Pathogen Identification of Small Leaf Spots on Sweet Corn Plants in Fujian

Sweet corn (Zea mays L.) is one of the most important economic crops in Fujian Province. The small leaf spots on the leaves from filamentous fungal infection significantly affect the yield and quality of the corn. To identify the pathogenic agents that caused the disease on sweet corns is essential for the disease control and prevention. Using the single-spore isolation methodology, 103 fungal species were obtained from the corn leaves showing typical small spots (lesion length < 5 mm) in Fuzhou, Putian, Zhangzhou, Nanping and Ningde, where the major corn-growing regions in Fujian are located. After a preliminary morphological observation, 8 representative isolates were selected for further examinations. Among them, 5 were morphologically identical to Bipolaris maydis, and 3 highly resembled Curvularia spp. A pathogenic assay on all plants inoculated with the pathogens exhibited similar symptoms as observed on the diseased corns in the field. The rDNA-ITS sequences of 5 isolates were subsequently identified as B. maydis, two as C. lunata, and one as C. eragrostidis. It suggested that the microorganisms that caused the small leaf spots on sweet corns in Fujian were any of those identified. For Fujian, to report C. eragrostidis as culprit of the disease was the first time in China. The degrees of virulence of the 8 identified isolates varied significantly toward 8 different corn varieties.