First Report of Alternaria alternata Causing Leaf Spot on Ipomoea purpurea in China

Ipomoea purpurea is widely used as an ornamental plant and in traditional Chinese medicine in China. Seed is used in treating edema and anuria, dispelling phlegm. In June 2016, severe leaf spot disease on I. purpurea with 30% disease incidence was observed in the Laoshan Mountain of Qingdao, China. Symptoms on leaves initially appeared as light to dark brown, necrotic spots with yellow borders or no borders. The spots gradually enlarged in size, becoming irregular. Tissue samples were taken from the margins of lesions, cut into small pieces, surface-disinfected with 70% ethanol for 30 seconds, rinsed with sterile water three times, placed on potato dextrose agar (PDA), and incubated at 25°C in the dark. A total of 10 isolates were obtained from 13 symptomatic leaf samples. Thereafter, 10 single spore isolates were obtained as described (Dong 2009) and transferred onto a potato carrot agar (PCA) medium (Mirkova 2003). After six days of growth on PCA at 25°C in the dark, colonies had round margins and aeria...