Characterization of Colletotrichum gloeosporioides responsible for anthracnose disease of Trichosanthes kirilowii Maxim in central China

Anthracnose disease is an important fungal disease on Trichosanthes kirilowii Maxim. (T. kirilowii), which has recently become a major problem in production areas of T. kirilowii in Anhui Province, central China. A total of 78 putative Colletotrichum spp. isolates were obtained from infected leaves and fruits of T. kirilowii showing anthracnose symptoms during the years 2009-12. All the fungal isolates were consistently identified as Colletotrichum gloeosporioides by a combination of morphological characteristics, species-specific PCR assays and sequence analysis of the ITS region. The results of pathogenicity tests showed difference in virulence among 24 isolates of C. gloeosporioides representatively selected from different regions, when disease symptoms were evaluated after artificially inoculation on the detached T. kirilowii fruits for 2 weeks. The mycelial growth and germination rate of C. gloeosporioides isolates in vitro were determined under temperatures of 10, 15, 20, 25, 28, 30, 33 and 36°C. The optimum growth temperatures of these isolates were observed at 25-30°C, and the germination rates were rather high in the range of 20-33°C. Host range study revealed that the pathogen, under experimental conditions, can infect nine cultivated and weed species belonging to six families (Cucurbitaceae, Rosaceae, Solanaceae, Convolvulaceae, Celastraceae and Cannabinaceae). Moreover, C. gloeosporioides can overwinter safely in infected tissues in field soil, suggesting the potential contribution of plant debris to disease epidemics in the region. The study presents useful information for epidemiological surveillance of T. kirilowii anthracnose caused by C. gloeosporioides in the central region of China.