First Report of Fusarium acuminatum Causing Postharvest Fruit Rot on Stored Vaccinium corymbosum in China

Highbush blueberry (Vaccinium corymbosum L.), a flowering plant with dark purple berries, mainly used for fresh consumption, juice, jellies, jams, and pies (Kwon et al. 2011), is cultivated in southwest and northeast China on approximately 20,000 ha. In August 2015 in Changchun City, Jilin Province, China, fungal fruit rot was observed on stored highbush blueberry at about 5% incidence. Symptoms consisted of soft, slightly sunken, water-soaked lesions covered with abundant white and pink mycelia. Diseased fruits were surface-disinfested with 75% ethanol for 30 s, 0.1% HgCl2 for 1 min, washed three times in sterile water, dried, plated on potato dextrose agar (PDA), and incubated at 25°C for 7 days. Four isolates with similar morphology were isolated from single spores. Colonies grew slowly with growth diameters of 48 mm after 7 days, producing white mycelia and gradually becoming floccose with bright orange to rose pigmentation on PDA. On carnation leaf agar (CLA), abundant macroconidia were formed in sporodochia. Macroconidia were 3-to 5-septate with a distinctly curved apical cells and foot-shaped basal cells and measured 29.0 to 41.8 × 3.2 to 4.9 μm (n = 50). Microconidia were few, 0-to 1-septate, fusiform or reniform, measuring 7.3 to 12.9 × 2.5 to 2.9 μm (n = 50). Chlamydospores formed in chains. The morphological characteristics of the isolates were consistent with those of Fusarium acuminatum (Leslie and Summerell 2006). The identity was confirmed by the translation elongation factor (TEF-1α, 681 bp, GenBank accession no. KT965740), which had 100% identity to seven published accessions of F. acuminatum (KP325409 et al.); the rDNA internal transcribed spacer (ITS, 589 bp, KT965739) region (Fogliata et al. 2013), and beta-tubulin (TUB2, 1,295 bp, KT965741) region (Wang et al. 2014), which showed 99% similarity to 16 accessions (KF181242 et al.) and one published accession (KP325410), respectively. The ITS and TEF-1α sequences revealed 99.64% and 100% identity to F. acuminatum FD_01726 in FUSARIUM-ID database. To confirm pathogenicity, five ripe, healthy highbush blueberry fruits (cv. Black pearl) wounded with sterilized needles were inoculated with 50 μl conidial suspension (106 conidia/ml) of each isolate and inoculated at 25°C and 90% RH. Five fruits were inoculated with sterilized water as controls. The experiment was repeated three times. Within 6 to 8 days, all inoculated fruits developed symptoms similar to those observed on diseased fruits; no symptoms were observed on control fruits. The pathogen was reisolated from the inoculated fruits and exhibited same morphological characteristics as those of F. acuminatum. Presence of F. acuminatum causing branch blight on blueberry has been reported in Argentina (Wright et al. 2014); however, this is the first report of F. acuminatum causing postharvest fruit rot on stored highbush blueberry in China. This new disease could cause serious damage to highbush blueberry production in China. A detailed survey of the geographic distribution in China should be conducted along with research to determine management options. © 2016, American Phytopathological Society. All rights reserved.