non-treated seeds; T6 = non-inoculated and non-treated seeds. The incidence of C. truncatum and S. sclerotiorum was reduced with the use of D. infecunda extract (12% and 10%, respectively) compared to the non-treated seeds (35% and 52%, respectively). However, there was a decrease in the seed germination with the D. infecunda extract. In conclusion, the extract of D. infecunda has potential to be used in seed treatment of soybean to control C. truncatum and S. sclerotiorum , however, further studies are required due to the decrease in seed germination.