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Use of host resistance is the most economical and environmentally safe way to control light leaf spot disease of oilseed rape (Brassica napus). The causal organism of light leaf spot, Pyrenopeziza brassicae , is one of the most economically damaging pathogens of oilseed rape in the United Kingdom and it is considered to have a high potential to evolve due to its mixed reproduction system and airborne ascospores. This necessitates diverse sources of host resistance, which are inadequate at present to minimize yield losses caused by this disease. To address this, we screened a doubled haploid (DH) population of oilseed rape, derived from a secondary gene pool (ancestral genomes) of B. napus for the introgression of resistance against P. brassicae. DH lines were phenotyped using controlled-environment and glasshouse experiments with P. brassicae populations obtained from three different geographic locations in the United Kingdom. Selected DH lines with different levels of resistance were further studied in a controlled-environment experiment using both visual (scanning electron microscope – SEM) and molecular (quantitative PCR) assessment methods to understand the mode/s of host resistance. There was a clear phenotypic variation for resistance against P. brassicae in this DH population. Quantitative trait locus (QTL) analysis identified four QTLs with moderate to large effects, which were located on linkage groups C1, C6, and C9. Of these, the QTL on the linkage group C1 appeared to have a major effect on limiting P. brassicae asexual sporulation. Study of the sub-cuticular growth phase of P. brassicae using qPCR and SEM showed that the pathogen was able to infect and colonise both resistant and susceptible Q DH lines and control B. napus cultivars. However, the rate of increase of pathogen biomass was significantly smaller in resistant lines, suggesting that the resistance segregating in this DH population limits colonisation/sporulation by the pathogen rather than eliminating the pathogen. Resistance QTLs identified in this study provide a useful resource for breeding cultivar resistance for effective control of light leaf spot and form a starting point for functional identification of the genes controlling resistance against P. brassicae that can contribute to our knowledge on mechanisms of partial resistance of crops against pathogens. [ABSTRACT FROM AUTHOR]

Summary: Potato cyst nematodes (PCN) are estimated to cause over £50 million worth of crop losses in the UK each year. It has been shown that the infective juveniles are able to alter their surface composition to avoid damage from host defence mechanisms. However, relatively few proteins present on the cuticle surface of PCN juveniles have been identified. We have developed a method based upon biotinylation that allows selective labelling of proteins present on the cuticle surface of PCN. Isolated proteins can consequently be affinity purified and identified using mass spectrometry proteomics. Using this technique, we identify a variety of proteins present on the surface of PCN, including all previously described PCN surface proteins. Identification of known surface coat proteins using these methods demonstrates the viability of the process for isolation of novel surface coat proteins. Subsequent analysis confirmed that the genes encoding seven of the novel proteins were expressed in the hypodermis. This work provides a technique for study of surface proteins in a wide range of nematodes and expands our knowledge of the surface proteome of PCN. [ABSTRACT FROM AUTHOR]

Between 1738 and 1741 Scotland experienced one of the harshest harvest crises and depressions in the eighteenth-century. After at least two consecutive harvest failures (in 1739 and 1740 and perhaps also in 1738) agrarian and industrial output contracted, the price level doubled, and average incomes fell below subsistence. Due to an increase in mortality, there was also a considerable contraction in aggregate demand. Data drawn from both the micro- as well as the macro-level shows the disastrous economic impact such deficient harvests -- the depression's initial trigger -- would have upon Scotland, a pre-industrial economy dominated by agriculture. Such shocks in agrarian supply tended to work out as general adverse shocks in aggregate supply, as the economy's business cycle was to a large extent determined by movements in the harvest cycle. The implicit task of the paper also is to point out the variety of available sources for, as well as one possible strategy of, writing a quantitative macro-economic history of eighteenth-century Scotland. [ABSTRACT FROM AUTHOR]

Field-trapping experiments with synthetic 2,7-nonadiyl dibutyrate, the female-produced sex pheromone of the orange wheat blossom midge, Sitodiplosis mosellana (Géhin), demonstrated that pheromone traps were highly attractive to males and caught very few non-target organisms. Different formulations of pheromone were tested to identify the optimum release rate and dispenser type for use in pheromone traps in the UK. Key findings were that racemic pheromone was as effective as enantiomerically pure (2S,7R)-2,7-nonadiyl dibutyrate, that release rates higher than 0.5 μg day-1 were not necessary and that the optimal formulation was a 1 mg pheromone loading in a rubber septum. Pheromone traps gave a reliable indication of peak midge emergence, onset of flight and abundance of midges throughout the season. A strong correlation between maximum trap catch and crop infestation levels was obtained. [ABSTRACT FROM AUTHOR]

Presents the speech of D. J. Royle, president of the British Society for Plant Pathology, regarding understanding and predicting epidemics related to pathosystems. Approaches towards understanding how diseases develop in terms of environmental, host and pathogen factors; Completion of a monocycle when infection occurs; Reduction in crop yields.

Alfalfa mosaic virus (AMV) and cucumber mosaic virus (CMV) were isolated from clones of Buddleia davidii collected at Long Ashton Research Station for assessment of horticultural characteristics. The AMV isolate investigated in this study (AMV-B) infected 18 species and cultivars of herbaceous test plants. The m vilto properties of AMV-B were determined. The virus was purified by permeation chromatography on controlled-pore glass beads and an antiserum prepared. AMV-B appeared to be serologically indistinguishable from AMV isolate 15/64. The sizes and shapes of the virus particles were those of classical AMV components. The capsid protein was a single polypepticle of Mr 24 375. Buddleia seedlings inoculated with AMV-B showed only mild chlorosis and slight distortion of leaves. [ABSTRACT FROM AUTHOR]

This article discusses a study which investigated cabbage aphid damage in commercial Brussels sprout crops during the 1951, 1952 and 1953 seasons in Great Britain. In the accurate measurement of crop losses attributable to aphids, damage to the host plant can be regarded as a product of pest density, pest activity, and plant growth--factors which are continually changing. Single observations, such as can conveniently be made on a large number of fields over a relatively short period in the course of a country-wide survey, cannot therefore lead to an accurate estimate of damage over the country as a whole. Estimates of this kind can lead to an approximate assessment of yield reduction, provided a relationship has been established between pest density at a given time and the final yield of the host plant.

This article discusses new or uncommon plant diseases and pests in Great Britain. Leaves of several plants of a species of Hieracium at Gullane showed yellow ring-like symptoms characteristic of tobacco rattle virus. The black stem rot of cucumber or Mycosphaerella melonis occurs commonly in crops of cucumber grown under glass in Essex and Hertfordshire. The significance of seed-borne infection in outbreaks of the disease is not known but the infected debris remaining in cucumber houses has shown to be important.

This article discusses a study which investigated the virus Yellows infestation in sugar beet in Great Britain in 1953. An independent estimate, based on the acreage carrying varying proportions of infected plants, gave an average of 8.1 percent infected plants at the end of August. This incidence of Yellows resembled that in 1942, 1946 and 1951, when the disease caused little loss. The calculated average loss of yield in 1953 was 0.39 tons per acre of roots. Although the actual yield in 1953 was a record for the country, this calculation suggests that the season was potentially not quite so favorable for growth of sugar beet as 1950, when Yellows caused greater loss.