Combinations Of Resistance Genes Research Articles

Genetic Characterization of Multidrug-Resistant E. coli Isolates from Bloodstream Infections in Lithuania.

Extraintestinal pathogenic Escherichia coli (ExPEC) isolates are a main cause of bloodstream infections. The aim of this study was to characterize 256 β-lactam–resistant, bacteremia-causing E. coli isolates collected from 12 healthcare institutions in Lithuania in 2014 and 2018. All isolates were identified as E. coli via MALDI-TOF MS and VITEK ®2. In addition, the isolates were analyzed for the presence of 29 resistance genes and 13 virulence genes, divided into phylogenetic groups (A, B1, B2, C, D, E, and F), and characterized using rep-PCR genotyping methods (BOX-PCR and (GTG)5-PCR). Analyzing the results of this study showed tetA-strB-sul2-TEM-NDM-strA-fosA-AIM-sul3-aadA-CTX-M-9 to be the most common resistance gene combination (67.2% of all isolates). Additionally, the most common virulence genes established were fimH (98.4% of all isolates), fyuA (91.8%), and traT (81.3%) and the most common gene combination was fuyA-fimH-iroN (58.6% of all isolates). Next, the isolates were separated into four phylogenetic groups: A, B1, B2, and F, where group A isolates were detected at a significantly higher frequency (79.3% of all isolates). Finally, a total of 235 genotyping profiles were established using rep-PCR methods, and all profiles were separated into fourteen genotypic clusters, with each cluster containing profiles with a variety of virulence and resistance genes not restricted to any specific cluster. The results of this study elucidate E. coli antimicrobial resistance patterns by highlighting the variability and diversity of resistance and virulence genes and providing phylogenetic classification, genetic profiling, and clustering data. These results may improve clinical control of multidrug-resistant infections in healthcare institutions and contribute to the prevention of potential outbreaks.

Virulence analysis of wheat stem rust (Puccinia graminis f. sp. tritici) in Horro Guduru Wollega, Western Ethiopia

AbstractStem rust caused by Puccinia graminis f. sp. tritici is one of Ethiopia's most serious wheat diseases. Because of mutation and genetic recombination, stem rust can rapidly evolve new virulence to resistant genes. The Ethiopian highlands are well‐known hotspots for the rapid emergence and spread of new wheat stem rust races. The objective of this study was to determine the virulence diversity and spatial distribution of Pgt races in the main wheat‐growing districts, Horro Guduru Wollega. Wheat stem rust samples were collected from Abay Chomen, Amuru, Guduru, Hababo Guduru, Horro, Jardaga Jarte, Jimma Ganati and Jimma Rare districts during the main cropping seasons of 2015 and 2016. In the study, 147 stem rust isolates were derived from 121 viable samples. The physiological races of stem rust were determined on seedlings of standard wheat stem rust differentials using the International System of nomenclature. Twelve (12) physiological races of stem rust were identified. TKTTF, TTKSK, JRCQC, TRTTF and TTTTF were the most common in all districts with a frequency of 53.1%, 15.6%, 14.3%, 6.8% and 2.7%, respectively. TKTTF and TTKSK, two highly virulent races, were found in all districts. Four stem rust resistance genes (Sr11, Sr31, Sr36 and SrTmp) confer resistance to the majority of the virulent races identified. Sr24 was effective against all virulent races in this study but ineffective against the Ug99 variant (race TTKTT) detected in the country. The findings could be helpful for breeders to select many effective resistance gene combinations to provide more durable stem rust resistance.

INVESTIGATION OF ANTIBIOTIC AND ANTISEPTIC RESISTANCE GENES IN METHICILLIN-RESISTANT AND METHICILLIN-SUSCEPTIBLE STAPHYLOCOCCUS AUREUS ISOLATES

Aim: This study aimed to determine the antibiotic susceptibility of Staphylococcus aureus isolated from different clinical materials sent to the Microbiology Laboratory of Hatay Mustafa Kemal University Hospital, to investigate the mechanisms mediating antibiotic and antiseptic resistance, to determine the SCCmec type of methicillin-resistant isolates. Materials and Method: Overall, 187 S. aureus were included in the study. Antibiotic susceptibilities of the isolates were performed by the disc diffusion method and evaluated according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. Antibiotic resistance, antiseptic resistance, and Staphylococcal Cassette Chromosome mec (SCCmec) types in MRSA strains were investigated using polymerase chain reaction (PCR). Results: While all of the isolates were found to be susceptible to linezolid and vancomycin; various rates of resistance for penicillin (87.1%), cefoxitin (49.93%), erythromycin (19.79%), ciprofloxacin (13.37%), tetracycline (11.23%), clindamycin (10.16%), trimethoprim-sulfamethoxazole (8.02%), gentamicin (17.82%), fusidic acid (64.2%) and rifampin (1.07%) were determined. A statistically significant difference was found between MRSA and MSSA strains in terms of MDR phenotype rates (p=0.001). Among S. aureus isolates, single resistance genes or various combinations of resistance genes were detected. SCCmec type III (52.4%) was the most common SCCmec type. Conclusions: The results of this study indicated that current control strategies should be revised to minimize antibiotic resistance and periodic surveillance studies must be carried out.

Genetic variation of infection degrees to blast disease among rice genotypes

AbstractThe blast of rice caused by Pyricularia oryzae is a disease prevalent throughout the world. The pathogen overwintering in rice straw and stubble for many years makes disease mitigation difficult. Among all available methods of managing disease, the use of resistant varieties is an economical approach. The objective of this study was to identify genotypes with slow‐blasting that could be used in breeding resistant hybrids. A total of 25 rice genotypes with different combinations of resistance genes were tested in 2013 and 2014 for rice blast resistance. The reactions of genotypes varied from highly resistant to highly susceptible. Of the 25 genotypes tested in 2013, only three were highly resistant to leaf blast (disease score: 1), while Rasi and RamanadStr3 were resistant (disease score: 2). Genotypes Co39 and HR12 were highly susceptible recording a disease score of 8 and the remaining genotypes were classified as susceptible with scores ranging from 5 to 7. In 2014, only Tetep genotype was found highly resistant to leaf blast with disease score ‘1’, and genotypes NILA57, RamanadStr3, Shia‐tia‐tsao, IR64, Rasi, and Tadukan were resistant with disease scores ranging from 2 to 3. The remaining genotypes were susceptible to leaf blast with disease scores of 4–7 and two genotypes Co39 and HR12 were highly susceptible to leaf blast (disease scores: 8–9). For neck blast, all genotypes were resistant (disease scores: 0–3) in both years except for CO39 and HR12, which were recorded as moderately resistant in 2013 and resistant in 2014. Based on 2 years of data on the apparent rate of infection, area under the disease progress curve, and components of slow‐blasting, the genotypes viz., IR64, Tadukan, Rasi, Tetep, and RamanadStr3 were identified as slow‐blasting types. Hence, these genotypes can be harnessed to develop blast‐resistant varieties in rice breeding programmes.

Breeding for resistance and integrated management of web blight in common bean

AbstractCommon bean (Phaseolus vulgaris L.) production in the humid tropics may increase if less predictable rainfall becomes a serious seed yield constraint in traditional areas of production. The successful production of common bean will require the effective management of common bean diseases favored by hot and humid conditions. Web blight (WB), caused by Thanatephorus cucumeris (Frank) Donk, is a serious disease of common bean in the humid tropics causing significant losses in both seed yield and seed quality. At present, only moderate levels of WB resistance have been identified. Leaf and seed damage and leaf lesion size are criteria that have been successfully used to screen common bean genotypes for WB resistance in the greenhouse and in the field. Pedigree selection has been successfully used to develop cultivars having moderate levels of resistance. Recurrent selection has been used to broaden the genetic base and to produce progeny having higher levels of WB resistance. Sources of resistance from secondary gene pools should be used to combine resistance genes from diverse sources. Common bean cultivars with earlier maturity, deep tap roots, and terminal drought tolerance may be desirable traits for farmers who plant later in the wet season to avoid WB. Seed production during the dry season using irrigation would help to reduce infection of the seed and transmission of the WB pathogen. Minimum tillage techniques are useful to help to reduce the spread of the disease. Biological control may contribute to the management of WB and complement genetic resistance.

A prebreeding study of introgression spring bread wheat lines carrying combinations of stem rust resistance genes, Sr22+Sr25 and Sr35+Sr25.

The Sr22, Sr35, and Sr25 genes attract the attention of bread wheat breeders with their effectiveness against Puccinia graminis f. sp. tritici race Ug99 and its biotypes. The effectiveness and impact of Sr22+Sr25 and Sr35+Sr25 gene combinations on agronomic traits have not yet been studied. In the present article, these traits were studied using the spring bread wheat lines L503/W3534//L503, L503/Sr35//L503/3/L503 carrying the Sr22+Sr25 and Sr35+Sr25 genes during 2016–2020. These lines were assessed for resistance to P. graminis f. sp. tritici under natural epiphytotics and to the Saratov, Lysogorsk and Omsk populations of the pathogen and to the PgtZ1 (TKSTF) and PgtF18.6 fungus isolates in laboratory conditions (TKSTF + Sr33). The presence of the studied Sr-genes was conf irmed by using molecular markers. Prebreeding studies were conducted during 2018–2020 vegetation periods. Under the natural epiphytotics of the pathogen and in the laboratory conditions, the Sr22+Sr25 combination was highly effective, while Sr35+Sr25 was ineffective. For grain yield, the lines with the Sr22+Sr25 and Sr35+Sr25 genes were superior to the recipient cultivar L503 in one year (Sr22+Sr25 in 2019; Sr35+Sr25 in 2018), with a decrease in 2020, but in general there were no differences. For the period 2018–2020, both combinations showed a decrease in 1000 grains weight and an increase in the germination-earing period. The line with Sr22+Sr25 genes showed insignif icant effects on gluten and dough tenacity, but the ratio of dough tenacity to extensibility was higher, and f lour strength, porosity and bread volume were lower; in the line with Sr35+Sr25 genes, the gluten content was lower, but the strength, tenacity of the dough and the ratio of dough tenacity to extensibility were higher, f lour strength and the porosity of the bread were at the recipient level, but the volume of bread was lower.

Resistance Gene Pyramiding and Rotation to Combat Widespread Soybean Cyst Nematode Virulence

Soybean cyst nematode (SCN) is an important pathogen of soybean causing >$1 billion in yield losses annually in the United States. Planting SCN-resistant soybean cultivars is the primary management strategy. Resistance genes derived from the plant introduction (PI) 88788 (rhg1-b) and PI 548402 (Peking; rhg1-a and Rhg4) are the main types of resistance available in commercial cultivars. The PI 88788 rhg1-b resistance allele is found in the majority of SCN-resistant cultivars in the north central United States. The widespread use of PI 88788 rhg1-b has led to limited options for farmers to rotate resistance sources to manage SCN. Consequently, overreliance on a single type of resistance has resulted in the selection of SCN populations that have adapted to reproduce on these resistant cultivars. Here we evaluated the effectiveness of rotating soybean lines with different combinations of resistance genes to determine the best strategy for combating the widespread increase in virulent SCN and limit future nematode adaptation to resistant cultivars. Eight SCN populations were developed by continuous selection of a virulent SCN field population (Heterodera glycines [HG] type 1.2.5.7) on a single resistance source or in rotation with soybean pyramiding different resistance gene alleles derived from PI 88788 (rhg1-b), PI 437654 (rhg1-a and Rhg4), PI 468916 (cqSCN-006 and cqSCN-007), and PI 567516C (Chr10). SCN population densities were determined for eight generations. HG type tests were conducted after the eighth generation to evaluate population shifts. The continued use of rhg1-b or 006/007 had limited effectiveness for reducing SCN type 1.2.5.7 population density, whereas rotation to the use of rhg1-a/Rhg4 resistance significantly reduced SCN population density but selected for broader SCN virulence (HG type 1.2.3.5.6.7). A rotation of rhg1-a/Rhg4 with a pyramid of rhg1-b/006/007/Chr10 was the most effective combination at both reducing population density and minimizing selection pressure. Our results provide guidance for implementation of a strategic SCN resistance rotation plan to manage the widespread virulence on PI 88788 and sustain the future durability of SCN resistance genes.

Capturing Multiple Disease Resistance in Wheat through Intergeneric Hybridization.

Simple SummaryProviding disease resistance in our crop plants is our ongoing exercise for plant pathologists/breeders/geneticists. Pathogens are continually evolving and releasing new variants. The variants arise through mutations or through sexual cycles on their respective alternate hosts. Thus, the search continues for unique genes for resistance. Another newer concept is the “pyramiding” of resistance genes. It has been shown that a cultivar may last only 3 years or so before being overcome by a new variant of the pathogen. The release of new cultivars with up to four resistance genes will delay their breakdown. In our ongoing work we have also produced pyramids containing a combination of resistance genes, including SrCad for resistance to new races of stem rust, Lr34, which is a major gene for resistance to leaf rust, and Fhb1, which is a common FHB QTL. This required the production of a series of doubled haploids (DH) to produce lines containing all four genes in reasonable-sized populations. A complex series of four-way crosses were required to generate the various gene combinations. In the studies reported here, the essential tools for marker-assisted-selection are produced, i.e., mapping populations containing the resistance genes and molecular makers assigned to each gene. It should be possible to simultaneously manipulate several resistance genes from existing genetic stocks without requiring complex cross combinations. Derivatives from 4 species from the secondary gene pool of wheat—1 diploid (T. monococcum), 2 tetraploid (T. carthlicum; T. timopheevi), and 1 hexaploid (T. miguschovae)—were screened for resistance to Fusarium head blight, leaf rust, stem rust, and stripe rust. Where screening, genetic studies, and mapping were completed it was shown that all species carried resistance to multiple plant diseases. Some derived lines carried resistance to up to four different diseases. Where mapping was completed, it was shown that different diseases mapped to different chromosomes within any one accession.

Breeding for Nutritional and Organoleptic Quality in Vegetable Crops: The Case of Tomato and Cauliflower

Due to novel and more demanding consumers’ requirements, breeding of vegetable crops confronts new challenges to improve the nutritional level and overall appearance of produce. Such objectives are not easy to achieve considering the complex genetic and physiological bases. Overtime, plant breeders relied on a number of technologies and methods to achieve ever changing targets. F1 hybrid seed production allowed the exploitation of heterosis and facilitated the combination of resistance and other useful genes in a uniform outperforming variety. Mutagenesis and tissue culture techniques permitted to induce novel variation, overcome crossing barriers, and speed up the achievement of true-breeding lines. Marker-assisted selection was one of the milestones in fastening selection, starting from the early ’90s in almost all seed companies. Only recently, however, are novel omics tools and genome editing being used as cutting-edge techniques to face old and new challenges in vegetable crops, with the potential to increase the qualitative value of crop cultivation and solve malnutrition in 10 billion people over the next 30 years. In this manuscript, the evolution of breeding approaches in vegetable crops for quality is reviewed, reporting case studies in tomato (Solanum lycopersicum L.) and cauliflower (Brassica oleracea var. botrytis L.) as model systems for fleshy fruit and floral edible parts, respectively.

Improvement of rice cultivar for bacterial blight disease through marker assisted breeding approach

The present investigation was undertaken with the objective to develop high yielding, fine grain rice varieties possessing broad spectrum durable resistance by transferring bacterial leaf blight (BLB) resistant genes viz., xa13 and Xa21 from Improved Pusa Basmati 1. A popular high yielding and fine grain rice variety, HUBR 2-1 (Malviya Dhan 2-1), susceptible to BLB and Improved Pusa Basmati 1 carrying resistant genes for BLB (xa13 & Xa21 genes) were selected as parents for crossing. Improved Pusa Basmati 1 was verified for the presence of target genes by using gene linked primers viz., xa13 promotor and pTA 248. The cross viz., HUBR 2-1 x Improved Pusa Basmati 1 was undertaken during Kharif 2011 and F1 progenies were confirmed during rabi 2011. The F1 plants confirmed as true hybrids for both the genes were advanced to the F2 generation and foreground selection was done using gene linked markers. Genetic analysis in the F2 population confirmed that the genes (xa13 & Xa21) governing BLB resistance followed Mendelian inheritance. The phenotypic data analysis revealed that the plants carrying two resistance gene combinations (xa13xa13 Xa21Xa21, xa13xa13Xa21xa21) showed BLB resistance (0-3 scale), while the gene combinations viz., Xa13Xa13Xa21Xa21, Xa13Xa13Xa21xa21 and Xa13xa13Xa21Xa21, Xa13xa13Xa21xa21 showed BLB resistance (5-30).

Molecular and phenotypic evaluation of wheat (Triticum aestivum) containing different combinations of rust resistance genes

AbstractLeaf, stem and stripe rust caused by Puccinia triticina, P. graminis f. sp. tritici and P. striiformis f. sp. tritici, respectively, are common wheat diseases. The deployment of complex rust resistance sources is likely to contribute to their durability. In this study, wheat varieties and experimental plants (F2), with different rust resistance gene combinations, were characterised using molecular markers, phenotypic evaluation and quantification of fungal biomass accumulation. The experimental wheat plants were developed from six donor parental varieties that in combination carry seven known rust resistance genes/quantitative trait loci (QTL). A timeline study revealed that quantification of fungal biomass accumulation for the rusts, 10‐day postinoculation (dpi), can successfully distinguish between resistant and susceptible wheat varieties. Phenotypic evaluation included seedling infection types and adult‐plant response types that were determined 15 dpi. Data obtained from the three methods were in support of each other and in combination successfully distinguished between rust‐resistant and susceptible experimental wheat plants. Resistance genes/QTL evaluated in this study, when deployed in combination, may lower the risk of rust outbreaks.

Emergence of new aggressive races of Puccinia striiformis f. sp. tritici causing yellow rust epiphytotic in Egypt

Yellow (stripe) rust, caused by Puccinia striiformis f. sp. tritici (Pst), has been consistently severe in the country during recent years. A survey data of the disease at five provinces in Egypt during 2018–2020 resulted in 42 physiologic races and revealed the emergence of six new aggressive races i.e., 151E80, 135E16, 160E173, 224E191, 238E143 and 72E8 that were first detected in Egypt in the current study. The new aggressive race 151E80 was detected in Kafr-Elsheikh in the first growing season (2018/19), while it occurred in Alexandria, Beheira and Kafr-Elsheikh in the second one (2019/20). The new aggressive races; 224E191 and 238E143 (Kafr-Elsheikh), 72E8 (Beheira) occurred during both growing seasons (2018/19 and 2019/20). Common genetic lineages of Pst races corresponding to respective yellow rust resistance genes (Yr,s) indicated that they belonging to six lineages represented by ten races. Seven of them were new, i.e., races PstS2v3, PstS2v10v24, PstS2v1v10, PstS4 (Triticale2006), PstS6, PstS12 (Hereford), and a new lineage termed as PstS19 (Egy19) first detected in the current study. The most aggressive race (with Yr1, Yr10 and Yr27 virulences) was a new lineage termed as PstS19 (new pathotype Egy19), while a new pathotype designed as PstS2v1v10 came in the second rank. Field response data revealed that among 15 Egyptian wheat cultivars tested to yellow rust, only four cultivars were moderately resistant i.e., Misr-3, Sakha-95, Giza-168 and Giza-171. Gene postulation revealed that these cultivars possessed effective resistance genes; Yr5 (Sakha-95), Yr15, Yr29 (Giza-168 and Giza-171), and Yr17 was present in Misr-3. Combination of durable resistance genes, Yr18 and Yr29 with broad-spectrum resistance genes Yr5 and Yr15 is the best available option to avoid disease epiphytotic on a large scale.

The relations of broad nematode resistance to quality characteristics as a consequence of marker-assisted selection in potato breeding programs.

Cultivating resistant varieties of potato is the most effective and environmentally sound method of protecting potato crops against pests and diseases. Potato cyst nematodes (PCN) are major nematode pests causing severe constraints in potato production worldwide. There are five pathotypes of Globodrea rostochiensis (Ro1–Ro5) and three of G. pallida Pa1–Pa3. Cultivation of potato varieties with broad nematode resistance may influence the growth of the wide spectrum of PCN pathotypes, but there is limited availability of such varieties on the market. The use of molecular markers allows for the effective selection of resistant genotypes at early stages of breeding. However, the impact of early selection for nematode resistance on the agronomic value of the final selected clones is a cause of concern for potato breeders. This study investigates the relationships between the presence of the combined resistance genes H1, Gro1-4 and GpaVvrn, which confer resistance to the nematodes, and certain agricultural traits. Clones with broad nematode resistance conferred by the genes H1, Gro1-4 and GpaVvrn presented yields and tuber morphology traits similar to those of the clones without identified resistance genes.

Virulence and antimicrobial resistance of Klebsiella pneumoniae strain NUBRI-K (ST14), Sudan

Background: Multidrug-resistant Klebsiella pneumoniae strain in Sudan has emerged as a major health threat that attracts researchers to understand their robust virulence and resistance that conferring surviving and adapting at the hospital environment. Even though, there is a paucity in research that describes the interplay between resistance and virulence in K. pneumoniae clinical isolates in addition to that their resistance profile has not yet been characterized. The aim of this study to investigate the virulence and antibiotic resistance of K. pneumoniae from the hospital in Sudan Methods and materials: One sample isolated from the patient with a pneumonia infection in Khartoum, Sudan. The antimicrobial susceptibility pattern was determined using Kirby–Bauer disk diffusion method. The QIAamp kit was used to extract genomic DNA. A paired-end library (2X300 bp) was prepared using a Nextera XT kit, and whole-genome sequencing (WGS) was carried out on a MiSeq machine. The WGS was analysis by different bioinformatics software. Results: The results demonstrate that the NUBRI-K genome contains virulence features such as an integrative conjugative element carrying the yersiniabactin siderophore, the yersiniabactin receptor gene fyuA. This strain carries genes conferring resistance to Penicillins, Cephalosporins, Fluoroquinolone, aminoglycoside, Fosfomycin, Sulphonamide, Tetracyclin, Co-trimoxazoal, Aztreonam, Amoxaclav, and Colstin. This strain none had the Carbapenems genes resistances for examples (blaKPC, blaIMP); however, we detected IncFII plasmid that was similar to the carbapenem resistance-associated plasmid pNDM-ma and the class B metallo-β-lactamases (MBLs) was detected. Class 1 integron (intI1) was predicted in this strain include carries (dfrA14/5) resistance to trimethoprim. Damage mutations (R359C and Y3F) were predicted in parC and blaSHV-28 genes respectively. Conclusion: This strain can produce many virulence factors that can play an important role in pathogenicity such as outer membrane lipoprotein and capsular polysaccharides. The R359C and Y3F mutations are novel and they confer high-level resistance to quinolones and β-lactams. With a combination of antibiotic resistance genes and virulence factors, the ST14 genetic repertoire may be a “perfect storm” allowing for a newly emerging, high-risk, extensively antibiotic-resistant clone. This clone appears adept at acquiring resistance and may perpetuate the dissemination of extensive antimicrobial resistance. This study is crucial for understanding the spread of antibiotic resistance.

Accomplishments in wheat rust research in South Africa

Rust diseases, although seasonal, have been severe constraints in wheat production in South Africa for almost 300 years. Rust research gained momentum with the institution of annual surveys in the 1980s, followed by race identification, an understanding of rust epidemiology, and eventually a focused collaboration amongst pathologists, breeders and geneticists. Diversity in South African populations of Puccinia triticina, P. graminis f. sp. tritici and P. striiformis f. sp. tritici has been described and isolates are available to accurately phenotype wheat germplasm and study pathogen populations at national, regional and global levels. Sources of resistance have been, and still are, methodically analysed and molecular marker systems were developed to incorporate, stack and verify complex resistance gene combinations in breeding lines and cultivars. Vigilance, capacity, new technologies, collaboration and sustained funding are critical for maintaining and improving the current research impetus for future management of these important diseases.
 Significance:
 
 Rust diseases threaten wheat crops worldwide, including in South Africa.
 Management of rusts includes regular surveillance, pathogen diversity studies, rigorous screening of wheat germplasm, and efficient breeding and selection for resistance.
 Collaboration among plant pathologists, geneticists and breeders has provided momentum in rust research and control in South Africa in recent years.

Identification of Wheat Leaf Rust Resistance Genes in Chinese Wheat Cultivars and the Improved Germplasms.

Leaf rust is an important wheat disease that is a significant hindrance for wheat production in most areas of the world. Breeding resistant cultivars can effectively and economically control the disease. In the present study, a wheat collection consisting of 100 cultivars from China and 18 improved germplasms from global landrace donors together with 36 known single Lr gene lines were tested with 20 strains of Puccinia triticina Eriks. in the seedling stage to postulate the Lr gene in the cultivars and germplasms. In addition, 12 diagnostic molecular markers specific to 10 Lr genes were used to detect the presence of the Lr genes in the wheat collection. Resistance to leaf rust of these cultivars at the adult plant stage was tested in fields under natural infection during the 2016 to 2018 cropping seasons in Baoding, Hebei Province. The gene postulation combined with molecular marker detection showed that six Lr genes (Lr1, Lr26, Lr33, Lr34, Lr45, and Lr46) were identified in 44 wheat accessions, including 37 cultivars and seven improved germplasms. Among the 44 wheat accessions postulated with Lr genes, Lr1 was present in four accessions, Lr26 in 12 accessions, Lr33 in two accessions, Lr34 in 14 accessions, Lr45 in three accessions, and Lr46 in 16 accessions. In the collection of 118 cultivars/germplasms, 34 wheat lines displayed adult-plant resistance carrying Lr34, Lr46, and/or underdetermined genes. Therefore, a high level of leaf rust resistance can be achieved through the combination of all-stage resistance and adult-plant resistance genes together in wheat cultivars.

Phenotypic synergy testing of ceftazidime–avibactam with aztreonam in a university hospital having high number of metallobetalactamase producing bacteria

Background Ceftazidime–avibactam combination with aztreonam and role of rapid synergy reporting has not been widely evaluated. Also the synergy correlation with various betalactamases has not been widely studied. Methods We studied phenotypic synergy testings and molecular detection of betalactamases in our university hospital where we have large number of mellatobetalactmase producing bacteria. We tested two phenotypic synergy methods for ceftazidime-avibactam with aztreonam (Disc-E strip method, E strip-Agar method) for rapid reporting to clinicians (153 isolates). The treatment (colistin, ceftazidime-avibactam, ceftazidime-avibactam with aztreonam) was guided as indicated in the synergy testings. The resistance genes in bacteria were identified by polymerase chain reaction (PCR) and correlated with synergy results. Results The highest synergy was seen in Klebsiella pneumoniae by Disc-E strip and E strip-Agar method (86% and 84% respectively). About 70% of Pseudomonas aeruginosa and 29% of Escherichia coli showed synergy. Molecular methods revealed multiple resistance gene combinations and bla NDM (96%) was predominant gene in isolates showing synergy. Among isolates that were sensitive to ceftazidime–avibactam, the predominant genes were bla OXA-48 and bla IMP. Rapid laboratory reporting led to proper utilization of antibiotic combinations. Conclusions Ceftazidime–avibactam and aztreonam rapid synergy testing will be highly beneficial in treatment of infections by metallobetalactamase producing resistant bacteria, especially K. pneumoniae and P. aeruginosa.

Breeding Wheat for Durable Leaf Rust Resistance in Southern Africa: Variability, Distribution, Current Control Strategies, Challenges and Future Prospects.

Leaf or brown rust of wheat caused by Puccinia triticina (Pt) is one of the most damaging diseases globally. Considerable progress has been made to control leaf rust through crop protection chemicals and host plant resistance breeding in southern Africa. However, frequent changes in the pathogen population still present a major challenge to achieve durable resistance. Disease surveillance and monitoring of the pathogen have revealed the occurrence of similar races across the region, justifying the need for concerted efforts by countries in southern Africa to develop and deploy more efficient and sustainable strategies to manage the disease. Understanding the genetic variability and composition of Pt is a pre-requisite for cultivar release with appropriate resistance gene combinations for sustainable disease management. This review highlights the variability and distribution of the Pt population, and the current control strategies, challenges and future prospects of breeding wheat varieties with durable leaf rust resistance in southern Africa. The importance of regular, collaborative and efficient surveillance of the pathogen and germplasm development across southern Africa is discussed, coupled with the potential of using modern breeding technologies to produce wheat cultivars with durable resistance.

Marker assisted selection of potato breeding lines with combination of PVY resistance genes from different wild species

Potato virus Y (PVY) is considered as one of the most harmful virus infections of this crop. Thus, it is a topical problem to breed potato varieties resistant against a wide range of PVY strains and to create initial breeding material that will have a combination of resistance genes from different species. The aim of the study was: (1) to genotype a collection of 376 breeding lines (BL), developed from complex interspecific hybrids, using DNA markers of PVY resistance genes, (2) to identify accessions with markers of resistance genes from different species for subsequent use in marker assisted selection (MAS), (3) to evaluate the suitability of DNA markers of PVY resistance genes for genotyping BL developed through interspecific hybridization. It was ascertained that the markers most widely represented in the collection were RYSC3 of the Ryadg gene (49.7%), Ry364 and RAPD38-530 of the Rychc gene (50.5% and 45.2%, respectively), and Yes3-3A of the Rysto gene (29.8%). The markers Ry186 of Rychc and GP122/EcoRV780 of Ryf-sto were found only in some accessions. The frequency of occurrence of BL that had markers of PVY resistance genes from two different species varied between 2.7% (Yes3-3a marker of Rysto and both two markers of Rychc) and 8.5-9.0% (RYSC3 marker of Ryadg and both two markers of Rychc, or only Ry364 marker of this gene). In total, the collection was found to contain 134 BL (47.6%) with markers of resistance genes from two different species. A combination of four markers for three genes of different origin (Ryadg, Rysto and Rychc) was found in 27 BL (7.2%). Extreme resistance to PVY of most BL (302 out of 357) was obviously determined by the presence in them of the currently used resistance genes detected by DNA markers applied in the study. Nevertheless, a significant part of accessions (55 of 61) that did not have any markers was resistant to PVY. At the same time, 13 BL (3.5%) with the markers were susceptible to the virus. Such a level of discrepancies is considered as acceptable for the initial MAS of breeding material. The obtained data on the presence of the markers of PVY resistance genes of different origin and their combination in BL ensures a more effective use of such BL in breeding in comparison with the BL resistant to the virus, though lacking corresponding markers.

Registration of hard white winter wheat germplasms KS14U6380R5, KS16U6380R10, and KS16U6380R11 with adult plant resistance to stem rust

AbstractResistance to the Ug99 group of races of the stem rust fungus Puccinia graminis f. sp. tritici is limited in winter wheat (Triticum aestivum L.) germplasm adapted to the Great Plains of the United States. Our objective was to generate regionally adapted hard winter wheat germplasm with combinations of adult plant resistance genes that are expected to provide durable resistance. KS14U6380R5 (Reg. no. GP‐1043, PI 689115), KS16U6380R10 (Reg. no. GP‐1044, PI 689116), and KS16U6380R11 (Reg. no. GP‐1045, PI 689117) were derived from backcrosses of the hard white winter wheat germplasm KS05HW14 to the stem rust‐resistant Kenyan spring wheat cultivar ‘Kingbird’. KS14U6380R5, KS16U6380R11, and KS16U6380R10 were developed by pedigree selection and were initially evaluated as U6380‐11‐2R‐0A, U6380‐210‐2R‐0A, and U6380‐148‐4R‐2T, respectively. The germplasms were developed by the USDA‐ARS and jointly released with the Kansas State University Agricultural Experiment Station. These germplasms provide parents for development of hard winter wheat cultivars with durable resistance to stem rust.