First report of race 3 of Bipolaris zeicola on corn in China.
In Meixian County of Shaanxi, China, during summer 2002, mature maize plants in a field plot showed severe leaf spot symptoms. The lesions were narrow (3.5-18 mm long and 0.4-1.5 mm wide), grayish tan, and surrounded by a light- to dark-pigmented border. Leaves wilted when lesions coalesced. From 2002 to 2005, the disease was observed in other Shaanxi Province counties, including Yangling, Wugong, Qianxian, Longxian and Qianyang, although in most cases, symptom development was less severe than it was in Meixian. Seven isolates from 4 counties were obtained by isolation from host tissue on potato dextrose agar (PDA), followed by single-spore culturing and incubation on PDA at 25°C in the dark for 7 days. On the basis of pathogenicity, morphology and random amplified polymorphic DNA (RAPD) band patterns of primer A20, the fungus was confirmed as B. zeicola [Cochliobolus carbonum]. The shape of leaf lesions and RAPD band patterns using primer A03 showed further that the pathogen was race 3 of B. zeicola. This is thought to be the first report of race 3 in China.