Nang Kyu Kyu Win

Biological Characterization of Marssonina coronaria Associated with Apple Blotch Disease

Abstract Marssonina coronaria associated with apple blotch disease causes severe premature defoliation, and is widely distributed in Korea. Thirteen isolates were collected from orchards located in Gyeongbuk Province from 2005~2007. All isolates displayed over 99.6% and 99.2% sequence similarity to each other in internal transcribed spacer regions and partial sequences of 28S rDNA, respectively. The isolates were phylogenetically closely related to Chinese isolates. Selected isolates did not differ in their pathogenicity. The optimum conditions for fungal growth were 20°C and pH 6 on peptone potato dextrose agar (PPDA). Peptone and mannose were the best nitrogen and carbon source, respectively. Fungal growth was better on PPDA than on common potato dextrose agar. This study provides valuable information for integrated disease management program and facilitates the routine culturing of M. coronaria.

Current Status of Phytoplasmas and their Related Diseases in Korea

Phytoplasmas have been associated with more than 46 plant species in Korea. Several vegetables, ornamentals, fruit trees and other crop species are affected by phytoplasma diseases. Six 16Sr groups of phytoplasmas have been identified and these phytoplasmas are associated with 63 phytoplasma diseases. Aster yellows phytoplasmas are the most prevalent group and has been associated with more than 25 diseases in Korea. Jujube witches` broom, paulownia witches` broom and mulberry dwarf diseases cause economic losses to host trees throughout the country. So far, Korean phytoplasmas belong to six species of ``Candidatus Phytoplasma``; ``Ca. P. asteris``, ``Ca. P. pruni*``, ``Ca. P. ziziphi``, ``Ca. P. trifolii``, ``Ca. P. solani*`` and ``Ca. P. castaneae``. The diseases are distributed throughout the country and most of them were observed in Gyeongbuk and Chonbuk provinces. At least four insect vectors; Cyrtopeltis tenuis, Hishimonus sellatus, Macrosteles striifrons and Ophiola flavopicta have been identified for phytoplasma transmission.

Molecular analysis of 'Candidatus Phytoplasma aurantifolia' associated with phytoplasma diseases in Myanmar

During 2010 and 2011, typical phytoplasma disease symptoms such as little leaves, phyllody and witches’ brooms were observed on black gram, green gram, long bean, shaggy button weed and sesame plants from different regions of Myanmar. The symptomatic samples were analyzed by PCR using universal phytoplasma primers and characterized by sequencing 16S rRNA, ribosomal protein and translocase protein genes. Based on sequence and phylogenetic analysis of the three genes, the phytoplasmas associated with those plants belonged to members of ‘Candidatus Phytoplasma aurantifolia’. To our knowledge, black gram and shaggy button are new hosts for ‘Ca. P. aurantifolia’.

Reclassification of aster yellows group phytoplasmas in Korea

Aster yellows group phytoplasmas were reclassified by analysis of the 16S rRNA gene sequence, their phylogeny and the presence of interoperon heterogeneity. Nine phytoplasmas were classified into subgroups 16SrI-B and 16SrI-D using the 16S rRNA gene sequence. Then, based on the presence of interoperon heterogeneity, subgroup 16SrI-B phytoplasmas were differentiated into three subunits as 16SrI-B(a): mulberry dwarf, sumac witches’ broom and porcelain vine witches’ broom; 16SrI-B(b): angustata ash witches’ broom and Japanese spurge yellows; and 16SrI-B(c): onion yellow dwarf, water dropwort witches’ broom and hare’s ear yellow dwarf phytoplasma.

Multiplex PCR Assay for Simultaneous Detection of Korean Quarantine Phytoplasmas

Animal, Plant and Fisheries Quarantine and Inspection Agency, Anyang 430-757, Korea(Received on August 23, 2011; Revised on October 16, 2011; Accepted on October 17, 2011)Multiplex PCR assays were developed for the simul-taneous detection of ten important Korean quarantinephytoplasmas. The species-specific primers were design-ed based on ribosomal protein, putative preproteintranslocase Y, immunodominant protein, elongationfactor TU, chaperonin protein and the 16S rRNA genesof ‘Candidatus (Ca.) Phytoplasma’ species. Three mainprimer sets were prepared from ten designed primerpairs to limit nonspecific amplification as much aspossible. The multiplex PCR assay using the threeprimer sets successfully amplified the correct conservedgenes for each ‘Ca. Phytoplasma’ species. In addition,ten important ‘Ca. Phytoplasma’ species could be easilydetermined by recognizing band patterns specific foreach phytoplasma species from three primer sets.Moreover, a high sensitivity of multiplex PCR for eachprimer set was observed for samples containing a lowDNA concentration (10 ng/µl). This study provides theuseful multiplex PCR assay as a convenient method todetect the presence of ten important quarantinephytoplasmas in Korea.Keywords : ‘Candidatus Phytoplasma’ species, Detection,Multiplex PCR, QuarantinePhytoplasma associated plant diseases occur in many cropsworldwide and more than 300 distinct plant diseases havebeen attributed to phytoplasmas, affecting hundreds of plantgenera (Hoshi et al., 2007). Phytoplasmas severely affectherbaceous and woody plants and are the primary limitingfactors for many important crops all over the world. Manyof the most important diseases from an economic stand-point are those affecting woody plants, including coconutlethal yellowing, peach X-disease, grapevine yellows andapple proliferation, and those affecting herbaceous plants,including vegetable crops, ornamental plants and legumes(Bertaccini and Duduk, 2009). Because of these diseases,the movement of the affected plant species should beinternationally restricted through quarantine regulations(Lee et al., 2000). In Korea, phytoplasma related diseases have been report-ed in about 50 different plant species and the phytoplasmaswere found to be associated with 6 ‘Candidatus (Ca.)Phytoplasma (P.)’ species including ‘Ca. P. asteris’, ‘Ca. P.pruni’, ‘Ca. P. trifolii’, ‘Ca. P. solani’, ‘Ca. P. castaneae’and ‘Ca. P. ziziphi’. Among them, ‘Candidatus Phyto-plasma asteris’ associated plant diseases were found toaffect the widest range of plants (Lee et al., 2004). TheKorea National Plant Quarantine Services (NPQS) listed 20phytoplasma diseases that should be prohibited and re-gulated including apple proliferation, strawberry witches’broom, walnut witches’ broom, etc. Those diseases wereassociated with 10 important ‘Ca. Phytoplasma’ speciesand among them; ‘Ca. P. asteris’ associated plant diseaseswere reported to be present in 54 plant families of 350 plantspecies (http://www.nqps.go.kr). Nowadays, molecularbased identification has been widely used to quickly detectpathogens. Nested PCR following PCR primed by phyto-plasma-universal primers are commonly used in phyto-plasma detection in Korea. Generally, identification of anunknown phytoplasma species from one disease requires asignificant amount of time. After PCR analyses, sequencingor restriction fragment length polymorphism analyses areneeded to further differentiate pathogen at the phytoplasmaspecies level. Thus, quick and efficient detection methodsfor ten important phytoplasma species are needed inregards to quarantine services. Simultaneous detection oftwo or more DNA targets can be achieved by duplex ormultiplex PCR in a single reaction by adding severalspecific primers into the PCR cocktail. Lopez et al. (2006)demonstrated that the multiplex PCR is a valuable tool fordetection and identification purposes in plant pathologybecause more than one pathogen frequently infect a singlecrop or host. Therefore, in this study, we developed amultiplex PCR assay by designing phytoplasma species-specific primer pairs based on various conserved genesincluding 16S rRNA, ribosomal protein gene operon (rp),

Occurrence of bacterial rot of onion caused by Bacillus amyloliquefaciens in Korea

In 2008, bacterial rot on onion bulbs (Allium cepa L.) was observed in several low-temperature warehouses in Changnyeong-gun, Korea. The causal pathogen was isolated and identified as Bacillus amyloliquefaciens based on morphological and biochemical characterization and sequence analysis of its genome. The isolated bacteria caused the same rot symptom on inoculated onion bulbs as found in naturally infected onions during storage and was reisolated from these bulbs. This is the first report of bacterial rot of onion caused by B. amyloliquefaciens in Korea.