First Report of Anthracnose in Chinese Hickory (Carya cathayensis) Caused by Colletotrichum gloeosporioides in China.

Abstract

Chinese hickory (Carya cathayensis) has become one of the important economic forest crops in Zhejiang and Anhui Provinces in China. In May 2009, sporadic occurrence of leaf damage by anthracnose in C. cathayensis was observed in Lin'an city, Zhejiang Province. During May 2011, nearly 50% of Chinese hickory orchards in Zhejiang Province were affected by anthracnose disease. Symptoms were extensive with lesions on stems and leaves. Under wet conditions, orange masses of conidia were produced in acervuli in the center of lesions. Infected tissue samples were surface sterilized with 1.5% sodium hypochlorite for 1.5 min, plated on 2% potato dextrose agar (PDA), and incubated at 26°C in the dark for 1 week. Developing colonies were gray and contained masses of orange conidia. Conidia were hyaline, aseptate, straight with rounded or bulbous ends, and averaged 15.3 ± 1.7 μm long and 2.5 ± 0.8 μm wide. The ribosomal internal transcribed spacers ITS1 and ITS2 were amplified with primers ITS1/ITS4 from DNA extracted from mycelium and nucleotide sequences showed 100% similarity to records for C. gloeosporioides in GenBank (Accession Nos. AY266391.1 and JQ676187.1). Uninfected leaves of C. cathayensis were sprayed either with a conidia suspension of 107 conidia per ml in distilled water as inoculum, or with distilled water only to provide an uninoculated control, wrapped in plastic bags to retain moisture, and incubated for 24 h. For each isolate, 10 leaves per tree and a total of 13 trees were inoculated. After 1 week, 11 of 13 isolates caused lesions on inoculated leaves whereas no symptoms developed on the non-inoculated controls. Cultures reisolated from lesions and cultured on PDA exhibited morphological characteristics identical to those of C. gloeosporioides (1, 2, 3), confirming Koch's postulates. Inoculation tests were repeated once. Since C. gloeosporioides was found in the main production area, it poses a threat to Chinese hickory production in China. The identification of the pathogen now allows for appropriate management measures. To our knowledge, this is the first report of anthracnose in C. cathayensis.