Thielaviopsis ethaceticathe etiological agent of sugarcane pineapple sett rot disease in Brazil

Sugarcane pineapple rot is an important sugarcane stem disease that also affects germination and sprouting. In Brazil, the disease is caused by Thielaviopsis paradoxa sensulato which has been split into at least five distinctive phylogenetic and biological species in the reinstated genus Thielaviopsis. In this study, three purported strains of T. paradoxas. lat. isolated from sugarcane stems were characterized and compared with a strain from pineapple fruit, using morphology, DNA sequence analyses and sexual compatibility tests. Inoculations were also performed on asymptomatic stems of plants to assess the pathogenicity of the four fungal strains on sugarcane. Based on results of the phylogenetic analyses of combined ITS and TEF-1a gene sequences, the strains were identified as T. ethacetica. This was also supported by sexual compatibility tests, as crossings between the pineapple strain and some sugarcane strains resulted in the formation of perithecia exuding ascospore masses at their apices. The inoculation test on sugarcane resulted in stem rot and in reduced germination of buds. Thielaviopsis ethaceticais thus the species causing pineapple sett rot disease in Brazil.