Mating type and spore killing characterization of Fusarium verticillioides strains

Abstract

Fusarium verticillioides is a heterothallic ascomycete causing maize ear rot, and produces fumonisin mycotoxins harmful to livestock and human health. A meiotic drive phenomenon called spore killing has been reported in several filamentous fungi including F. verticillioides. F. verticillioides reference genome strain M-3125 (FGSC 7600) is spore killer sensitive (SK S ), and genetic crosses of M-3125 with a strain carrying SK K (the killer element) result in only four viable ascospores per ascus instead of the normal eight ascospores. We sought to identify a strain of F. verticillioides that is SK S and MAT1-2 for use in genetic analysis with M-3125. To accomplish this, we screened 50 F. verticillioides strains from the Fusarium Research Center at The Pennsylvania State University, USA for spore killing. To characterize the mating types of these strains, portions of the MAT locus idiomorphs were amplified using polymerase chain reaction, and genetic crosses were performed. The PCR amplification results show that 18 of the 50 strains are MAT1-2 and 32 are MAT1-1. Genetic crosses between M-3125 and 11 of the 18 MAT1-2 strains produced normal perithecia. Crosses between two (M-8024 and M-7815) of the 11 strains and M-3125 produced perithecia with eight ascospores per ascus, and nine others had only four ascospores per ascus, suggesting that M-8024 and M-7815 are SK S and the other nine are SK K . This study expands our knowledge of mating type and spore killing in F. verticillioides and identifies two SK S , MAT1-2 strains for use in genetic crosses with genome reference strain M-3125.