Pear Skin Stain Caused by Mycosphaerella graminicola on Niitaka Pear (Pyrus pyrifolia Nakai).

Pear skin stains on 'Niitaka' pears, which occur from the growing stage to the cold storage stage, reportedly negatively influence the marketing of pears. These stains on fruit skin are likely due to a pathogenic fungus that resides on the skin and is characterized by dark stains; however, the mycelium of this fungus does not penetrate into the sarcocarp and is only present on the cuticle layer of fruit skin. A pathogenic fungus was isolated from the skin lesions of infected fruits, and its pathogenicity was subsequently tested. According to the pathogenicity test, Mycosphaerella sp. was strongly pathogenic, while Penicillium spp. and Alternaria spp. showed modest pathogenicity. In this present study, we isolated the pathogenic fungus responsible for the symptoms of pears (i.e., dark brown-colored specks) and identified it as Mycosphaerella graminicola based on its morphological characteristics and the nucleotide sequence of the beta-tubulin gene. M. graminicola was pathogenic to the skin of 'Niitaka' pears, which are one of the most widely growing varieties of pears in South Korea.

Identification of Acremonium acutatum and Trichothecium roseum isolated from Grape with White Stain Symptom in Korea.

During 2010 and 2012 grape harvest seasons in Gyeonggi-do, Korea, a white stain symptom was observed on the harvested grape fruits in 'Campbell-Early' and 'Kyoho' varieties. In samples collected from the infected vine, two different strains of pathogenic fungi have been found and identified as Acremonium acutatum and Trichothecium roseum based on fungal morphology and nucleotide sequence of internal transcribed spacer (ITS) and supported by the phylogenetic analysis of the rDNA-ITS region. The DNA homologies of the isolated strains were 99.8% and 99.6% identical with T. roseum (IFB-22133) and A. acutatum (CBS682.71), respectively. In the pathogenicity test, the spores of A. acutatum and T. roseum sprayed on the grapes caused white stain symptoms on the fruits in two weeks after the artificial inoculation, which is similar to observations in the field. To our knowledge, this is the first report of white stain symptoms caused by A. acutatum and T. roseum on the grapes in Korea.