Incidence Of Virus Disease Research Articles

Incidence and infection rate of Maize streak virus disease by Cicadulina triangular on maize plants and its distribution from the lowest diseased leaf under tropical conditions

Several programmes have been initiated for the development of maize varieties with resistance traits of Maize streak virus (MSV) by International Institute of Tropical Agriculture (IITA), Ibadan, and have been released to farmers and research scientists. Therefore, a survey was conducted in five states in the south west of Nigeria (Oyo, Ogun, Ondo, Ekiti and Osun) during the raining planting season to determine the incidence of MSV disease by visual examination and sero-diagnostic screening of symptomatic plants. The determination of infection rate of MSV disease by Cicadulina triangular on maize plant and its distribution from the lowest diseased leaf was also studied. The mean MSV disease incidence observed in these states was 35.95% which confirms the presence of MSV in the south west of Nigeria. Sero-diagnostic screening of virus-induced symptomatic leaf samples indicated that out of the 250 leaves sampled per state, 24.4% tested positive for MSV in Oyo, 25.6% in Ondo, 34% in Ogun, 19.6% in Ekiti and 38.8% in Osun. In two-week-old plants, symptoms developed on the leaves that were emerging at the time of inoculation, while in six-week-old plants, symptoms developed on the leaves directly below the emerging leaves irrespective of the number of C. triangular used. These suggest that the lowermost leaf with symptoms of the disease indicates the growth stage at which a plant was infected. There was a relationship between symptom expression and plant age which could be very effective when carrying out surveys to gather information for epidemiological studies. In addition, the 10 varieties of maize inoculated with MSV through C. triangular transmission showed no significant difference in disease severity over time irrespective of the number of C. triangular used.

Genetic erosion of traditional varieties of vegetable crops in Europe: tomato cultivation in Valencia (Spain) as a case Study

Ever since the arrival of the tomato to Spain in the 16 th century, great diversification of the crop has taken place, giving rise to a rich collection of varietal types. The ‘Comunidad Valenciana’, with its deep-rooted agricultural tradition, is one of the Spanish regions with the greatest diversity in traditional tomato varieties, characterised by their local adaptation and high fruit quality. Nevertheless, traditional varieties of tomato have been progressively abandoned over recent decades. A survey was carried out in the ‘Huerta de Valencia’ area of the ‘Comunidad Valenciana’ in order to evaluate the factors involved in the genetic erosion of traditional tomato varieties, as a model of the process affecting vegetable crops in Europe. The growth of urban areas that absorb horticultural land, the change in agricultural techniques, the low profitability of farms and their small size, the advanced age of farmers, the conversion of vegetable gardens to other crops and the incidence of viral diseases, have been identified as the major factors affecting genetic erosion in this analysis. The development of resistant traditional varieties through a formal plant breeding programme, and the consolidation of the specialised markets that efficiently exploit the organoleptic quality of these varieties, would help to assure the profitability of these varieties, and hence their active conservation on an on-farm basis. Consequently, the loss of these materials that make up gene combinations of an outstanding value could be prevented, and farmers would obtain a profitable alternative in a highly competitive agriculture.

A case-crossover study of infectious diseases and new diagnosis of type 1 diabetes

Infectious diseases have been associated with increased risk of type 1 diabetes (T1D). The objective of this case-crossover was to quantify the role of infectious diseases as triggers for T1D, 1 and 2 yr preceding disease diagnosis. All children aged 2-18 yr diagnosed with T1D between 2004 and 2009 among a two million member Israeli healthcare organization were identified (n = 368). For each patient, visits to physicians with symptomatic infectious diseases during 1 and 2 yr before T1D diagnosis were collected and compared. A similar analysis was conducted in a population of non-diabetic members matched on exact date of birth, sex and socioeconomic status (n = 307). The rate of systemic viral infections was significantly higher in the year before T1D onset, as compared to the prior year [27 vs. 7%, respectively, odds ratio (OR) = 4.7, 95% confidence intervals (CI): 2.9-8.2]. This difference was most significant among patients diagnosed with T1D at the age of 2 to 6 (5 vs. 46%, respectively, OR = 27.0, 95% CI: 4.5-1105.4). Among non-T1D patients of the same age group, no difference was found in the proportion of patients with viral diseases 1 and 2 yr prior to T1D diagnosis (44 vs. 49%, respectively, OR = 0.8, 95% CI: 0.4-1.6). This unique association was limited only to viral diseases and to patients diagnosed with T1D at young age. Our results indicate that T1D occurring in toddlers is characterized with a relatively low incidence of viral disease 2 yr prior to diagnosis and a much higher incidence in the subsequent year.

Serological detection of yam viruses in farmers' fields in Ogun State, Nigeria

A field survey was conducted in eight local government areas (LGA) of Ogun state, Nigeria to assess the incidence of viral diseases of yams in the areas. Leaf samples were collected from 90 yam plants which were either symptomatic or asymptomatic. These were bulked into 45 during serological tests and the viruses indexed include yam mosaic virus (YMV); Dioscorea alata bacilliform virus (DaBV) and cucumber mosaic virus (CMV). DaBV was the most prevalent virus on the field with incidence of 48.9% (22/45) followed by YMV which occurred in 42.2% (19/45). CMV had the lowest percentage of incidence; 2.2% (1/45). Of all the LGAs visited, Abeokuta north and Abeokuta south had the highest incidence of YMV and DaBV, respectively. Mixed virus infections were also detected.

Ameixeira no Brasil

Tânia Eidam; Alexandre Pozzobom Pavanello; Ricardo Antonio AyubSource of B complex vitamins, vitamin C, potassium, riboflavin, phosphorus, and high laxative power, plums stands out for its nutritional composition and low caloric value of approximately 36 kcal per 100 grams. Moreover, this fruit also has antibacterial and antiviral action arousing the interest of the consumer.The plum tree is cultivated in Brazil for many years, but no one knows for sure when this species has been introduced in the country. Currently, the major producers are the states of Rio Grande do Sul, with annual production estimated at 12,200 tons, followed by Santa Catarina, with 11,000 tons, Parana with 7,000 tons, Sao Paulo with 6,011 tons and Minas Gerais with 1,600 tons. And the main cultivars are Gulfblaze, Irati Reubennel, Harry Pickstone, Polli Rose, Fortune and Leticia.However, the domestic production of fruits is not enough to supply the market. Annually are imported about 10,000 tons of plums from countries next to Brazil, while the exports do not exceed 400 kg per year, demonstrating the potential for expansion of the culture in the country.Belonging to the Rosaceae family, subfamily Prunoidae and genus Prunus, the plum is part of the stone fruit group, typically grown in regions of temperate climate. Among these fruit group the plum tree showed the smallest improvements due to the lack of suitable cultivars, phytosanitary problems and fruit yield of low quality.In the 70s, the bacterium Xylella fastidiosa, which causes leaf scald, was responsible for the eradication of orchards from the south of the state of Rio Grande do Sul until the state of Parana. The plum planting in the region was taken from the 80’s, with the use of seedlings free of bacteria obtained by tissue culture.Ever since breeding programs have been working with the objective to make available to the producer cultivars well adapted to climatic conditions and less susceptible to the leaf scald. However, the incidence of viral diseases has been observed in the culture, representing a new limit to their deve-lopment. As is the case of the bacteria causing the scalding, the main way to control viruses is to use quality seedlings.As to the management of the plum culture, research institutions have been working with the objective of providing support to the producer to produce better quality fruits. In order to increase the size of the fruits, hand thinning is being replaced by chemical thinning.The commercialization of the fruits is also a challenge for the producers, since the main market in Brazil is the fresh fruit marketing, given that the main form of plum industrialization is dehydrated, unusual technique used in Brazil because of the absence of tradition of such processing.Therefore the culture still finds some barriers to their advancement, highlighting the uncertainty of the farmer in relation to recommendations for the sector. However, when using cultivars well adapted to the region, it can achieve very good yields and good financial return. When harvested in September, October and November, with a caliber of IV and V, good health and coloration, the marketing prices reach values ranging from R$ 3.00 to 3.50 per kilogram. Agronomist, Master Student– UEPG – Ponta Grossa-PRE-mail: taniaeidam@hotmail.comAgronomist, Master Student– UEPG – Ponta Grossa-PRE-mail: alexandrepavanello@hotmail.comAgronomist, Prof. Dr., Dept. of Plant Science. UEPG – Ponta Grossa-PRE-mail: rayub@uepg.br

Excellent Results With High-Dose Mizoribine Combined With Cyclosporine, Corticosteroid, and Basiliximab in Renal Transplant Recipients: Multicenter Study in Japan

We performed a multicenter study in Japan to assess the efficacy and safety of immunosuppressive therapy with high-dose mizoribine (MZR; 6 mg/kg) combined with basiliximab (Bas), cyclosporine (CyA), and a corticosteroid in 90 patients. MZR was adjusted to maintain a target trough level of 1 to 2 μg/mL. CyA was started at 7 mg/kg to maintain blood levels in the target therapeutic range of 200 ng/mL (trough [C0]), 1200 ng/mL (2-hour post-dose [C2]), and 6000 ng·h/mL (area under the curve0–9). Bas (20 mg/body weight) was administered on the day of transplantation and on postoperative day 4. Rejection was diagnosed by episode and protocol biopsies. Cytomegalovirus (CMV) antigenemia (direct immunological staining of leukocytes using peroxidase-labeled monoclonal antibody [C7-HRP]) levels were measured every 2 weeks for 6 months. At 12 months, all patients and grafts were surviving except for one death from infection: the 1-year patient and graft survival rate was 98.9%. The acute rejection rate was 21.1%. The mean serum creatinine level at 1 year was 1.51 ± 0.61 mg/dL. The incidence of CMV disease was 0% with 28.9%, CMV antigenemia and 5.6%, ganoyclovir treatment. The incidence of BK virus disease was 2.2%. The mean serum uric acid level was 7.15 ± 1.79 mg/dL at 1 month and 7.06 ± 1.78 mg/dL at 3 months. We observed that a high-dose MZR regimen in combination with CyA, Bas, and corticosteroid was safe and effective to reduce the frequency of CMV and BK virus-related events in renal transplant recipients.

The virus infection of South-Hungarian corn fields

The past years cereal diseases, including the virus diseases have been increased in Hungary as well as worldwide. The aim of our work was to survey the virus infection of South Hungarian wheat fields. Leaf samples were collected in Szeged at the experimental farm of Cereal Research Nonprofit Co., in April and Junes of 2009 and 2010. DAS ELISA tests were carried out using Loewe antisera of Brome mosaic virus (BMV), Barley yellow dwarf virus (BYDV), Barley stripe mosaic virus (BSMV), Brome streak mosaic virus (BStMV), Wheat dwarf virus (WDV), and Wheat streak mosaic virus (WSMV) and measured with Labsystem Multiscan RC Elisa reader at 405nm. In the samples of 2009 the Wheat dwarf and Wheat streak mosaic viruses were dominated. It was also significant the appearance of the. Barley yellow dwarf virus. 2010. was favourable for the spread of the virus vectors, therefore the incidence of virus diseases increased.

Relationship between Tomato Yellow Leaf Curl Viruses and the Whitefly Vector

Tomato Yellow Leaf Curl Virus (TYLCV) and Tomato Leaf Curl Virus (ToLCV) are the currently known begomoviruses in Uganda. The relationship with their whiteflies (Bemisia tabaci) vector and its management were not known in Uganda. A direct relationship was expected between these begomoviruses and whiteflies at Buwama in Mpigi district of Uganda. Farmer practices were expected to have limited efficacy. To investigate this, a completely randomised block design was used for all trials with six treatments replicated three times. Treatments evaluated were farmer whitefly pest management practices. These included both chemical pesticide and non-pesticide applications. Data on whitefly population and tomato yellow leaf curl virus disease incidence was recorded weekly, and analysed using SAS and SPSS statistical programmes for ANOVA, and correlations. Ranked means, coefficients of variation and standard errors were noted. Virus-vector relationship field studies established that virus occurrence varied in space and time, and with management practices, crop development stage, and weather conditions. A negative relationship (R = -0.14, p 0.04) was established between number of plants infected with TYLCV (sensu lato) and percentage marketable tomato yield. Tomato maturity was inversely propotional to whitefly infestation (R = -0.5, p 0.0001). Uprooting and application of dimethoate was most effective of the six treatments. Tomato leaf curl virus diseases and whitefly management options were established in Uganda.

Effects of Variety and Planting Density on the Incidence of Common Viral Diseases of Cowpea (Vigna unguiculata) in a Southern Guinea Savannah Agro-ecology

Effects of Variety and Planting Density on the Incidence of Common Viral Diseases of Cowpea (Vigna unguiculata) in a Southern Guinea Savannah Agro-ecology

Climate changes, environment and infection: Facts, scenarios and growing awareness from the public health community within Europe

Climate change is a current global concern and, despite continuing controversy about the extent and importance of causes and of its effects, it seems likely that it will affect the incidence and prevalence of both residual and imported infections in Europe. Climate affects mainly the range of infectious diseases, whereas weather affects the timing and intensity of outbreaks. Climate change scenarios include a change distribution of infectious diseases with warming and changes in outbreaks associated with weather extremes. The largest health impact from climate change for Europe doesn’t come from vector borne infectious diseases. This does not mean that these types of health impacts will not arise in Europe. The ranges of several vector-borne diseases or their vectors are already changing in altitude due to warming. In addition, more intense weather events create conditions conductive to outbreaks of infectious diseases: Heavy rains leave insect breeding sites, drive rodents from burrows, and contaminate clean water systems. The incidence of mosquito-borne parasitic and viral diseases, are among those diseases most sensitive to climate. Climate change affect disease transmission by shifting the vector’s geographic range and by shortening the pathogen incubation period. climate-related increases in temperature in sea surface and level would lead to higher incidence of waterborne infectious and toxin-related illnesses, such as cholera and seafood intoxication. Climate changes all around the world with impact in Europe are demonstrated by the fact that recent cases of cholera have been imported to Europe from Kenya, where spreading epidemic has been linked to the El Niño phenomenon, originated from the Pacific Ocean. Human migration and damage to health infrastructures from aberrant climate changes could indirectly contribute to disease transmission. Human susceptibility to infections might be further compounded by alterations in the human immune system caused by increased exposure to ultraviolet radiation and malnutrition due to alterations in agricultural products. Different kind of incidents in Europe with extreme weather events demonstrated effects on public health. The recent outbreak of the insect-borne Chikungunya virus in Italy in 2007 is an example of the kind of new health threat that the EU must be vigilant to confront. In addition, health effects of flooding, have been related to an excess cases of leptospirosis and campylobacter enteritis. Such examples have been demonstrated reported after flooding in the Czech Republic. Similarly, an increase of cryptosporidiosis in the United Kingdom has been related to flooding. Changing vector distributions associated with tickborne encephalitis and malaria have also been dempostrated in EU. A recently reported case of malaria in Italy in June 2008, suspected to be indigenously acquired, has shown how easily malaria could be reintroduced into several countries in the region. Another case of malaria in Greece in May 2010 affecting a young man living in a forestry region was claimed at KEELPNO-the Greek Center for disease control. Would this latest case be considered closely related to the one from Italy? If yes, then Public Health Services should elaborate plans to affront possible tickborne diseases. Heat waves are important causes of mortality on mortality are important. The deaths seen in France in 2003 from a heat wave are projected to be repeated, as heat waves become more severe. However, heat waves impacts on the transmission and severity of infectious diseases have not been elucidated. Finally scientific challenges include the elucudation of climate changes and extreme weather condition impact on infection transmission and outcome, human immune system changes and infection response, outbreak scenarios, animal and plant health and public health preparedness. European action plans to affront climate changes related health and infection problems are developed by the EU Commission at different levels and jointly by different DGs. In a few words within the EU the following points on human, animal and plant health are considered a priority: * Strengthening cooperation between the services of these three branches of health (human, animals, plants); * Developing action plans in the event of extreme weather conditions, in order to be better prepared and to react in the best way; * Gathering more reliable information on the risks of climate change whilst maintaining international cooperation, in particular with the WHO, as cooperation beyond that between Member States will be required to be more effective; * Providing additional effort to identify the most effective measures; * Improving the surveillance and the control of the animal diseases. The European Commission has decided to consider climate change, and the consequences it has on health, with greater importance whilst being aware that it is at the root of numerous diseases.

Interactions in a host plant-virus–vector–parasitoid system: Modelling the consequences for virus transmission and disease dynamics

A full understanding of plant virus epidemiology requires studies at different scales of integration: from within-plant cell processes to vector population dynamics, behaviour and broader ecological interactions. Vectors respond to cues derived from plants (both healthy and virus-infected), from natural enemies and from other environmental influences, and these directly affect the temporal and spatial patterns of disease development. The key element in linking these scales is the transmission process and the determining factors involved. We use a mathematical model to show how the presence of natural enemies, by increasing virus transmission, can increase the rate of virus disease development while at the same time reducing vector population size, supporting recent empirical evidence obtained in microcosm studies. The implication of this work is that biological control of arthropod pests, which are also virus vectors, using parasitoid wasps, may have unanticipated and negative effects in terms of increased incidence of virus disease.

Virus symptom expressions on Musa landraces in 1999, 2000 and 2004 in southern Nigeria: Cucumber mosaic virus (CMV) disease incidence and subgroup differentiation

Musa landraces (469) from 73 villages in 10 states in 1999, 2000 and 2004 in southern Nigeria were visually assessed to determine virus symptoms associated with CMV disease. CMV indexing was done using dot-blot immunoassay and ELISA. Monoclonal antibodies were used to group CMV isolates in 2004. Symptoms of interveinal chlorosis and chlorotic streaks were observed in 22.4 and 17.9% of the Musa samples with CMV disease incidences of 17.1% and 14.7%, respectively. Other virus symptoms accounted for between 1.5 and 12.2% of the total leaf samples while 13.9% were asymptomatic. CMV incidence in asymptomatic leaf samples was as high as 10.4% while the virus incidence in the other symptom types were between 0.9 and 7.9%. The incidences of CMV in both the symptomatic and asymptomatic plants in 1999, 2000 and 2004 were between 1.3 and 18.7%, 1.9 and 26.9% and 4.9 and 26.4%, respectively.

Incidence of potato viruses and bacterial wilt disease in the west Amhara sub-region of Ethiopia.

SUMMARY A survey of virus diseases and bacterial wilt was carried out in four major potato growing administrative zones in the west Amhara sub-region of Ethiopia in 2008. Leaf samples with symptoms suggestive of virus infection were collected from 38 randomly selected fields in 16 locations, whilst for bacterial wilt detection tuber and stem samples were collected from 23 and 12 fields in 15 and 12 locations, respectively. Disease incidences were visually assessed in the field and the identities of the pathogens were confirmed by laboratory testing using double antibody sandwich (DAS)-ELISA for viruses, and nitrocellulose membrane (NCM)-ELISA kits for Ralstonia solanacearum. In addition, an enrichment procedure was used to determine latent infection by R. solanacearum. Virus disease incidence varied from zero to 100% in different potato growing systems, whilst bacterial wilt incidence as high as 25% was recorded in farms in the west Gojam and north Gonder zones when assessed based on visual field symptoms. Results of laboratory testing for viruses confirmed the occurrence of at least five viruses, with Potato virus S (PVS) being the most widely distributed. Other viruses identified included Potato virus X (PVX), Potato virus M (PVM), Potato leaf roll virus (PLRV) and Potato virus Y (PVY), in order of importance. Mixed infections with two or more viruses were also detected. Potato virus A (PVA) was not detected in any of the samples tested. Latent infection by R. solanacearum was found in various potato fields, including experimental plots, farmers’ seed potato production fields, suggesting the need to consider strict quarantine measure and restrict the free movement of seed tubers.

Evaluation of Genotype and Environment Effects on Taste and Aroma Flavor Components of Spanish Fresh Tomato Varieties

Taste and aroma related compounds have been analyzed in a collection of four traditional varieties and two tomato hybrids, representing a wide variability in fruit shape and color, grown in different environments: screenhouse and open field. Protected cultivation tended to show lower sugar concentration (fructose and glucose) but similar acid contents (citric, malic, and glutamic acids). The decreased levels of sucrose equivalents and the similar ratios of sucrose equivalents to citric or glutamic acid contents indicated that protected cultivation, despite being useful to reduce the incidence of pests and viral diseases, reduces the organoleptic quality. Additionally, it doubles the interaccession variability and increased the level of intra-accession variability. In the case of aroma, the genotypic effect was considerably higher than the environmental component on the 12 main volatiles analyzed. Only hexanal and methyl salicylate were significantly affected by environment, while 10 out of 12 volatiles were affected by the genotype. Biplot analysis showed that, even in considerably different environments, it is possible to identify genotype-dependent main aroma profiles. In the case of 13 background volatiles, the environment showed no significant effects and the genotypic effect was lower, though it is possible to identify genotypic trends in background notes.

Regional Differences in the Association Between Land Cover and West Nile Virus Disease Incidence in Humans in the United States

West Nile virus (WNV) is generally considered to be an urban pathogen in the United States, but studies associating land cover and disease incidence, seroprevalence, or infection rate in humans, birds, domesticated and wild mammals, and mosquitoes report varying and sometimes contradictory results at an array of spatial extents. Human infection can provide insight about basic transmission activity; therefore, we analyzed data on the incidence of WNV disease in humans to obtain a comprehensive picture of how human disease and land cover type are associated across the United States. Human WNV disease incidence in Northeastern regions was positively associated with urban land covers, whereas incidence in the Western United States was positively associated with agricultural land covers. We suggest that these regional associations are explained by the geographic distributions of prominent WNV vectors: Culex pipiens complex (including Cx. pipiens and Cx. quinquefasciatus) in the Northeast and Cx. tarsalis in the Western United States.

Efficacy and Safety of Thymoglobulin Induction as an Alternative Approach for Steroid-Free Maintenance Immunosuppression in Pediatric Renal Transplantation

Given the recent withdrawal of daclizumab (DAC), the safety and efficacy of thymoglobulin (TMG) was tested as an alternative induction agent for steroid-free (SF) immunosuppression in pediatric kidney transplant recipients. Thirteen pediatric renal transplant recipients meeting defined high-risk criteria at transplantation were offered TMG induction and SF immunosuppression with maintenance mycophenolate mofetil and tacrolimus between October 2008 and January 2010. Patients were closely monitored at baseline, 3, 6, 9, and 12 months posttransplant for protocol biopsy and clinical outcomes. Outcomes were compared with 13 consecutively transplanted low-risk patients receiving an established DAC-based SF protocol (Sarwal et al., WA, American Transplant Congress 2003). There was a significant trend for overall decrease in the absolute lymphocyte counts in TMG group (F=5.86, mixed model group effect P=0.02), predominately at 3 months compared with DAC group (0.7±0.6 vs. 2.1±1.0, P=0.0004); however, lymphocyte count was recovered and was back to reference range by 6 months in TMG. There was trend toward more subclinical cytomegalovirus (15% vs. 0%) and BK viremia (17% vs. 0%) in the TMG group, with no differences in the incidence of subclinical Epstein Barr virus viremia (23% vs. 31%) or clinical viral disease. Mean graft function was excellent, and with a minimum follow-up of 6 months, there were no episodes of acute rejection. TMG seems to be a safe alternative induction strategy in patients for SF immunosuppression in pediatric renal transplantation. Extended follow-up and greater enrollment are necessary to fully explore the impact of TMG dosing on viral replication posttransplantation.

Ribgrass Mosaic Tobamovirus Occurred on Chinese Cabbage in Korea

A tobamovirus, Ribgrass mosaic virus (RMV), was identified newly from chinese cabbage (Brassica campestris L. pekinensis) in Korea. Virus disease incidence of RMV on chinese cabbage was 37.9% in alpine area on August in 1993. RMV induced the symptoms of necrotic ring spots, necrotic streak on midrib and malformation. RMV, Ca1 and Ca3 isolate, could infect 35 species out of 45 plants including Chenopodium amaranticolor. Physical properties of RMV Ca1 isolate were very stable as 10.8 over for dilution end point, <TEX>$95^{\circ}C$</TEX> for temperature inactivation point and 18 weeks for longevity in vitro. RMV had the soil transmission rate of 75.0% for the chinese cabbages, 'Chunhawang' and 'Seoul' cultivars. The purified virions of RMV had the typical ultraviolet absorption spectrum of maximum at 260 nm and minimum at 247 nm. RMV of Ca1 isolate was related serologically with antisera of Tobacco mosaic virus (TMV)-Cym, TMV-O and Pepper mottle virus, but not related with antiserum of Odontoglossum ring spot virus. coat protein gene of RMV-Ca1, sized 473 nucleotides, encoded 158 amino acid residues. Nucleotide identity of RMV-Ca1 CP gene was 96.4% with RMV-Shanghai (GenBank accession No. of AF185272) from China and 96.0% with RMV-Impatiens (GenBank accession No. of AM040974) from Germany. Identity of amino acids between RMV-Ca1 and the two RMV isolates was 96.8%. Specific three primers were selected for rapid and easy genetic detection of RMV using Virion Captured (VC)/RT-PCR method.

Evaluation of maize/pepper intercropping model in the management of pepper veinal mottle virus, genus Potyvirus, family Potyviridae on cultivated pepper (Capsicum annuum L.) in Nigeria

Three pepper cultivars obtained from National Horticultural Research Institute (NIHORT) Idi-Ishin, Ibadan were intercropped with maize for two planting seasons between March and September in each year. These pepper cultivars were NHV1-D96, and NHV1-E96 and NHV1-F96. A 90-day maturing maize variety (DMSR-1) was used as the intercropping companion plant. The pepper seedlings were raised in a greenhouse. A randomised complete block design was used for this experiment. Each variety was intercropped with maize and replicated three times including the sole plot. The results obtained for each year were not significantly different from each other. There was a significant difference in pepper veinal mottle virus (PVMV) disease incidence and severity at a probability of less than 5% in the treatment used. PVMV disease incidence and severity was relatively higher in the sole pepper crop compared with pepper intercropped with maize. In the three varieties of peppers intercropped with maize, less than 17% disease incidence and 15% disease severity were recorded in all the varieties with a minimum yield of 4 tons per hectare compared with the sole pepper cropping of the same variety that recorded as high as 75% disease incidence and 72% disease severity with a maximum yield of 3.3 tons per hectare. There was a significant negative correlation at probability less than 0.05 between disease incidence, severity and the fruit yield of pepper. Variety NHV1-F96 in the maize intercrop recorded the highest yield of 15.99 tons/ha with a land equivalent ratio of 2.4 tons/ha. The success of the PVMV disease management evaluated in this study was judged by the extent of reduction in number of diseased plants and by an increase in vigor of the cultivated pepper crop, with an increase in fruit yield and quality. This signifies that for devising effective viral disease management for any crop it is important that the vectors of the virus present in the particular area are exactly controlled from having contact with the target plant. The reduction of pest incidence with intercropping of non-host plants should be carefully considered.

Incidence and Severity of Common Viral and Fungal Diseases of Dry Season Tomato Crop in a Southern Guinea Savannah Agro-Ecology

The incidence and severity of common fungal and viral diseases affecting dry season tomato crop were determined on the tomato field of the Teaching and Research farm of the University of Ilorin, situated in the Southern Guinea savannah ecological zone of Nigeria. Seeds were sown in January in the nursery and seedlings were transplanted to the field, inJanuary 2005 and 2006 at the age of 4 weeks. The growth period of tomato was partitioned into three stages viz: seedling/vegetative stage (1), pre-flowering stage (2), and flowering/fruiting stage (3), during which the incidence of fungal, viral or mixed fungal and viral diseases wereinvestigated. The aim was to identify the relative prevalence of the disease categories for each growth stages. The results showed plants in the earliest stage of growth with the lowest rate of infection. Nevertheless, viral disease incidence was the significantly highest (22.7%) at this stage. The incidence of double infections increased gradually from the second growth stagereaching 29% in the third stage. Comparatively, infection with virus alone in the third stage was 28.5%, while fungus alone was 0. 59%. The highest disease severity was in plants that were mixed infected by the two categories of pathogens. Such plants had significant retardation ofgrowth (height and mean number of leaves/ leaflets) and yield attributes such as the number of fruits produced per plant compared to singly infected and apparently healthy plants.Keywords: Disease incidence, dry season, tomato, Southern Guinea savannah ecology

Differing cell population structure reflects differing activity of Percoll-separated pronephros and peritoneal leucocytes from barramundi ( Lates calcarifer)

Aquaculture of barramundi or Asian sea bass ( Lates calcarifer L) is expanding throughout the Asia-Pacific region in both marine and freshwater systems. Incidence of bacterial and viral diseases is high in this species throughout the region yet little is known about the immune system of this highly adaptable euryhaline fish. Ultimately, most pathogens are eradicated by the phagocytic cells, however there is great diversity and plasticity amongst these cell populations in mammals and in fish. To better understand disease processes in barramundi, Percoll-purified leucocyte populations from haematopoietic tissues of the head kidney were compared with populations isolated from the peritoneal cavity morphologically, cytochemically and in terms of the ability to respond to stimulation, using flow cytometry, light microscopy and fluorimetric/luminometric assays. The peritoneal cells comprised predominantly of macrophages and putative mature monocytes whilst the head kidney cells comprised lymphocytes, including immunoglobulin-positive B-lymphocytes, some small monocytes and macrophages. The differing population structures were reflected in the ability of the cells to respond to stimulation with either lipopolysaccharide or phorbol myristate acetate, as the chemiluminescence response of peritoneal cells was 7 to 9-fold higher than head kidney cells. Both populations were capable of being primed by LPS, but the kinetics differed, with optimal priming in peritoneal cells occurring after 6 h exposure whilst head kidney cells required at least 24 h exposure to LPS for optimal priming. Both head kidney and peritoneal populations produced nitric oxide in response to stimulation with LPS and interferon gamma, but again, response was higher in peritoneal cells. The implications of the differing population structures and activities amongst these cells should be considered when developing models for further study of host–pathogen interactions in this increasingly important fish.