Genotypic differences in storage losses of sugar beet – causes and indirect criteria for selection

To improve the storability of sugar beets, this study aimed at determining reasons for genotypic variability in sugar losses and invert sugar accumulation during storage, and at identifying indirect criteria to select for varieties with low storage losses prior to storage. In 2011 and 2012, 18 genotypes, and in 2012 and 2013, six genotypes cultivated at two locations were stored for 8 and 12 weeks at 8°C under controlled conditions. The same 18 genotypes were grown under stress conditions in Spain in 2012/2013. Sugar losses were closely correlated with the invert sugar accumulation after storage. Genotypic differences in storage losses were primarily caused by differences in the level of infestation with microorganisms. The invert sugar accumulation was lower for genotypes with high marc concentration before storage, pointing to a non‐specific resistance. Additionally, the sugar concentration in dry matter before storage, and the invert sugar concentration after cultivation under stress conditions correlated with the invert sugar concentration after storage. These parameters are therefore suggested as criteria to select for improved storability of sugar beet genotypes.     

Target and non-target site mechanisms of fungicide resistance and their implications for the management of crop pathogens

Fungicides are indispensable for high-quality crops, but the rapid emergence and evolution of fungicide resistance have become the most important issues in modern agriculture. Hence, the sustainability and profitability of agricultural production have been challenged due to the limited number of fungicide chemical classes. Resistance to site-specific fungicides has principally been linked to target and non-target site mechanisms. These mechanisms change the structure or expression level, affecting fungicide efficacy and resulting in different and varying resistance levels. This review provides background information about fungicide resistance mechanisms and their implications for developing anti-resistance strategies in plant pathogens. Here, our purpose was to review changes at the target and non-target sites of quinone outside inhibitor (QoI) fungicides, methyl-benzimidazole carbamate (MBC) fungicides, demethylation inhibitor (DMI) fungicides, and succinate dehydrogenase inhibitor (SDHI) fungicides and to evaluate if they may also be associated with a fitness cost on crop pathogen populations. The current knowledge suggests that understanding fungicide resistance mechanisms can facilitate resistance monitoring and assist in developing anti-resistance strategies and new fungicide molecules to help solve this issue. © 2023 Society of Chemical Industry.     

牛心朴子生物碱对奶牛乳房炎病原菌的体外抑菌试验

对4例临床型奶牛乳房炎的乳汁进行病原分离及鉴定,分离出了金黄色葡萄球菌、无乳链球菌和大肠杆菌。选择牛心朴子生物碱,采用试管2倍稀释法进行体外抑菌试验,测其最小抑菌浓度（MIC）和最小杀菌浓度（MBC）。结果显示：牛心朴子生物碱对3种菌都有不同程度的抑制作用,对金黄色葡萄球菌、无乳链球菌、大肠杆菌分离株的MIC及MBC分别是12.5mg/mL、1.561 25mg/mL、6.25mg/mL和6.25mg/mL、1.561 25mg/mL、3.125mg/mL。     

Applications of ionizing radiation for the control of postharvest diseases in fresh produce: recent advances

Postharvest diseases cause considerable losses to harvested fruits and vegetables worldwide. In addition to various treatments to control postharvest losses caused by pathogens, the global trend is shifting toward more ecofriendly alternatives safer to human health. Thus far, the main approach to postharvest disease control has mostly relied on the use of chemicals. However, the intense use of chemical fungicides has caused side effects such as environmental issues and evolution of fungicide‐resistant isolates. With increasing demand for the use of non‐chemicals, ionizing radiation has been investigated for application in many aspects of postharvest treatment, especially as an approach with significant potential for the control of postharvest disease. Recently, a number of more or less technologically advanced methodologies, e.g. irradiation combined with other types of treatments and induced disease‐resistance, have been developed to control postharvest diseases as well as to increase the quality and storage life of fresh commodities. Challenges for future application of irradiation in fresh produce are the cost, lack of irradiation facilities, lack of knowledge about optimal conditions for different commodities, and lack of acceptance of irradiated fresh produce. This review aims to document the advances in understanding of the effects of irradiation on postharvest disease, the possible modes of action, and the perspectives in commercial use.     

Relation between cropping frequency of peas and other legumes and foot and root rot in peas

The relation between the frequency of legume crops in a rotation and the root rot severity in pea was examined in a field survey. Additionally, greenhouse experiments were performed with soil samples from legume rotation trials or from farmers' fields. The frequency of pea crops in current rotations proved to be much less than the recommended value of one in six years. The correlation between pea root rot and the number of years that pea or other legumes were not grown on the field under consideration (called crop interval) was weak. Root rot severity correlated better with the frequency of peas or legumes in general over a period of 18 years, but the frequency still explained only a minor fraction of the variation in disease index. Some experimental data pointed to the occurrence of a highly specific pathogen microflora with continuous cropping of only one legume species, but this phenomenon probably does not occur in farmers' fields. In field samples, root disease index for pea correlated well with that for field bean. The survival of resting structures of pathogens such asAphanomyces euteiches probably explains why the frequency of legume cropping has a higher impact than crop interval on root disease incidence. Pea-free periods and legume frequencies have a poor predictive value for crop management purposes.     

Clonal Spread of Salmonella enterica Serovar Infantis in Serbia: Acquisition of Mutations in the Topoisomerase Genes gyrA and parC Leads to Increased Resistance to Fluoroquinolones

Quinolone‐resistant Salmonella Infantis (n = 64) isolated from human stool samples, food and poultry during the years 2006–2011 were analysed for their resistance phenotypes, macrorestriction patterns and molecular mechanisms of decreased susceptibility to fluoroquinolones. Minimum inhibitory concentrations (MICs) of nalidixic acid (NAL) and ciprofloxacin (CIP) were determined by the agar dilution procedure, and the susceptibility to additional antimicrobial agents was determined by the disc diffusion method. To assess the influence of enhanced efflux activity, MICs were determined in the presence and absence of the inhibitor PAβN. The results of pulsed‐field gel electrophoresis (PFGE) typing revealed that quinolone‐resistant S. Infantis in Serbia had similar or indistinguishable PFGE profiles, suggesting a clonal spread. All S. Infantis showed combined resistance to NAL and tetracycline, whereas multiple drug resistance to three or more antibiotic classes was rare (2 isolates of human origin). The MICs ranged between 512 and 1024 μg/mL for NAL and 0.125–2 μg/mL for CIP. A single‐point mutation in the gene gyrA leading to a Ser83→Tyr exchange was detected in all isolates, and a second exchange (Ser80→Arg) in the gene parC was only present in eight S. Infantis isolates exhibiting slightly higher MICs of CIP (2 μg/mL). The inhibitor PAβN decreased the MIC values of CIP by two dilution steps and of NAL by at minimum 3–6 dilution steps, indicating that enhanced efflux plays an important role in quinolone resistance in these isolates. The plasmid‐mediated genes qnr, aac(6′)‐lb‐cr and qepA were not detected by PCR assays.     

含双病原物诱导启动子植物安全表达载体的构建

 本研究用来自烟草的具有高度病原物特异性的两个诱导启动子EAS4和hsr203J,串联驱动GUS基因的表达,同时考虑到转基因植物的安全性,引入双边界序列,构建了含双病原物诱导启动子的植物安全表达载体。将表达载体转化烟草获得转基因植株。分析显示,在正常生长情况下转基因烟草检测不到GUS活性,或活性极低;而受疫霉激发子parasiticein、Phytophthora nicotianea[0]的孢子悬浮液和Ralstonia solanacarum的菌悬液诱导后,转基因烟草叶片中可检测到明显的GUS活性。结果表明,构建的植物表达载体所含双病原物诱导启动子均具有良好的诱导活性,可用于植物遗传转化。     

Molecular and serological detection of animal and human vector-borne pathogens in the blood of dogs from Côte d’Ivoire

In Côte d’Ivoire, limited information are available on vector-borne pathogens, their prevalence and distribution. Here, we assess the occurrence and diversity of canine vector-borne diseases (CVBDs) in Abidjan and Yamoussoukro cities. Blood from a total of 123 dogs were tested for Leishmania infantum and Ehrlichia canis antibodies and screened for Leishmania and Trypanosoma spp., Piroplasmida, Filariidae and Anaplasmataceae by PCR and sequencing. Among dogs, 39 % were positive for at least one pathogen. Seroprevalences were: 15.4 % and 12.2 % for L. infantum and E. canis, respectively. DNA of L. infantum and T. congolense (4.1 %), Baabesia vogeli (1.6 %), Filariidae (Dirofilaria immitis, D. repens and Acanthocheilonema reconditum) (10.6 %) has been detected. Anaplasmataceae were detected in (17.1 %) and E. canis was the only identified specie. Co-infections were observed in 13.8 % of dogs: E. canis-L. infantum co-infection was the most prevalent (4.9 %). Age, breed and sex of dogs do not seem to influence infections. Village dogs were more susceptible to CVBDs than kennel dogs (PV = 0.0000008). This study reports for the first time the presence of L. infantum, B. vogeli, A. reconditum, D. immitis and D. repens in dogs from Côte d’Ivoire and determines the prevalence and diversity of CVBD pathogens. The results indicate that human and animal pathogens are abundant in Ivoirian dogs which requires attention of veterinarians, physicians and authorities against these diseases, especially against major zoonosis such as visceral leishmaniasis (L. infantum).