Elevated genetic variation within virulence-associated Botrytis cinerea polygalacturonase loci

Area of Science:

• Mycology
• Plant Pathology
• Evolutionary Genetics

Background:

• Botrytis cinerea, or gray mold, is a widespread fungal pathogen impacting numerous plant species.
• Understanding the genetic diversity of B. cinerea is crucial for explaining its broad host range.
• Pathogenesis-associated genes, like cell-wall-degrading polygalacturonases (PGs), are key to fungal virulence.

Purpose of the Study:

• To investigate the level and structure of genetic variation at three polygalacturonase-encoding loci (BcPG1, BcPG2, BcPG3) in Botrytis cinerea.
• To determine if genetic variation at these loci is associated with host specialization or virulence.
• To explore the evolutionary forces shaping the genetic diversity of pathogenesis-related genes in B. cinerea.

Main Methods:

• Sequencing of three PG-encoding loci (BcPG1, BcPG2, BcPG3) in 34 B. cinerea isolates.
• Analysis of genetic variation and population structure within these loci.
• Correlation of sequence variation with virulence on Arabidopsis and growth rate on pectin.

Main Results:

• Limited evidence of host-mediated genetic subdivision was found within the studied PG loci.
• BcPG1 and BcPG2 exhibited high polymorphism, contrasting with conserved BcPG3.
• Sequence variation in BcPG1 and BcPG2 was not linked to virulence on Arabidopsis, but BcPG2 variation correlated with pectin growth rate.

Conclusions:

• The genetic variation at PG loci in B. cinerea does not strongly indicate host-specific adaptation.
• Evolutionary forces act differently across PG loci, with some showing high polymorphism and others conservation.
• Findings support PG specialization and diversification in response to host interactions, rather than broad host-mediated subdivision.