First confirmed report of downy mildew caused by Hyaloperonospora parasitica on broccoli in Korea

Abstract

In January 2007, broccoli plants ( Brassica oleracea var. italica ) showing symptoms of downy mildew were found in Jeju, the chief producing area in Korea. Broccoli growers report that downy mildew is the only disease of economic importance in their greenhouses, occasionally resulting in 100% loss of yield. Initial symptoms were irregular yellow-green spots on upper leaf surfaces and white fluffy growth underneath. Floral heads developed pale brown or greyish discoloration. Systemic infections caused internal dark grey to black spots and streaks in stems and floret branches. These internal symptoms are found only in broccoli and cauliflower, not in other brassicaceous crops. A sample was deposited in the herbarium of Korea University (Acc. No. KUS-F22524). The conidiophores were hyaline, 310-520 × 10-20 μ m, monopodially branched 4-7 times. The ultimate branchlets were usually strongly curved, 20-42 μ m long, 2-3 μ m wide at the base. Conidia were hyaline and measured 23·3-31·2 × 20-27·5 μ m (length/width = 1·0-1·22). This fungus was concordant with known characteristics of Hyaloperonospora parasitica (syn. Peronospora parasitica , Constantinescu & Fatehi, 2002).The amplification and sequencing of the ITS rDNA were performed with procedures outlined by Cooke et al . (2000), and the sequence deposited in GenBank (Acc. No. EU137726). Comparison of the ITS sequences in the GenBank database revealed that it was identical to H. parasitica found on Brassica campestris (AY210985, AY210986), and shows only one base pair substitution with one on B. napus subsp. napus (AY531407, AY531409).Hyaloperonospora parasitica ( Peronospora parasitica ) has a worldwide distribution and is an important pathogen of numerous crop hosts. In Korea, H. parasitica has previously been recorded on various brassicaceous plants including Brassica rapa subsp. pekinensis and B . juncea (Cho & Shin, 2004). Due to the recent taxonomic revision of the Peronospora , this is the first confirmed record of this pathogen from broccoli. Downy mildew of broccoli has previously been reported in Australia, Brazil, Canada, and USA. To our knowledge, this is only the second record of a downy mildew on broccoli in East Asia, the first being from Japan in 1991 (Satou et al ., 1991). Commercial cultivation of broccoli in East Asia started in Japan in the 1980s and has expanded to Korea and China in the 2000s. Broccoli downy mildew appears to be spreading in Asian countries. References Division of Environmental Science and Ecological Engineering, Korea University, Seoul 136-701, KoreaChinese cabbage ( Brassica rapa ssp. pekinensis ; syn. B. pekinensis ) is the second most important vegetable in Korea after red pepper. In November 2006 seedlings in a glasshouse in Suwon, Korea, showed typical powdery mildew symptoms. Symptoms first appeared as circular to irregular white colonies, which subsequently developed into abundant growth on both leaf surfaces. Severe infections often caused leaf distortion, withering and premature senescence. Superficial mycelium and ...

New Downy Mildew Disease Caused by Hyaloperonospora brassicae on Pak choi (Brassica rapa) in Korea

“…1J-K). All morphological characteristics closely matched those of H. brassicae known on Brassica species (Choi et al, 2012;Gäumann, 1923;Hong et al, 2008).…”

“…Over the last 100 years, H. brassicae (formerly, Peronospora parasitica) was one of the most destructive pathogens in cultivations of Brassica plants in the world (Channon, 1981;Kluczewski and Lucas, 1983;Monot et al, 2010;Sherriff and Lucas, 1990). In Korea, this pathogen has been attributed the downy mildew diseases occurring on brown mustard, Chinese cabbage, cabbage, broccoli, and tatsoi (Choi et al, 2012;Hong et al, 2008;Shin and Choi, 2006; The Korean Society of Plant Pathology, 2004). On pak choi, the disease has been previously recorded in China, Fiji, Malaysia, Papua New Guinea (Farr and Rossman, 2019), and Japan (Chu, 1935).…”

Pseudomycosis and mycosis of rocket plant (arugula)

“…se javila na rukoli u Koreji i Španiji (Choi et al, 2010). Na drugim biljnim vrstama, Hyaloperonospora parasitica registrovana je na brokoliju u Koreji (Hong et al, 2008), na brokoliju i karfi olu u Francuskoj (Monot et al, 2010), na kineskom kupusu na Kubi (Ariosa Terry et al, 2013), na uljanoj repici u Kentakiju, SAD (Amsden et al, 2017). U literaturi ima više podataka za Peronospora parasitica na rukoli koja se javlja širom sveta (Channon, 1981), u svim regionima gde se ona gaji Gilardi et al, 2013).…”

Diversity, Phylogeny, and Host-Specialization of Hyaloperonospora Species in Korea

“…In Korea, commercial crops, including brassicas and radishes, have experienced ongoing severe economic losses [ 14 ]. Furthermore, the active importation and cultivation of various overseas crops have led to the emergence of new diseases affecting broccoli [ 15 ], tatsoi [ 16 ], and spider flower [ 17 ]. Previously, Choi et al [ 18 ] described a high phylogenetic diversity for Hyaloperonospora specimens collected in Korea, but the discovered lineages could not be assigned at the species level because of the lack of morphological data and the broad species concept, which prevailed at that time in the taxonomy of downy mildews.…”