| Soybean is one of the most important crops in the global market and is the leading agricultural export of the United States. However, yield is compromised by frogeye leaf spot, with losses of 10-60% reported in the U.S. Frogeye leaf spot is caused by the fungal pathogen Cercospora sojina K. Hara. Although C. sojina is not known to reproduce sexually, cryptic sexual reproduction was recently postulated among closely related species based on the mating type distribution. Fungi that reproduce both sexually and asexually have a high evolutionary potential and are more likely to overcome genetic resistance. The purpose of this study was to develop a PCR assay which may be used to rapidly screen isolates of C. sojina for mating type and to evaluate the mating type distribution of populations in Arkansas. A multiplex PCR assay was developed using primers designed to amplify partial regions of the MAT1-1 and MAT1-2 idiomorphs and the internal transcribed spacer region of rDNA. The latter was used to test for the presence of amplifiable DNA. The assay was used to categorize 545 isolates into mating types. These isolates were collected in two locations in Arkansas, namely Kibler and Wynne. Although both mating types were present at both locations, their distribution deviated significantly from the expected 1:1 ratio of a sexually reproducing population. The described assay could be used for high throughput screening of isolates for mating type. The study is the first to provide insight into the population dynamics of C. sojina in Arkansas, which may aid attempts to develop effective genetic resistance. |
