An updated phylogenetic classification of Corynespora cassiicola isolates and a practical approach to their identification based on the nucleotide polymorphisms at the ga4 and caa5 loci

Abstract

ABSTRACT Corynespora cassiicola (Burk. & M.A. Curtis) C.T. Wei. is an anamorphic fungus that affects more than 530 plant species, including economically important crops. Several lineages of this pathogen have been recognized, but the classification of isolates into clades is time-consuming and still sometimes leads to unclear results. In this work, eight major phylogenetic clades (PhL1–PhL8) including 245 isolates of C. cassiicola from 44 plant species were established based on a Bayesian inference analysis of four combined C. cassiicola genomic loci retrieved from GenBank, i.e., rDNA internal transcribed spacer (ITS), actin-1,ga4, and caa5. The existence of PhL1–PhL5 and PhL7 as clonal lineages was further confirmed through the analysis of full-genome single-nucleotide polymorphisms of 39 isolates. Haplotypes of the caa5 locus were PhL specific and encode isoforms of the LDB19 domain of a putative α-arrestin N-terminal–like protein. Evolution of the Caa5 arrestin is in correspondence with the PhLs. ga4 and caa5 PhL consensus sequences and a cleaved amplified polymorphic sequence (CAPS) procedure were generated based on the conserved nucleotide sequences and enzyme restriction patterns observed among isolates from the same lineage, respectively. The CAPS method was validated in silico, and its practical use allowed us to differentiate between tomato and papaya isolates, as well as to reveal the prevalence of PhL1 among isolates infecting soybean in Brazil. This novel approach could be useful in the efforts to control the diseases associated with C. cassiicola.