Efficacy of silver ions against Sacbrood virus infection in the Eastern honey bee Apis cerana

Although silver is known to be a broad-spectrum biocidal agent, the effects of this metal against Sacbrood virus have not yet been investigated. In this study, we evaluated the efficacy of silver ions against natural Korean sacbrood virus (KSBV) infection of Apis (A.) cerana. Ten KSBV-infected colonies containing A. cerana with similar strength and activity were selected from an apiary located in Bosung-gun (Korea). Among these, five colonies were randomly assigned to the treatment group that was fed sugar syrup containing 0.2 mg/L silver ions. The other colonies were assigned to the untreated control group in which bees were given syrup without the silver ions. To assess the efficacy of the silver ions, colony strength, colony activity, and the number of dead larvae per hive were measured. During the experimental period, the test group maintained its strength and activity until day 32 while those of bees in the control group decreased sharply after day 8 to 16. Survival duration of the test group was significantly longer (40 days) than that of the control group (21 days). These results strongly indicated that silver ions are effective against KSBV infection in A. cerana.     

Hydrolysable tannins depress cardiac papillary muscle contraction and propranolol-induced negative inotropism

We studied effects of hydrolysable tannins on rat papillary muscle contractions induced by propranolol. The developed force of papillary muscle was measured isometrically with an inductive force transducer. The IC₅₀ values for digallic acid, gallic acid, germin D, praecoxin A and 1-desgalloyl rugosin F were 4.2 × 10^− 5 M, 1.3 × 10^− 4 M, 1,4 × 10^− 4 M, 1.5 × 10^− 4 and 1.7 × 10^− 4 M, respectively. Incubation with tannins significantly attenuated the propranolol-induced negative inotropic contractile response. These results show that hydrolysable tannins depress muscle contractions and potentiate the activities of β-adrenergic blocker.     

Serodiagnosis of porcine reproductive and respiratory syndrome virus infection with the use of glycoprotein 5 antigens

Glycoprotein 5 (GP5) of porcine reproductive and respiratory syndrome virus (PRRSV) has been studied extensively as a target for vaccine development. This study evaluated the serodiagnostic application of PRRSV GP5 by enzyme-linked immunosorbent assay (ELISA). Two immunodominant peptides (VR #1 and VR #2) and two neutralizing ectodomain-containing peptides (Ecto #1 and Ecto #2), as well as recombinant GP5 (rGP5) as a control, were prepared. Serum from unvaccinated pigs was screened for the antibodies that bind to these peptide and protein antigens. The results were compared with those from a commercially available diagnostic ELISA kit (HerdChek), which uses the nucleocapsid (N) protein as an antigen. Only VR #1+#2 showed a result statistically similar to that of N protein. Ecto #1 and Ecto #2 had a lower sensitivity than VR #1+#2 and rGP5. The peptides and rGP5 showed significant associations with the N protein (P < 0.05 or 0.01), which suggests that GP5 may also be a candidate serodiagnostic antigen. Since antibodies against GP5 persist much longer than those against the N protein, GP5 itself and some of its fragments are thought to be good targets for serodiagnosis. In addition, the presence of antibodies against the PRRSV structural antigens showed significant antigen-dependent differences.     

Estimating the economic damage caused by jellyfish to fisheries in Korea

Jellyfish cause a range of problems: they sting beach vacationers in the summer, block nuclear power plant intakes (thus disrupting the supply of electricity), decrease fishery catches, cause fishing activities to be delayed, decrease product value, and damage fishing gear. This study gauged the types and amount of damage directly caused by jellyfish. Using jellyfish monitoring data, the decreases in catch and product value for each fishery type as well as the estimated damage to each fishery type caused by jellyfish were evaluated. The results showed that the decrease in catch ranged between 6.5 and 33.7?%, and the decrease in product value ranged between 6.8 and 25.3?%, depending on fishery type. The annual direct damage caused by jellyfish was estimated to be between US$ 68.2 million and US$ 204.6 million. This corresponds to a minimum of 2.1?% and a maximum of 25?% of the annual production value, demonstrating that jellyfish cause considerable damage to the fishing industry.     

Development of elite breeding lines conferring Bph18 gene-derived resistance to brown planthopper (BPH) by marker-assisted selection and genome-wide background analysis in japonica rice (Oryza sativa L.)

Brown planthopper (BPH) is a serious threat to rice production. In this study, we have used the novel resistance gene Bph18 derived from Oryza australiensis and incorporated it into an elite japonica cultivar, Junambyeo, which is highly susceptible to BPH. The Bph18 gene was introduced by marker-assisted backcross (MAB) breeding into Junambyeo. The backcrossed progenies were evaluated for desirable agronomic and grain quality traits and the selection of improved breeding lines while simultaneously evaluating BPH resistance by bioassays in the greenhouse and foreground selection. Of the 26 advanced backcross breeding lines (ABL), four lines showed agronomic traits similar to those of the recurrent parent, with strong resistance to BPH. Molecular genotyping of the four ABL revealed the conversion of genotypes closely resembling the genotype of Junambyeo. The percentage of donor chromosome segments in ABL decreased from 12.3% in the BC₂ to 9.4%, 8.4% and 5.3% in BC₃, BC₄ and BC₅ generations, respectively. ABL retained small sizes of the donor chromosome segments on chromosomes 1, 2, 10, 11 and 12 but the genomes of ABL2, ABL3 and ABL4 were homosequential to the recurrent parent on chromosomes 3, 4, 5, 6, 7 and 9 without donor chromosome segment introgression. The ABL1 and ABL2 retained only some small segments of the donor genome on chromosomes 9 and 8, respectively. Fine structure analysis of the Bph18 flanking region between RM511 and RM1584 markers on chromosome 12 showed a progressive elimination of donor-derived chromosome segments from BC₂ to BC₅ generations. The percentage of O. australiensis derived chromosome segment substitution in the recurrent parent background decreased from 28% of the donor parent to 6.7%, 3.9%, 3.4% and 3.4% in BC₂, BC₃, BC₄ and BC₅ generations, respectively. However, it was revealed that the O. australiensis-derived chromosome segment (1320 kb) in ABL containing the Bph18 gene was consistently maintained irrespective of advances in backcross generations. BPH resistant elite breeding lines with agronomic and grain quality traits similar to those of the recurrent parent were successfully developed by foreground and background analysis in japonica background without linkage drag.     

Armoured scale insects (Hemiptera: Diaspididae) intercepted at the ports of entry in the Republic of Korea over the last 20 years

A total of 88 species of armoured scale insects from 40 different countries were intercepted by quarantine inspectors in the Republic of Korea on consignments of plants and plant products at the ports of entry in the Republic of Korea from 1996 to 2015. A list of all the species identified, along with a dichotomous key to the 88 intercepted species of armoured scale insects, is provided to help in the detection and identification of species of this important group of plant pests.     

Expression levels of three bacterial blight resistance genes against K3a race of Korea by molecular and phenotype analysis in japonica rice (O. sativa L.)

Bacterial blight, caused by Xanthomonas oryzae pv. oryzae (Xoo) is a destructive disease of rice in the major rice growing countries of Asia. In 2003, a serious bacterial blight epidemic occurred in the southwestern coastal areas in Korea, causing significant yield loss due to the emergence of a new race, K3a. IR24 near-isogenic lines containing Xa4, xa5, Xa7 and Xa21 genes conferred different degrees of resistance to the most virulent K3a isolate, HB01009 in an inoculation experiment in the greenhouse. Expression levels of the resistance genes, Xa4, xa5 and Xa21 were studied in two F2 populations derived from the crosses between elite japonica cultivars and an advanced backcross breeding line possessing Xa4, xa5 and Xa21 genes. F₂ progenies segregated for K3a resistance (R) and susceptible (S) phenotypes in a ratio of 3(R):1(S) indicated that K3a resistance was controlled by a major dominant gene. Three PCR markers tightly linked to the resistance genes Xa4, xa5 and Xa21 confirmed the presence of the genes and their interaction with each gene. This study demonstrated that the Xa21 gene dominantly contributed to K3a resistance. However, the Xa4 gene also contributed to the full expression of resistance. The level of expression of strong resistance to K3a race was attributed to the presence of Xa21 and Xa4 genes irrespective of the presence of xa5 gene. Our results suggest that the R-gene combinations of Xa4+Xa21 could be a useful and effective strategy toward improving resistance to K3a race of Korean japonica cultivars.     

Application of SSR markers and real-time PCR for variety identification in azuki-bean [Vigna angularis (Willd.) Ohwi and Ohashi]

The azuki bean in Korea consists of seven domestic varieties which have been developed and registered for the public during last 25 years. Here, we present a simple but reliable method to screen and identify Korean azuki bean varieties. A method based on simple sequence repeat (SSR) markers is widely used for prominent gene identification and variety discrimination. In molecular biology, real-time polymerase chain reaction (PCR) is a laboratory technique based on the polymerase chain reaction that is used to amplify and simultaneously quantify a targeted DNA molecule. It enables easy detection of a specific sequence in a DNA sample without performing electrophoresis and further processes. For separation of seven Korean azuki bean varieties, 110 unique azuki bean SSR markers from an (AG)n-enriched library were selected, synthesized and used for polymerase chain reaction (PCR). Data were taken through acrylamide gel electrophoresis and automated multi-capillary electrophoresis system for selection of specific markers and then changed into proper formats for data mining analysis. Ten primer pairs that showed high polymorphism were chosen for the indepth study. These ten primers were re-amplified with real-time PCR and checked the cycle threshold (Ct) and temperature (Tm) for comparison of amplification sequence in seven varieties. Consequently, a total of 20 alleles and 6 SSR primers were detected from the standard PCR amplification. Within these 6 primers, 7 alleles of 3 SSR primers were isolated for variety identification. From real-time PCR results, 3 SSR primers were selected as efficient markers for discrimination of seven Korean azuki bean varieties. The approach described here could be applied in monitoring our varieties and can be adapted in the azuki bean breeding program.     

A method of capability evaluation for upland soils

Utilizing the data and materials accumulated in the project “Observations on Soil Fertility Changes” organized by Ministry of Agriculture and Forestry and executed by 16 Prefectural Agricultural Experiment Stations throughout Japan, an attempt was made to derive a prediction equation for soil loss due to erosion.

Five Prefectural Agricultural Experiment Stations provided us with rainfall records from which monthly rainfalls by three intensity grades, under 2 mm/10 min (LE2R), 2-4 mm 10 min (MEDRi) and over 4 mm/10 min (GT4R), were read. Multiple regression of log-transformed soil loss upon these rainfall data gave the following regression equation

Log soil loss = -0.783 0.0185**GT4R+0.00597**LE2R -0.00763**MEDR for which multiple correlation coefficient (R) was 0.74. The units of measurement were kg are for soil loss mm/month for LE2R, MEDR, and GT4R.

In order to account for the contribution of slope and soil factors to soil loss, Hayashi's theory of quantification No. I was applied after coding the relevant data. R of log-transformed soil loss on GT4R, MEDR, LE2R, slope, bulk density (BD), and texture (TEXT), reached 0.80. GT4R had the highest partial correlation coefficient, followed successively by MEDR, slope, and LE2R. Bulk density (BD) and texture (TEXT) were taken from among the data available to represent characters relevant to erosion, but they had onlv low partial correlations with soil loss in this Particular study.

The method developed in this study appears to be promising only if properly collected data are available. Conditions that should be satisfied in the planning of experiments for the purpose derivation of a prediction equation have been put forward.     

Plant material as an alternative tool for management of aphid in country bean field

The aphids Aphis craccivora Koch attack country bean Lablab purpureus L. both in its vegetative and reproductive stages and cause severe damage. To develop an integrated management of aphid powders of black pepper, chili, turmeric, and coriander; oils of mahogany, neem, and eucalyptus; aqueous extracts of neem, basil, and garlic leaves; and water were evaluated in field conditions. The treatments were applied at 7?day intervals and aphid abundance per inflorescence was counted at 24, 48, and 72?h after treatment. All the plant materials reduced aphid abundance and flower infestation, ensuring a higher yield with larger and heavier pods. The neem oil treatment had the lowest abundance of aphid and consequently produced the highest marketable and gross yields. Predatory insects were abundant in the field, but their populations were lower in the treatments than the control. An economic analysis indicated that the highest gross return, net return, adjusted net return, and benefit-cost ratio were obtained from the mahogany oil treatment. The plant materials have insecticidal potential against aphids, and the oils of mahogany and neem showed better performances.