Screening Method For Resistance Research Articles

Establishment of an Efficient Screening Methods for Resistance of Chinese Cabbage to Clubroot Disease

Clubroot caused by <i>Plasmodiophora brassicae</i> is an important disease of crucifer crops worldwide. This study aimed to establish an efficient screening method to determine resistant cultivars of Chinese cabbage against <i>P. brassicae</i>. To do this, we investigated the virulence of seven <i>P. brassicae</i> isolates using seedlings of susceptible Chinese cabbage cultivar. The isolates exhibited different virulence in the plants and were divided into three groups based on their virulence. When we explored the disease occurrence in Chinese cabbage seedlings according to photoperiod after inoculation of <i>P. brassicae</i> and incubation temperature, the plants with all-day light showed higher disease severity than seedlings cultivated under 14 hr of light a day. The occurrence of clubroot disease was most severe at 25<sup>o</sup>C, followed by 20<sup>o</sup>C and 18<sup>o</sup>C, but the fresh weight of clubroot of the seedlings cultivated at 20<sup>o</sup>C was the highest, followed by plants grown at 25<sup>o</sup>C and 18<sup>o</sup>C. When the seedlings of two commercial resistant cultivars were inoculated with the mixed spore suspensions of two different pathotype isolates of <i>P. brassicae</i>, disease severity increased as the spore concentration of the susceptible <i>P. brassicae</i> isolate among the two strains increased, suggesting that the clubroot development by different pathotype isolates was independent and not influenced by each other. Taken together, our results provide a faster and more accurate screening methods to determine the resistance of Chinese cabbage against <i>P. brassicae</i>.

Three novel multiplex PCR assays for rapid detection of virulence, antimicrobial resistance, and toxin genes in Acinetobacter calcoaceticus-baumannii complex species.

The Acinetobacter calcoaceticus-baumannii (ACB) complex is an often-overlooked group of nosocomial pathogens with a significant environmental presence. Rapid molecular screening methods for virulence, antimicrobial resistance, and toxin (VAT) genes are required to investigate the potential pathogenicity of environmental isolates. This study aimed to develop and apply novel ACB complex-specific multiplex PCR (mPCR) primers and protocols for the rapid detection of eight VAT genes. We optimized three single-tube mPCR assays using reference DNA from ACB complex and other Acinetobacter species. These assays were then applied to detect VAT genes in cultured ACB complex isolates recovered from clinical and environmental sources. Widespread detection of VAT genes in environmental isolates confirmed the validity, functionality, and applicability of these novel assays. Overall, the three newly developed ACB complex species-specific mPCR assays are rapid and simple tools that can be adopted in diagnostic and clinical lab settings. The detection of VAT genes in environmental isolates suggests that environmental niches could serve as a reservoir for potentially pathogenic ACB complex and warrants further investigation. The newly developed mPCR assays are specific, sensitive, and efficient, making them well-suited for high-throughput screening in epidemiological studies and evaluating the potential pathogenicity of ACB complex recovered from various sources.

Detection of antimicrobial resistance in

Antimicrobial resistance in Neisseria gonorrhoeae compromises gonorrhoea treatment and rapid antimicrobial susceptibility testing (AST) would be valuable. We have developed a rapid and accurate flow cytometry method (FCM) for AST of gonococci. The 2016 WHO gonococcal reference strains, and WHO Q, R and S (n = 17) were tested against seven clinically relevant antibiotics (ceftriaxone, cefixime, azithromycin, spectinomycin, ciprofloxacin, tetracycline and gentamicin). After 4.5 h incubation of inoculated broth, the fluorescent dye Syto™ 9 was added, followed by FCM analysis. After gating, the relative remaining population of gonococci, compared with unexposed growth control samples, was plotted against antimicrobial concentration, followed by non-linear curve regression analysis. Furthermore, the response at one single concentration/tested antibiotic was evaluated with the intention to use as a screening test for detection of resistant gonococci. A dose-dependent response was seen in susceptible isolates for all tested antimicrobials. There was a clear separation between susceptible/WT and resistant/non-WT isolates for ceftriaxone, cefixime, spectinomycin, ciprofloxacin and tetracycline. In contrast, for azithromycin, only high-level-resistant isolates were distinguished, while resistant isolates with MICs of 4 mg/L were indistinguishable from WT (MIC ≤ 1 mg/L) isolates. For gentamicin, all tested 17 isolates were WT and FCM analysis resulted in uniform dose-response curves. Using a single antibiotic concentration and a 50% remaining cell population cut-off, the overall sensitivity and specificity for resistance detection were 93% and 99%, respectively. By providing results in <5 h for gonococcal isolates, FCM-based AST can become a rapid screening method for antimicrobial resistance or antimicrobial susceptibility in gonococci.

Evaluation of screening methods for anthracnose fruit rot resistance in chilli (Capsicum spp.)

Anthracnose fruit rot caused by Colletotrichum spp. is a serious production constraint causing severe marketable yield loss in chilli. Field evaluation of chilli accessions for resistance to Colletotrichum spp. depends on various factors affecting disease expression such as edaphic conditions, temperature, rainfall, humidity and other variables that are difficult to control, therefore considered less accurate. Also, high chances of cross contamination with different Colletotrichum species leads to inconclusive assays for specific pathogen species and isolate. To identify a stable and reliable screening method, various chilli accessions were subjected to in vitro pin-prick and non-wounding spray methods using a specific pathogen isolates. When chilli accessions were screened against C. gloeosporioides isolate ‘IHRCg-1’, the in vitro pin- prick method showed positive correlation with the non- wounding spray method, except in the accession PBC80. The change in bioassay influenced the disease reaction pattern in the accession PBC 80, probably the pin pricks break the basal cuticle defense mechanism that was retained in spray inoculation method indicating varied resistance pattern. However, in the accession PBC 81 stable resistance pattern was observed against isolates of both species viz., C. truncatum ‘IIHR Ct-1’ and C. gloeosporioides ‘IIHR Cg-1’ and in the accession PBC 80 against C. truncatum ‘IIHR Ct-1’ in both the inoculation methods that depicted the expression of resistance genes during both methods of inoculation. Based on disease development pattern, the red ripe chilli expressed a variant reaction to infection by C. truncatum and C. gloeosporioides. The peak anthracnose infection at 10 DAI and 14 DAI is an accurate duration to record ‘IIHR Cg-1’ and ‘IIHR Ct-1’ infection, respectively on chilli ripe fruit for assaying the resistance.

Evaluation on current screening methods for insecticide resistance in mosquito vectors

Mosquito-borne illnesses are a major concern for worldwide public health and insecticides persist as the principal method for reducing potential vectors and disease control. As a result of widespread insecticide use emergence of resistance in mosquitoes is a global problem. In order to overcome this issue vector control programmers should routinely check localized mosquito vectors for insecticide resistance, which is essential for the efficient management of vector-borne diseases and schedule preventive actions in accordance. The major techniques for determining mosquito vectors insecticide resistance (such as dose-mortality bioassay, WHO tube testing, and CDC bottle bioassay) are highlighted in this review along with some insights into challenges that researchers are encountering when evaluating resistance.

Abstract 13925: Initial Triglyceride Glucose Index as a Predictor of No-Reflow After Primary Percutaneous Coronary Intervention

Introduction: The triglyceride glucose (TyG) index is a screening method for insulin resistance that can be used on a daily clinical basis and only requires two laboratory determinations: serum triglycerides and serum glucose. Prospective studies of predictive values of the TyG index for cardiovascular diseases (CVD) have primarily focused on pre-existing coronary arterial disease or diabetes mortality, and the TyG index has been shown to be associated with subclinical atherosclerosis symptoms, such as arterial stiffness and preclinical coronary arterial calcification. The study aimed to investigate the possible correlation between the TyG index and the no-reflow phenomenon in patients presented with acute STEMI undergoing primary percutaneous coronary intervention (PPCI). Methods: A total number of 702 patients who presented with acute STEMI in the period from 1/9/2015 to 1/9/2019 who underwent PPCI according to the standard techniques were included. Patients with a previous history of diabetes, dyslipidemia, or on statin therapy were excluded from the study. Initial triglyceride levels as well as fasting blood glucose were tested in all patients at the time of admission. TyG index was calculated for all patients. No-reflow was defined as distal Thrombolysis in Myocardial Infarction (TIMI) flow less than III. Results: 618 patients (88 %) had normal flow while 84 patients (12%) had no-reflow. The mean TyG index was 4.3±0.4 in the no-reflow group versus 4.2±0.4 in the normal reflow group (P = 0.03). After propensity matching, the mean TyG index was 4.2 ± 0.3 in both groups. (P = 0.99) Conclusion: In a retrospective observational study, there was no statistically significant difference between no-reflow and normal flow groups after propensity matching. Further research is required to detect whether the TyG index can be used as a readily available independent predictor of cardiovascular morbidity and mortality.

Extracellular Alterations in pH and K+ Modify the Murine Brain Endothelial Cell Total and Phospho-Proteome.

Pathologies of the blood–brain barrier (BBB) have been linked to a multitude of central nervous system (CNS) disorders whose pathology is poorly understood. Cortical spreading depression (CSD) has long been postulated to be involved in the underlying mechanisms of these disease states, yet a complete understanding remains elusive. This study seeks to utilize an in vitro model of the blood–brain barrier (BBB) with brain endothelial cell (b.End3) murine endothelioma cells to investigate the role of CSD in BBB pathology by characterizing effects of the release of major pronociceptive substances into the extracellular space of the CNS. The application of trans-endothelial electrical resistance (TEER) screening, transcellular uptake, and immunoreactive methods were used in concert with global proteome and phospho-proteomic approaches to assess the effect of modeled CSD events on the modeled BBB in vitro. The findings demonstrate relocalization and functional alteration to proteins associated with the actin cytoskeleton and endothelial tight junctions. Additionally, unique pathologic mechanisms induced by individual substances released during CSD were found to have unique phosphorylation signatures in phospho-proteome analysis, identifying Zona Occludins 1 (ZO-1) as a possible pathologic “checkpoint” of the BBB. By utilizing these phosphorylation signatures, possible novel diagnostic methods may be developed for CSD and warrants further investigation.

Present status and future directions for management of root lesion nematode (Pratylenchus thornei) in chickpea

Chickpea is a popular legume crop in Asia and Africa's semi-arid regions. Crop production gains, on the other hand, have been modest, owing to biotic and abiotic stressors. Among the different biotic stresses, nematodes portray serious threat to chickpea production and colossal losses have been reported due to stress-free infection by other pathogens on infection with root lesion nematode (RLN). The worldwide distribution of two major species of RLN namely P. thornei and P. neglectus made them a focus research area especially on management aspect. In dryland farming areas of southeastern Australia, the P. thornei alone can cause yield losses of up to 40% in cereals and legumes. Despite the fact that chickpea breeders have been working persistently to generate superior chickpea varieties with increased resilience or tolerance to biotic and abiotic challenges, contemporary biotechnology technologies can help to speed up this process. To incorporate these tools and/or accelerate breeding programmes, identification of RLN resistant source with its genetic factor is first step in developing improved cultivars. However, study of resistance screening methods for chickpea against RLN is limited and standardization of different factors for development of a stable screening methodology distinguishing various levels of resistance is the need of the hour in RLN research.

Occurrence of Macrophomina phaseolina in Israel: Challenges for Disease Management and Crop Germplasm Enhancement.

Macrophomina phaseolina is a soil-borne fungal pathogen infecting many important crop plants. The fungus, which can survive on crop debris for a long period of time, causes charcoal rot disease by secreting a diverse array of cell-wall degrading enzymes and toxins. M. phaseolina thrives during periods of high temperatures and arid conditions, as typically occur in Israel and other countries with a Mediterranean climate. Crop losses due to charcoal rot can be expected to increase and spread to other countries in a warming global climate. Management of this pathogen is challenging, requiring an array of approaches for the various crop hosts. Approaches that have had some success in Israel include grafting of melons and watermelons on resistant squash rootstocks and soil application of fungicide to reduce disease incidence in melons, fumigation and alterations in planting date and mulching of strawberries, and alteration in irrigation regime of cotton. Elsewhere, these approaches, as well as soil amendments and addition of organisms that are antagonistic to M. phaseolina, have had success in some crop situations. Management through host resistance would be the most sustainable approach, but it requires identifying a resistant germplasm for each crop and introgressing the resistance into the leading cultivars. Resistance to charcoal rot is under complex genetic control in most crops, posing a great challenge for its introgression into elite germplasm. Moreover, fast, reliable methods of screening for resistance would have to be developed for each crop. The toothpick-inoculation method used by us holds great promise for selecting resistant germplasm for melons and possibly for sesame, but other methodologies have to be devised for each individual crop.

A rapid leaf-disc vacuum-infiltration screening for assessing resistance to bacterial leaf spot disease in anthurium

Resistance to Acidovorax anthurii, the causal agent of bacterial leaf spot disease (BLS) of anthurium was investigated using leaf-disc vacuum-infiltration inoculation towards developing a rapid non-destructive method of screening for resistance to BLS in segregating populations. The effect of age of the plant, developmental stage of the leaf used, inoculum concentration and type of leaf disc employed (midrib disc vs. lamina disc) were investigated to optimize the leaf-disc infiltration method of inoculation that best differentiates between levels of resistance to BLS. A screening method based on vacuum-infiltration (vacuum = 15 psi, 10 s) of leaf lamina discs (2.52 cm diameter obtained away from the midrib of stage-4 leaves) with an inoculum concentration of 9.7 × 107 CFU per ml was best able to effectively and quantitatively differentiate levels of resistance of 13 anthurium cultivars to BLS, as early as 5 days post-inoculation on a repeatable basis. On the other hand, plant ages between 2 and 5 years of age did not influence resistance levels to BLS. The lesion sizes elicited in response to inoculation using the optimized method showed a strong association (Pearson's r = 0.84; P < 0.05) with cumulative number of diseased leaves of cultivars obtained under natural epiphytotics (Holder et al., 2017) and also a strong correlation (r = -0.72, 0.77 to 0.91, P < 0.01) with resistance to BLS identified from a destructive screening study using the same 13 anthurium cultivars (Holder et al., 2021). The implications of the findings of this study are discussed.

Xylem characteristics in Ulmus americana cultivars and their potential use as a preliminary screening method for Dutch elm disease resistance

AbstractTraditional screening of American elm (Ulmus americana) for resistance to Dutch elm disease (DED) often requires many years between initial propagation of trees and inoculation of older trees in the field. Previously published studies have found an association between smaller vessel diameters and increased resistance to DED, but further validation was needed to determine whether it could provide a rapid screening method to identify candidate trees for further testing. This investigation examined xylem characteristics in main stems of three‐year‐old trees for five cultivars and two wild‐type seedling populations of U. americana with varying levels of resistance to DED. Cultivars with low disease severity ratings tended to have smaller vessel diameters and higher vessel densities than cultivars with high disease severity ratings. Xylem characteristics were also assessed in branches and main stems of larger plant material. Data suggest that the use of main stems is preferential to branches when evaluating large trees, as main stems provided more resolution in differentiating between the genotypes. Results from this study indicate that there is potential for the use of xylem characteristics, such as vessel diameter and vessel density, for selecting trees with putative resistance. However, caution should be used due to the potential effects of the environment, such as the effect of water availability and its impacts on xylem development.

Fast screening of capacity and internal resistance for cascade utilization of the retired power lithium-ion batteries

The residual capacity and internal resistance of lithium-ion batteries are important indicators for evaluating the retired batteries, and they are also prerequisites for the cascade utilization of retired batteries. Screening of capacity and internal resistance of retired batteries was studied in this paper. In terms of battery residual capacity, the battery charging system is used to obtain the battery charging curves from which IC characteristics are extracted and screened. The relationship between the IC characteristics and the battery capacity is obtained using a neural network algorithm to achieve capacity estimation. In terms of internal resistance, the charge and discharge strategies of batteries connected in series was first studied, and then a screening method for battery internal resistance was designed based on such charge and discharge strategies. The overall results of this paper provided the basis for the selection of retired power batteries.

Cost-Effective and Time-Efficient Molecular Assisted Selection for PPV Resistance in Apricot Based on ParPMC2 Allele-Specific PCR

Plum pox virus (PPV) is the most important limiting factor for apricot (Prunus armeniaca L.) production worldwide, and development of resistant cultivars has been proven to be the best solution in the long-term. However, just like in other woody species, apricot breeding is highly time and space demanding, and this is particularly true for PPV resistance phenotyping. Therefore, marker-assisted selection (MAS) may be very helpful to speed up breeding programs. Tightly linked ParPMC1 and ParPMC2, meprin and TRAF-C homology (MATH)-domain-containing genes have been proposed as host susceptibility genes required for PPV infection. Contribution of additional genes to PPV resistance cannot be discarded, but all available studies undoubtedly show a strong correlation between ParPMC2-resistant alleles (ParPMC2res) and PPV resistance. The ParPMC2res allele was shown to carry a 5-bp deletion (ParPMC2-del) within the second exon that has been characterized as a molecular marker suitable for MAS (PMC2). Based on this finding, we propose here a method for PPV resistance selection in apricot by combining high-throughput DNA extraction of 384 samples in 2 working days and the allele-specific genotyping of PMC2 on agarose gel. Moreover, the PMC2 genotype has been determined by PCR or by using whole-genome sequences (WGS) in 175 apricot accessions. These results were complemented with phenotypic and/or genotypic data available in the literature to reach a total of 325 apricot accessions. As a whole, we conclude that this is a time-efficient, cost-effective and straightforward method for PPV resistance screening that can be highly useful for apricot breeding programs.

Changes in reflectance of rice seedlings during planthopper feeding as detected by digital camera: Potential applications for high-throughput phenotyping.

Damage to grasses and cereals by phloem-feeding herbivores is manifest as nutrient and chlorophyll loss, desiccation, and a gradual decline in host vigour. Chlorophyll loss in particular leads to a succession of colour changes before eventual host death. Depending on the attacking herbivore species, colour changes can be difficult to detect with the human eye. This study used digital images to examine colour changes of rice seedlings during feeding by the brown planthopper, Nilaparvata lugens (Stål) and whitebacked planthopper, Sogatella furcifera (Horváth). Values for red (580 nm), green (540 nm) and blue (550 nm) reflectance for 39 rice varieties during seedling seed-box tests were derived from images captured with a digital camera. Red and blue reflectance gradually increased as herbivore damage progressed until final plant death. Red reflectance was greater from plants attacked by the brown planthopper than plants attacked by the whitebacked planthopper, which had proportionately more green and blue reflectance, indicating distinct impacts by the two planthoppers on their hosts. Analysis of digital images was used to discriminate variety responses to the two planthoppers. Ordination methods based on red-green-blue reflectance and vegetation indices such as the Green Leaf Index (GLI) that included blue reflectance were more successful than two-colour indices or indices based on hue, saturation and brightness in discriminating between damage responses among varieties. We make recommendations to advance seed-box screening methods for cereal resistance to phloem feeders and demonstrate how images from digital cameras can be used to improve the quality of data captured during high-throughput phenotyping.

Rapid methods for screening sugarcane clones resistance against smut disease (Sporisorium scitamineum Syd.)

The Indonesian government has a program to increase sugarcane productivity for domestic and export purposes. One constraint to sugarcane production is smut disease caused by Sporisorium scitamineum Syd. New resistant clones should be released since this disease already spreads to sugarcane varieties that are widely grown by farmers. Sugarcane clones are actually available, unfortunately the standard procedures for screening of clones resistance requires up to 5 mo. This experiment was conducted to develop a rapid screening method for smut resistance. The method was based on injecting 2 mL of S. scitamineum spores (106 spores/mL) on 4-mo-old plants. Injection was carried out on stem, 15 cm from the ground to avoid contamination; a maximum humidity of 72 hr in the inoculation area was maintained by sterile water droplets. Incidence of dried leaves and occurrence of smut spores at the leaves was observed as indication of plant responses to smut infection. With this method, plant responses can be obtained in less than 3 mo. This rapid screening method can be used as an alternative to shorten the testing period of sugarcane resistance to sugarcane smut.

Recurrent phenotypic selection for resistance to diseases caused by Bipolaris oryzae in switchgrass (Panicum virgatum L.)

Switchgrass (Panicum virgatum L.) is a biomass candidate crop which has been improved for yield, but disease resistance development has largely been ignored. Bipolaris oryzae (Breda de Haan) Shoemaker can cause Bipolaris seed rot, reducing seedling establishment, and Bipolaris leaf spot, reducing biomass yield. In order to initiate a breeding program, heritability based on half-sib progenies of the disease resistance were conducted in 47 half-sib progenies of lowland ‘Kanlow’ and upland ‘Cave-in-Rock’. Test crosses of progenies from resistant and susceptible parents in upland ‘Shelter’ and Cave-in-Rock were conducted to determine genetic control of resistance to Bipolaris leaf spot. To breed for resistance to two diseases, two cycles of recurrent phenotypic selection were done separately in Shelter and Cave-in-Rock at 10% selection intensity. As a result, resistance to Bipolaris seed rot showed moderate to high heritability (0.33 ± 0.16 to 0.83 ± 0.09) in both individual- and half-sib-based computations, reflecting actual genetic gain (44.5–125.3%) from two cycles of selections. However, resistance to Bipolaris leaf spot showed non-significant heritability (0.02 ± 0.06 to 0.19 ± 0.19) and non-significant progress of selection for the trait. Results from test crosses suggested that the resistance was not controlled by R genes but possibly was quantitatively inherited by many alleles with small effects. Such a difference in the gains resulted in non-significant correlation between two resistances. Due to high progress in selection resistance to Bipolaris seed rot, the screening method for resistance can be integrated to existing breeding programs.

Pyrethroid resistance in the pest mite, Halotydeus destructor: Dominance patterns and a new method for resistance screening

An L1024F substitution in the para gene, which encodes a subunit of the voltage-gated sodium channel, has been implicated in pyrethroid resistance in a mite pest, Halotydeus destructor, which attacks rape and other grain crops. A high-resolution melt (HRM) genotyping assay was developed for testing the relative pyrethroid susceptibility of different para genotypes and for high-throughput field screening of resistant alleles. The L1024F mutation was found to be incompletely recessive in phenotypic laboratory bioassays with the pyrethroid pesticide, bifenthrin. While the resistance ratio of heterozygotes (RS) to susceptible homozygotes (SS) was <6 in 24 h bioassays, the resistant homozygotes (RR) (with a resistance ratio > 200,000) survived the recommended field rate of bifenthrin (100 mgL−1). HRM genotyping of mites from field populations across Australia indicated the presence of resistant alleles in Western Australia and South Australia, but not in Victoria and New South Wales. The assay developed will be useful for routine screening of pyrethroid resistance, and the dominance relationships established here point to useful resistance management strategies involving the maintenance of reservoirs of susceptible mites to dilute resistant homozygotes in a population.

Enhanced melatonin production via aralkylamine N-acetyltransferase overexpression enhances NaCl resistance in transgenic Chlamydomonas reinhardtii (Volvocales, Chlorophyceae)

ABSTRACTThe hormone melatonin (MT) is produced by the pineal gland in animals and can also be found in plants and algae. MT regulates not only sleep, reduces the effects of jet lag, and has anti-aging properties in animals, but also eliminates intracellular reactive oxygen species and promotes vegetative growth in plants. However, research on its biological function in microalgae is still rare. The present study involved the construction of the Chlamydomonas reinhardtii expression vector pDBle-AANAT, which harbours the gene of one of the enzymes of the MT synthesis pathway, aralkylamine N-acetyltransferase (AANAT). The AANAT gene was introduced into the genome of the model microalga C. reinhardtii via glass bead transformation. The AANAT transgenic algal strain was identified by resistance screening, culture, and molecular biology methods. Changes in MT content between transformed algal strain and nontransformed algal strains were detected and the antioxidant capacity of the AANAT overexpressing algal strain was analysed under salt stress. The results showed that genetically engineered algae can increase the content of MT in algal cells by overexpressing AANAT. Under salt stress conditions, this can help to improve the enzymatic activity of the antioxidant system of algal cells and reduce membrane damage to counteract the adverse external stress. This enhances the self-protection ability of C. reinhardtii. This study reveals the effects of MT overproduction on the physiological functions of C. reinhardtii. Additionally, the potential functions of MT in the response of C. reinhardtii to stress have been elucidated, thus broadening the functional scope of MT in plants.

The validation of VIPcheck™ plates to screen Aspergillus fumigatus isolates for phenotypic resistance to triazole antifungal agents in St. James’s Hospital, Dublin

Triazole resistance is an emerging problem in Aspergillus fumigatus (AF) resulting in failure of azole therapy. Triazole resistant AF is acquired through one of two routes – previous exposure to triazole therapy or an environmental source. In vitro antifungal susceptibility testing (AFST) on all AF strains isolated in a microbiology laboratory would be both labour intensive and impractical. A method to screen for triazole resistance would be more favourable. VIPcheck™ plates provide a simple agar based screening method. Each 4-well plate contains a growth control (GC) well and 3 wells containing itraconazole (4 mg l−1), voriconazole (2 mg l−1) and posaconazole (0.5 mg l−1). Briefly, 25 µl of a 0.5-2 McF suspension AF is inoculated into each well and plates are read after 48 h incubation at 37 °C. Any growth in a triazole containing well is suggestive of resistance. Currently in SJH, AFST is carried out using gradient strips (Liofilchem™) and results are interpreted using EUCAST breakpoints. We validated the VIPcheck™ plates with the intention to include this screening method as part of our AFST for AF isolated from clinical samples. A total of 18 isolates (clinical and environmental) of AF were tested using the VIPcheck™ plates (n=2 wild type, n=18 resistant to ≥1 triazole drug as previously determined by AFST and/or molecular methods). The wild type isolates showed growth only in the GC well while the resistant strains all showed growth in one or more of the triazole containing wells. Our results suggest that the VIPcheck™ plate is a reliable screening method for triazole resistance.

Potato Common Scab: a Review of the Causal Pathogens, Management Practices, Varietal Resistance Screening Methods, and Host Resistance

Potato common scab is a widespread disease in which scab-like lesions develop on tubers. The disease is caused by pathogenic Streptomyces species, which synthesize the phytotoxin thaxtomin. The txtAB operon, responsible for thaxtomin production, can be used as a marker to identify pathogenic strains of the bacterium. Screening methods to assess scab susceptibility in breeding programs are time-consuming and can produce variable results. Management practices to control the disease vary and include crop rotation, tolerant varieties, monitoring soil pH, avoiding low soil moisture at tuber initiation, and application of soil- and/or seed-applied pesticides. There is a wide range in levels of tolerance among potato varieties. Many public research programs are committed to breeding for scab-tolerant varieties and evaluating management methods. Topics reviewed target readers focused on breeding and disease management objectives to reduce the incidence and severity of potato common scab.