Biological Control Potential of Trichoderma Species and Bacterial Antagonists against Sclerotinia sclerotiorum on Canola in Western Australia

Fifteen fungal and three bacterial biological control agents (F-BCA and B-BCA, respectively) were isolated from the canola production areas of Western Australia to investigate their potential for controlling sclerotinia stem rot (SSR) caused by Sclerotinia sclerotiorum under in vitro and field conditions. The capacity of these isolates to inhibit mycelial growth and sclerotia formation by S. sclerotiorum was assessed in dual culture tests in Petri dishes. Using Sanger Sequencing of the ITS regions, the F-BCAs were identified as Trichoderma atroviride (four isolates), T. gamsii (three isolates), T. koningiopsis (two isolates), T. longibrachiatum (two isolates), T. paraviridescens (two isolates), T. pseudokoningii (one isolate) and T. viridescens (one isolate). Four of the seven Trichoderma species (T. koningiopsis, T. gamsii, T. atroviride and T. viridescens) are reported for the first time from Western Australia. 16S rRNA sequencing identified B-BCA1 and B-BCA2 as Serratia proteamaculans and B-BCA3 as Ochrobactrum anthropi. There were significant differences among F-BCAs (P≤0.001) in their effect on radial mycelial growth (40–60% inhibition) and sclerotia formation (65–100% inhibition). Two isolates of T. atroviride (F-BCA12 and F-BCA15) completely blocked sclerotial formation of the pathogen on Potato dextrose agar + 10 ppm/L Aureomycin (PDAA). Incubation of sclerotia in soil inoculated with F-BCA indicated that sclerotia were colonized by the conidia of each F-BCA, and all sclerotia in the presence of F-BCAs failed to germinate on PDAA. The B-BCAs reduced radial mycelial growth by 57–59% and formation of sclerotia by 89–95%. Selected isolates of F-BCAs (T. koningiopsis and T. atroviride) and B-BCAs (O. anthropi and S. proteamaculans) significantly reduced disease incidence of S. sclerotiorum under glasshouse and field conditions. Field efficacy of tested BCAs was similar or better than the commercial fungicide Prosaro®. © 2022 Friends Science Publishers