First Report of Stem and Leaf Anthracnose on Blueberry Caused by Colletotrichum gloeosporioides in China

Pestalotiopsis Species Associated with Blueberry Leaf Spots and Stem Cankers in Sichuan Province of China

Blueberry leaf spots and stem cankers caused by Pestalotiopsis spp. have become a serious threat for the production of blueberry in Sichuan Province. To characterize the etiology of the diseases connected with these fungi, samples showing leaf spot and stem canker symptoms were collected from the 12 main blueberry-growing areas of Sichuan Province from 2015 to 2020 and used for pathogen isolation. In total, 91 fungal isolates were obtained with preliminary morphological identification and 48 representative strains were selected for further pathogenicity test and molecular identification. Four species, including Pestalotiopsis clavispora (Neopestalotiopsis clavispora) (57.14%), P. trachicarpicola (28.57%), P. chamaeropis (13.19%), and P. adusta (1.10%), were identified based on conidial morphology, cultural characteristics, and phylogenetic analysis of the internal transcribed spacer region, partial sequence of the β-tubulin gene, and the translation elongation factor 1-α. Pathogenicity tests showed that four species were pathogenic to leaves and stems of blueberry. Among them, P. clavispora (N. clavispora) was the most aggressive as the predominant species to cause both leaf spot and stem canker. P. trachicarpicola and P. chamaeropis were mainly isolated from leaves but also pathogenic to stems. P. adusta was only isolated from stems but also pathogenic to leaves. To the best of our knowledge, this is the first report of P. chamaeropis and P. adusta as pathogens causing leaf spots and stem canker on blueberry. The results provide helpful information in disease diagnosis and management of blueberry.

Neofusicoccum vaccinii: A Novel Species Causing Stem Blight and Dieback of Blueberries in China

Blueberries (Vaccinium spp.) have been considered to be a superfood because of their health benefits. Stem blight or dieback of blueberry has been frequently observed in commercial plantations, with incidences between 15 and 30% being observed in China. The causal agents of blueberry stem blight and dieback were surveyed at four commercial blueberry plantations in the Shandong, Fujian, Guizhou, and Yunnan Provinces of China during 2017 and 2019. Twenty-eight isolates of Neofusicoccum were obtained from 75 diseased and dead stem samples. Two taxa were identified. Of these, one novel species, Neofusicoccum vaccinii, was identified based on morphological characteristics and DNA sequence analysis of the concatenated internal transcribed spacer, the translation elongation factor-1α gene, and the beta-tubulin gene. Koch's postulates tests indicated that N. vaccinii was pathogenic toward blueberry. N. parvum is the other species isolated in this study. The optimal temperature for mycelial growth was 30°C for both N. vaccinii and N. parvum. N. vaccinii, however, was more virulent than N. parvum in this study at temperatures ranging from 25 to 30°C. Coinoculation of N. vaccinii and N. parvum did not lead to increased disease severity. On the contrary, the aggressiveness of N. vaccinii was suppressed by the presence of N. parvum at 25 to 35°C.

Identification of Colletotrichum Species Associated with Blueberry Anthracnose in Sichuan, China

Anthracnose caused by Colletotrichum spp. is an important disease of blueberries and results in large economic losses for blueberry growers. Samples of anthracnose were collected from six main blueberry cultivation areas in Sichuan Province. In total, 74 Colletotrichum isolates were obtained through a single-spore purification method and identified to the species through morphological characteristics and phylogenetic analyses based on partial DNA sequences of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), internal transcribed spacer (ITS) regions, and the β-tubulin (TUB2), actin (ACT) and calmodulin (CAL) genes. Among all species, Colletotrichum fructicola was the most dominant species, with an isolation percentage of up to 66.2% in Sichuan, followed by Colletotrichum siamense (17.6%), C. kahawae (5.4%), C. karstii (5.4%), C. nymphaeae (2.7%) and C. sichuaninese (2.7%). Pathogenicity tests showed all species were able to cause typical anthracnose symptoms on blueberry leaves and stems. Colletotrichum fructicola was the predominant species with strong aggressiveness. Moreover, C. fructicola, C. kahawae, C. sichuaninese and C. nymphaeae are first reported here to cause blueberry anthracnose. This study provides a comprehensive reference for the association of different Colletotrichum spp., which may support the sustainable management of blueberry anthracnose.