Etiology and Symptoms of Maize Leaf Spot Caused by Bipolaris spp. in Sichuan, China

Many species of the genus are important plant pathogens and often cause leaf spot, root rot, and seedling blight in an extremely wide range of hosts around the world. In recent years, maize leaf spot caused by species has frequently occurred with complex symptoms and is becoming increasingly serious in Sichuan Province of China. To investigate the population diversity of spp. and their corresponding symptoms in maize, 747 samples of maize leaf spot were collected from 132 sampling sites in 19 administrative districts of Sichuan Province from 2011 to 2018. Based on morphological characteristics, pathogenicity testing, and phylogenetic analysis of the rDNA internal transcribed spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes, a total of 1186 isolates were identified as , , , , and , among which and were the dominant pathogenic species, accounting for 57.34% and 42.07% of the isolates, respectively. We found that isolates were mainly distributed in high altitude and cool mountainous areas, while was more widely distributed in Sichuan Province. The typical symptoms caused by the species were clearly distinct in maize. The typical symptoms caused by were elongated strip lesions, or fusiform, elliptical lesions, and those caused by were narrow linear lesions. Herein, was first reported on maize and caused subrotund lesions. This study provides useful information for disease diagnosis and management for leaf spot in maize.