The draft genome sequence and characterization of Exserohilum rostratum, a new causal agent of maize leaf spot disease in Chinese Mainland.

Corn is one of the most important crops globally. A new maize leaf spot disease (Exserohilum leaf spot) caused by Exserohilum rostratum has been found frequently in the Henan Province of China during the surveys of fungal diseases of maize between 2017 and 2020. A total of four Exserohilum isolates were obtained from the typical disease spots of corn leaves, which were all identified as pathogenic by inoculation tests based on Koch's postulates. They can produce three distinctive types of conidia (A, B and C) when cultured in dark on the water agar medium with corn leaves for seven days. Based on their morphological characters and the sequence analysis of ITS, LSU, gapdh, tef1 and rpb2 gene regions, all these isolates undoubtedly belong to the species E. rostratum. To our knowledge, this is the first report of maize leaf spot caused by E. rostratum in China. Studies on the biological properties of E. rostratum showed that PDA medium, 25–30 °C, pH 6–9, and continuous light are the optimal conditions for its mycelial growth. The best carbon and nitrogen sources were starch and yeast extract, respectively. Here, we also presented the genomic assembly of E. rostratum with a size of 36.34 Mb, which is the first reported genome sequence of E. rostratum isolated from infected plant tissue. All the above research results would provide a theoretical basis for the comprehensive control of Exserohilum leaf spot disease of corn. [ABSTRACT FROM AUTHOR]