Modeling quantitative interactions: the disease outcome of generalist
fungal pathogen 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, a
genome-wide association study (GWAS) was performed and revealed 124
genes associated with host specificity and virulence. The genetic
architecture of these traits is distinct, polygenic and widespread
across B. cinerea genome. The complexity of the disease outcome is best
explained by the additivity of small effect genes that adjust the
infection to diverse hosts.