Synergistic/antagonistic interactions between Neopseudocercosporella, Alternaria, Leptosphaeria, and Hyaloperonospora determine aggregate foliar disease severity in rapeseed

Abstract

White leaf spot (Neopseudocercosporella capsellae), Alternaria leaf spot (Alternaria brassicae), blackleg (Leptosphaeria maculans), and downy mildew (Hyaloperonospora brassicae) commonly co‐occur on rapeseed (Brassica napus). In controlled environment studies, the synergistic/antagonistic interactions between these four pathogens were determined using two cultivars (Surpass 400, Thunder TT) with contrasting susceptibilities/resistances towards these pathogens. A spectrum of significant (p < 0.001) contrasting synergistic/antagonistic interactions between the four pathogens was observed and specific pathogen–pathogen interaction outcomes were determined by sequence of inoculation of different pathogens on each cultivar. On Thunder TT, Alternaria leaf spot was more severe (p < 0.001) when A. brassicae was applied prior to N. capsellae, but was reduced (p < 0.001) when A. brassicae was applied following N. capsellae. On Surpass 400, Alternaria leaf spot was enhanced (p < 0.001) when A. brassicae was applied following N. capsellae. For interactions involving H. brassicae on Thunder TT, downy mildew was reduced (p < 0.001) when co‐inoculated with N. capsellae, A. brassicae, or L. maculans, irrespective of co‐inoculating pathogen application sequence. This study highlights how disease severity of one or more co‐occurring pathogens is enhanced/decreased in the presence of other co‐occurring pathogens and emphasizes the importance of both pathogen inoculation sequence and relative host plant resistances/susceptibilities to different pathogens in together determining the total disease burden from these co‐occurring rapeseed diseases. Clearly, there is a need for rapeseed germplasm selection and breeding programmes to seriously consider the implications of co‐occurring pathogen complexes rather than solely relying upon single‐pathogen screening tests.

Correlation between fine root traits and pathogen richness depends on plant mycorrhizal types

“…In the natural environment, plants are generally confronted with multiple pathogens with diverse modes of action (Abdullah et al 2017), and synergistic pathogenicity in plants has been widely detected (López‐Villavicencio et al 2011, Tollenaere et al 2012, Zhang et al 2018, Murtza et al 2022). As a higher richness of soil pathogens may mean a greater possibility of pathogen co‐infection, a stronger negative PSF may be observed (Semchenko et al 2018).…”

Artificial Cultivation Changes Foliar Endophytic Fungal Community of the Ornamental Plant Lirianthe delavayi

“…Previously, white leaf spot ( Neopseudocercosporella capsellae , Mycosphaerellaceae), and Alternaria leaf spot ( Alternaria brassicae ), as well as other fungal pathogenic species, commonly co-occur in rapeseed ( Brassica napus ). In controlled environment studies, Alternaria leaf spot was reduced on cultivar Thunder TT of B. napus when A. brassicae was applied following N. capsellae inoculation, suggesting an antagonistic interaction between these two pathogens [ 63 ].…”