Abstract:
The genus Calonectria includes many important plant pathogens with a wide global distribution. In order
to better understand the reproductive biology of these fungi, we characterised the structure of the mating type locus
and flanking genes using the genome sequences for seven Calonectria species. Primers to amplify the mating type
genes in other species were also developed. PCR amplification of the mating type genes and multi-gene phylogenetic
analyses were used to investigate the mating strategies and evolution of mating type in a collection of 70 Calonectria
species residing in 10 Calonectria species complexes. Results showed that the organisation of the MAT locus and
flanking genes is conserved. In heterothallic species, a novel MAT gene, MAT1-2-12 was identified in the MAT1-2
idiomorph; the MAT1-1 idiomorph, in most cases, contained the MAT1-1-3 gene. Neither MAT1-1-3 nor MAT1-2-12
was found in homothallic Calonectria (Ca.) hongkongensis, Ca. lateralis, Ca. pseudoturangicola and Ca. turangicola.
Four different homothallic MAT locus gene arrangements were observed. Ancestral state reconstruction analysis
provided evidence that the homothallic state was basal in Calonectria and this evolved from a heterothallic ancestor.
