Variation In Symptom Expression Research Articles

Long-Term Esca Monitoring Reveals Disease Impacts on Fruit Yield and Wine Quality.

Esca is a widespread grapevine trunk disease, and a global increase in esca incidence has been observed in recent decades. Estimates attribute considerable economic losses to esca, and the disease is considered one of the major causes of vine mortality and vineyard dieback. However, accurate quantification of esca incidence is difficult due to symptom inconsistency, and there are very few studies precisely quantifying yield losses and impacts on fruit composition and wine quality. This study carried out an extensive esca surveying program; annually monitoring approximately 57,000 vines across 12 estates in the Bordeaux region for 9 years. In conjunction with this surveying program, we quantified the yield losses of vines with known esca symptom histories and assessed their fruit composition and resulting wine quality. The study revealed that, because of year-to-year variation in symptom expression, accurate rates of esca can only be obtained through monitoring over many years. We found that yield losses in individual vines exhibiting esca can reach up to 50% but they are rarely unproductive, and when scaled to the parcel scale yield losses are low, never exceeding 1 hl/ha. In addition, the quality of the grapes produced is similar to that obtained from vines without symptoms. Finally, the majority of mortality observed in vineyards was not due to esca, with only 40% of dead vines exhibiting an esca history. These results suggest that the impact of esca is likely overestimated and that it is necessary to more broadly investigate other factors contributing to vine mortality and vineyard dieback.[Formula: see text] Copyright © 2022 The Author(s). This is an open-access article distributed under the CC BY 4.0 International license.

Genetic diversity of Chilli veinal mottle virus infecting different chilli landraces in North East India indicates the possibility of transboundary movement of virus.

Diverse chilli genetic resources of North East India occupy a unique niche in the Nation's chilli gene pool. Widely cultivated chilli landraces (King chilli: Capsicum chinense, bird eye chilli: Capsicum frutescens and Capsicum annuum) of North East India in general and Manipur in particular suffer from decline complex due to high incidence of viral diseases. With this background and the known prominent distribution of Chilli veinal mottle virus (ChiVMV) in Asian region, we studied its prevalence and association with diverse symptoms of chilli landraces. Molecular indexing of samples from 40 chilli plantation groves of Manipur using reverse transcription (RT)-PCR targeting the coat protein (CP) region of ChiVMV genome revealed a high incidence and wide prevalence. Out of a total of 127 chilli samples collected from different groves of Manipur, 81 chilli samples (63.78%) were positive for ChiVMV. Interestingly, ChiVMV infection rate was comparatively higher in the hilly groves (69.23% samples positive) compared to the valley groves (60% samples positive). Present study through the extensive surveys and molecular indexing work, conclusively reported the association of ChiVMV with diverse symptoms like cupping of leaf lamina with mottling, vein banding and puckering in different chilli landraces. Further, five representative ChiVMV isolates sampled from different groves of Manipur upon mechanical inoculation showed significant variation in symptom expression, indicating wide pathogenic diversity among them. Partial coat protein (CP) sequence analysis of five ChiVMV isolates from Manipur although indicated genetic homogeneity among them, but distinctiveness from ChiVMV isolates reported from the other parts of India. Phylogenetic clustering of ChiVMV isolates from Manipur near Chinese isolates rather than other Indian isolates suggested the possibility of transboundary movement.

Informant discrepancy defines discrete, clinically useful autism spectrum disorder subgroups.

Discrepancy between informants (parents and teachers) in severity ratings of core symptoms commonly arise when assessing autism spectrum disorder (ASD). Whether such discrepancy yields unique information about the ASD phenotype and its clinical correlates has not been examined. We examined whether degree of discrepancy between parent and teacher ASD symptom ratings defines discrete, clinically meaningful subgroups of youth with ASD using an efficient, cost-effective procedure. Children with ASD (N=283; 82% boys; Mage =10.5years) were drawn from a specialty ASD clinic. Parents and teachers provided ratings of the three core DSM-IV-TR domains of ASD symptoms (communication, social, and perseverative behavior) with the Child and Adolescent Symptom Inventory-4R (CASI-4R). External validators included child psychotropic medication status, frequency of ASD-relevant school-based services, and the Autism Diagnostic Observation Schedule (ADOS-2). Four distinct subgroups emerged that ranged from large between-informant discrepancy (informant-specific) to relative lack of discrepancy (i.e. informant agreement; cross-situational): Moderate Parent/Low Teacher or Low Parent/Moderate Teacher Severity (Discrepancy), and Moderate or High Symptom Severity (Agreement). Subgroups were highly distinct (mean probability of group assignment=94%). Relative to Discrepancy subgroups, Agreement subgroups were more likely to receive psychotropic medication, school-based special education services, and an ADOS-2 diagnosis. These differential associations would not have been identified based solely on CASI-4R scores from one informant. The degree of parent-teacher discrepancy about ASD symptom severity appears to provide more clinically useful information than reliance on a specific symptom domain or informant, and thus yields an innovative, cost-effective approach to assessing functional impairment. This conclusion stands in contrast to existing symptom clustering approaches in ASD, which treat within-informant patterns of symptom severity as generalizable across settings. Within-child variability in symptom expression across settings may yield uniquely useful information for characterizing the ASD phenotype.

Detection and survey of coffee ringspot virus in Brazil.

Coffee ringspot virus (CoRSV) a member of the proposed genus "Dichorhavirus", was surveyed on commercial and research farms spanning an area responsible for the majority of Coffea arabica production in Brazil. Virus-infected plants were found at one hundred percent of locations (n = 45) sampled. All cultivars, regardless of cherry color, were found to serve as hosts, suggesting that there is limited resistance in commercially employed germplasm. Reverse transcription PCR analysis revealed that the virus is contained within symptomatic lesions, with little systemic spread throughout leaves. Phylogenetic analysis based on the ORF1 (nucleocapsid) gene identified a strong geo-spatial relationship among isolates, which clustered into three clades. Despite low genetic diversity among isolates, variation in symptom expression was observed in the experimental host Chenopodium quinoa. Our analyses support the hypothesis that the spread of CoRSV is constrained by the clonal expansion of thelytokous populations of Brevipalpus phoenicis. The widespread occurrence of this virus suggests that it is much more prevalent than previously thought.

Variability in yellow leaf symptom expression caused by the Sugarcane yellow leaf virus and its seasonal influence in sugarcane

Yellowing of leaf midrib, its extending to adjoining lamina and necrosis of discoloured tissues from the tip portion are the common yellow leaf (YL) symptoms observed in tropical climatic conditions in India. As symptoms of this disease vary among the varieties, the progress of these symptoms was studied in Coimbatore from disease free status in the plant, using a newly devised YL 0-5 disease severity scale. Progress of recovery of symptoms in symptomatic leaves was monitored with a 0-4 symptom severity scale for four seasons. Detailed observations with ten symptomatic varieties have very clearly indicated a clear variation in symptom expression among them. First symptoms were recorded in leaf 1 and 2 in few plants of the cvs CoPant 84211 and B38192. Apart from yellow discoloration of midrib, reddish discoloration, pinkish midrib and laminar discoloration were recorded in cvs B38192, Co 86010 and Co 85019, respectively. Progress of laminar discoloration on both sides parallel to the midrib varied from ~0.5 to 3.0 cm in different varieties. Apart from severe laminar discoloration progressive leaf drying from the tip region along the midrib towards leaf base and bunching of leaves in the crown were identified as the severe form of disease in sugarcane varieties. For such leaf drying with characteristic pattern of ‘V’ or ‘Y’ shape and in a bunchy top, leaf yellowing was recorded up to -7th leaf and drying was recorded up to -1st leaf in severe YL-affected variety B38192. Progressive increase in disease symptom was noticed in most of the varieties till nine months after planting and later a fluctuation in disease expression was noticed among the varieties. Subsequently decrease of yellowing was observed leaving behind the dried laminar region at the tip. The correlation and regression analyses with meteorological parameters established that ~ 50 % of variability in disease severity grades is explained by minimum temperature and relative humidity in the afternoon. This study on the disease symptomology has clearly revealed variation in YL symptom expressions among the varieties and impact of prevailing weather factors on the fluctuation of disease expressions.

Cultural and morphological variability amongRhizoctonia solaniisolates from trans-gangetic plains of India

Banded leaf and sheath blight incited by Rhizoctonia solani f. sp. sasakii Khunn. (Teleomorph: Thanatephorus cucumeris) is gaining devastating potentials in India. The pathogen is reported to show variation in expression of symptoms on the same genotypes grown in different locations. Fifteen isolates from trans-gangetic plains of India were collected to examine the cultural and morphological variability and pathogenic behaviour on host Zea mays. The isolates were from maize and rice host origins. Considerable variability was found among the isolates. The isolates of maize origin were poor sclerotia producing in culture, formed compact dense/fluffy, pale white to yellowish growth on PDA, producing irregular to organized, smooth surfaced sclerotia, faster radial growth in culture, acute branching of hyphae and high pathogenicity. The rice isolates showed a contrasting behaviour in forming sub-central to scattered, pitted sclerotia lighter in weight than maize counterparts, compact sparse colony, slow to medium radial growth, light brown to dark brown colony. Aerial bearing was not recorded in most of these isolates. All the rice isolates were fast sclerotia initiating in culture; however, higher incubation period was recorded in pathogenicity tests. The lesions were also scattered and disease score ranged from 2.6–3.1. The cultural and morphological parameters used in this investigation may be used to examine the biology of R. solani isolates from other agro-climatic regions also.

On demand treatment and home therapy of hereditary angioedema in Germany - the Frankfurt experience

BackgroundManifestation of acute edema in hereditary angioedema (HAE) is characterized by interindividual and intraindividual variability in symptom expression over time. Flexible therapy options are needed.MethodsWe describe and report on the outcomes of the highly individualized approach to HAE therapy practiced at our HAE center in Frankfurt (Germany).ResultsThe HAE center at the Frankfurt University Hospital currently treats 450 adults with HAE or AAE and 107 pediatric HAE patients with highly individualized therapeutic approaches. 73.9% of the adult patients treat HAE attacks by on-demand therapy with pasteurized pd C1-INH concentrate, 9.8% use additional prophylaxis with attenuated androgens, 1% of the total patient population in Frankfurt has been treated with Icatibant up to now. In addition adult and selected pediatric patients with a high frequency of severe attacks are instructed to apply individual replacement therapy (IRT) with pasteurized pd C1-INH concentrate. Improvement on Quality of Life items was shown for these patients compared to previous long-term danazol prophylaxis. Home treatment of HAE patients was developed in the Frankfurt HAE center in line with experiences in hemophilia therapy and has so far been implemented over a period of 28 years. At present 248 (55%) of the adult patients and 26 (24%) of the pediatric patients are practicing home treatment either as on demand or IRT treatment.ConclusionsIn conclusion, the individualized home therapies provided by our HAE center, aim to limit the disruption to normal daily activities that occurs for many HAE patients. Furthermore, we seek to optimize the economic burden of the disease while offering a maximum quality of life to our patients.

Good days and bad days in dementia: A qualitative analysis of variability in symptom expression

Good days and bad days in dementia: A qualitative analysis of variability in symptom expression

Structure and variation in the wild-plant pathosystem: Lactuca serriola–Bremia lactucae

Over the past decade, extensive research on the wild-plant pathosystem, Lactuca serriola (prickly lettuce)–Bremia lactucae (lettuce downy mildew), has been conducted in the Czech Republic. Studies focused on pathogen occurrence and distribution, host range, variation in symptom expression and disease severity, interactions of B. lactucae with another fungal species (Golovinomyces cichoracearum) on L. serriola, variation in resistance within natural populations of L. serriola, the structure and dynamics of virulence within populations of B. lactucae, sexual reproduction of B. lactucae, and a comparison of virulence structure and changes in B. lactucae populations occurring in wild (L. serriola) and crop (L. sativa) pathosystems. The incidence of B. lactucae on naturally growing L. serriola and other Asteraceae was recorded. Lactuca serriola was the most commonly occurring host species, followed by Sonchus oleraceus. Over the duration of these studies, the incidence of B. lactucae in L. serriola populations varied between 45–87%. Disease incidence and disease prevalence were partly related to the size, density and different habitats of L. serriola populations. In addition to B. lactucae infection, infection by the lettuce powdery mildew fungus (Golovinomyces cichoracearum) was quite common, including co-infection. Variation in resistance to B. lactucae was studied by using ten isolates (NL and BL races with known virulence patterns) at a metapopulation level, i.e. 250 L. serriola samples representing 16 populations from the Czech Republic (CZ). Our comparisons revealed broad variation in host resistance among host populations and also intrapopulation variability. In the CZ populations, 45 resistance phenotypes were recorded, the most frequent were race-specific reaction patterns. Structural and temporal changes in virulence variation of B. lactucae populations on L. serriola were studied during 1998–2005. Altogether, 313 isolates of B. lactucae originating from the Czech Republic were examined for the presence of 32 virulence factors (v-factors), and 93 different virulence phenotypes (v-phenotypes) were recorded. A study of v-factor frequency showed that common v-factors in B. lactucae populations match some of the race-specific resistance genes/factors (Dm genes or R-factors) originating from L. serriola. The highest frequency was recorded by v-factors v7, v11, v15–17, and v24–30. In contrast, v-factors (e.g. v1–4, 6, and 10) matching Dm genes originating from L. sativa were very rare. This demonstrates the close adaptation of B. lactucae virulence to the host (L. serriola) genetic background. Temporal changes in virulence frequencies over the period were recorded. In many v-factors (v11, v14, v16, and v25–28), fluctuations were observed, some (v14 and v17) shifting to higher frequencies, and others (v5/8 and v23) decreasing. The occurrence of mating types was studied (1997–1999) in a set of 59 B. lactucae isolates. Both compatibility types (B1 and B2) were recorded; however the majority of the isolates (96%) were type B2. A comparative study of B. lactucae virulence variation between the wild (L. serriola) and crop (L. sativa) pathosystems showed major differences. Migration and gene flow between both pathosystems and the potential danger of wild B. lactucae populations for cultivated lettuce are discussed. This paper summarizes comprehensive and unique research on an oomycete pathogen (B. lactucae) that is shared between a crop (lettuce, L. sativa) and its close wild relative (prickly lettuce, L. serriola). The data demonstrate clear evidence about race-specific interactions, variation and changes in virulence, and coevolutionary relationships in the wild pathosystem L. serriola–B. lactucae. Conclusions contribute to the broadening and better understanding of gene-for-gene systems in natural host–pathogen populations and their relationships to crop pathosystems.

Improving RLS diagnosis and severity assessment: Polysomnography, actigraphy and RLS-sleep log

Restless legs syndrome (RLS) has proven to often have both a difficult differential diagnosis and also problems with assessing severity. These problems contribute to some of the confusion about medication effects on RLS and also to the large placebo effect seen in clinical trials. We need to find better diagnostic and evaluative methods. The following three promising methods for better diagnosis and evaluation have been somewhat overlooked. (1) The polysomnogram with a preceding suggested immobilization test offers objective measures of the motor sign of RLS, the periodic leg movements in sleep (PLMS) under standard conditions of sleep and during quiet resting, both of which provoke RLS symptoms. The diagnostic sensitivity and specificity for these measures is about the same as that for MSLT diagnosis of narcolepsy and the use of these tests deserves to be reconsidered. (2) Leg activity measures provide an attractive less costly and more accessible alternative to the polysomnogram and can be used on repeated nights, reducing measurement problems occurring because of the well-recognized variability in symptom expression across days. (3) RLS-logs provide a more concurrent assessment of RLS symptom occurrence that provide a more direct measure of severity than questionnaires completed at clinic visits. Similar logs have been found useful in evaluating other sensory disorders such as headache. These methods need to be developed and evaluated in both our research and clinical trials of RLS because they may enhance accuracy of diagnosis and reduce the placebo response to treatments.

A new technique for monoconidial culture of the most aggressive isolate in a given population of Bipolaris sorokiniana, cause of foliar spot blotch in wheat and barley

We developed a new technique for monoconidial culture of the most aggressive isolate in a given population of Bipolaris sorokiniana, to facilitate the evaluation of spot blotch resistance in wheat and barley. Blotched portions of infected barley leaves were placed on a glass slide in a moist chamber for production of conidia by associated fungal hyphae. Conidia were collected separately and grown on water agar discs. Individual water agar discs having conidium growth were inoculated on barley leaves. The conidium producing the earliest symptom with the largest lesion was considered most aggressive. This lesion was incubated in a moist chamber and the conidial offspring were tested for pathogenicity. When a uniform infection was observed, a small piece of the lesion was cut using a sterilized scalpel, surface sterilized with NaOCl, and inoculated in the centre of Petri dishes containing potato dextrose agar medium. The inoculated Petri dishes were incubated at 25 ± 1 °C to yield monoconidial cultures of the most aggressive isolate. Variability in symptom expression caused by the most aggressive isolate of a given population was much less than variability in symptom expression caused by all isolates collectively. The techniques will be useful for plant pathologists and breeders in screening for spot blotch resistance in wheat and barley.

Back to basics and beyond: increasing the level of resistance to Septoria tritici blotch in wheat

Septoria tritici blotch (STB), caused by the ascomycete Mycosphaerella graminicola (anamorph: Septoria tritici), is one of the most ubiquitous and important diseases of wheat worldwide. Losses to STB can range from 30 to 50% in disease-conducive climates. Little progress was made in increasing the level of resistance to STB in wheat prior to 1990, due to a variety of factors, including slow growth of the pathogen in culture, long latent period of the disease, the need for specific environmental conditions for infection, and variability in symptom expression, which complicated the scoring of inoculated plants. To identify and map genes for resistance to STB in the wheat genome, to understand how they function in their interactions with the pathogen and, ultimately, to increase the level of resistance so that the disease can be managed without extensive use of fungicides, crosses between parents differing in response to STB were made or obtained from collaborators for the resistance genes Stb1, Stb2, Stb3, Stb4 and Stb8. Plants were grown and inoculated with one or more isolates of M. graminicola in a greenhouse. The five targeted resistance genes Stb1-Stb4 and Stb8 were mapped to wheat chromosomes 5BL, 3BS, 6DS, 4DS, and 7BL, respectively. All of the genes had at least one linked microsatellite locus, and two of them (Stb2 and Stb8) were mapped between flanking microsatellites. These experiments plus those in other laboratories worldwide have determined the map locations for 12 genes for resistance to STB in wheat during the past 7 years. Most of these genes have associated molecular markers that will be useful for future marker-assisted selection. These analyses were aided by accurate phenotypic analysis, which remains the most difficult part of the process. Technological approaches for improving phenotypic evaluation show promise, including measuring fungal biomass and estimating expression of host genes that are associated with disease resistance by real-time PCR, but they will work better when augmented with improved methods of plant inoculation. Although there is still a great need for more markers, additional mapped genes, and a better understanding of defence responses, recent results now provide the basis for rapid progress in increasing the level of resistance to STB in wheat.

Cross-ethnic evaluation of psychotic symptom content in hospitalized middle-aged and older adults

Objective The objective of this study was to examine ethnic differences in the content of delusions and hallucinations among a tri-ethnic sample of adult psychiatric inpatients older than 40 years who were hospitalized with an acute psychotic episode. Methods A chart review of inpatient episodes for 133 middle-aged and older adult patients (31 African Americans, 50 Latinos, and 52 Euro-Americans) with a mean age of 50 years was performed at an acute behavioral medicine unit at a university hospital. All patients were diagnosed with a severe psychotic disorder. The content and frequency of psychotic symptoms were systematically reviewed using a structured checklist and comparisons across ethnic groups were made using χ 2 statistics. Results Ethnic group differences were found in the contents and subtypes of delusions and hallucinations. Significant ethnic differences were found in symptom content, consistent with findings from studies on younger samples of inpatients. Euro-Americans were nearly twice as likely as Latinos to report delusions of grandiosity. African Americans were more likely than Latinos to report general paranoid delusions of persecution. Latinos reported more culturally influenced contents than the other groups. Conclusion Raising provider awareness of ethnic variation in symptom expression is a key step in the process of developing effective treatments for ethnically diverse middle-aged and older patient populations.

Diagnosis and Management of Mild Bleeding Disorders

Mild bleeding disorders are a common reason for a referral to a hematologist and these conditions can be challenging to evaluate. Recent research has highlighted that some bleeding symptoms are quite common in the general population and that there is clinical variability in symptom expression among individuals with defined bleeding problems. Moreover, bleeding risks for many bleeding disorders are unknown. This article reviews symptoms and problems that can be considered suspicious of a mild form of bleeding disorder and the diagnostic investigations useful to evaluate these problems. A stepwise approach is presented for the diagnostic evaluation, to allow detection of common and rare coagulation and fibrinolytic defects, and adequate assessments of potential von Willebrand factor and platelet problems. Some common problems in the diagnosis and management of mild bleeding problems are reviewed, including the common failure to establish a diagnosis with testing. An approach is proposed for translation of knowledge to patients who are challenged by mild bleeding problems.

Ozone injury on cutleaf coneflower ( Rudbeckia laciniata) and crown-beard ( Verbesina occidentalis) in Great Smoky Mountains National Park

Incidence and severity of visible foliar ozone injury on cutleaf coneflower ( Rudbeckia laciniata L.) and crown-beard ( Verbesina occidentalis Walt.) were determined along selected trails at three locations in Great Smoky Mountains National Park during the summers of 2000 and 2001: Clingmans Dome, Cherokee Orchard Road and Purchase Knob. Cutleaf coneflower exhibited a greater amount of foliar injury than crown-beard each year of the 2-year study. Incidence and severity of injury was significantly greater for cutleaf coneflower growing near the edge of the Clingmans Dome trail than in the interior of the stand. Injury was greater at Clingmans Dome than Purchase Knob (70% vs. 40% ozone-injured plants, respectively), coincident with greater ozone exposures. In contrast to Clingmans Dome, there were no differences in injury between plants growing near- and off-trail at Purchase Knob. Differences in sensitivity to ozone were not observed for crown-beard growing near the edge compared with the interior of the stand adjacent to the Cherokee Orchard Road Loop. Ozone injury was greatest on the lower leaves for both species sampled with over 95% of the injured leaves occurring on the lower 50% of the plant. This is the first report of foliar ozone injury on these plant species in situ, in the Park, illustrating the great variability in symptom expression with time, and within and between populations.

Interpreting spatial variation in ozone symptoms shown by cutleaf cone flower, Rudbeckia laciniata L.

Visible injury caused by ozone is recorded every year in native plant species growing in Great Smoky Mountains National Park (USA). One of the most sensitive species, cutleaf coneflower ( Rudbeckia laciniata L.), shows great variation in symptoms between and within populations but the causes of this variation and its ecological significance are currently unknown. This paper presents data relating to genetic variation, ozone concentrations, stomatal conductance and light (PAR) within populations. The data show that populations differ in genetic diversity, one consisting of only three genets while another was very diverse. In the former population, symptoms varied greatly within a single genet, pointing to a large micro-environmental influence. Measurements of ozone, stomatal conductance and PAR within plant canopies suggest that variation in symptom expression is unlikely to be due to differences in ozone flux and more likely to be due to variation in light. The variation in visible symptoms raises the question of what bioindicators actually indicate, and it suggests that symptoms should be interpreted with great caution until the underlying causes of that variation are fully understood.

Correlation between sensitivity of barley to Pyrenophora teres toxins and susceptibility to the fungus

Detached leaves of 25 barleys, ranging from highly susceptible to highly resistant to Pyrenophora teres f. teres and Pyrenophora teres f. maculata, were tested for their reaction to three phytotoxins isolated from cultures of the fungus: toxin A [ L, L - N -(2-amino-2-carboxyethyl)aspartic acid], toxin C (aspergillomarasmine A) and toxin B (anhydroaspergillomarasmine A). 0.75m M toxin A caused mainly dark yellow chlorotic symptoms but little necrosis, whereas leaves treated with 0.25m M toxin C developed distinct necrotic symptoms and zones of light yellow chlorosis. Toxin B is only weakly toxic, and toxin B and control solutions containing aspartic acid in the concentration of 0.75m M did not cause any symptoms. The best differentiation between the barleys was obtained by scoring chlorosis after 120h, and the optimal toxin concentrations for this differentiation were 0.75m M toxin A and 0.25m M toxin C, respectively. Results with different toxin concentrations inducing distinct variation in symptom expression indicate that the two toxins have different potencies as phytotoxins. The reaction of the barleys to toxins A and C correlated well with their reaction to infection by P. teres f. teres and P. teres f. maculata, suggesting that toxins A and C may be used to select resistant barley lines in the early stages of a breeding programme.

Blood parameters indicative of oxidative stress are associated with symptom expression in chronic fatigue syndrome

Full blood counts, ESR, CRP, haematinics and markers for oxidative stress were measured for 33 patients diagnosed with chronic fatigue syndrome (CFS) and 27 age and sex matched controls. All participants also completed symptom questionnaires. CFS patients had increases in malondialdehyde (P <0.006), methaemoglobin (P <0.02), mean erythrocyte volume (P <0.02) and 2,3-diphosphoglycerate (P <0.04) compared with controls. Multiple regression analysis found methaemoglobin to be the principal component that differentiated between CFS patients and control subjects. Methaemoglobin was found to be the major component associated with variation in symptom expression in CFS patients (R2 = 0.99, P <0.00001), which included fatigue, musculoskeletal symptoms, pain and sleep disturbance. Variation in levels of malondialdehyde and 2,3-diphosphoglycerate were associated with variations in cognitive symptoms and sleep disturbance (R2 = 0.99, P <0.00001). These data suggest that oxidative stress due to excess free radical formation is a contributor to the pathology of CFS and was associated with symptom presentation.

First Report of the Presence of East African Cassava Mosaic Virus in Cameroon.

Cassava mosaic disease (CMD) occurs in all cassava-growing regions of Africa, India, and Sri Lanka. Characterized by mosaic and distortion of cassava leaves and reduced plant growth, causing high yield losses, CMD is caused by geminiviruses (genus Begomovirus, family Geminiviridae) transmitted through infected cuttings or by the whitefly, Bemisia tabaci. Three such geminiviruses have been described: African cassava mosaic virus (ACMV) occurs in most of the cassava-producing zones of Africa; East African cassava mosaic virus (EACMV) in East Africa; and Indian cassava mosaic virus (ICMV) in the Indian subcontinent (1). The two components of ACMV and ICMV genomes, DNA-A and DNA-B, have been sequenced; only DNA-A of EACMV has been identified and sequenced. Variations in symptom expression and severity within the same cassava variety have been observed in Cameroon. To determine the nature of the virus species inducing such variations, 50 samples were collected from CMD-infected plants in the savannah and rainforest zones of Cameroon: 2 from the sahel/savannah plain, 13 from the western highland savannah, and 35 from the main cassava-producing belt of the southwestern rainforest. There is a high incidence of CMD in the rainforest region, with some farms completely infected, while in the savannah regions farms generally have less than 25% incidence. Variation in symptom expression was more common in the rainforest region. Samples were collected from plants with distinct symptoms and/or different extents of symptom severity, then analyzed with the polymerase chain reaction (PCR) with specific primers: JSP1, ATG TCG AAG CGA CCA GGA GAT; JSP2, TGT TTA TTA ATT GCC AAT ACT; and JSP3, CCT TTA TTA ATT TGT CAC TGC. Primer JSP1 anneals to the 5' end of the coat protein (CP) of ACMV and EACMV; primers JSP2 and JSP3 anneal to the 3' ends of ACMV and EACMV, respectively. Virus identification was based on presence of an amplified fragment of either virus. ACMV was detected in all 50 samples; EACMV was detected in 8. All samples infected with EACMV were from the southwestern rainforest of Cameroon and were more severely affected by the disease than single infected plants. Previous reports have limited occurrence of EACMV to East Africa (1). This is the first report of the occurrence of EACMV in West Africa. The CP gene of three isolates of EACMV from Cameroon (EACMV/CM) was sequenced from cloned PCR products. There was a high CP nucleotide sequence identity (>99%) with only two amino acid differences among all three EACMV isolates. In contrast, there was a rather low sequence identity (94%) with EACMV/TZ from Tanzania (2), suggesting they may belong to a previously undescribed West African strain of EACMV. This indicates the geminiviruses causing CMD in Africa are more widely distributed than previously reported. None of the Cameroon isolates showed the type of recombination of the EACMV isolate from Uganda (EACMV/ UG) (having the CP core segment the identical to the corresponding ACMV CP sequence) (2). This emphasizes the need for characterization of the viruses causing CMD in different cassava-growing regions of Africa since appropriate control strategies depend on adequate knowledge of disease etiology.

Studies on a Nigerian isolate of banana streak badnavirus: II. Effect of intraplant variation on virus accumulation and reliability of diagnosis by ELISA

SummaryMonitoring of banana streak badnavirus (BSV) antigens and symptoms in naturally BSV‐infected plantain and banana (Musa spp.) plants showed a great variation in symptom expression, distribution and relative concentration of BSV between and within plants. Expression and distribution of symptoms was erratic within individual leaves as well as between different leaves of the same plant. The concentration of BSV antigens detected by triple antibody sandwich enzyme linked immunosorbent assay (TAS‐ELISA) varied in different plant parts including leaf lamina, midrib and pseudostem, roots and young ‘cigar’ leaf. The concentration of BSV antigens was high in symptomatic tissues but was low or below the limits of detection in most asymptomatic tissues. During ‘hot dry’ seasons when symptoms were not fully expressed, the concentration of BSV antigens in leaf tissues declined drastically, often below the detection limit of TAS‐ELISA. These results suggested that for more reliable detection of BSV antigens by TAS‐ELISA, it is advisable to index plants using composite tissue samples comprising as many leaves as possible for each plant and collected during cool and/or rainy seasons when symptom expression is generally severe.