Combinations Of Resistance Genes Research Articles

Isolation and evaluation of the pathogenicity of a hybrid shiga toxin-producing and Enterotoxigenic Escherichia coli in pigs.

Porcine pathogenic Escherichia coli (E. coli), the globally recognized important pathogen, causes significant economic loss in the field. Enterotoxigenic E. coli (ETEC) causes porcine neonatal and post-weaning diarrhea (PWD), frequently carrying F4 adhesin, F18 adhesin, Heat-Stable toxin (ST), and Heat-Labile toxin (LT). Shiga Toxin-Producing E. coli (STEC) produces F18 adhesin and Shiga toxin type 2e (stx2e), majorly leading to systemic endothelial cell damage and edema disease. In this study, hemolytic pathogenic hybrid STEC/ETEC strains carrying ST and LT genes of ETEC and the Stx2e gene of STEC isolated from pigs with PWD in Taiwan were identified. The pathogenicity of a Taiwan hybrid STEC/ETEC strain was evaluated by oral inoculation in post-weaning pigs. Next generation sequencing and multilocus sequence typing of two hybrid Taiwan porcine STEC/ETEC isolates indicated that these two isolates were closely related to the ST88 porcine hybrid STEC/ETEC isolated from pigs with watery diarrhea. Furthermore, the two hybrid Taiwan porcine STEC/ETEC isolates also displayed combinations of multiple resistance genes encoding mechanisms for target modification and antibiotic inactivation. Animal experiments confirmed that the Taiwan hybrid STEC/ETEC could cause watery diarrhea in post-weaning pigs with no signs of edema disease and minimal histopathological lesions. To the best of the authors' knowledge, the present study is the first study demonstrating intestinal pathogenicity of the hybrid STEC/ETEC in pigs. The result suggests that the hybrid STEC/ETEC should be considered as a new emerging pathogen and a new target for vaccine development.

Genomic characterization of third-generation cephalosporin-resistant Escherichia coli strains isolated from diseased dogs and cats: Report from Japanese Veterinary Antimicrobial Resistance Monitoring

This study investigates the genomic characteristics of canine and feline cefotaxime (CTX, a third-generation cephalosporin)-resistant Escherichia coli using the JVARM, Japanese Veterinary Antimicrobial Resistance Monitoring System, a nationwide monitoring.In this study, whole-genome sequencing (WGS) was performed on 51 canine and 45 feline CTX-resistant E. coli isolates, with certain isolates subjected to pulsed-field gel electrophoresis with S1 nuclease for plasmid–chromosome separation.The most common blaCTX-M genes were blaCTX-M-27 (dogs: 11/51 [21.6 %]; cat: 10/45 [22.2 %]), followed by blaCTX-M-14 (dogs: 10/51 [19.6 %]; cats: 10/45 [22.2 %]), and blaCTX-M-15 (dogs: 9/51 [17.6 %]; cats: 5/45 [11.1 %]). Besides β-lactamase genes, all isolates harbored mdf(A), a multidrug efflux pump, with resistance genes for aminoglycosides, sulfonamides, trimethoprims, macrolides and tetracyclines. None of the isolates had carbapenemase genes, such as blaOXA-48, blaNDM, and blaIMP, whereas most of the isolates showed double mutations in gyrA and parC, which affected quinolone resistance. For the isolates separately analyzed for plasmid and chromosomal DNA via WGS, the majority of CTX-M genes were present on the plasmids. Some plasmids also harbored the same combination of resistance genes and plasmid replicon type, although they differed from isolates derived from different areas of Japan. The predominant plasmids were blaCTX-M-27,aadA5, aph(6)-Id, aph(3”)-Ib, sul1, sul2, tet(A), dfrA17, and mph(A) on IncF. The predominant combination of ST131, O25:H4, and B2 isolates comprised the largest cluster in the minimum spanning tree and the ST131 E. coli harboring blaCTX-M-27 from human in Japan was closely related to these isolates.The results indicated that CTX-resistant canine and feline E. coli harbored multiple plasmids carrying the same combination of resistance genes and emphasizes the need to prevent the spread. Data AvailabilityAll raw short-read sequence data have been deposited in the DNA Data Bank of Japan. (DRR Run No, DRR335726–335821).

Gene pyramiding an advanced approach for disease management in rice: A review

Gene pyramiding is a vital strategy for varietal development in different crops. By using fewer generations than conventional breeding, molecular marker genotyping can streamline the gene pyramiding process. Enhancing the genetic foundation of resistance is crucial for reducing the burden of pesticide residues in the food chain, making it an effective strategy. The development of different pyramided lines carrying single or in combination of different diseases resistant genes in rice viz., Xa4, xa5, xa13, Xa21, and Xa38 for bacterial leaf blight; Pi1, Pi2, Pi9, Pi54, Pi46, and Pita for blast; qSBR7-1, qSBR11-1, and qSBR11-2 for sheath blight. The pyramided lines consist of either single or combinations of various resistance genes, which are instrumental in disease-resistant genetic improvement programs. These lines are utilized to develop profitable varieties that exhibit resistance to multiple diseases.

A Combination of Resistance Genes Confers High and Durable Resistance Against Stripe Rust in Wheat Cultivar Lantian 26.

'Lantian 26', a leading elite winter wheat cultivar in Gansu Province since its release in 2010, exhibits high resistance or immunization to stripe rust in the adult-plant stage under a high disease pressure in Longnan (southeastern Gansu). Identifying the resistance genes in 'Lantian 26' could provide a basis for enhanced durability and high levels of resistance in wheat cultivars. Here, a segregating population was developed from a cross between a highly susceptible wheat cultivar Mingxian 169 and the highly stripe rust-resistant 'Lantian 26'. The F2 and F2:3 progenies of the cross were inoculated with multiple prevalent virulent races of stripe rust for adult-plant-stage-resistance evaluation in two different environments. Exon sequence alignment analysis revealed that a stripe rust resistance gene on the 718.4- to 721.2-Mb region of chromosome 7BL, tentatively named as YrLT26, and a cosegregation sequence-tagged site (STS) marker GY17 was developed and validated using the F2:3 population and 103 wheat cultivars. The other two resistance genes, Yr9 and Yr30, were also identified in 'Lantian 26' using molecular markers. Therefore, the key to high and durable resistance to stripe rust at the adult stage is the combination of Yr9, Yr30, and YrLT26 genes in 'Lantian 26'. This could be a considerable strategy for improving the wheat cultivars with effective and durable resistance in the high-pressure region for stripe rust.

New insights on mcr-1-harboring plasmids from human clinical Escherichia coli isolates.

Mobile colistin resistance (mcr) genes were described recently in Gram-negative bacteria including carbapenem-resistant Enterobacterales. There are ten mcr genes described in different Gram-negative bacteria, however, Escherichia coli harboring mcr-1 gene is by far the most frequent combination. In Argentina, mcr-1 gene was characterized only on plasmids belonging to IncI2 group. The aim of this work was to get new insights of mcr-1-harboring plasmids from E. coli. Eight E. coli isolates from a larger collection of 192 clinical E. coli isolates carrying the mcr-1 gene were sequenced using next generation technologies. Three isolates belonged to ST131 high-risk clone, and five to single ST, ST38, ST46, ST226, ST224, and ST405. Eight diverse mcr-1-harboring plasmids were analyzed: IncI2 (1), IncX4 (3), IncHI2/2A (3) and a hybrid IncFIA/HI1A/HI1B (1) plasmid. Plasmids belonging to the IncI2 (n = 1) and IncX4 (n = 3) groups showed high similarity with previously described plasmids. Two IncHI2/HI2A plasmids, showed high identity between them, while the third, showed several differences including additional resistance genes like tet(A) and floR. One IncFIA/H1A/H1B hybrid plasmid was characterized, highly similar to pSRC27-H, a prototype plasmid lacking mcr genes. mcr-1.5 variant was found in four plasmids with three different Inc groups: IncI2, IncHI2/HI2A and the hybrid FIA/HI1A/HI1B plasmid. mcr-1.5 variant is almost exclusively described in our country and with a high frequency. In addition, six E. coli isolates carried three allelic variants codifying for CTX-M-type extended-spectrum-β-lactamases: blaCTX-M-2 (3), blaCTX-M-65 (2), and blaCTX-M-14 (1). It is the first description of mcr-1 harboring plasmids different to IncI2 group in our country. These results represents new insights about mcr-1 harboring plasmids recovered from E. coli human samples from Argentina, showing different plasmid backbones and resistance gene combinations.

Identification and evolution of ICE-PmuST394: a novel integrative conjugative element in Pasteurella multocida ST394.

The emergence of macrolide and tetracycline resistance within Pasteurella multocida isolated from feedlot cattle and the dominance of ST394 in Australia was reported recently. To establish the genetic context of the resistance genes in P. multocida 17BRD-035, the ST394 reference genome, and conduct a molecular risk assessment of their ability to disperse laterally. A bioinformatic analysis of the P. multocida 17BRD-035 genome was conducted to determine if integrative conjugative elements (ICEs) carrying resistance genes, which hamper antibiotic treatment options locally, are in circulation in Australian feedlots. A novel element, ICE-PmuST394, was characterized in P. multocida 17BRD-035. It was also identified in three other isolates (two ST394s and a ST125) in Australia and is likely present in a genome representing P. multocida ST79 from the USA. ICE-PmuST394 houses a resistance module carrying two variants of the blaROB gene, blaROB-1 and blaROB-13, and the macrolide esterase gene, estT. The resistance gene combination on ICE-PmuST394 confers resistance to ampicillin and tilmicosin, but not to tulathromycin and tildipirosin. Our analysis suggests that ICE-PmuST394 is circulating both by clonal expansion and horizontal transfer but is currently restricted to a single feedlot in Australia. ICE-PmuST394 carries a limited number of unusual antimicrobial resistance genes but has hotspots that facilitate genomic recombination. The element is therefore amenable to hosting more resistance genes, and therefore its presence (or dispersal) should be regularly monitored. The element has a unique molecular marker, which could be exploited for genomic surveillance purposes locally and globally.

Inheritance of Resistance to Bacterial Halo Blight and Bacterial Leaf Spot in Arabica Coffee.

Developing coffee cultivars resistant to multiple diseases by combining resistance genes is a top priority in breeding programs. To create cultivars resistant to diseases and nematodes, we transferred genes for resistance to bacterial infections caused by Pseudomonas coronafaciens pv. garcae, which causes bacterial halo blight (BHB), and P. amygdali pv. tabaci, which causes bacterial leaf spots (BLS), into Arabica coffee. Genetic analyses were conducted on breeding populations to estimate the number and function of genes that confer resistance to BHB and BLS. In total, 2,109 plants in the F2 generation and reciprocal backcrosses were inoculated with P. coronafaciens pv. garcae, while 1,996 plants were inoculated with P. amygdali pv. tabaci. Results showed that resistance to both pathogens had a heritability of 0.99, and the segregations of resistance indicated that each disease was controlled by a single dominant gene. The analyses also revealed that the resistance genes for BHB and BLS were linked, with an average distance of 10.75 cM between them on the same chromosome.

Comprehensive transcriptome and WGCNA analysis reveals the potential function of anthocyanins in low-temperature resistance of a red flower mutant tobacco

The anthocyanin is a protective substance in various plants, and plays important roles in resisting to low-temperature. Here, we explored transcriptome analysis of pink flower (as CK) and the natural mutant red flower (as research objects) under low-temperature conditions, and aimed to reveal the potential functions of anthocyanins and anthocyanin-related regulatory factors in resistance to low-temperature. Our results showed that most of the differentially expressed genes (DEGs) encoding key enzymes in the late stage of anthocyanin metabolism in the mutant were significantly up-regulated. Meanwhile, several genes significantly differentially expressed in CK or mutant were obtained by classification and analysis of transcription factors (TFs), phytohormones and osmoregulators. Additionally, WGCNA was carried out to mine hub genes resistanted to low-temperature stress in flavonoid pathway. Finally, one UFGT family gene, three MYB and one bHLH were obtained as the future hub genes of this study. Combined with the above information, we concluded that the ability of the red flower mutant to grow and develop normally at low-temperatures was the result of a combination of flavonoids and cold resistance genes.

Developing adapted wheat lines with broad-spectrum resistance to stem rust: Introgression of Sr59 through backcrossing and selections based on genotyping-by-sequencing data.

Control of stem rust, caused by Puccinia graminis f.sp. tritici, a highly destructive fungal disease of wheat, faces continuous challenges from emergence of new virulent races across wheat-growing continents. Using combinations of broad-spectrum resistance genes could impart durable stem rust resistance. This study attempted transfer of Sr59 resistance gene from line TA5094 (developed through CSph1bM-induced T2DS·2RL Robertsonian translocation conferring broad-spectrum resistance). Poor agronomic performance of line TA5094 necessitates Sr59 transfer to adapted genetic backgrounds and utility evaluations for wheat improvement. Based on combined stem rust seedling and molecular analyses, 2070 BC1F1 and 1230 BC2F1 plants were derived from backcrossing BAJ#1, KACHU#1, and REEDLING#1 with TA5094. Genotyping-by-sequencing (GBS) results revealed the physical positions of 15,116 SNPs on chromosome 2R. The adapted genotypes used for backcrossing were found not to possess broad-spectrum resistance to selected stem rust races, whereas Sr59-containing line TA5094 showed resistance to all races tested. Stem rust seedling assays combined with kompetitive allele-specific PCR (KASP) marker analysis successfully selected and generated the BC2F2 population, which contained the Sr59 gene, as confirmed by GBS. Early-generation data from backcrossing suggested deviations from the 3:1 segregation, suggesting that multiple genes may contribute to Sr59 resistance reactions. Using GBS marker data (40,584 SNPs in wheat chromosomes) to transfer the recurrent parent background to later-generation populations resulted in average genome recovery of 71.2% in BAJ#1*2/TA5094, 69.8% in KACHU#1*2/TA5094, and 70.5% in REEDLING#1*2/TA5094 populations. GBS data verified stable Sr59 introgression in BC2F2 populations, as evidenced by presence of the Ph1 locus and absence of the 50,936,209 bp deletion in CSph1bM. Combining phenotypic selections, stem rust seedling assays, KASP markers, and GBS data substantially accelerated transfer of broad-spectrum resistance into adapted genotypes. Thus, this study demonstrated that the Sr59 resistance gene can be introduced into elite genetic backgrounds to mitigate stem rust-related yield losses.

Molecular characterization of highly prevalent Escherichia coli and Escherichia marmotae resistant to extended-spectrum cephalosporins in European starlings (Sturnus vulgaris) in Tunisia.

European starlings are widespread migratory birds that have already been described as carrying bacteria resistant to extended-spectrum cephalosporins (ESC-R). These birds are well known in Tunisia because they spend the wintertime in this country and are hunted for human consumption. The goal of our study was to estimate the proportion of ESC-R in these birds and to characterize the collected isolates using whole-genome sequencing. Results showed that 21.5% (42/200) of the birds carried either an extended-spectrum beta-lactamase (ESBL) or an acquired AmpC gene. Diverse bla CTX-M genes were responsible for the ESBL phenotype, bla CTX-M-14 being the most prevalent, while only bla CMY-2 and one bla CMY-62 were found in AmpC-positive isolates. Likewise, different genetic determinants carried these resistance genes, including IncHI2, and IncF plasmids for bla CTX-M genes and IncI1 plasmids for bla CMY-2 genes. Three chromosomally encoded bla CTX-M-15 genes were also identified. Surprisingly, species identification revealed a large proportion (32.7%) of Escherichia marmotae isolates. This species is phenotypically indistinguishable from Escherichia coli and has obviously the same capacity to acquire ESC-R genes. Our data also strongly suggest that at least the IncHI2/pST3 plasmid can spread equally between E. coli and E. marmotae. Given the potential transmission routes between humans and animals, either by direct contact with dejections or through meat preparation, it is important to closely monitor antimicrobial resistance in European starlings in Tunisia and to set up further studies to identify the sources of contamination of these birds. IMPORTANCE The One Health concept highlighted knowledge gaps in the understanding of the transmission routes of resistant bacteria. A major interest was shown in wild migratory birds since they might spread resistant bacteria over long distances. Our study brings further evidence that wild birds, even though they are not directly submitted to antibiotic treatments, can be heavily contaminated by resistant bacteria. Our results identified numerous combinations of resistance genes, genetic supports, and bacterial clones that can spread vertically or horizontally and maintain a high level of resistance in the bird population. Some of these determinants are widespread in humans or animals (IncHI2/pST3 plasmids and pandemic clones), while some others are less frequent (atypical IncI1 plasmid and minor clones). Consequently, it is essential to be aware of the risks of transmission and to take all necessary measures to prevent the proportions of resistant isolates from increasing uncontrollably.

Detecting Locus of Resistance to Scab in Local Apple Varieties in Uzbekistan Using Molecular Genetic Markers

The apple tree (Malus sp.) is the most cultivated plant in the world. Apple orchards cover a large area. scab (Venturia inaequalis) causes significant damage to the economies of many countries that are engaged in the production of apple trees. In Uzbekistan, most of the orchards are apple orchards. The present study includes a molecular genetic analysis of the resistance of local apple cultivars to pathogens Venturia inaequalis in local apple cultivars grown in Uzbekistan and the results of identification of resistance genes. The paper presents the results of molecular genetic analysis of the combination of scab resistance genes (Vf, Vfa1, Vfa2) found in 15% of samples. In 58.7% of the studied samples, a “high level of resistance” to scab was revealed.

Characteristics and properties of Serratia marcescens isolated in bacteremia in children

Introduction. Serratia marcescens is an opportunistic gram-negative microorganism, currently has been detected with increasing frequency in various clinical biomaterials from sick persons is the causative agent of nosocomial infections.
 The aim of the work is to determine microbiological and clinical features of S. marcescens in bloodstream infections in children. 
 Materials and methods. Nineteen isolates of S. marcescens were isolated from blood cultures. Antibiotic sensitivity was determined by broth microdilution method. Carbapenemase gene were determined using real-time polymerase chain reaction. Biofilm formation was studied on abiotic surfaces using polystyreneplates. Population diversity was determined by multilocus genotypic analysis. 
 Results. Carbapenems, fosfomycin and biseptol showed the highest antimicrobial activity in vitro. Resistance to aminoglycosides, aztreonam, cefepime, and ticarcillin/clavulanate was over 50%. According to PCR data, only OXA-48 carbapenemases were found in 11% of isolates, NDM — in 5%, and a combination of carbapenemases — in 15%. Biofilms of moderate intensity were formed in 13 (68%) isolates, and weak biofilms — in 6 (32%). According to the genotypic analysis, a large proportion of isolates with multiple resistance were included in one group. All of them were singled out over one year from one department — perhaps there was a single source. In 3 cases, patients were diagnosed with sepsis, 1 of them had an unfavourable outcome. Bacteremia occurred on the 3rd day after the initial isolation of S. marcescens. An unfavourable outcome occurred on the 10th day of bacteremia. S. marcescens in this case had multiple resistance and a combination of resistance genes, also belonged to genotypic group I, which is often found in our work.
 Conclusion. S. marcescens in bloodstream infections is a serious problem for pediatric patients. Natural resistance to polymyxins, as well as acquired resistance to carbapenems and aminoglycosides, cause particular alertness and attention to this microbial agent.

Analysis of resistance to stem rust and identification of <i>Sr</i> genes in introgressive lines of spring bread wheat

Background. Due to the increase in the harmfulness of wheat stem rust (Puccinia graminis f. sp. tritici Erikss. & E. Henn.) in the Volga region, and the likelihood of the spread of the aggressive Ug99 race, an assessment of the genetic diversity of wheat breeding lines and identification of effective Sr genes are of fundamental importance.Materials and methods. Ninety spring bread wheat introgressive lines with stem rust resistance, developed at the Federal Center of Agriculture Research of the South-East Region, were analyzed. Molecular markers were used to identify resistance genes: Sr24/Lr24, Sr25/Lr19, Sr26, Sr28, Sr31/Lr26, Sr32, Sr36, Sr38/Lr37, Sr39 and Sr57/Lr34. The analysis of plants for resistance was carried out according to standard methods; the Stakman scale was applied to determine the type of reaction.Results. The genes Sr31/Lr26, Sr25/Lr19, Sr57/Lr34, Sr38/Lr37 and Sr39/Lr35 were identified in the analyzed breeding lines. Sr25 was found in 51 lines (56,7% of samples), Sr31 in 41 lines (45.6%), Sr57/Lr34 in 5 lines, Sr38 in 10 lines and Sr39 in one line. Combinations of resistance genes were identified: Sr31+Sr25 in 28 lines (31.1%), Sr25+Sr38 in 5 lines, and Sr25+Sr39 in one line. The Sr24/Lr24, Sr26, Sr28, Sr32 and Sr36 genes were not identified.Conclusion. As a result, promising highly resistant introgressive wheat lines with promising combinations of Sr31+Sr25, Sr25+Sr38 and Sr25+Sr39 genes were identified. They can be used in Russian breeding programs for immunity.

Evaluation of Short-Season Soybean Genotypes for Resistance and Partial Resistance to Phytophthora sojae.

Phytophthora root and stem rot caused by Phytophthora sojae Kaufmann and Gerdemann is a soil-borne disease severely affecting soybean production worldwide. Losses caused by P. sojae can be controlled by both major genes and quantitative trait locus. Here, we tested 112 short-season soybean cultivars from Northeast China for resistance to P. sojae. A total of 58 germplasms were resistant to 7-11 P. sojae strains. Among these, Mengdou 28 and Kejiao 10-262 may harbor either Rps3a or multiple Rps genes conferring resistance to P. sojae. The remaining 110 germplasms produced 91 reaction types and may contain new resistance genes or gene combinations. Partial resistance evaluation using the inoculum layer method revealed that 34 soybean germplasms had high partial resistance, with a mean disease index lower than 30. Combining the results of resistance and partial resistance analyses, we identified 35 excellent germplasm resources as potential elite materials for resistance and tolerance in future breeding programs. In addition, we compared the radicle inoculation method with the inoculum layer method to screen for partial resistance to P. sojae. Our results demonstrate that the radicle inoculation method could potentially replace the inoculum layer method to identify partial resistance against P. sojae, and further verification with larger samples is required in the future.

Distribution of Xanthomonas oryzae pv. oryzae Pathotypes in Basmati-Rice-Growing Areas of Jammu and Kashmir, India

Rice is an important staple food for more than half of the world’s population. Though the genetic potential of commonly cultivated varieties of rice is diminished due to various biotic and abiotic constraints, bacterial leaf blight (BLB) of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is considered one of its most destructive diseases in India. Based on morpho-cultural characteristics, bacterial pathogens isolated from the leaves of a rice plant showing typical BLB symptoms were identified as Xanthomonas oryzae pv. oryzae. Morphological studies revealed that the pathogen is Gram-negative, a short rod, with rounded ends, single or in pairs, light yellow, circular, whitish yellow to straw-colored, convex, yellow, slightly raised, motile with a single polar flagellum, capsulate and non-spore-forming. Biochemical tests, viz., the Gram reaction, KOH test and catalyst test, showed a positive reaction for all the isolates. Twenty isolates of Xoo were collected from the basmati-growing areas of the Jammu, Samba and Kathua districts in the Jammu sub-tropics during 2019, and their pathogenicity was confirmed on five susceptible rice cultivars, viz., Basmati-370, Pusa-1121, TN-1, SJR and Jaya, by the leaf-clipping method, and subsequently, Koch’s postulate was established in each case. Seven Xoo pathotypes, viz., Pathotype 1, Pathotype 2, Pathotype 3, Pathotype 4, Pathotype 5, Pathotype 6 and Pathotype 7, were identified from the total sample of 20 isolates. Pathotype 2 was the most dominant (100%), followed by Pathotype 5 (44.44%), Pathotype 4 (40%), Pathotype 6 (40%), Pathotype 7 (33.33%), Pathotype 3 (22.22%) and Pathotype 1 (20%), in the Jammu sub-tropics. In Jammu district, Pathotype 5 was highly distributed (44.44%) followed by Pathotype 7 (33.33%) and Pathotype 3 (22.22%). Pathotype 4 and Pathotype 6 each showed a 40 percent distribution in Kathua district, followed by Pathotype 1 (20%). Only one pathotype, i.e., Pathotype 2, was recorded in Samba district with a 100 percent distribution. Five genes, viz., Xa13, Xa4, Xa13 and Xa5 + Xa13, showed complete resistance, whereas Xa4, Xa5, Xa7, Xa8, Xa21, Xa4 + Xa5 and Xa4 + Xa21 showed susceptible response against the test isolates. It was observed that most of the single BLB-resistant genes were moderately to highly susceptible to almost all the Xoo isolates, whereas combinations of BLB resistance genes possessed high resistance against all the Xoo isolates. The studies revealed that diverse pathogenic variations existed in the Xoo population in the basmati-growing region of Jammu and Kashmir. Based on the response exhibited by Xoo isolates on differential lines, seven pathotypes (Pathotype 1–7) were identified, and their virulence spectrum on rice differentials showed the occurrence of 5, 3, 10, 10, 20, 10 and 15 percent, respectively, in the Jammu sub-tropics. To develop durable and sustainable resistant cultivars, it is essential to identify predominate race(s) in a specific geographical area and continuously monitor the virulence pattern there.

A large bioassay identifies Stb resistance genes that provide broad resistance against Septoria tritici blotch disease in the UK.

Septoria tritici blotch (STB) is one of the most damaging fungal diseases of wheat in Europe, largely due to the paucity of effective resistance genes against it in breeding materials. Currently dominant protection methods against this disease, e.g. fungicides and the disease resistance genes already deployed, are losing their effectiveness. Therefore, it is vital that other available disease resistance sources are identified, understood and deployed in a manner that maximises their effectiveness and durability. In this study, we assessed wheat genotypes containing nineteen known major STB resistance genes (Stb1 through to Stb19) or combinations thereof against a broad panel of 93 UK Zymoseptoria tritici isolates. Seedlings were inoculated using a cotton swab and monitored for four weeks. Four infection-related phenotypic traits were visually assessed. These were the days post infection to the development of first symptoms and pycnidia, percentage coverage of the infected leaf area with chlorosis/necrosis and percentage coverage of the infected leaf area with pycnidia. The different Stb genes were found to vary greatly in the levels of protection they provided, with pycnidia coverage at four weeks differing significantly from susceptible controls for every tested genotype. Stb10, Stb11, Stb12, Stb16q, Stb17, and Stb19 were identified as contributing broad spectrum disease resistance, and synthetic hexaploid wheat lines were identified as particularly promising sources of broadly effective STB resistances. No single Z. tritici isolate was found to be virulent against all tested resistance genes. Wheat genotypes carrying multiple Stb genes were found to provide higher levels of resistance than expected given their historical levels of use. Furthermore, it was noted that disease resistance controlled by different Stb genes was associated with different levels of chlorosis, with high levels of early chlorosis in some genotypes correlated with high resistance to fungal pycnidia development, potentially suggesting the presence of multiple resistance mechanisms.The knowledge obtained here will aid UK breeders in prioritising Stb genes for future breeding programmes, in which optimal combinations of resistance genes could be pyramided. In addition, this study identified the most interesting Stb genes for cloning and detailed functional analysis.

SCREENING OF RICE LINES OF DIVERSE ORIGIN RESISTANT TO BACTERIAL LEAF BLIGHT UNDER LOCAL CONDITIONS


 
 
 Current study comprised of 20 donor parent lines and four indica elite strains resistant against bacterial leaf blight having diversity in origin viz. Bangladesh, Philippine, Indonesia, Senegal and India. The lines were tested to check resistance against Bacterial Leaf Blight (BLB), having BLB resistance genes Xa-4, xa-5, Xa-7 and xa-13. The experiment was conducted at Agronomic Research Station, Farooqabad, Sheikhupura. Artificial inoculation was done to study disease reaction. DNA marker analysis was also conducted to study the gene status of these lines. Results indicated that seven donor lines were completely resistant to Bacterial Leaf Blight whereas twelve lines exhibited moderate resistance. Among rest of the five susceptible genotypes, three were showing comparatively low susceptibility whereas two completely susceptible to BLB. Most of the lines with three or four gene combinations showing resistant behavior against BLB except AUS-298 that showed moderately susceptible behavior. Combination of genes for Bacterial Leaf Blight resistance can be explored further in targeted research program for disease resistance.
 
 

Incorporation of Two Bacterial Blight Resistance Genes into the Popular Rice Variety, Ranidhan through Marker-Assisted Breeding

The bacterial blight (BB) disease of rice is a major disease that reduces yield heavily in susceptible varieties. Ranidhan is a late maturing popular rice variety but shows high susceptibility to the disease. Two BB resistance genes were transferred into the variety through a marker-assisted backcross breeding approach. Tightly linked molecular markers were deployed to track the BB resistance genes in the plants carrying the target genes in each backcross generation. Foreground screening detected 17, 16 and 15 progenies to carry the 3 BB resistance genes in BC1F1, BC2F1 and BC3F1 generations, respectively. The selected BC3F1 plant was selfed and three different combinations of BB resistance genes were tracked in homozygous state in seven BC3F2 plants. The pyramided lines carrying three resistance genes in homozygous conditions were evaluated for BB disease resistance by inoculating with eight virulent Xoo strains. Five pyramided lines carrying two resistance gene combinations (Xa21+xa13 and Xa21+xa5) exhibited enhanced resistance against the BB pathogens. The disease resistance was in the order of Xa21+xa5 < Xa21+xa13 < xa13+xa5 gene combinations in conferring the resistance. The developed pyramided lines were similar to the recipient parent for the majority of the important agro-morphologic and grain quality traits.

Molecular characterization and screening of Xanthomonas oryzae pv. oryzae, isolated from Pakistan for prediction of bacterial leaf blight-resistant basmati rice

Bacterial leaf blight (BLB) is a devastating disease of rice caused by Xanthomonas oryzae pv.oryzae (Xoo), severely affects grain quality and reduces yield in all rice-growing areas of Pakistan. The pathogen is highly dynamic and quickly evolves itself when encountered with new resistant genes, hence, the knowledge about existing virulence range within the pathogen population and availability of corresponding resistance gene source is of immense importance. The present study focused on molecular dissection and evaluating the effectiveness of different resistance gene combinations against Xoo isolates collected from seven major rice-growing districts of Punjab Pakistan. Phenotypic characterization of collected Xoo isolates has shown that all of them were rod-shaped Gram-negative bacteria. However, oryzae species and oryzae pathovar were confirmed in only 22 out of 50 isolates using multiplex PCR. Analysis of loop-mediated isothermal amplification validated the lineage and close relatedness of Pakistani Xoo isolates with the already reported Asian Xoo population. Pathogenicity test on susceptible rice variety Super Basmati has shown that out of twenty-two tested Xoo isolates, four isolates from three different districts fell into the most virulent category with an average lesion length of ≥15 cm. Pathotyping of selected resistant rice lines against Xoo isolates distributed 22 isolates into nine pathotypes based on their interaction with R genes. Current molecular and phenotypic profiling of isolated Pakistani Xoo isolates may serve as a valuable reference for global comparison to manage BLB disease of rice in real-time.

Occurrence and Characteristics of ESBL- and Carbapenemase- Producing Escherichia coli from Wild and Feral Birds in Greece.

Wild and feral birds are known to be involved in the maintenance and dissemination of clinically-important antimicrobial-resistant pathogens, such as extended-spectrum β-lactamase (ESBL) and carbapenemase-producing Enterobacteriaceae. The aim of our study was to evaluate the presence of ESBL- and carbapenemase-producing Escherichia coli among wild and feral birds from Greece and to describe their antimicrobial resistance characteristics. In this context, fecal samples of 362 birds were collected and cultured. Subsequently, the antimicrobial resistance pheno- and geno-type of all the obtained E. coli isolates were determined. A total of 12 multidrug-resistant (MDR), ESBL-producing E. coli were recovered from eight different wild bird species. Eleven of these isolates carried a blaCTX-M-1 group gene alone or in combination with blaTEM and one carried only blaTEM. AmpC, fluoroquinolone, trimethoprim/sulfamethoxazole, aminoglycoside and macrolide resistance genes were also detected. Additionally, one carbapenemase-producing E. coli was identified, harboring blaNDM along with a combination of additional resistance genes. This report describes the occurrence of ESBL- and carbapenemase-producing E. coli among wild avian species in Greece, emphasizing the importance of incorporating wild birds in the assessment of AMR circulation in non-clinical settings.