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Fusarium proliferatum: A New Pathogen Causing Fruit Rot of Peach in Ningde, China

Xie, S. H., Zhang, C., Chen, M. S., Wei, Z. P., Jiang, Y. B., Lin, X., Zheng, Y. Q.
Plant disease 2018 v.102 no.9 pp. 1858
DNA, Fusarium proliferatum, Prunus persica, conidia, crop yield, culture media, fruits, growth chambers, microscopy, mycelium, oligodeoxyribonucleotides, orchards, pathogenicity, pathogens, peaches, peptide elongation factors, photoperiod, pigments, plant rots, planting, plastic bags, polymerase chain reaction, relative humidity, sequence analysis, sodium hypochlorite, streptomycin, sulfates, tissues, China
Peach (Prunus persica L.) is an economically important tree fruit crop worldwide. China’s planting area and yield of peaches are the first in the world (Verde et al. 2013). During June to July 2017, losses of at least 20% associated with fruit rot of peaches (cv. Zhongtao No. 5) were observed in several commercial orchards of Ningde, Fujian Province (26.67°N, 119.52°E). Affected fruit showed water-soaked areas on the skin and extensive internal decay, with white mycelium on the surface of decayed areas. Fifteen diseased fruit were collected from three different orchards. Diseased fruit tissues were cut into 5-mm pieces, surface disinfested with 1% sodium hypochlorite for 1.5 min, and placed on 1.5% potato dextrose agar (PDA) amended with 0.02% streptomycin sulfate. A total of 12 pure cultures were collected by single-spore isolations. The isolates produced abundant, white, aerial mycelium and violet-to-dark (with age) pigments in the PDA. Based on observations of 1-week-old isolates, macroconidia were 2 to 5 septate and 21.4 to 46.8 × 2.7 to 4.5 μm in size, average 34.6 × 3.6 μm (n = 25), and microconidia were 6.0 to 13.3 × 2.2 to 4.6 μm in size, average 8.5 × 3.4 μm (n = 25). These morphological characteristics were consistent with previous descriptions of Fusarium (Mun et al. 2012; Summerell et al. 2003); therefore, we preliminarily identified the cultures as Fusarium spp. Genomic DNA was extracted from single conidial cultures of three representative isolates. The isolates were further identified by polymerase chain reaction (PCR) sequencing using two different primer sets: ITS1/ITS4 and EF1/EF2. Primers ITS1/ITS4 (White et al. 1990) resulted in a 508-bp amplicon (GenBank accession no. MF963046). The BLASTn analysis showed a 100% sequence identity with F. proliferatum (KU527804). Primers EF1/EF2 amplified translation elongation factor (TEF) (Geiser et al. 2004), and the resulting TEF sequence (MF963047) was 99% similar to that of F. proliferatum (AB674284). Pathogenicity was confirmed by inoculating 12 surface-sterilized peach fruit with a conidial suspension (1 × 10⁶ conidia/ml). The peaches were stab inoculated to a depth of 1 mm using a sterile needle. Controls were inoculated with sterile distilled water. The peaches were wrapped in plastic bags and stored in a growth chamber at 25°C, 90% relative humidity, and a daily 12-h photoperiod. After 5 days, symptoms of soft rot similar to those in the commercial fields were observed from all inoculated peaches. Controls displayed no symptoms. The pathogen was reisolated from the diseased fruit but not from the controls, and it was confirmed to be F. proliferatum by microscopy and PCR sequencing. To our knowledge, this is the first report of F. proliferatum causing rot disease on peach in China. Considering the economic importance of peach in China and throughout the world, further study of fruit decay of peach caused by F. proliferatum is warranted.