A Post-Harvest Pink Rot of Pepper Caused by Trichothecium roseum in China

Peppers (Capsicum spp.) are high cash value vegetable crops worldwide. In September 2014, harvested sweet pepper (C. annuum) exhibited rot symptoms with white mycelial growth associated with a profuse salmon-colored sporulation on the fruits of pedicel collected from field samples in Shanghai, China. The incidence of diseased fruit in each field ranged from 5.8 to 12.3%. Single spores were removed using an inoculating needle and incubated on potato dextrose agar (PDA) at 25°C for 7 days. Eighteen isolates were morphologically similar and produced pink to white colonies on PDA containing several conidiophores with abundant conidia. Mycelia displayed hyaline hyphae, 4 µm in diameter, and conidiophores were simple or branched (110 to 286 × 2 to 4 µm). Conidia were hyaline, two-celled, and single-septate, ellipsoid to pyriform (17 to 26 × 8 to 12 µm), with slanting and truncate basal mark, and produced in clusters. These characteristics of the fungus were similar to Trichothecium roseum (Pers.) as reported previously (Hamid et al. 2014; Tang et al. 2015). Genomic DNA of a representative isolate PC9 was extracted by using the CTAB method (Lin et al. 2011). PCR analysis was performed for rDNA-ITS and large subunit (LSU) genes (Scorzetti et al. 2002). Single fragments 580 and 573 bp in length from ITS and LSU genes were amplified and sequenced (GenBank Accession Nos. KP982888 and KP982889, respectively). Sequence analysis showed 99% similarity (KU882104 and KR154473, respectively) with T. roseum isolates from different regions of the world. Pathogenicity tests were performed on sweet pepper (cv. zhongjiao-5) by inoculating five fruits. Fruits and stem were wounded by sterile toothpick. Spore suspension (1 × 106 conidia/ml of sterilized distilled water) were sprayed onto the surface of wounded fruits (five wounds/fruit) and incubated at 25°C for the development of symptoms. Five wounded fruits were inoculated with sterilized distilled water as control. The fruits were kept in plastic boxes and incubated in humid chambers at 25°C for 7 days. The symptoms were observed as pinkish spores with water-soaked lesion on the inoculation point. The fungus developed mycelium and abundant spores on the surface and caused rotting inside the pepper. Control fruits remained asymptomatic. The fungus was reisolated from the infected fruits using the method as above and confirmed by morphological feature and molecular techniques. T. roseum was previously reported as a pathogen of mango, tomato, apple, and orange (Hamid et al. 2014; He et al. 2011). To our knowledge, this is the first report of T. roseum causing pepper fruit rot in China. © 2016, American Phytopathological Society. All rights reserved.