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991.
C. F. E. Topp G. Hughes I. M. Nevison A. Butler S. J. P. Oxley N. D. Havis 《Plant pathology》2019,68(6):1179-1187
A programme of field trials for the study of the winter barley–Rhynchosporium commune pathosystem is reported. The associated seedborne disease rhynchosporium leaf scald is regarded as having an important impact on barley yields. The analysis in this study relates to the impact of the seed source (commercial or farm-saved seed) on disease incidence and to the spatial pattern of rhynchosporium leaf scald disease incidence. Disease incidence data were calculated from field data recorded as disease severity. Mean disease incidence was higher in the crops grown from farm-saved seed than in those grown from commercial seed, although great agronomic significance cannot be attached to this result. The spatial pattern of rhynchosporium leaf scald disease incidence was characterized in terms of the binary power law (BPL) and was indicative of an aggregated pattern. Programme-wide BPL results were described using a novel phytopathological application of a random coefficients model. These results have application in field sampling for rhynchosporium leaf scald disease. 相似文献
992.
Synchytrium endobioticum is one of the most important pathogens of potato and is known for its persistent propagation structures. Under favourable conditions, infection of highly susceptible potato cultivars leads to clearly visible cauliflower‐like tissue warts, the typical symptom of potato wart disease. However, unfavourable infection conditions or low infection pressure may result in symptoms being overlooked. Thus, the introduction of pathogen structures into stages of the processing industry cannot be ruled out. As the amounts of processed potato products continue to rise, phytosanitary risks from processing discarded potatoes and potato waste in biogas plants have to be considered. Hence, the resilience of resting spores against mesophilic anaerobic digestion was analysed in stirred tank reactors. Laboratory‐scale results show that S. endobioticum not only withstands mesophilic anaerobic digestion but also subsequent storage of the digestate for at least 4 weeks. Large numbers of viable resting spores were detectable by microscopic assessment in all samples. Viability was proved and verified additionally by bioassay. Consequently, potatoes, potato waste and processing water from potato processing industries used in biogas plants pose a phytosanitary risk if the accruing digestates are returned as fertilizer to arable land. 相似文献
993.
J. P. Renvois F. Chambon M. Gleize N. Pradeilles S. Garnier M. Rolland 《EPPO Bulletin》2019,49(1):111-121
The aim of the study was to select, optimize and characterize RT‐PCR tests for the detection of Tobacco ringspot virus (TRSV) in post‐entry quarantine. Among five different tests, the Poojari et al. (Journal of Virological Methods 235, 112–118) and Jossey & Babadoost (Plant Disease 90, 1361) conventionnal RT‐PCR tests were chosen and optimized for this purpose. Ten TRSV isolates, 17 healthy plants from the genera Vitis, Prunus and Malus, four other Nepoviruses or Secoviridae isolates and serial dilutions of three TRSV isolates were used for the complete characterization of the optimized tests. In the tested conditions, the Poojari and Jossey & Babadoost tests respectively showed 100% and 95% inclusivity, 100% and 100% exclusivity, 100% and 96.4% analytical specificity, 100% and 100% diagnostic specificity, [10?7; 10?1] and [10?8; 10?2] limit of detection dilution factors (analytical sensitivity), 91.1% and 90.0% repeatability, 90.3% and 91.1% reproducibility and 100% and 100% selectivity. Due to its higher inclusivity, the optimized Poojari test is recommended for the detection of TRSV isolates for post‐entry quarantine purposes, but can also be used for global surveys. The optimized Jossey & Babadoost test showed the best analytical sensitivity, suggesting that combining both tests can further enhance detection. 相似文献
994.
Plant eradication is difficult, particularly in remote, protected areas. The Southern Ocean Islands are very isolated and highly protected, but the flora contains many alien plants. Small restricted populations have been eradicated, but eradication of established species has proven difficult. A better understanding of the efficacy of control methods at sub‐Antarctic temperatures and their off‐target impacts may increase eradication success. With interest in controlling non‐native Poa annua in the region, we aimed to determine if physical and chemical methods can control P. annua (the sub‐Antarctic biotype) in sub‐Antarctic conditions and examined their impact on native plants. We quantified the effectiveness of physical control methods on P. annua in situ on sub‐Antarctic Macquarie Island through field‐based experiments and assessed their selectivity on P. annua compared with native grasses. We also quantified the effectiveness of several herbicides on P. annua at sub‐Antarctic temperatures and assessed their selectivity on native grasses. Of the four physical disturbance methods tested, none effectively reduced P. annua cover as one‐off treatments. Of the herbicide treatments, glyphosate and trifloxysulfuron sodium were effective and were less damaging to native grass species, indicating potential selectivity. Physical control was of limited effectiveness, but did not affect native species richness. An integrated weed management programme utilising the strategic use of selective herbicides with follow‐up chemical and physical intervention may balance control and biodiversity outcomes. This research highlights the importance of site‐specific testing of control methods and understanding off‐target impacts of control when managing alien plant species in protected areas. 相似文献
995.
J. M. Zeng J. Nifong Y. Liu C. J. Huang D. H. Fang R. S. Lewis Y. P. Li 《Plant pathology》2019,68(9):1616-1623
Black shank, caused by the soilborne pathogen Phytophthora nicotianae, is one of the most devastating diseases affecting tobacco production in China. The most effective strategy for reducing economic loss from this pathogen is development and use of resistant tobacco varieties. Multiple sources and systems of resistance have been developed in the Western Hemisphere; however, populations of P. nicotianae are variable around the world, including the predominance of different races. Different P. nicotianae isolates may react differently on tobacco plants with different systems of resistance, a possibility that could complicate the breeding of cultivars with resistance that is effective in different tobacco production regions worldwide. The objective of this research was to evaluate an array of tobacco germplasm possessing different systems of genetic resistance to black shank disease in tobacco-growing regions of Yunnan, China. Resistance types included simply inherited resistance mechanisms introgressed from wild Nicotiana relatives and polygenic partial resistance systems of N. tabacum origin. The loci of Wz exhibited high level resistance to black shank in the five diverse disease environments in Yunnan, China. K326 Php/−Wz/− genotype and Beinhart 1000 exhibited the greatest levels of resistance in both 2015 and 2016. Field observed results for 13 tobacco genotypes were highly correlated with those tested in growth chamber evaluation. These findings suggest that both Wz− and Beinhart 1000-mediated resistance have important commercial value in flue-cured tobacco breeding programmes in China. Cultivars developed for black shank resistance in China may also have utility in other tobacco-growing areas. 相似文献
996.
Tomato is the most economically important fruit/vegetable crop grown worldwide. However, viral diseases remain an important factor limiting its productivity, with estimated quantitative and qualitative yield losses in tomato crops often reaching up to 100%. Many viruses infecting tomato have been reported, while new viral diseases have also emerged. The climatic changes the world is experiencing can be a contributing factor to the successful spread of newly emerging viruses, as well as the establishment of disease in areas that were previously either unfavourable or where the disease was absent. Because antiviral products are not available, strategies to mitigate viral diseases rely on genetic resistance/tolerance to infection, control of vectors, improvement in crop hygiene, roguing of infected plants and seed certification. Tomato brown rugose fruit virus (ToBRFV) is an emerging viral threat to tomato productivity and is currently spreading into new areas, which is of great concern to the growing global production in the absence of mitigation measures. This review presents the current knowledge about ToBRFV and future prospects for an improved understanding of the virus, which will be needed to support effective control and mitigation of the impact it is likely to cause. 相似文献
997.
A modelling investigation was conducted into optimizing the number of sprays and inter-spray interval to reduce an insect population to a low level, for example, prior to pheromone trapping or the release of sterile males. The model population was age-structured and density-dependent. If spray mortality is 100% for each spray, then the ideal spraying schedule is easily determined from the durations of the various life stages. For spray mortality of less than 100%, a simulation was used to determine optimal spraying schedules. Relative length of the larval period, fertility rate and age to first oviposition were found to be the most important biotic parameters for this determination. Their importance is magnified as spray mortality decreases. The stage targeted by sprays and the percent mortality caused by each spray are also important in determining the required number of sprays. Using medfly (Ceratitis capitata Wiedmann) biotic parameters as an example when the spray targets adults, it appeared that neither the stage at which density-dependent mortality takes effect, nor the form of the adult survivorship curve are important in determining the optimal spray schedule. 相似文献
998.
Abstract. Formalin and β-propiolactone (BPL) were compared for efficacy in inactivating infectious pancreatic necrosis virus (IPNV) for vaccine use. Incubation with a 1:200 dilution of formalin at 20°C for four days or longer, or a 1:200 dilution of BPL at 4°C for six days or longer, completely inactivated the virus infectivity. However, whereas treatment with formalin caused only a slight reduction in anti-genicity as titrated by in vitro tests, treatment with BPL destroyed over 50% of the antigenicity of the virus. Virus inactivated with formalin also proved highly effective at inducing high titres of neutralizing antibody in trout. 相似文献
999.
Effects of lysine and methionine supplementation on growth,body composition and digestive function of grass carp (Ctenopharyngodon idella) fed plant protein diets using high‐level canola meal
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J. Jiang D. Shi X.‐Q. Zhou L. Feng Y. Liu W.‐D. Jiang P. Wu L. Tang Y. Wang Y. Zhao 《Aquaculture Nutrition》2016,22(5):1126-1133
A 76‐day feeding trial was carried out to evaluate the effects of Lysine and Methionine supplementation on growth and digestive capacity of grass carp (Ctenopharyngodon idella) fed plant protein diets using high‐level canola meal (CM). Fish with initial average weight 103.9 ± 0.6 g were fed three extruded diets. Fish meal (FM) diet was formulated as the normal control with 40 g kg?1 FM and 300 g kg?1 CM; CM diet was prepared by replacing all FM with CM (total 340 g kg?1) without Lys or Met supplementation; CM supplement (CMS) diet was similar to CM diet but was supplemented with essential amino acids (EAA) to ensure the levels of Lys and Met similar to those in the FM diet. Feed intake, feed efficiency and specific growth rate of the grass carp fed CMS and FM diets were similar (P > 0.05), but higher than those of the grass carp fed CM diet (P < 0.05). The hepatosomatic index, relative gut length, intestosomatic index and intestinal folds height were significantly improved in fish fed FM and CMS diets as compared to CM diet (P < 0.05). Lower activities of trypsin, lipase and amylase in hepatopancreas were observed in fish fed CM diet (P < 0.05). Three hundred and forty gram per kilogram CM without Lys or Met supplementation significantly decreased trypsin, lipase and amylase mRNA levels in hepatopancreas (P < 0.05). These results indicated that the high supply of CM (340 g kg?1) in plant protein (200 g kg?1 soybean meal and 100 g kg?1 cottonseed meal) diets decreased digestive ability through decreasing digestive enzyme activities and enzyme gene's expressions of grass carp, and these side effects can be reversed by supplementing Lys and Met. Therefore, CM could be high level used in a plant protein blend‐based extruded diet for grass carp as long as EAA were supplemented. 相似文献
1000.
Comparison of PCR and dot blot diagnostic techniques for detection of white spot syndrome virus (WSSV) was made on different tissues of infected Penaeus monodon including eye stalk, eye stalk with eye, gills, cuticle, pleopod, periopods, uropods and telson. Dot blots of crude DNA extracted from infected tissue samples showed positive reactions with all the samples; however, the sensitivity of the dot blot was reduced with the purification of DNA samples extracted from pleopod, telson and uropod. PCR was found to be more sensitive when compared to dot blot. Both crude DNA and purified DNA samples extracted from all the tissues except for eye stalk with eye showed single step nested PCR positive reaction. The amplification of all or either of the three bands of 941 bp, 525 bp and 204 bp size varied with the tissues analysed. The severity of infection assessed by PCR amplification was found to be maximum in cuticle and telson followed by gill. Other tissues such as eye stalk, pleopod, periopods and uropod were observed to have mild infection. The maximum intensity of the PCR product was for the smallest amplified product of 204 bp followed by 525 bp and the weakest intensity was observed for the 941 bp size. The limitation of PCR due to inhibiting factors present in tissues could be overcome with the use of dot blot which gave positive reaction from the DNA extracted from eye stalk including the eye but yielded no amplification by PCR. 相似文献