The polyphagous plant pathogenic fungusBotrytis cinereaencompasses host-specialized and generalist populations

Abstract

The host plant is often the main variable explaining population structure in fungal plant pathogens, because specialization contributes to reduce gene flow between populations associated with different hosts. Previous population genetic analysis revealed that French populations of the grey mould pathogen Botrytis cinerea were structured by hosts tomato and grapevine, suggesting host specialization in this highly polyphagous pathogen. However, these findings raised questions about the magnitude of this specialization and the possibility of specialization to other hosts. Here we report specialization of B. cinerea populations to tomato and grapevine hosts but not to other tested plants. Population genetic analysis revealed two pathogen clusters associated with tomato and grapevine, while the other clusters co-occurred on hydrangea, strawberry and bramble. Measurements of quantitative pathogenicity were consistent with host specialization of populations found on tomato, and to a lesser extent, populations found on grapevine. Pathogen populations from hydrangea and strawberry appeared to be generalist, while populations from bramble may be weakly specialized. Our results suggest that the polyphagous B. cinerea is more accurately described as a collection of generalist and specialist individuals in populations. This work opens new perspectives for grey mold management, while suggesting spatial optimization of crop organization within agricultural landscapes.

Population Genomics Reveals Molecular Determinants of Specialization to Tomato in the Polyphagous Fungal PathogenBotrytis cinereain France

“…Previous work using microsatellite data revealed differentiation between populations of B. cinerea collected on tomato and grapevine (Mercier et al . 2019; Walker et al .…”

“…No pattern of geographical subdivision was observed, consistent with previous findings (Walker et al . 2015); Mercier et al ., 2019). The neighbor-net network inferred with SPLITSTREE revealed three main groups, corresponding to the three main clusters identified with S NMF, with cluster G2 (isolates Vv8, Vv9, Vv11 and Vv15) more closely related to T than to G1 (Figure 1B).…”

“…In two recent studies comparing the aggressiveness of isolates coming from diverse hosts, the disease severity caused by isolates from tomato was significantly greater than the severity caused by isolates from grape or other crops, thus indicating that B. cinerea populations parasitizing tomato were specialized to this host (Bardin et al . 2018; Mercier et al . 2019).…”

“…2015; Mercier et al ., 2019). For each region and each host, we randomly selected three to nine isolates with high membership proportions ( q >0.9) in the cluster matching their host of origin in a previous analysis of population structure based on microsatellite genotyping (Table 1; Mercier et al . 2019).…”

A molecular epidemiology study reveals the presence of identical genotypes on grapevines and ground cover weeds and the existence of separate genetic groups in a Botrytis cinerea population

“…cinerea is considered a highly polyphagous pathogen, with a range of 586 host plant genera (Elad et al ., 2016), even though signatures of specialization of B . cinerea populations to tomato and grapevine hosts have been observed (Mercier et al ., 2019).…”