Identification of Botryosphaeriaceae Species Causing Kiwifruit Rot in Sichuan Province, China

Species of Botryosphaeriaceae fungi are important plant pathogens causing cankers, blight, and fruit rot in an extremely wide range of host. In recent years, kiwifruit rot has been a serious problem in Sichuan Province, one of the important kiwifruit production areas of China. Botryosphaeria dothidea has previously been associated with kiwifruit rot but little is known regarding whether other Botryosphaeriaceae genera also constitute kiwifruit rot pathogens in China. Accordingly, diseased fruit were collected from six different areas of Sichuan Province. Based on morphological characteristics, pathogenicity testing, and comparisons of DNA sequences of the internal transcribed spacer, transcription elongation factor 1-alpha, and p-tubulin genes, 135 isolates of Botryosphaeriaceae were identified as B. dothidea, Lasiodiplodia theobromae, and Neofusicoccum parvum. All of these species were found to cause kiwifruit rot. To understand the infection cycle of kiwifruit rot pathogens, these three species were used to inoculate leaves and shoots of kiwifruit. The results showed that these species could cause spots on leaves and lesions on shoots, producing abundant pycnidia on leaves and shoots surfaces. Moreover, B. dothidea conidia and ascospores from overwintered pycnidia and pseudothecia in kiwifruit orchards in April and August could cause fruit rot and spots on leaves of kiwifruit. Therefore, we concluded that overwintered pycnidia and pseudothecia of B. dothidea in kiwifruit orchards are the primary inoculum for kiwifruit rot, with new pycnidia that develop during the growing season serving as a secondary inoculum. This is the first report of N. parvum and L. theobromae causing kiwifruit rot in China and is also the first report that B. dothidea is able to overwinter as pycnidia and pseudothecia in kiwifruit orchards and serve as the primary inoculum for kiwifruit rot.