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Anthracnose caused by Colletotrichum species is a serious disease on a range of economically important hosts. To determine the Colletotrichum species in coffee plantations in Hainan, China, 55 isolates were obtained from Coffea arabica (arabica) and C. canephora var. robusta (robusta) in five counties. Initially, partial sequences of glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) were used to measure fungal genetic diversity. Then a subset of 23 isolates was selected to represent the range of genetic diversity, varieties and geographic origin for further multilocus phylogenetic analyses. These isolates belong to eight known Colletotrichum species from three Colletotrichum species complexes, including gloeosporioides (C. endophytica, C. fructicola, C. ledongense, C. siamense and C. tropicale), boninense (C. karstii), gigasporum (C. gigasporum), and one singleton species (C. brevisporum). Of these, C. siamense was isolated in all sampled counties and C. fructicola was identified in three counties. The other six species were isolated only in one or two counties. Only C. siamense and C. fructicola were isolated from arabica, whereas all eight species were isolated from robusta. Occurrence of C. brevisporum, C. endophytica, C. ledongense and C. tropicale in coffee has not been reported previously. Pathogenicity tests showed that all eight species were pathogenic to coffee leaves and fruit. In vitro tests showed that Colletotrichum isolates from coffee in Hainan were most sensitive to prochloraz, less sensitive to carbendazim, propiconazole and difenoconazole, and least sensitive to myclobutanil. [ABSTRACT FROM AUTHOR]

The soilborne fungus Sclerotinia sclerotiorum infects many important crop plants. Central to the success of this pathogen is the production of sclerotia, which enables survival in soil and constitutes the primary inoculum. This study aimed to determine how crop plant type and S. sclerotiorum isolate impact sclerotial production and germination and hence inoculum potential. Three S. sclerotiorum isolates (L6, L17, L44) were used to inoculate plants of bean, carrot, lettuce, oilseed rape (OSR) and potato, and the number and weight of sclerotia per plant quantified. Carpogenic germination of sclerotia collected from different hosts was also assessed for L6. Production of sclerotia was dependent on both crop plant type and S. sclerotiorum isolate, with OSR and lettuce supporting the greatest number (42–122) and weight (1.6–3.0 g) of sclerotia per plant. The largest sclerotia were produced on OSR (33–66 mg). The three S. sclerotiorum isolates exhibited a consistent pattern of sclerotial production irrespective of crop type; L6 produced large numbers of small sclerotia while L44 produced smaller numbers of large sclerotia, with L17 intermediate between the two. Germination rate and percentage was greatest for larger sclerotia (4.0–6.7 mm) and also varied between host plants. Combining sclerotial production data and typical field crop densities suggested that infected carrot and OSR could produce the greatest number (3944 m−2) and weight (73 g m−2) of S. sclerotiorum sclerotia, respectively, suggesting these crops potentially contribute a greater increase in inoculum. This information, once further validated in field trials, could be used to inform future crop rotation decisions. [ABSTRACT FROM AUTHOR]

Abstract: International trade in live plant materials has increased worldwide over the last four decades. This has led to a dramatic increase in the introduction, establishment and spread of non‐native plant pathogens. Regulatory authorities need advice on measures that may mitigate these adverse consequences of trade. Risk models may be used to underpin such advice. In this review, we give a systematic overview of the data needed for a quantitative risk model for Phomopsis vaccinii, which causes stem and fruit infections on Vaccinium species, and sometimes death, potentially also on native wild Vaccinium species in the EU. P. vaccinii is a quarantine organism worldwide, except for North America, where it is endemic. Despite extensive knowledge of the aetiology of the diseases caused by this pathogen and its taxonomy, quantitative data on transportation and detection of infected plants for planting and berries are scarce, and quantitative assessment of the future introduction, establishment and spread of P. vaccinii is difficult. Estimation of the potential impact of this pathogen in production fields and wild Vaccinium stands is even more difficult. P. vaccinii is not unique in this respect, and this review indicates the need for more and better quantitative data for assessment of the risks posed by newly introduced plant pathogens in areas where they are not endemic. [ABSTRACT FROM AUTHOR]

Pyrenopeziza brassicae (anamorph Cylindrosporium concentricum) is an ascomycete fungus that causes light leaf spot ( LLS) disease of brassicas. It has recently become the most important pathogen of winter oilseed rape ( Brassica napus) crops in the UK. The pathogen is spread by both asexual splash-dispersed conidia and sexual wind-dispersed ascospores. Such inoculum can be detected with existing qualitative and quantitative PCR diagnostics, but these require time-consuming laboratory-based processing. This study describes two loop-mediated isothermal amplification ( LAMP) assays, targeting internal transcribed spacer ( ITS) or β-tubulin DNA sequences, for fast and specific detection of P. brassicae isolates from a broad geographical range (throughout Europe and Oceania) and multiple brassica host species ( B. napus, B. oleracea and B. rapa). Neither assay detected closely related Oculimacula or Rhynchosporium isolates, or other commonly occurring oilseed rape fungal pathogens. Both LAMP assays could consistently detect DNA amounts equivalent to 100 P. brassicae conidia per sample within 30 minutes, although the β-tubulin assay was more rapid. Reproducible standard curves were obtained using a P. brassicae DNA dilution series (100 ng-10 pg), enabling quantitative estimation of amounts of pathogen DNA in environmental samples. In planta application of the β-tubulin sequence-based LAMP assay to individual oilseed rape leaves collected from the field found no statistically significant difference in the amount of pathogen DNA present in parts of leaves either with or without visible LLS symptoms. The P. brassicae LAMP assays described here could have multiple applications, including detection of symptomless host infection and automated real-time monitoring of pathogen inoculum. [ABSTRACT FROM AUTHOR]

Leaf blotch is a globally important disease of barley crops and other grasses that is caused by at least five host-specialized species in the fungal genus Rhynchosporium. The pathogen R. commune (specialized to barley, brome-grass and Italian ryegrass) has long been considered to reproduce only by asexual means, but there has been accumulating evidence for recombination and gene flow from population genetic studies and the detection of complementary MAT1 -1 and MAT 1-2 isolates in a c. 1:1 ratio in the field. Here, it is demonstrated that 28 isolates of the closely related species R. agropyri (on couch-grass) and R. secalis (on rye and triticale), collected from Europe, were also either of MAT 1-1 or MAT 1-2 genotype and that the distribution of mating types did not deviate significantly from a 1:1 ratio. Evidence is then provided for MAT 1-1-1 and MAT 1-2-1 gene expression during mycelial growth for all three species. By contrast, 27 isolates of the more distantly related R. orthosporum (on cocksfoot) and R. lolii (on Italian and perennial ryegrasses) from Europe were exclusively of the MAT 1-1 genotype, and expression of the MAT 1-1-1 gene could not be detected during mycelial growth. These data suggest that cryptic sexual cycles are more likely to exist for R. commune, R. agropyri and R. secalis than for either R. orthosporum or R. lolii. A phylogenetic analysis of partial MAT 1-1 idiomorph sequences resolved these five species into two distinct groups ( R. commune, R. agropyri and R. secalis versus R. orthosporum and R. lolii) but provided only limited resolution within each group. [ABSTRACT FROM AUTHOR]

Rain-splash dispersal of Phyllosticta citricarpa (syn. Guignardia citricarpa) conidia (pycnidiospores) from infected oranges was studied in still air and combined with wind. High power microscopy demonstrated the presence of conidia in splash droplets from diseased oranges, which exuded conidia for over one hour during repeated wetting. The largest (5 mm) incident drops produced the highest splashes (up to 41.0 cm). A linear-by-quadratic surface model predicted highest splashes to be 41.91 cm at a horizontal distance of 25.97 cm from the target orange. Large splash droplets contained most conidia (4-5.5 mm splashes averaged 308 conidia), but were splashed <30 cm horizontal distance. Most (80-90%) splashes were <1 mm diameter but carried only 0-4 conidia per droplet. In multiple splash experiments, splashes combined to reach higher maxima (up to 61.7 cm; linear-by-quadratic surface model prediction, 62.1 cm) than in the single splash experiments. In combination with wind, higher wind speeds carried an increasing proportion of splashes downwind travelling horizontally at least 8 m at the highest wind speed tested (7 m/s), due to a small proportion of droplets (<1 mm) being aerosolised. These experiments suggest that P. citricarpa conidia can be dispersed from infected oranges by splashes of water in rainfall events. [ABSTRACT FROM AUTHOR]

The phenotype of the R gene-mediated resistance derived from oilseed rape ( Brassica napus) cv. Imola against the light leaf spot plant pathogen, Pyrenopeziza brassicae, was characterized. Using a doubled haploid B. napus mapping population that segregated for resistance against P. brassicae, development of visual symptoms was characterized and symptomless growth was followed using quantitative PCR and scanning electron microscopy on leaves of resistant/susceptible lines inoculated with suspensions of P. brassicae conidia. Initially, in controlled-environment experiments, growth of P. brassicae was unaffected; then from 8 days post-inoculation (dpi) some epidermal cells collapsed ('black flecking') in green living tissue of cv. Imola and from 13 to 36 dpi there was no increase in the amount of P. brassicae DNA and no asexual sporulation (acervuli/pustules). By contrast, during this period there was a 300-fold increase in P. brassicae DNA and extensive asexual sporulation in leaves of the susceptible cv. Apex. However, when leaf tissue senesced, the amount of P. brassicae DNA increased rapidly in the resistant but not in the susceptible cultivar and sexual sporulation (apothecia) was abundant on senescent tissues of both. These results were consistent with observations from both controlled condition and field experiments with lines from the mapping population that segregated for this resistance. Analysis of results of both controlled-environment and field experiments suggested that the resistance was mediated by a single R gene located on chromosome A1. [ABSTRACT FROM AUTHOR]

This paper presents a statistically designed experimental program to present and analyze an effective and practical strengthening system for deteriorated crossarms of the Gulfport timber structures using glass-fiber-reinforced polymer (GFRP) wrap. In this research, a total of 14 strengthened and six control specimens with a length of approximately 3.1 m were tested to failure. The experimental program was conducted in two phases: feasibility study and parameter optimization designed by using the Taguchi method and analysis of variation (ANOVA). The feasibility study concluded that the proposed strengthening system was sufficient for increasing the strength of the deteriorated crossarms of the Gulfport structures well above the critical end-of-life (EOL) design threshold value of the crossarms. The parametric optimization of the strengthening system identified the critical variables to be the crack-repair material, the width of the wrap, and sanding the surface. Using statistical advantages of the Taguchi method of experimental design, the mean strength of the strengthened specimens was estimated, and a 95% confidence interval for that mean was calculated. This estimated mean was 70% higher than the EOL threshold of the crossarms. [ABSTRACT FROM AUTHOR]

Phoma stem canker (blackleg disease) of Brassica napus (oilseed rape, canola) is caused by the fungus Leptosphaeria maculans. Frequencies of avirulent alleles for loci where virulence can be associated with gene deletion ( AvrLm1 and AvrLm6) were determined in samples of L. maculans airborne ascospore inoculum using quantitative PCR. The accuracy, reproducibility and limitations of detection were determined. Changes in the frequency of avirulent alleles were determined for the 2006/2007, 2007/2008 and 2008/2009 growing seasons for winter oilseed rape in the UK. The frequency of AvrLm1 remained small (between 9% and 16%), whilst the frequency of AvrLm6 fluctuated between 35% and 66%. Estimation of frequencies of avirulent alleles in airborne pathogen inoculum gives an efficient and unbiased method to assess the potential of crop cultivars with corresponding resistance genes being at risk of disease. [ABSTRACT FROM AUTHOR]

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Global food security is threatened by crop diseases that account for average yield losses of 16 per cent, with the greatest losses experienced by subsistence farmers in the developing world. Climate change is exacerbating the threats to food security in such areas, emphasizing the need to increase food production in northern European countries such as the UK. However, the crops must be grown in such a way as to minimize greenhouse gas (GHG) emissions associated with their production. As an example, it is estimated that production of UK winter oilseed rape is associated with GHG of 3300 kg CO2 eq. ha-1 of crop and 834 kg CO2 eq. t-1 of seed yield, with 79 per cent of the GHG associated with the use of nitrogen fertilizer. Furthermore, it is estimated that control of diseases by use of fungicides in this UK oilseed rape is associated with a decrease in GHG of 100 kg CO2 eq. t-1 of seed. Winter oilseed rape cultivar disease resistance is associated with a decrease in GHG of 56kg CO2 eq. t-1, although this figure is an underestimate. These results demonstrate how disease control in arable crops can make a contribution to both climate change mitigation and sustainable arable crop production to ensure global food security. [ABSTRACT FROM AUTHOR]

This paper reports the development of a new specific diagnostic technique to accurately quantify airborne inoculum of Sclerotinia sclerotiorum and discusses its potential use in disease-forecasting schemes, using examples of three contrasting epidemic seasons: 2007, when there was a severe epidemic of sclerotinia stem rot (SSR) in England and high numbers of airborne ascospores were trapped at Rothamsted, and, in contrast, 2003 and 2004, when the incidence of SSR in England was low and low numbers of airborne ascospores were trapped at Rothamsted. DNA was extracted from wax-coated plastic tapes, such as those used in Burkard (Hirst-type) spore traps and rotating-arm traps. A SYBR-green quantitative PCR (qPCR) method produced a linear relationship between ascospore numbers and S. sclerotiorum DNA (mean 0·35 pg DNA per spore) and was able to detect DNA representing as few as two ascospores. The technique was insensitive to DNA of the host plant, Brassica napus, and other plant pathogens, including Sclerotinia minor, S. trifoliorum and Botrytis cinerea, and common airborne fungal genera such as Cladosporium and Penicillium. There was no relationship between rainfall and numbers of airborne ascospores of S. sclerotiorum present at Rothamsted during the period of infection in the severe SSR season (2007). [ABSTRACT FROM AUTHOR]

Data from a controlled environment experiment investigating effects of temperature on maturation of Leptosphaeria maculans pseudothecia were used to derive equations describing the times until 30% or 50% of pseudothecia were mature as a function of temperature. A wetness sensor was developed to estimate the oilseed rape debris wetness and operated with debris exposed in natural conditions in 2000 and 2001. The maturation of L. maculans pseudothecia on debris and concentrations of airborne L. maculans ascospores were observed from 1999 to 2004. There were considerable differences between years, with the first mature pseudothecia observed in September in most years. There were linear relationships between the first date when 10% of maximum ascospore release was observed and the dates when 30% or 50% of pseudothecia were mature. By summing the daily temperature-dependent rate of pseudothecial maturation for days after 1 August with rainfall >0.5 mm, the dates when 30% or 50% of pseudothecia were mature were predicted. There was good agreement between predicted and observed dates when 30% or 50% of pseudothecia were mature. These equations for predicting the timing of L. maculans ascospore release could be incorporated into schemes for forecasting, in autumn, the severity of phoma stem canker epidemics in the following spring/summer in the UK. [ABSTRACT FROM AUTHOR]

At Rothamsted during 1997/98, 1998/99 and 1999/2000 winter oilseed rape growing seasons, numbers of air-borne ascospores of Leptosphaeria maculans were often > 4 m-3 from autumn (September/October) to spring (April/May), while few or no ascospores were detected during the summer. Mature pseudothecia were generally not observed on debris of the previous crop until September. One-year-old debris (harvested in July 1998) had 95% discharged and 5% mature pseudothecia in August 1999, but by 15 September new pseudothecia (of which 30% were mature) were observed and the first increase in air-borne ascospores (> 4 m-3 ) occurred. Phoma leaf spotting appeared in untreated field plots 14–25 days after the first increase in air-borne ascospores in autumn. The fungicide mixture difenoconazole plus carbendazim decreased the incidence of new leaf lesions for 1 month after application in autumn and for 2 months in mid-winter. When L. maculans was isolated from infected leaves, the growth rate of isolates from leaves to which fungicide was applied was less than that of those from untreated leaves. Foliar applications of fungicide to field plots in the autumn and winter not only decreased the incidence of crown cankers but also reduced the rate of canker development on stem bases in the spring and early summer (when severity of crown cankers increased linearly with time). In untreated crops, when phoma leaf spots appeared early in the autumn, crown cankers developed early in the spring but only became severe enough before harvest to reduce yield greatly in 1997/98. Yield loss was associated with crown cankers that girdled more than half of the stem by harvest (mean severity > 3 on a 0–5 scale). Infections of new leaves produced after stem extension, from January onwards, led to phoma stem lesion development above the crown. In the three seasons, phoma stem lesions became moderately severe (> 2) by harvest only in untreated plots in 1997/98. [ABSTRACT FROM AUTHOR]

The colonization of winter oilseed rape plants and epidemiology of phoma stem canker differed between A/Tox+ and B/Tox0 Leptosphaeria maculans . In France and England, where plant colonization was investigated during two and three growing seasons, respectively, there was a difference in timing of leaf infection; A/Tox+ L. maculans was predominant on leaves in the autumn (October/November) but there was an increase in the incidence of B/Tox0 in the winter (January/February). In May, June and July both species could be isolated from all external parts of the plant (root to the upper stem) and all crown (stem base) tissues, although they differed in their distribution. At the root and crown, A/Tox+ L. maculans was predominant and was located throughout the cortex, wood and pith tissues, but the rarer B/Tox0 was located mainly in the cortex. Approximately equal numbers of A/Tox+ and B/Tox0 isolates were obtained from the upper stem – there was a greater proportion of B/Tox0 isolates than at the crown. In England, after harvest in 1999 and 2000, pseudothecia on the lignified tap root and crown tissues produced predominantly A/Tox+ ascospores (94%), while pseudothecia higher up the stem produced more B/Tox0 ascospores (60%) than A/Tox+ ascospores (40%). The timing of the onset of leaf spotting, earlier in the season for A/Tox+ than B/Tox0 L. maculans , and the predominance of mycelium of A/Tox+ at the crown are consistent with the assumption that A/Tox+ is more likely to cause the most damaging stem cankers than B/Tox0 L. maculans . Identification as A/Tox+ or B/Tox0 by cultural characteristics differed only slightly (2·3%) from identification by molecular techniques. [ABSTRACT FROM AUTHOR]

In controlled-environment experiments, ascospores of both A-group and B-group Leptosphaeria maculans were able to infect leaves of oilseed rape and produce phoma leaf spot lesions at temperatures from 5 to 20°C and wetness durations from 8 to 72 h after inoculation. Lesions formed on leaves inoculated with B-group ascospores had few pycnidia and were darker, smaller and less noticable than the larger, pale grey lesions with many pycnidia produced by A-group ascospores. Lesions formed by A-group or B-group L. maculans on naturally infected winter oilseed rape experimental crops were similar to lesions produced by the two groups on inoculated plants. The greatest numbers of lesions were produced with a leaf wetness duration of 48 h and at temperatures of 15–20°C for both A-group and B-group ascospores. As leaf wetness duration and temperature decreased below the optimal values, the number of lesions decreased. The incubation period, estimated as the time from inoculation to the appearance of the first lesions (t1), or the time to the appearance of 50% of the lesions (t50), of B-group was often shorter than that of A-group L. maculans. As temperature decreased below 20°C, the length of the incubation period of both A-group and B-group L. maculans increased. [ABSTRACT FROM AUTHOR]

Phoma stem canker (blackleg), caused by Leptosphaeria maculans, is an important disease on oilseed rape (canola, rapeseed, Brassica napus, Brassica juncea, Brassica rapa) causing seedling death, lodging or early senescence in Australia, Canada and Europe, but not in China. The two forms of L. maculans (A group and B group) that occur on oilseed rape are now considered to be separate species. The epidemiology and severity of phoma stem canker differs between continents due to differences in the pathogen population structure, oilseed rape species and cultivars grown, climate and agricultural practices. Epidemics are most severe in Australia, where only the A group occurs, and can be damaging in Canada and western Europe, where both A and B groups occur, although their proportions vary within regions and throughout the year. Epidemics are slight in China, where the A group has not been found. Dry climates (Australia, western Canada) lengthen the persistence of infected debris and may synchronize the release of airborne ascospores (after rain) with seedling emergence. L. maculans spreads from cotyledon and leaf infections down petioles to reach the stem, with infections on cotyledons and leaves early in the season producing the most damaging stem cankers at the stem base (crown). Development of both crown cankers and phoma stem lesions higher up stems is most rapid in regions with high temperatures from flowering to harvest, such as Australia and Canada. Breeding for resistance (genetic, disease escape or tolerance), stubble management, crop rotation and fungicide seed treatments are important strategies for control of phoma stem canker in all areas. Fungicide spray treatments are justified only in regions such as western Europe where high yields are obtained, and accurate forecasts of epidemic severity are needed to optimize their use. [ABSTRACT FROM AUTHOR]

The authors discuss a testing program aimed to compare the natural aggregate concrete specimens and the recycled concrete aggregate (RCA) concrete specimens based on the relative bond force required to initiate a bond splitting failure. They mention the measurement of beam-end slip both at the free end of the test bar using linear variable differential transformers. They also note the aggregate crushing value (ACV) that was considered as a secondary parameter influencing the bond strength.

A correction to the article "Detection and quantification of airborne inoculum of sclerotinia sclerotiorum using qantitative PCR" is presented.