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In this paper, a general framework of user-based collaborative filtering (CF) is developed with a new p -moment-based similarity measure. The p -moment-based statistics (PMS) of individual rating data are employed to analyze the user rating habit, thereby facilitating the performance improvement of the CF algorithm. On the basis of the PMS, a new yet comprehensive similarity measure is proposed to quantify the distance between two users with focus on both the users' preferences on items and their rating habits. Compared with the traditional ones, our proposed similarity measure is more general with clearer application insights in complicated situations. Furthermore, the weights of different statistics are regarded as adjustable parameters that are determined by utilizing the particle swarm optimization technique so as to achieve good prediction performance. Based on the proposed similarity measure with optimized weights, the neighborhood set consisting of similar users is formed and then the user-based rating prediction is eventually provided. The developed CF algorithm has advantages of high prediction accuracy and wide application potential. Moreover, this CF algorithm is applied on a real-world disease (Friedreich's ataxia) assessment system in order to assist diagnosis for patients with uncertain/missing information. Experimental results demonstrate the validity and efficiency of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Abstract: Anthracnose of cashew (Anacardium occidentale) was studies on various genotypes and locations in Mozambique. Colletotrichum gloeosporioides was identified as the anthracnose causal agent using polymerase chain reaction. The relationships between incidence and severity of anthracnose on cashew genotypes were statistically analyzed by regression. Anthracnose leaf incidence, which is practically easy to evaluate, was consistently associated with leaf severity, and their relationships can be estimated using the restricted exponential function across locations, crop seasons, genotype and fungicide trials. Pooled data enabled estimation of initial incidence of 1.43% with percentage variance accounting for 83.2 and standard error of 8.3. By computing incidence data into the summary equation, 24 changes of 0, 1, 5, 10 and 40%, resulted in changes of severity estimates of 0.01, 0.05, 0.10, 0.50 and 1.00%, respectively. The maximum disease incidence was estimated as 80% when the severity reached only 5%. Increase in severity was observed afterward, approached a maximum of 25% when leaf detachment is observed. The use of incidence data for epidemic comparisons, genotype and fungicide evaluation in cashew orchards is recommended. Anthracnose incidence on leaves however, could not predict incidence on nuts. [Copyright &y& Elsevier]

This study aimed to develop and validate a standard area diagram set (SADS) to quantify the severity of blast, caused by Pyricularia oryzae, on wheat leaves. The SADs has ten levels: 0.1, 1, 5, 10, 22, 32, 42, 52, 62 and 72 % blast severity. To validate the SADs, 12 inexperienced raters estimated disease severity on 50 images of leaves from cultivars BR-18 (susceptible) and BRS-229 (partially resistant). Blast severity was first estimated without the use of the SADs on 50 leaves with a range of blast severity. The same raters evaluated the same 50 leaves using the SADs as an aid. The SADs improved accuracy (coefficient of bias, C = 0.88 and 0.99, without and with SADs, respectively) and agreement (Lin's concordance correlation coefficient, ρ = 0.84 and 0.96 without and with SADs, respectively) of the estimates of severity. The absolute error was (-) 52 % without the SADs and (-) 24 % when using SADs as an aid. Severity estimates were more reliable when using SADs (R = 0.87 unaided and R = 0.92 with SAD). The SADs proposed in this study will improve accuracy and reliability of estimates of blast severity on wheat leaves. [ABSTRACT FROM AUTHOR]

Takayasu's arteritis (TAK) is a rare, chronic large-vessel vasculitis (LVV) that predominantly affects aorta, its major branches, and the pulmonary arteries. Segmental stenosis, occlusion, dilatation, or aneurysm formation may occur in the vessel wall during the course of the disease. The vascular involvement can be shown with different imaging modalities to make the diagnosis of TAK. Conventional angiography, the gold standard method for initial diagnosis, seems to be replaced with the new imaging modalities such as magnetic resonance angiography (MRA) and F-fluorodeoxyglucose positron emission tomography (FDG-PET) in recent years. The data coming from the new studies support that MRA and FDG-PET are also promising for the assessment of disease activity. Prognosis is possibly getting better with lower mortality in recent years; however, it is difficult to assess the widely different vascular intervention rates among the clinical series. Leflunomide, TNF-α antagonists, and tocilizumab are new options in patients resistant to conventional therapies. There is a clear need to develop a validated set of outcome measures for use in clinical trials of TAK. The OMERACT Vasculitis Working Group has taken on this task and aims to develop a core set of outcomes for LVV. [ABSTRACT FROM AUTHOR]

Pecan scab ( Fusicladium effusum) causes losses of pecan nutmeat yield and quality in the southeastern United States. Disease assessment relies on visual rating, which can be inaccurate and imprecise, with poor inter-rater reliability. A standard area diagram (SAD) set for pecan scab on fruit valves was developed. A set of 40 images of diseased fruit valves with known severity was assessed twice by 23 raters. The first assessment was conducted without SADs, and the second assessment was made using the SADs as an aid. SADs improved rater accuracy (correction factor, Cb = 0·86 and 0·97, without and with SADs, respectively) and agreement (Lin's concordance correlation coefficient, ρc = 0·79 and 0·89 without and with SADs, respectively) with true values. SADs improved inter-rater reliability (intra-class correlation coefficient, ρ = 0·77 and 0·96 without and with SADs, respectively). The least accurate and precise raters without SADs improved more using SADs compared to the most accurate and precise raters. Experienced raters had significantly higher accuracy and precision compared to inexperienced raters, but only when unaided by the SAD set. There was no significant difference in time to assess images without SADs, but experienced raters using SADs were faster compared to inexperienced raters. There was a slight tendency for faster raters to assess more slowly, and slower raters to assess faster when using SADs. SADs improve rater estimates of pecan scab severity on fruit, and this SAD set should be useful for assessment where greater precision, accuracy and inter-rater reliability are required. [ABSTRACT FROM AUTHOR]

Yam anthracnose is caused by the pathogenColletotrichum gloeosporioidesPenz. and has been identified as the most important biotic constraint to yam production worldwide. Rapid assessment of the disease is vital to its effective diagnosis and management. In this study, tissue-cultured yam plantlets of five lines ofDioscorea alataand nine ofD. rotundatawere rapidly assessed for their reactions to two isolates of yam anthracnose. The plantlets, obtained from meristem of the nodal cuttings, were grown for 8 weeks on Murashige and Skoog (MS) basal medium, acclimatised for 3 weeks, hardened for an additional 3 weeks, arranged in screen house in completely randomised design and sprayed with spore inocula prepared from 7 day-old culture of the two strains ofColletotrichum gloeosporioidiesPenz. The relative resistance of the differentDioscoreaspp. was evaluated using three disease indices – severity at seventh day after inoculation, SD7; area under disease progress curve, AUDPC; and disease severity rate, Rd. A modified rank-sum classification method put TDa 1425 and TDr 2040, with rank sum of 2.0 each, as resistant. TDr 2121, TDr 2287 and TDr 2048 were susceptible with rank sum of 27.50, 25.50 and 24.50, respectively.Dioscorea alataTDa 1425 andDioscorea rotundataTDr 2040 were recommended in areas endemic with yam anthracnose, and also as parent lines while breeding for resistance to anthracnose. [ABSTRACT FROM PUBLISHER]

Inoculation of detached strawberry leaves with Colletotrichum species may provide an accurate, rapid, non-destructive method of identifying anthracnose resistant germplasm. Two assessments of anthracnose disease severity were compared on detached strawberry leaves inoculated with Colletotrichum fragariae and C. gloeosporioides: a quantitative assessment made via computer-based image analysis and a visual assessment made by two independent raters. The image analysis provided a precise measurement of percent lesion area of infected leaves. There was a strong positive correlation between percent lesion area and the visual disease scores of the raters. [ABSTRACT FROM AUTHOR]

The reaction of five apple cultivars to olive wilt caused by Verticillium dahliae Kleb was evaluated. Five apple cultivars (Royal Gala, Delicious Anabri, Double Red, Golden Delicious, Granny Smith) and one olive cultivar (Nabali Mohassan) were inoculated with V. dahliae and grown under partially controlled greenhouse conditions. Typical symptoms of the disease were developed on the inoculated olive seedlings. However, all tested apple cultivars did not show the typical symptoms of Verticillium wilt except cv. Delicious Anbari, which showed 8.31% disease severity. The average percentage of disease severity was 61.2% in Nabali Mohassan. The pathogen was positively re-isolated from the inoculated seedlings of cvs Nabali Mohassan and Delicious Anbari after 12 months from the inoculation date. Results indicate that an apple plantation to replace dead or severely diseased olive trees infested with Verticillium wilt is an appropriate low-cost and environmentally sound IPM alternative approach to control Verticillium wilt. [ABSTRACT FROM AUTHOR]

Controlled-environment studies were conducted on two Brassica crops (canola, Brassica napus; and Shanghai pak choi, B. rapa subsp. chinensis var. communis) to examine the effects of temperature on infection and subsequent development of clubroot caused by Plasmodiophora brassicae. In the first experiment, canola seedlings were grown in infested soil for 3 weeks at 14-26°C to assess the impact on primary and secondary infection and transferred to 20°C for 3 weeks to assess symptom development under uniform conditions, or started at 20°C for 3 weeks and then placed at the treatment temperatures for the final 3 weeks to assess the impact of temperature on symptom development. A second experiment examined a wider range of temperatures (10-30°C). Similar experiments were also conducted on Shanghai pak choi. The studies demonstrated that clubroot severity was affected by temperature during both infection and vegetative development of the crop. Both early and late in crop development, little or no clubroot developed at temperatures at or below 17°C, and development was slower above 26°C than at 23-26°C for both crops throughout the study. In canola, the high levels of inoculum used in the study resulted in a high incidence of clubroot irrespective of temperature, but in pak choi incidence showed the same pattern as severity. This is the first study to demonstrate under controlled conditions that temperature during vegetative growth of the crop affects symptom development of clubroot. [ABSTRACT FROM AUTHOR]

Abstract: Fusarium head blight is a fungal disease causing yield losses and mycotoxin contamination in wheat and other cereals. Wheat kernels (cultivar Ritmo) were sampled in 2001, 2002, 2003, and 2006 and Fusarium-damaged kernels were separated from sound grain based on visual assessment. Subsequently, grain lots containing 0, 20, 40, 60, 80, and 100% of damaged kernels were compiled. Each lot was split and the spectrometric reflectance (wavelengths 350–2500nm) was measured using subgroup one, while the concentration of the mycotoxin deoxynivalenol (DON) was determined by high-performance liquid chromatography in subgroup two. DON concentrations in batches classified as sound were not significantly different from 0. Estimating DON contents from the percentage of Fusarium-damaged kernels was impeded by vast variability, resulting in a coefficient of determination of 0.49. Using spectrometric data subjected to partial least square regression allowed estimating DON contents with higher accuracy, in particular at elevated percentages of damaged kernels. The coefficient of determination was 0.84 for the relationship between DON contents estimated based on spectrometric data and the DON contents measured. The intercept of a regression line fitted through a plot of estimated versus measured DON contents was 0.89±3.61mg/kg. Since intercept+standard error was larger than the actual legal limit (1.25mg DON per kg dry grain in the European Union), the spectrometric procedure was still not precise enough to allow a reliable separation of grain samples with DON contents below 1.25mg/kg from samples with DON contents above the limit. However, spectrometric data also allowed estimating the DON content of the average damaged kernel within a given lot composed of sound and damaged kernels, which is probably the reason for the reduction of the fraction of unexplained variance by 35% compared to the visual approach and illustrates that spectrometric approaches can make a contribution to reducing DON contents of wheat grain. [Copyright &y& Elsevier]

Development of phoma leaf spot (caused by Leptosphaeria maculans) on winter oilseed rape (canola, Brassica napus) was assessed in two experiments at Rothamsted in successive years (2003–04 and 2004–05 growing seasons). Both experiments compared oilseed rape cultivars Eurol, Darmor, Canberra and Lipton, which differ in their resistance to L. maculans. Data were analysed to describe disease development in terms of increasing numbers of leaves affected over thermal time from sowing. The cultivars showed similar patterns of leaf spot development in the 2003–04 experiment when inoculum concentration was relatively low (up to 133 ascospores m−3 air), Darmor developing 5.3 diseased leaves per plant by 5 May 2004, Canberra 6.6, Eurol 6.8 and Lipton 7.5. Inoculum concentration was up to sevenfold greater in 2004–05, with Eurol and Darmor developing 2.4 diseased leaves per plant by 16 February 2005, whereas Lipton and Canberra developed 2.8 and 3.0 diseased leaves, respectively. Based on three defined periods of crop development, a piece-wise linear statistical model was applied to the progress of the leaf spot disease (cumulative diseased leaves) in relation to appearance (‘birth’) and death of leaves for individual plants of each cultivar. Estimates of the thermal time from sowing until appearance of the first leaf or death of the first leaf, the rate of increase in number of diseased leaves and the area under the disease progress line (AUDPL) for the first time period were made. In 2004–05, Canberra (1025 leaves ×°C days) and Lipton (879) had greater AUDPL values than Eurol (427) and Darmor (598). For Darmor and Lipton, the severity of leaf spotting could be related to the severity of stem canker at harvest. Eurol had less leaf spotting but severe stem canker, whereas Canberra had more leaf spotting but less severe canker. [ABSTRACT FROM AUTHOR]

Abstract: Premature ripening (PR) is one of the most important diseases of sunflower in France since the 90s. Previous results indicated that girdling canker of the stem base, caused by Phoma macdonaldii was its primary cause but elucidation of critical environmental factors involved is crucial for better control of the disease. A field study was conducted in three contrasting cropping seasons (2006–2008) and investigated the effect of N fertilization (0, 75 and 150kgNha−1) and water regime (rainfed, irrigated) on two cultivars with artificial inoculation (AI) and natural infection (NI). Disease assessment was recorded weekly to calculate the area under disease progress curve (AUDPC) and the final percentage of PR plants. Data showed that high levels of N fertilization led to significantly (P <0.05) more PR than non-fertilization. Water deficit conditions were significantly (P <0.05) involved in disease severity, and AUDPC and PR were increased when dry conditions were associated with high N supply. This was true for two cultivars which differed in their susceptibility to the disease but cv. Heliasol RM was significantly (P <0.05) more affected than cv. Melody, partially resistant to PR. Despite contrasting weather patterns, these results demonstrated a clear role of crop management and environmental conditions on the incidence and severity of stem base attacks responsible for the PR syndrome. These findings suggest that sunflower crop husbandry should be adapted to minimize premature ripening induced by P. macdonaldii. [Copyright &y& Elsevier]

Three diagrammatic grading keys were designed for the assessment of the severity of late blight (caused by Phytophthora infestans) in tomato leaves. Simplified and broad keys considered, respectively, six (3, 12, 22, 40, 60 and 77%) and eight (3, 6, 12, 22, 40, 60, 77 and 90%) levels of disease severity, whilst a modified key based on a previous proposal for potato late blight considered six levels (1, 5, 10, 16, 32 and 50%). The keys were validated by 24 evaluators who assessed digital images of tomato leaves exhibiting different areas with lesions. Evaluator errors were compared using a mixed model in which evaluators were considered as random effects and the keys and evaluations as fixed effects. The accuracy and precision of the evaluators were compared by simple linear regression between the estimated and actual values of disease severity. The repeatability of evaluators was assessed using Pearson’s correlation coefficient. There was significant ( P ≤ 0·001) variability amongst the errors made by evaluators, although the precision of each of the three keys was high with a coefficient of determination (R2) of 0·96, 0·93 and 0·83 for the simplified, broad and modified key, respectively. Repeatability of estimations amongst the evaluators was adequate (correlation coefficients of 0·91, 0·91 and 0·90 for the three keys, respectively). The simplified and broad keys resulted in higher precision and accuracy for the estimation of severity than did the modified key. Since the simplified key considers a smaller number of disease severity levels, its use is recommended in the assessment of late blight in tomato leaves. [ABSTRACT FROM AUTHOR]

Abstract: Fusarium wilt disease of banana is one of the most harmful fungal diseases affecting banana production worldwide. We hypothetically proposed that the loss of indigenous endophytes in tissue culture propagation of banana might be related to increased disease severity on banana plants. In the present study, a mixture of uncultivated endophytes, which was originally derived from native healthy banana plant in plantation, was used to artificially inoculate banana tissue culture plantlets. A broad spectrum of bacterial communities was detected in the roots of artificially inoculated plantlets by 16S ribosomal RNA gene analysis, and γ-Proteobacteria was identified as the dominant group. Banana wilt pathogen Fusarium oxysporum f. sp. cubense race 4 was inoculated to the plantlets after potting to investigate disease progress. With early diagnosis of fungal pathogen infection, 54% reduction was detected in artificially inoculated plantlets compared to endophyte-free control plantlets. The re-introduction of naturally-occurring endophytes into tissue culture banana plantlets led to a 67% suppression rate of wilt disease at the fifth month after pathogen infection on plantlets in the greenhouse. In addition to disease suppression, growth of host plantlets was also promoted with the inoculation of endophytes. The artificial inoculation method provided a foundational understanding of ecological enrichment to control banana wilt disease in future. [Copyright &y& Elsevier]

Abstract: Rust resistance of 23 commonly grown biomass willow varieties and 71 genotypes produced from a UK-based willow-breeding programme was tested in laboratory inoculation experiments. Leaf discs were inoculated with six pathotypes of Melampsora larici-epitea and disease was scored based on uredinial pustule area and inoculum density. In the field, rust severity of the same varieties and genotypes was scored using an assessment key. Of the varieties and commonly grown willows tested, several North American willows and Salix schwerinii×Salix viminalis ‘Bjorn’ and ‘Tora’ were highly resistant. Overall, the great majority of the willows produced through breeding showed high levels of resistance to rust. There was a significant correlation between infection-type scores obtained from the laboratory testing and field rust severity (Spearman''s rank correlation coefficient=0.624, P<1×10−6). There was also a good agreement in field disease severity scores between the years (Kendall''s coefficient of concordance=0.669, P<0.001). [Copyright &y& Elsevier]

Crohn's disease (CD) demonstrates great heterogeneity in its presentation and severity. Management of CD is similarly diverse but the aim remains the same - remission of disease activity and improvement of health related quality of life (HR-QoL). Treatment options include steroids, 5-ASA derivatives, immunomodulators and surgery. The aim of this study was to define the variation in practice of consultant gastroenterologists and colorectal surgeons treating CD in Wales. Methods: Consultant gastroenterologists and colorectal surgeons treating CD in Wales were sent a questionnaire aimed at determining their current practice and their responses were analysed. Results: Eighty-eight consultants - 46 (52%) gastroenterologists and 42 (48%) surgeons - were invited to participate in the survey. Sixty-one (69%) of them responded. Coherent practice was seen across Wales, especially with respect to diagnosis of CD in line with British Society of Castroenterology guidelines. Variation was detected in disease severity assessment and some aspects of management. Conclusion: Practice in Wales is in line with the guidelines for managing CD. While the diagnostic process follows a standard approach, variations exist in treatment and monitoring of disease. Validated disease measurement instruments are seldom used in routine practice. Disease assessment tools need to be simpler to use if they are to help objective measurement of disease activity and treatment decisions. [ABSTRACT FROM AUTHOR]

The abundance of leaf rust (Melampsora sp.) was assessed on four willow clones in four experimental Estonian willow short-rotation forest plantations. Three plantations were established on poor mineral soil and one was constructed for wastewater purification. Clones 78183 and 81090 were most severely damaged in all four plantations, whereas clones 78021 and 78195 were fairly resistant to rust. In addition to clone type, the number of uredinia on leaves depended on plantation, sampling date, and fertilization. Infection increased significantly during the growing season, and the leaves collected from fertilized plants had more and larger rust pustules than those from unfertilized plants. Uredinia were smaller on older shoots and larger on younger shoots. [ABSTRACT FROM AUTHOR]

Methods to assess light leaf spot ( Pyrenopeziza brassicae) on winter oilseed rape cultivars were compared in laboratory, controlled-environment and field experiments. In controlled-environment experiments with seedling leaves inoculated at GS 1,4, the greatest differences in percentage area affected by P. brassicae sporulation were observed with inoculum concentrations of 4 × 103 or 4 × 104 spores mL−1, rather than 4 × 102 or 4 × 105 spores mL−1, but older leaves had begun to senesce before assessment, particularly where they were severely affected by P. brassicae. In winter oilseed rape field experiments, a severe light leaf spot epidemic developed in 2002/03 (inoculated, September/October rainfall 127·2 mm) but not in 2003/04 (uninoculated, September/October rainfall 40·7 mm). In-plot assessments discriminated between cultivars best in February/March in 2003 and June in 2004, but sometimes failed to detect plots with many infected plants (e.g. March/April 2004). Ranking of cultivar resistance differed between seedling experiments done under controlled-environment conditions and field experiments. The sensitivity of detection of P. brassicae DNA extracted from culture was greater using the PCR primer pair PbITSF/PbITSR than using primers Pb1/Pb2. P. brassicae was detected by PCR (PbITS primers) in leaves from controlled-environment experiments immediately and up to 14 days after inoculation, and in leaves sampled from field experiments 2 months before detection by visual assessment. [ABSTRACT FROM AUTHOR]

Rhizoctonia foliar blight, caused by Rhizoctonia solani Kuhn anastomosis group 1, causes rapid and severe destruction of soybean foliage and pods during hot, wet weather. The objectives of this study were to determine the yield components affected by this disease and whether rating pod damage or foliar damage provides a more reliable method of assessing disease severity relative to impact on yield. Disease severity in the moderately resistant cv. NK S57-11 and the susceptible cv. Buckshot 723 was assessed in field plots in 1996 and 1997 using foliar and pod ratings (0-to-10 scale corresponding to 0 to 100% of tissue affected). Based on results from regression analysis, pod number, seed number, and seed weight per plot decreased as disease severity increased, whereas the proportion of partially filled pods and the weight of 100 seed were not affected. Yield loss appeared to be due primarily to loss of entire pods. Foliar and pod assessments of disease severity correlated positively in 1996 (r = 0.8343) and 1997 (r = 0.5958) for both cultivars, which suggests that either method can be used to identify relative differences among cultivars. However, pod assessments accounted for more variability than foliar assessments under low-disease conditions. Plants exhibiting moderate to severe symptoms of Rhizoctonia foliar blight also retained green stems and pods at harvest, which was evidence of delayed maturity. [ABSTRACT FROM AUTHOR]

Quantification of the damaging effects of pathogens on diseased plants and inclusion of these damaging functions in crop simulation models is of great importance for a more complete understanding of yield response to diseases. In this study, the effect of Septoria tritici blotch (STB) on net photosynthetic and dark respiration rates of wheat flag leaves was quantified. Bastiaans' model: Y=(1–x)β was used to characterize the relationship between relative leaf photosynthesis (Y, considering Ynet and Ygross) and STB severity (with x the proportion of the diseased area). The value of β indicates whether the effect of disease on photosynthesis is larger (β >1), lower (β <1), or equal (β =1) to the proportion of visible diseased area. In the experimental conditions used here, leaf nitrogen content (in a range from 0.18 to 0.24 mg cm−2), and leaf number (flag and second leaves) did not significantly influence the effect of STB on leaf gas exchange. By contrast, damage depended strongly on the developmental stages of the STB lesions. STB lesions had no effect on inoculated leaves before visible symptoms appeared. Chlorotic symptoms had less effect on leaf net photosynthetic rate than could be accounted for by the visible diseased area (βnet=0.81). The effect of necrotic lesions on the leaf net photosynthetic capacity was slightly greater than that accounted for by visible symptoms (βnet=1.35). Our results suggest that the effect of the necrotic symptoms on the net photosynthesis expressed by βnet >1 is due to a combination of a decrease in the gross photosynthesis (βgross still >1) and to an increase in the dark respiration rate (βgross<βnet). Finally, it is discussed how the results could improve the prediction of crop loss caused by an STB epidemic in wheat fields. [ABSTRACT FROM PUBLISHER]

Peanut ( Arachis hypogaea) crops in Benin often experience late leafspot ( Cercosporidium personatum), which causes severe yield losses associated with leaf defoliation and necrosis. The objective of this research was to determine the best method of disease assessment and to test its utility in the CROPGRO-peanut model to simulate growth and yield as affected by late leafspot in early and late maturing peanut cultivars grown at different sowing dates under rain-fed conditions (without irrigation) in northern Benin. Two peanut cultivars TS 32-1 and 69–101 were sown on three dates between May and August during 1998 and 1999. In both years there was severe occurrence of late leafspot and the progression of disease was earlier and faster with later sowing dates. Overall, the long duration cultivar 69–101 produced greater yield than the short duration cultivar TS 32-1. The CROPGRO-peanut model was able to predict and simulate the observed crop and pod dry matter over time when input on percent diseased leaf area and percent defoliation were provided. Of several disease assessments, the best approach was to input measured percent main-stem defoliation above the fourth node and percent diseased leaf area estimated from visual leafspot score. [ABSTRACT FROM AUTHOR]

During the period 2000–03, local potato cultivars in Estonia, Latvia, Lithuania, Poland and Denmark were tested for foliar resistance toPhytophthora infestans(late blight) in an international field trial network. Four standard cultivars were included in the trials: Sava, Oleva, Danva and Kuras. Primary disease-assessment data were entered into a common database, and parameters from the disease progress curves were calculated and made available on interactive web pages. A regression model, using relative area under disease progress curve (RAUDPC) values for cv. Oleva as a reference, was developed for the estimation of 1–9 scale values, where 1 = most susceptible. Standard deviations for the estimated 1–9 scale values and a nonparametric rank stability analysis of RAUDPC were used to evaluate the stability of resistance of the cultivars. Overall, the results showed stability of resistance for cvs Sava, Oleva and Danva, but not for Kuras. Use of the Internet-based Web-Blight service in this study facilitated comparison of results among countries for the level and stability of resistance. The estimated 1–9 scale values were similar to, or slightly lower than, those from official cultivar lists or from the European Cultivated Potato Database, especially for the more resistant cultivars. Possible reasons for discrepancies from different sources and locations are discussed. It is concluded that RAUPDC and the derived 1–9 scale values are useful for ranking cultivars for resistance toP. infestans, but this information is not detailed enough for use in a decision support system for late blight control. [ABSTRACT FROM AUTHOR]

Anthracnose caused by the fungus Apiognomonia veneta (Sacc. et Speg.) Höhnel., is the most important and frequent disease affecting mature ornamental plane trees ( Platanus × hybrida Brot.= P. × acerifolia (Ait.)Willd.) of central Spain. Symptoms of the disease are: leaf vein and petiole necrosis, bud death, defoliation, proliferation of shoots growing in whorls, short internodes, cankers, necrotic lesions and twigs and branches growing in angles. Based on our previous experience, a disease severity rating scale (DSRS) has been established, consisting of six levels: 0=healthy, 1=initial, 2=low, 3=medium, 4=high and 5=dead. In order to achieve a better and more efficient measure of disease intensity we tried to quantify this visual scale using mathematical criteria. In 2000, 610 mature trees up to 200 years old, divided into 4 age classes, were selected and systematically evaluated using a visual estimation based method. The trees were located in central Spain, mainly in two periurban areas of the town of Aranjuez (south of Madrid) and in three urban areas of Madrid city. Trees were observed in late spring, summer and winter. We recorded visual estimation of disease severity, foliage cover, healthy new shoots, dead branches, shoot growth in whorls and branch growth in angles. The statistical relationship between the parameters, disease severity and all the variables recorded (defoliation, healthy new shoots, etc.) has been evaluated. “Leaf density”, “dead branches” and “healthy shoots” were the variables that help to discriminate better between the different levels of the DSRS. A clearer definition of the different phases of disease severity will facilitate the application of possible control methods and the prediction of the behaviour of other Platanus spp. [ABSTRACT FROM AUTHOR]

Reflectance from barley field trial plots was measured to determine whether it could be used as an accurate estimate of disease and yield response to fungicide, and whether this was consistent over a range of agronomic factors. Three trials were used to test the effects of cultivar, assessment date, fungicide and dose, different disease and fertiliser. Correlations with predominant disease and resulting yield loss were high, often better than visual disease or green leaf area measurements alone. Certain ratios of two reflectance wavelength measurements were more robust predictors than single wavelengths. Cultivar and development stage had a large influence on measurements and calibration for such morphology-based characters would be essential for practical deployment. Whilst weather conditions and solar angle restrict opportunities for usage of reflectance tools such as the 'Cropscan Radiometer', it may prove useful in crop loss assessments as an additional objective tool. [ABSTRACT FROM AUTHOR]

Compares alfalfa yield models based on visual disease intensity and remote sensing assessments. Foliar disease levels in alfalfa; Relationship between alfalfa attainable yield potential and damage coefficients.

Seven disease assessment methods to measure severity of downy mildew (Peronospora farinosa f.sp. chenopodii) were tested in eight cultivars of quinoa (Chenopodium quinoa) in two field experiments in Peru, one at low (Lima) and one at high (Huancayo) disease pressure. Two levels of downy mildew were established by means of fungicide treatments. Area under disease progress curve (AUDPC) values were calculated for each method and correlated to the grain yield. In addition to the severity measurements, spectral reflectance was measured throughout the growth season in Huancayo and area under reflectance curve (AURC) values calculated and correlated to yield. The disease level was ten-fold higher in Huancayo compared to Lima. AUDPC based on the Three-leaf method (mean disease severity of three leaves per plant selected randomly from the lower, middle and upper part of the plant), showed the highest negative correlation to yield (r=−0.736) and is regarded as the best method to predict yield loss caused by downy mildew. In addition, this method proved to be the quickest and easiest compared to the other six methods included in the study, which were based on assessments of disease severity of the entire plant or parts of the plant. Yield losses recorded in the tested cultivars ranged from 33% to 99% under the high-disease conditions. The reflectance method was superior to all other methods by showing a higher correlation between AURC and yield (r=0.853), which is explained by its ability to measure pathogen-induced defoliation. Remote sensing is an excellent tool to compare the effect of treatments on disease severity within a cultivar. However, the method does not allow for comparison of disease severity among cultivars as the spectral reflectance is determined by size, shape and colour of the plant.The Three-leaf method provides an easy, cheap and readily applicable tool for researchers and plant breeders to study downy mildew of quinoa, characterise germplasm for resistance and compare results across regions and years. [Copyright &y& Elsevier]

In foliage of two hybrid poplars, clone DN-34 (Populus deltoides ′ P. nigra) and clone NM-6 (P. nigra × P maximowiczii), we examined relationships between photosynthesis and severity of leaf spot induced by Marssonina brunnea f. sp. brunnea, a common disease of many tree species in the Populus genus with the potential to affect growth. Gas exchange was measured on asymptomatic and diseased foliage in monoculture stands of each clone. The equation Y = (1 - x)β was used to characterize the relationship between relative photosynthesis (Y) and percent leaf spot (x), where β represents the ratio between functional impairment and measured lesion area. Leaf photosynthesis was strongly and negatively correlated with leaf spot severity in both hybrids, and β-values indicated that photosynthetic impairment extended beyond visibly damaged leaf tissue. However, large differences in β between hybrids indicated differential photosynthetic consequences for a given leaf spot severity. For each hybrid, values of β were positively related to photosynthetic photon flux density incident upon the leaf during gas exchange measurement. Declines in leaf photosynthesis appeared to result from a disruption of the photosynthetic apparatus by the invading pathogen. However, specific causes for the differential photosynthetic responses of the two hybrids to disease remained elusive. [ABSTRACT FROM AUTHOR]