Mapping of clubroot (Plasmodiophora brassicae) resistance in canola (Brassica napus)

Clubroot disease, caused by Plasmodiophora brassicae, has become a major problem in the production of cruciferous crops worldwide. In this study, a population of 121 doubled haploid (DH) lines derived from a crossing between a resistant and a susceptible canola (Brassica napus) genotype was subjected to phenotypic and genotypic studies to determine the inheritance and location of the resistance gene(s). After inoculation with pathotype 3 of P. brassicae, the lines showed a 1:1 segregation ratio for resistance, indicating that resistance in this population is controlled by a single gene. Fifteen PCR‐based markers that were known to be linked to clubroot resistance (CR) genes were screened against genomic DNA from parents and resistant and susceptible bulks. Marker GC1680, linked to the CR gene CRa, exhibited polymorphism between the parents and between the resistant and susceptible bulks. CRa target primers were used to amplify fragments from the two parents and the resultant sequences were compared. A high degree of sequence similarity was found between the parents in the nucleotide binding site domain of CRa. In contrast, sequence polymorphisms were detected in the leucine‐rich repeat (LRR) domain. One pair of primers that amplify a band from the LRR region of the resistant parent but not the susceptible parent was used to screen the DH population. Amplicons were obtained from 60 of the 61 resistant lines and two of the 60 susceptible lines; thus, three recombinants were found. Based on these results, a resistance locus linked to CRa was found.     

Antiviral activity of exopolysaccharides from Arthrospira platensis against koi herpesvirus

Although koi herpesvirus (KHV) has a history of causing severe economic losses in common carp and koi farms, there are still no treatments available on the market. Thus, the aim of this study was to test exopolysaccharides (EPS) for its antiviral activity against KHV, by monitoring inhibition and cytotoxic effects in common carp brain cells. These substances can be easily extracted from extracellular algae supernatant and were identified as groups of sulphated polysaccharides. In order to reach this aim, Arthrospira platensis, which is well known for its antiviral activity of intra‐ and extracellular compounds towards mammalian herpesviruses, was investigated as standard organism and compared to commercial antiviral drug, ganciclovir, which inhibits the viral DNA polymerization. The antiviral activity of polysaccharides of A. platensis against KHV was confirmed in vitro using qualitative assessment of KHV life cycle genes, and it was found by RT‐PCR that EPS, applied at a concentration of >18 μg mL^?1 and a multiplicity of infection (MOI) of 0.45 of KHV, suppressed the viral replication in common carp brain (CCB) cells even after 22 days post‐infection, entirely. Further, this study presents first data indicating an enormous potential using polysaccharides as an additive for aquacultures to lower or hinder the spread of the KHV and koi herpesvirus disease (KHVD) in future.     

Paralytic shellfish poison as an attractant for toxic snails

The attracting effect of paralytic shell poison (PSP) on eight toxic snail species (Polinices didyma, Natica lineata, N. vitellus, Zeuxis sufflatus, Niotha clathrata, Oliva miniacea, O. mustelina, O. hirasei) and two non-toxic species (Pomacea canaliculata, Satsuma bairdi) was investigated. Eight toxic species were reported to contain tetrodotoxin, and three out of these contained minor PSP. The minimum lethal dose of PSP in most toxic gastropods was estimated to be more than 150 MU PSP/20 g body weight, but in non-toxic gastropods was less than 15 MU PSP/20 g body weight. After the attracting test, all toxic gastropods showed significant positive linear relationship (Y=3.716X+0.363, r=0.8427) between comparative attracting variation and the toxicity reported. The relationship between PSP resistance ability and the toxicity also had a positive correlation (Y=0.91X+210.090, r=0.6803). However, the non-toxic species showed a negative response. This indicates that PSP is an attractant for toxic snails.     

The wheat germ agglutinin binding sites and development of the mitochondria-rich cells in gills of tilapia (Oreochromis mossambicus)

By labelling with gold-colloid-conjugated wheat germ agglutinin (WGA), the WGA-binding sites were identified in the apical region of certain mitochondria-rich (MR) cells in gills of freshwater-adapted tilapia (Oreochromis mossambicus). Bromo-deoxyuridine (BrdU) injection was used to discern the differentiation of the WGA binding sites during development of MR cells. Double labeling of gill sections of fish 2, 4, 6, and 8 days after a single BrdU injection showed that the BrdU labeled MR cells 2 and 4 days after injection were mostly WGA negative, whereas 6 and 8 days after injection, WGA and BrdU-labeled MR cell increased gradually in number. Furthermore, the ratio of the WGA-positive to total MR-cells was higher in gills of tilapia adapted to low calcium ([Ca] = 0.015 mm) freshwater than in hard freshwater ([Ca] = 1.898 mm). The results indicate that WGA binding site may be a marker expressed late during differentiation of MR cells, and physiologically functional in assisting uptake of calcium when environmental calcium is low. According to their WGA binding and also characteristics their likely function in calcium absorption, the WGA positive MR cells shown in this study are considered to be similar to the cells described by Pisam et al. (1995).     

Distribution and migration of Japanese common squid, Todarodes pacificus, in the southwestern part of the East (Japan) Sea

Data on squid catches of Korean and Japan, water temperatures at depth of 100 m, and night-visible images of fishing boats collected in the East (Japan) Sea from 1970 to 1999 were analyzed to examine the distribution and migration of the Japanese common squid, Todarodes pacificus, in the southwestern part of the East (Japan) Sea. The main fishing grounds detected from squid catch in each grid (0.5° latitude × 0.5° longitude) by Korean squid fishery and night-visible images provided by the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) were situated in the southwestern part of the East (Japan) Sea. The distribution and migration route was illustrated from squid catch in each grid and DMSP OLS image. In years of high catches, the fishing grounds were situated mainly between Ulleung Island and the eastern coastal waters of Korea, while in years of low catches they were situated between Ulleung Island and the Yamato Bank in the central East (Japan) Sea. The center of fishing activity began moving northward from around the Korea/Tsushima strait to the northern boundary of the Tsushima Warm Current in March, reaching into the Yamato Bank in September, and then returning to the strait by February. The northward and southward migration routes differed; the northward migration route occurred closer to the mainland coast of Korea than the southward migration route did. This work suggests T. pacificus begin their northward migration almost 2 months earlier than previously suggested.     

A natural infection by the red sea bream iridovirus‐type Megalocytivirus in the golden mandarin fish Siniperca scherzeri

An outbreak of a Megalocytivirus infection was found in the golden mandarin fish Siniperca scherzeri during September and October 2016, in Korea. Phylogeny and genetic diversity based on the major capsid protein (MCP) and adenosine triphosphatase (ATPase) genes showed a new strain. Designated as GMIV, this strain derived from the golden mandarin fish was suggested to belong to the red sea bream iridovirus (RSIV)‐subgroup I. Additionally, this train clustered with the ehime‐1 strain from red sea bream Pagrus major in Japan and was distinguished from circulating isolates (RSIV‐type subgroup II and turbot reddish body iridovirus [TRBIV] type) in Korea. The infection level, evaluated by qPCR, ranged from 8.18 × 10² to 7.95 × 10⁶ copies/mg of tissue individually, suggesting that the infected fish were in the disease‐transmitting stage. The diseased fish showed degenerative changes associated with cytomegaly in the spleen as general sign of Megalocytivirus infection. The results confirm that the RSIV‐type Megalocytivirus might have crossed the environmental and species barriers to cause widespread infection in freshwater fish.     

Epidemiological investigation of equine hindlimb ataxia with Setaria digitata in South Korea

BackgroundSince 2013, the number of requests for diagnosis for horses based on neurological symptoms has increased rapidly in South Korea. The affected horses have commonly exhibited symptoms of acute seasonal hindlimb ataxia. A previous study from 2015–2016 identified Setaria digitata as the causative agent.ObjectivesThis study is an epidemiological investigation to find out risk factors related to the rapid increase in hindlimb ataxia of horses due to aberrant parasites in South Korea.MethodsAn epidemiological investigation was conducted on 155 cohabiting horses in 41 horse ranches where the disease occurred. The surrounding environment was investigated at the disease-causing horse ranches (n = 41) and 20, randomly selected, non-infected ranches.ResultsHindlimb ataxia was confirmed in nine cohabiting horses; this was presumed to be caused by ectopic parasitism. Environments that mosquitoes inhabit, such as paddy fields within 2 km and less than 0.5 km from a river, had the greatest association with disease occurrence.ConclusionsMost horse ranches in South Korea are situated in favorable environments for mosquitoes. Moreover, the number of mosquitoes in the country has increased since 2013 due to climate change. Additional research is required; however, these data show that it is necessary to establish guidelines for the use of anthelmintic agents based on local factors in South Korea and disinfection of the environment to prevent disease outbreaks.     

Microscopic structure features changes of rice straw treated by boiled acid solution

This study focuses on the determination of structure change of surface area, morphology, crystallinity and pyrolysis characteristics of cellulosic feedstock treated by hot acid solution. The microscopic structure change of acid-treated samples was examined by using BET, SEM/EDX, XRD and pyrolysis–GC–MS under reasonable condition. Results showed that both surface area and pore volume of treated sample were conspicuous increased partial due to dissolution of silica and organic polar-components. Morphological change of plant cell wall surface was viewed as damage such as exfoliation, cave and fracture appeared on epidermis, vascular bundles. The crystallinity index of residual cellulose microcrystalline was widely enhanced because amorphous hemicellulose was removed off while crystalline was changeless. Under hot acid solution reaction, amorphous hemicellulose was hydrolyzed and leaving larger perfect cellulose thus increasing of crystalline size. Those available cellulose was obvious exposed after acid treatment and gave intensive characteristic peak on pyrogram analyzed by pyrolysis–GC–MS.