Details

Autor(en) / Beteiligte

• Kwon, J.-H.
• Kang, D.-W.
• Kim, S.-R.
• Kim, J.

Titel

First Report of Gray Mold Caused by Botrytis cinerea on Passiflora edulis in Korea

Ist Teil von

• Plant disease, 2016-07, Vol.100 (7), p.1504-1504

Erscheinungsjahr

2016

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Passion fruit (Passiflora edulis) is a vine species of passion flower that is native to Brazil, Paraguay, and northern Argentina. In South Korea, it is widely grown for its sweet and seedy fruit. In March 2014, passion fruit flowers with gray mold (approximately 50% incidence) were sampled from the exhibition field of the Agricultural Technology Service Center in Jinju, South Korea. Symptoms first appeared on flowers, which turned brown and then died, with masses of gray or brownish spores produced on infected tissues. No gray mold symptoms were observed on leaves, stems, or fruit. To isolate fungal pathogens, diseased flower tissues excised from the margins of lesions were surface-disinfested in 1% NaOCl for 10 s, rinsed three times with sterile distilled water, and placed on water agar and cultured at 25[degrees]C for 2 days. Mycelial tips of developing fungal cultures were transferred to potato dextrose agar (PDA) for identification. Five Botrytis isolates were recovered from the infected plant samples. All fungal colonies were gray brown and produced sclerotia on PDA. The conidia were one-celled, mostly ellipsoid or ovoid, and colorless or pale brown. The conidia were 6 to 19 x 4 to 12 [mu]m (n= 50) and conidiophores were 15 to 33 [mu]m long. Based on the morphological characteristics, the fungi were placed in the Botrytis cinerea group (Ellis and Waller 1974). To confirm the identity of the fungus, the complete internal transcribed spacer (ITS) rDNA region of a representative isolate MHGNU F114 was amplified using ITS1/ITS4 primers (White et al. 1990). The DNA products were cloned into the pGEM-T Easy vector (Promega, Madison, WI) and the resulting plasmid (pOR187) was sequenced using universal primers at Macrogen Services (Daejeon, South Korea). A BLASTn search of the ITS rDNA sequence of the isolate MHGNU F114 (GenBank Accession No. KU234690) confirmed the identity of the fungus; the sequence obtained was homologous and shared 99% identity with the B. cinerea isolate LGM002 from Brazil and clone GTB from Florida, causing gray mold on pea (KC683713) and German thyme (KT737373), respectively (Dallagnol et al. 2014). For further confirmation, two nuclear protein-coding genes were sequenced: heat-shock protein 60 (HSP60) and DNA-dependent RNA polymerase subunit II (RPB2) (Staats et al. 2005). The HSP60 and RPB2 sequences (KU760985 and KU760986) of the isolate were 99 to 100% identical to those of B. cinerea strains B05.10 and T4, respectively. Isolate MHGNU F114 was used to conduct pathogenicity tests on the flowers of two 1-year-old passion fruit plants grown in pots. Five flowers from one passion fruit plant were inoculated by spraying a conidial suspension of 3 x 10 super(5) conidia/ml until run-off. Five negative control flowers of another passion fruit plant were treated with sterilized distilled water. The two plants were stored in a moist chamber with >90% relative humidity at 25[degrees]C, and after 2 days the plants were placed in a greenhouse. Seven days after inoculation, gray mold symptoms similar to those observed in the field developed on the inoculated flowers, whereas the control flowers remained asymptomatic. B. cinerea was reisolated from the lesions of the inoculated flowers to fulfill Koch's postulates. The morphological features of fungi reisolated from inoculated flowers were the same as those of the original isolates. To our knowledge, this is the first report of gray mold caused by B. cinerea on P. edulis in Korea.