Title：
First Report of Pestalotiopsis microspora Causing Postharvest Rot of Kiwifruit in Hubei Province
Authors：
Corresponding
Author：
L. Li, H. Pan, M. Y. Chen, and C. H. Zhong
Pubyear：
2016
Title of
Journal：
Plant Disease
Paper
Code：
Volume：
100
Number：
10
Page：
2161
Others：
Classification：
Source：
Abstract：
Postharvest rot disease of kiwifruit has recently become a serious problem in China,the world’s largest kiwifruit (Actinidia sp.) cultivating and exporting country (Huang et al. 2014). During cold storage, symptoms began as slightly shriveled areas on fruit peel. After 6 to 10 days at room temperature, the inside of these infected fruits became milky white and watery, then finally, severely decayed and sour smelling. Botryosphaeria dothidea and Phomopsis sp. were previously identified in affected fruits in Sichuan Province and Shanghai fruit market, respectively (Li et al. 2015; Zhou et al. 2015), but kiwifruit rot-causing pathogens have not been systematically studied across China. Between October and December 2014, we collected kiwifruit of five cultivars (Jinyan, Hongyang, Jinkui, Guichang, and Qinmei) from seven provinces (Hubei, Sichuan, Henan, Chongqing, Jiangxi, Guizhou, and Shaanxi), China’s main kiwifruit-cultivating regions. After 2 months’ cold storage, 28 fruits Issue Date: 14 Sep 2016 Published: 8 Aug 2016 First Look: 1 Jun 2016 Accepted: 20 May 2016 1/2 developed soft rot symptoms. Symptomatic fruits were surface-sterilized in 70% ethanol for 10 s, 0.1% mercuric chloride for 1 min, then three rinses in sterile distilled water. Samples of internal tissue were placed on potato dextrose agar (PDA) and incubated at 25°C for 3 days with an alternating light-dark cycle. Emerging colonies were transferred to new PDA plates by the hyphal-tip method to obtain pure cultures. The common pathogens B. dothidea and Phomopsis sp. were isolated from most rotting fruit, but four novel, morphologically identical isolates were identified from Jinyan cultivars from Wuhan (Hubei Province). Confocal optical microscopy revealed a match to Pestalotiopsis microspora (Speg.) (Batista et al. 1966). Conidia were slightly curved, fusiform to clavate, five-celled with constricted septa. Dimensions were 17.2 to 21.1 × 4.8 to 7.7 μm, with hyaline apical and basal cells. Apical cells had two (22%) or three appendages 9.8 to 21.3 μm long. The three median cells were brown to olive green. Identification was confirmed by sequencing one isolate (KFRD-2). The rDNA internally transcribed spacer (ITS) and beta-tubulin (BT) regions were amplified using ITS4/ITS5 and Bt2A/Bt2B primers, respectively (Hu et al. 2007). A BLAST search of GenBank showed that the ITS and BT sequences of the isolates (accession nos. KR703275 and KU377338) were 100% homologous with P. microspora (EU273522 and JN314419). For pathogenicity testing of mature A. chinensis ‘Jinyan’ fruit, we applied 10 μl spore suspension (1 × 106 conidia/ml) to the upper area of each of 10 fruits (five wounded, five unwounded), and 10 μl sterile water to the bottom (negative control). In a second test, a mycelial plug (5 mm) of actively growing P. microspora was rubbed onto the upper area of 10 fruits (five wounded, five unwounded), while the bottom area of each fruit (negative control) was treated with sterile agar. Fruit were incubated at 22/18°C (day/night), 80% humidity. Typical symptoms were observed on all wounded, infected sites after 6 days, but none on unwounded fruit or negative control areas. Experiments were repeated three times and the fungus was reisolated each time and identified as P. microspora by morphological and molecular analysis. This is the first report of P. microspora causing kiwifruit rot in China. The economic importance of kiwifruit industry in China warrants further study of postharvest rot disease caused by P. microspora.
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