Genetic Diversity of Botrytis cinerea Revealed by Multilocus Sequencing, and Identification of B. cinerea Populations Showing Genetic Isolation and Distinct Host Adaptation

Abstract

Botrytis cinerea is a world-wide occurring plant pathogen, causing pre- and post-harvest gray mold rot on a large number of fruit, vegetable, and flower crops. B. cinerea is closely related to Botrytis pseudocinerea, another broad host range species which often occurs in sympatry with B. cinerea, and to several host-specific species including Botrytis fabae and Botrytis calthae. B. cinerea populations have been shown to be genetically heterogeneous, and attempts have been made to correlate genetic markers to virulence and host adaptation. Here, we present the development of a multilocus sequence typing (MLST) scheme, with 10 genes selected for high variability and phylogenetic congruence, to evaluate the genetic diversity of B. cinerea, B. fabae, and B. pseudocinerea. Using PacBio-assisted simultaneous mass sequencing of PCR products, MLST analysis of about 100 strains from diverse geographical origins and years of isolation was performed, which resulted in high-resolution strain differentiation and robust species separation. Several B. cinerea strains formed an as yet unknown population, referred to as group B, which was well separated from all other B. cinerea strains. Furthermore, the gene cluster for biosynthesis of the phytotoxin botcinic acid was missing in B. cinerea B strains. B. cinerea strains from the monocot Iris pseudacorus were found to form a genetically distinct population, and contained an intact gene cluster for production of the red pigment bikaverin, which is usually degenerated in B. cinerea. Remarkably, these strains were much more aggressive on Iris than other B. cinerea strains, which is the first unequivocal example for host specialization in B. cinerea. Our data reveal new insights into the genetic diversity of B. cinerea and provide evidence for intraspecific differentiation and different degrees of host adaptation of this polyphagous necrotrophic pathogen.

Multiple knockout mutants reveal a high redundancy of phytotoxic compounds that determine necrotrophic pathogenesis of Botrytis cinerea

“…Recently, we have discovered a group of B. cinerea field strains which lack the complete botcinin biosynthesis cluster. These strains are less virulent than other B. cinerea strains on tomato leaves but not on other host tissues (Plesken et al 2021). These data confirm that botrydial and botcinin together play a significant role for B. cinerea pathogenesis, but their mode of action is unknown, and their individual contributions to the infection process remain unclear.…”

Multiple knockout mutants reveal a high redundancy of phytotoxic compounds contributing to necrotrophic pathogenesis of Botrytis cinerea

“…These strains are less virulent than other B . cinerea strains on tomato leaves but not on other host tissues [ 63 ]. In the present study, the 12xbb mutant lacking bot2 and boa6 was significantly less virulent than its 10x mutant parent, on all host tissues tested except on maize leaves, and this mutant was confirmed to be unable to produce botrydial and botcinins, in contrast to the 10x mutant.…”

Mechanisms of Action of Microbial Biocontrol Agents against Botrytis cinerea

“…This has resulted in a separation into four genetically different types of B. cinerea inside the species: Boty or Fliper, depending on which element it possesses; trasposa if it has both elements; and vacuma if it has none of them. The fungi that possess transposable elements are more virulent, and even those belonging to the Boty type are able to release small RNAs that knock out some plant defense genes [18].…”