Global insight into the distribution of velvet-like B protein in Cochliobolus species and implication in pathogenicity and fungicide resistance.

The Cochliobolus genus consist of over 55 species among which the 5 most devastating are Cochliobolus carbonum, Cochliobolus heterostrophus, Cochliobolus miyabeanus, Crocus sativus and Cochliobolus lunatus causing damages in sorghum, wheat, rice, maize, cassava and soybean estimated at over 10 billion USD per annum worldwide. The dynamic pathogenicity of Cochliobolus species and the plethora of infected hosts is determined by the evolution of virulence determinants such as the velvet-like B protein (VelB). Nonetheless, the knowledge on the distribution of Cochliobolus VelB and its implication in pathogenicity and fungicide resistance are often lacking. By scanning through the annotated genomes of C. lunatus, C. heterostrophus, C. carbonum, C. victoriae, C. sativus and C. miyabeanus, it is revealed that the numbers of ortholog VelB and cognates vary. By using the phylogenetic approach, it is established that the diversification rates among velvet-domain-containing proteins for phytopathogenic Cochliobolus species could impact differently on their oxidant and fungicide resistance potentials, ability to form appressoria-like structures and infection pegs during infection. This study provides new insights into the pathogenicity evolution of Cochliobolus species at the VelB locus which is relevant for designing effective strategies for durable management of Cochliobolus diseases.