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The development of resilient cropping systems with high yield stability is becoming increasingly important due to future climatic and agronomic challenges. Consequently, it is essential to compare the effects of different agronomic management practices, such as cropping sequences and nutrient supply, on the stability of crop yields. Long-term experiments are a valuable resource for investigating these effects, as they provide enough time to accurately estimate stability parameters. The objective of the current study was to compare the effects of different cropping sequencing (#1: continuous v. rotational), fertilization (#2: mineral v. organic) and straw management techniques (in the case of continuous wheat; #3: removal v. incorporation) on the yield stability of winter wheat; yield risk (the probability of yield falling below a threshold yield level) and inter-annual yield variability were used as stability indicators of the effects. Long-term yield data from the Broadbalk Wheat Experiment (Rothamsted, UK) were analysed using a mixed model. Overall, the results showed that rotational cropping combined with sufficient mineral N fertilizer, with or without organic manure, ensured stable wheat yields while reducing yield risk. In contrast, higher yield risks and inter-annual yield variabilities were found in continuous wheat sections with less mineral N fertilizer or with organic manure only. [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]

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]