The 'Dr Jekyll and Mr Hyde fungus': noble rot versus gray mold symptoms of Botrytis cinerea on grapes

Abstract

Many cryptic species have recently been discovered in fungi, especially in fungal plant pathogens. Cryptic fungal species co-occurring in sympatry may occupy slightly different ecological niches, for example infecting the same crop plant but specialized on different organs or having different phenologies. Identifying cryptic species in fungal pathogens of crops and determining their ecological specialization are therefore crucial for disease management. Here, we addressed this question in the ascomycete Botrytis cinerea, the agent of gray mold on a wide range of plants. On grape, B. cinerea causes severe damage but is also responsible for noble rot used for processing sweet wines. We used microsatellite genotyping and clustering methods to elucidate whether isolates sampled on gray mold versus noble rot symptoms in three French regions belong to genetically differentiated populations. The inferred population structure matched geography rather than the type of symptom. Noble rot symptoms therefore do not seem to be caused by a specific B. cinerea population but instead seem to depend essentially on microclimatic conditions, which has applied consequences for the production of sweet wines.

Keywords: Ascomycete; Botrytis cinerea; genetic structure; gray mold; microsatellites; noble rot; population structure.

Figure 1

Barplots of the Structure analysis without any prior information (A), with the symptom as prior information (B) or with the geographic origin as prior information (C).

Figure 2

Scatter plot of the DAPC analysis without any prior information (A), and comparison of individual assignment between DAPC and Structure analyses without prior information (B). Individuals are considered assigned to a cluster if their posterior probability in that cluster is at least 0.75.

Figure 3

Scatter plot of the DAPC analysis with the geographic origin of isolates as prior information (A), and comparison of individual assignment between DAPC and Structure analyses with geography as prior information (B). Individuals are considered assigned to a cluster if their posterior probability in that cluster is at least 0.75.

Figure 4

Proportions of individuals assigned to the three clusters inferred with Structure using geographic prior information, in each of the three sampled regions. Light gray: cluster K1, dark gray: cluster K2, black: cluster K3, white: admixed individuals. The different French vineyards are indicated.