Quantitative interactions: the disease outcome of Botrytis cinerea across the plant kingdom

Botrytis cinerea is a fungal pathogen that causes necrotic disease on more
than a thousand known hosts widely spread across the plant kingdom. How B.
cinerea interacts with such extensive host diversity remains largely
unknown. To address this question, we generated an infectivity matrix of
98 strains of B. cinerea on 90 genotypes representing eight host plants.
This experimental infectivity matrix revealed that the disease outcome is
largely explained by variations in either the host resistance or pathogen
virulence. However, the specific interactions between host and pathogen
account for 16% of the disease outcome. Furthermore, the disease outcomes
cluster among genotypes of a species but are independent of the
relatedness between hosts. When analyzing the host specificity and
virulence of B. cinerea, generalist strains are predominant. In this
fungal necrotroph, specialization may happen by a loss in virulence on
most hosts rather than an increase of virulence on a specific host. To
uncover the genetic architecture of Botrytis host specificity and
virulence, a genome-wide association study (GWAS) was performed and
revealed up to 1492 genes of interest. The genetic architecture of these
traits is widespread across B. cinerea genome. The complexity of the
disease outcome might be explained by hundreds of functionally diverse
genes putatively involved in adjusting the infection to diverse hosts.