First report of corn kernel brown spot disease caused by Mucor irregularis in China.

In October 2012, a brown spot disease was found on corn kernels during a field survey in Nanyang city (33°01′ N, 112°29′ E), China. The incidences of affected ears and kernels were 2 to 10% (n = 600) and 0.08 to 0.4% (n = 25,000), respectively. Symptoms first appeared as circular or irregular brown spots on the endosperm. These spots subsequently enlarged or coalesced, resulting in the formation of a large light-brown or light-yellow irregular speckle commonly surrounded by a dark-brown edge. Pure fungal cultures with similar morphological characteristics were obtained from surface-disinfected symptomatic kernels using a conventional method for isolation of culturable microbes. The isolated fungal cultures were purified by single-spore isolation (3). A representative isolate F1 was randomly selected, used for pathogenicity tests, and identified using morphological and molecular methods. Colonies on PDA were circular with abundant villiform aerial mycelia. The color of colonies was white-gray at first and ...