Introduction Of Resistance Genes Research Articles

Genetic manipulation of Indian mustard genotypes with WRR-gene(s) confers resistance against Albugo candida.

Brassica species is the second most important edible oilseed crop in India. Albugo candida (Pers.) Kuntze, a major oomycete disease of oilseed brassica causing white rust, leads to 60% yield loss globally. The prevalence of A. candida race 2 (Ac2V) that specifically infects B. juncea, coupled with limitations of conventional methods has resulted in a dearth of white rust resistance resources in cultivated varieties. In an effort to develop resistant plants, Agrobacterium mediated genetic transformation of three B. juncea genotypes viz., susceptible host var. Varuna, along with its doubled haploid mutant lines C66 and C69 (showing moderate tolerance to field isolates of A. candida) was initiated to transfer resistance genes (WRR8Sf-2 and WRR9Hi-0) identified in Arabidopsis thaliana against race Ac2V, that encode for Toll-like/interleukin-1 receptor-nucleotide binding-leucine-rich repeat proteins that recognize effectors of the pathogen races. Our results demonstrate that introduction of resistance genes from a tertiary gene pool by genetic transformation enhances disease resistance in B. juncea genotypes to a highly virulent Ac2V isolate.

The application of CRISPR genome editing technologies in the pathogenesis studies, diagnosis, prevention and treatment of infectious diseases.

The CRISPR genome editing technology shows great application prospects in gene manipulation and infectious disease research, and is of great value for effective control and cure of infectious diseases. It has been utilized to generate specific disease models in cells, organoids and animals, which provide great convenience for research into the molecular mechanisms associated with infectious diseases. CRISPR screening technology enables high-throughput identification of risk factors. New molecular diagnostic tools based on CRISPR offer a more sensitive and faster method for detecting pathogens. The use of CRISPR tools to introduce resistance genes or to specifically destroy risk genes and virus genomes is intended to help prevent or treat infectious diseases. This review discusses the application of CRISPR genome editing technologies in the construction of disease models, screening of risk factors, pathogen diagnosis, and prevention and treatment of infectious diseases, thereby providing a reference for follow-up research in pathogenesis, diagnosis, prevention and treatment of infectious diseases.

Microbial communities, resistance genes, and resistome risks in urban lakes of different trophic states: Internal links and external influences

Anthropogenic discharge of nutrients, metals, and antibiotics poses multiple threats to the health of aquatic ecosystems and humans, e.g., causing eutrophication, and introduction of resistance genes into human pathogens. The potential link between microbial communities, resistance genes, and eutrophication levels in urban lakes is complex and remains unclear, which is crucial for ecological and human health risk assessment. Here, five urban lakes of different trophic conditions were investigated to quantify their microbial diversity, and high-resolution profiles of antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) were established. Metagenome and multivariance analyses indicated that the microbial structures, distribution of resistance genes and mobile genetic elements (MGEs), and virulence factor genes (VFGs) significantly differed between the lakes. The hypereutrophic lake Nanhu harbored the lowest microbial diversity but the highest level of resistance genes. Microbial communities and MGEs were identified as the main drivers in shaping the profiles of ARGs and MRGs, while external environmental factors played an indirect role in the changing resistance genes. Two members of Proteobacteria, Aestuariivirga and Limnohabitans were identified as predominant bacterial hosts of ARGs in most samples. In addition, the resistome risk scores were found positively correlated with water quality factors and negatively correlated with microbial diversity in the urban lakes. Our study provides novel insights into the link between microbial diversity, MGEs, and the potential dissemination risk of ARGs in urban lakes.

Development and Molecular Cytogenetic Characterization of Novel Primary Wheat-Rye 1RS.1BL Translocation Lines from Multiple Rye Sources with Resistance to Stripe Rust.

Stripe rust (caused by Puccinia striiformis f. sp. tritici) is one of the most severe diseases for wheat production. An important method to improve the stripe rust resistance of wheat is to introduce resistance genes from related species into the wheat genome. The 1RS.1BL wheat-rye translocation from Petkus rye has contributed substantially to wheat resistance breeding worldwide. However, given the breakdown of the stripe rust resistance gene Yr9 in 1RS, its importance for wheat improvement has decreased. In this study, we developed 166 new primary 1RS.1BL translocation lines by crossing rye varieties Weining, Baili, and Aigan with several wheat cultivars. Cytogenetic and molecular analyses indicated that all of these lines contained a pair of intact 1RS.1BL translocation chromosomes. The stripe rust resistance of these translocation lines and their wheat parents was evaluated in southwestern China during the severe stripe rust epidemics in 2015 and 2021. The results showed diverse effects of the 1RS.1BL translocations from different rye cultivars on resistance to stripe rust. The highest genetic diversity was observed in 1RS.1BL translocations derived from diverse rye varieties but in the same wheat background. The development of diverse 1RS.1BL translocation lines offers ample opportunities to introduce new variations into wheat for improving stripe rust resistance. Finally, 71 new translocation lines, including nine developed from the cross of MY11 × Aigan, four from MY11 × Baili, 40 from MY11 × Weining, 14 from A42912 × Baili, and four from A42912 × Weining. These lines showed consistent resistance to stripe rust in fields under frequent changes of the pathogen races and could be useful genetic stocks for breeding wheat cultivars with resistance to stripe rust.

Technical considerations towards commercialization of porcine respiratory and reproductive syndrome (PRRS) virus resistant pigs

The selection and introduction of disease resistance genes in livestock not only provide health benefits to animals but opportunities for breeders and farmers to meet the growing demand for high-quality meat and milk while reducing agriculture’s footprint on the environment. As traditional methods of classical breeding and selection for trait improvement are slow, recent progress in several areas of biology including (a) understanding host–pathogen interactions, (b) inexpensive and rapid DNA sequencing, and (c) robust gene editing like CRISPR-Cas provide geneticists tools to accelerate discovery and deployment of disease resistance alleles in livestock. Using these advances, the introduction of resistance genes into commercially relevant germplasm requires access to genetically superior livestock, an infrastructure for scalable allele deployment, freedom to operate, global regulatory approvals, and acceptance of gene edited livestock by producers and consumers. Importantly, academic researchers have recently discovered that modification of the CD163 gene in pigs can confer resistance to the virus that causes porcine reproductive and respiratory syndrome (PRRS). While this achievement represents a major step towards solving an important disease in livestock, to realize the positive impact on animal health while benefiting the pork industry and consumers, it is necessary to introduce this recessive disease resistance allele into commercial breeding populations. Rather than backcrossing the resistance gene from a few non-commercial founders, as a global supplier of high genetic merit livestock genetics, Genus plc and its pig division PIC (Pig Improvement Company) with Genus R&D have mobilized advances in reproductive biology, gene editing, DNA sequencing, and bioinformatics to simultaneously generate and introduce a single modified CD163 allele across four genetically diverse porcine lines of commercial importance that prevents PRRS virus (PRRSV) infection. This report focuses on technical aspects for a scaled gene editing program to consider for rapid and efficient generation and advancement of a small population of non-transgenic founder pigs for commercial breeding. This high genetic merit herd containing a PRRS disease resistance allele will provide important benefits to animal health and food chain value once approved for commercial sale and export.

Introgression of anthracnose resistance gene(s) into common bean (Phaseolus vulgaris)

Abstract. Kazimoto GK, Nchimbi-Msolla SF, Mabagala RB. 2022. Introgression of anthracnose resistance gene(s) into common bean (Phaseolus vulgaris). Cell Biol Dev 6: 20-31. Common bean anthracnose disease caused by the fungus Colletotrichum lindemuthianum causes significant yield losses. It is most destructive in areas with cool temperatures and high humidity (90-100%). The study aimed to introduce resistance genes into adapted but susceptible local cultivars of Masai Red and Soya Njano using conventional breeding methods. Five races of C. lindemuthianum were isolated and named from thirty-two common bean-diseased plant samples collected from Northern Tanzania. The sources of resistant genes were bean cultivars G2333 and AB136. Early developed populations were evaluated under field conditions in high altitude and humid environments at Bashnet in the Manyara region, in the Northern highlands of Tanzania. Both F2 and F3 populations of Soya Njano x G2333 were segregated for C. lindemuthianum resistance at a 9:7 ratio. Such segregation implied that two dominant epistatic genes conferred from G2333, the resistance being in the mode of epistatic gene interaction. The crosses between Masai Red x G2333 and F2 and F3 populations segregation ratio was 10:6, implying two dominant resistant genes were transferred to developed populations. The F2 and F3 progenies obtained from crossing Soya Njano and AB136 showed a ratio of 3:1. The F2 progenies from a cross between Masai Red and AB136 were segregated at a ratio of 3:1 and F3 progenies were 3:1. The 3:1 ratio confirmed single dominant gene inheritance conferred to developed progenies. The heritability (h²) from populations of Soya Njano x G2333 and Masai Red x G2333 was between 0.41 and 0.45. While Soya Njano, Masai Red, and A136 were between 0.2 and 0.53, which implied moderate heritability. F2 and F3 populations developed need further testing using MAS to confirm the presence of resistant genes. Multi-location testing should be done to verify the resistance levels of the developed bean population in later generations.

Biosolids for safe land application: does wastewater treatment plant size matters when considering antibiotics, pollutants, microbiome, mobile genetic elements and associated resistance genes?

SummarySoil fertilization with wastewater treatment plant (WWTP) biosolids is associated with the introduction of resistance genes (RGs), mobile genetic elements (MGEs) and potentially selective pollutants (antibiotics, heavy metals, disinfectants) into soil. Not much data are available on the parallel analysis of biosolid pollutant contents, RG/MGE abundances and microbial community composition. In the present study, DNA extracted from biosolids taken at 12 WWTPs (two large‐scale, six middle‐scale and four small‐scale plants) was used to determine the abundance of RGs and MGEs via quantitative real‐time PCR and the bacterial and archaeal community composition was assessed by 16S rRNA gene amplicon sequencing. Concentrations of heavy metals, antibiotics, the biocides triclosan, triclocarban and quaternary ammonium compounds (QACs) were measured. Strong and significant correlations were revealed between several target genes and concentrations of Cu, Zn, triclosan, several antibiotics and QACs. Interestingly, the size of the sewage treatment plant (inhabitant equivalents) was negatively correlated with antibiotic concentrations, RGs and MGEs abundances and had little influence on the load of metals and QACs or the microbial community composition. Biosolids from WWTPs with anaerobic treatment and hospitals in their catchment area were associated with a higher abundance of potential opportunistic pathogens and higher concentrations of QACs.

Introgression of the Powdery Mildew Resistance Genes Pm60 and Pm60b from Triticum urartu to Common Wheat Using Durum as a 'Bridge'.

Powdery mildew, caused by the fungus Blumeria graminis f. sp. tritici (Bgt), has limited wheat yields in many major wheat-production areas across the world. Introducing resistance genes from wild relatives into cultivated wheat can enrich the genetic resources for disease resistance breeding. The powdery mildew resistance gene Pm60 was first identified in diploid wild wheat Triticum urartu (T. urartu). In this study, we used durum as a ‘bridge’ approach to transfer Pm60 and Pm60b into hexaploid common wheat. Synthetic hexaploid wheat (SHW, AABBAuAu), developed by crossing T. urartu (AuAu) with durum (AABB), was used for crossing and backcrossing with common wheat. The Pm60 alleles were tracked by molecular markers and the resistance to powdery mildew. From BC1F1 backcross populations, eight recombinant types were identified based on five Pm60-flanking markers, which indicated different sizes of the introgressed chromosome segments from T. urartu. Moreover, we have selected two resistance-harboring introgression lines with high self-fertility, which could be easily used in wheat breeding system. Our results showed that the durum was an excellent ‘bridge’ for introducing the target gene from diploid T. urartu into the hexaploid cultivated wheat. Moreover, these introgression lines could be deployed in wheat resistance breeding programs, together with the assistance of the molecular markers for Pm60 alleles.

Relationship of Colletotrichum lindemuthianum races and resistance loci in the Phaseolus vulgaris L. genome

AbstractAnthracnose caused by Colletotrichum lindemuthianum is one of the most critical diseases in the common bean (Phaseolus vulgaris L.). The characterization and localization of pathogenic fungal races are essential for understanding pathogen population dynamics and developing resistant cultivars. Here, we discussed the relationship between the diversity of C. lindemuthianum and common bean resistance genes against anthracnose disease. Indeed, several studies using a system of 12 differential bean cultivars have been carried out since 1991 to monitor anthracnose, reporting the constant appearance of new races. Colletotrichum lindemuthianum shows high virulence diversity, with 298 races distributed across 29 countries. In Brazil, we identified 89 races, with races 73, 65, and 81 as the most frequent. Moreover, we highlighted the common bean gene clusters, their unique location on chromosomes, and their relationship with races and resistance genes. The genetic mapping studies, molecular markers linked to anthracnose resistance alleles, and the specific races were integrated on the seven‐chromosome map using the reference genome of common bean. Recently, the ease of use of genome sequences and the development of molecular technologies have allowed molecular markers for marker‐assisted selection applied to anthracnose‐resistant cultivars. As a result, it is feasible that Mesoamerican genes Co‐5, Co‐42, Co‐6, Co‐16, and Co‐17, and the Andean genes Co‐12, Co‐14, Co‐Bf, Co‐15, Co‐AC, and CoPv01CDRK are well known to confer resistance to most races reported in Brazil and around the world. Thus, pyramiding these genes through molecular markers can help reduce the time and cost of introducing resistance genes in commercial common bean cultivars.

QTL mapping of adult-plant resistance to leaf rust based on SSR markers and SNP sequencing of Chinese wheat landrace Xu’ai (Triticum aestivum L.)

Leaf rust (Puccinia recondite f. sp. Tritici) is the prevalent wheat (Triticum aestivum) disease in many areas of the world. The preferred method of control is to introduce resistance genes against this disease into elite wheat germplasm, an approach that is more environmentally friendly than applying fungicides and that has underpinned sustained wheat production to date. Identifying new adult-plant resistance (APR) genes and quantitative trait loci (QTL) for leaf rust resistance can expand the sources of disease resistance and contribute to breeding for durable resistance, allowing the pyramiding of multiple APR genes in elite wheat lines. In this study, simple sequence repeat (SSR) markers, together with the bulked segregant and single nucleotide polymorphism analyses (BSA and SNP), were used to identify QTL in F2:3 lines derived from Xu’ai and Zhengzhou 5389. Yield data for the population lines were used to detect QTL by inclusive composite interval mapping analysis. Six QTL were identified, namely, QLr.hebau-1BL, QLr.hebau-2AS, QLr.hebau-2BS, QLr.hebau-2BL, QLr.hebau-4B and QLr.hebau-6AL. Both QLr.hebau-2BS and QLr.hebau-4B were detected in five environments, explaining 23.1–37.5% and 7.6–18.3% of the phenotypic variation for resistance, respectively. After analysis, QLr.hebau-1BL and QLr.hebau-4B were identified as Lr46 and Lr12, respectively. QLr.hebau-2BS is very close to the temperature-sensitive gene LrZH22, but requires further detection. QLr.hebau-2AS, QLr.hebau-2BL and QLr.hebau-6AL constitute new resistance loci. These genes or QTL for reduced disease severity were derived from the resistant parent Xu’ai. The QTL identified and their flanking markers could be useful for fine mapping and marker-assisted selection (MAS).

Research status and prospect of genes related with resistance to powdery mildew of wheat

Wheat (Triticum aestivum L.) is one of the major grain crops in the world. Wheat powdery mildew is a fungal disease caused by the infection of Blumeria graminis F. sp. tritici. It is one of the most severe wheat diseases globally, seriously affecting the yield and quality of wheat. At present, the main ways to control powdery mildew are the use of fungicides and the cultivation of disease-resistant varieties. The extensive spraying of fungicides causes pesticide residues and environmental pollution. At present, no matter wild type or artificially bred wheat powdery mildew resistant varieties are scarce, so it is urgent to cultivate resistant varieties quickly and efficiently. Traditional cross breeding has a long time and low efficiency. Still, it is a fast and effective way to get disease-resistant sorts by using modern molecular biological means to transfer disease-resistant genes into cultivated varieties. Although the cultivation of resistant varieties is the most economical and effective way to control powdery mildew in wheat, there are some limitations in the cultivation of resistant varieties by introducing resistance genes by conventional means in actual production. With the increase of disease each year, this situation will be more and more unable to meet the needs of wheat genetic improvement. It is urgent to explore a new way of breeding to improve the wheat to powdery mildew lasting broad-spectrum resistance. The disease-resistant breeding needs from cloning in plant and pathogen affinity interactions play a vital role in the study of disease genes and their mechanism of action. At present, in the wheat by manipulating disease genes make infected material gain lasting broad-spectrum resistance is less. In the case of disease genes and mutations after its disease-resistant mechanism are still not clear. So the breeding of resistant varieties need mining and utilization of resistance genes. The paper summarizes the harm and distribution of wheat powdery mildew, the genes resistance mechanism of wheat powdery mildew, and functional analysis, wheat powdery mildew resistance genes in the field of molecular biology research status, and VIGS, RNAi, such as for the prevention and control of wheat powdery mildew, explore new powdery mildew resistance genes and resistance regulation, breeding disease-resistant varieties of wheat provide the feasible scheme.

A Biological Inventory of Prophages in A. baumannii Genomes Reveal Distinct Distributions in Classes, Length, and Genomic Positions.

Acinetobacter baumannii is of major clinical importance as the bacterial pathogen often causes hospital acquired infections, further complicated by the high prevalence of antibiotic resistant strains. Aside from natural tolerance to certain antibiotic classes, resistance is often acquired by the exchange of genetic information via conjugation but also by the high natural competence exhibited by A. baumannii. In addition, bacteriophages are able to introduce resistance genes but also toxins and virulence factors via phage mediated transduction. In this work, we analyzed the complete genomes of 177 A. baumannii strains for the occurrence of prophages, and analyzed their taxonomy, size and positions of insertion. Among all the prophages that were detected, Siphoviridae and Myoviridae were the two most commonly found families, while the average genome size was determined to be approximately 4 Mbp. Our data shows the wide variation in the number of prophages in A. baumannii genomes and the prevalence of certain prophages within strains that are most “successful” or potentially beneficial to the host. Our study also revealed that only two specific sites of insertion within the genome of the host bacterium are being used, with few exceptions only. Lastly, we analyzed the existence of genes that are encoded in the prophages, which may confer antimicrobial resistance (AMR). Several phages carry AMR genes, including OXA-23 and NDM-1, illustrating the importance of lysogenic phages in the acquisition of resistance genes.

Ovine haemonchosis: a review.

Sheep farming is the backbone of a rural economy in developing countries, and haemonchosis is a major impediment in the way of its progress. Haemonchus contortus (H. contortus) infection persists all over the world particularly in the tropical and sub-tropical regions. Various review articles have been published to substantially cover one or more aspects of its morphology, prevalence, pathogenesis, symptoms, diagnosis, immune response, drug resistance, treatment, and control measure. The objective of this paper is to briefly review past and present information available in the aforementioned areas in one place to enable the readers to fully understand the problem from a broader perspective. H. contortus parasite harbours in abomasum of affected animal and feeds on its blood, producing mild to severe symptoms and even death in acute form. The parasite thus inflicts heavy production losses and is of economic importance. H. contortus has developed diverse characters over the years leading to limited success in the production of vaccines. Indiscriminate use of the anthelmintics has produced drug resistance against almost all conventional products. Efficacy of medicinal plants and non-conventional chemicals has been reported under controlled experiments; however, research on their adverse effects on growth and fertility is yet to be studied. Research on molecular tools for identification and introduction of resistant genes into the flock is also underway but still a long journey to find its field application. Crossbreeding may compromise the production traits of the existing flock. In given circumstances, a targeted selective treatment approach along with selective breeding, culling of more susceptible animals, and maintaining a good body condition score through the provision of a balanced diet remains a workable strategy to control haemonchosis in sheep.

Coexistence between antibiotic resistance genes and metal resistance genes in manure-fertilized soils

Antibiotics and metals introduced during manure application are believed to be the major drivers of the bloom and spread of antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) in agricultural environments. However, the coexistence of multidrug resistance (MDR) and metal resistance and the effects of manure application on the coexistence are less studied. Here, we profiled the coexistence patterns of 9919 MDR genes (MDRGs) and 25,312 MRGs in paddy fields with manure or inorganic fertilization. The abundances of both MDRGs and MRGs were higher under manure fertilization than inorganic fertilization. Network analysis determined that coexistence between MDRGs and MRGs was much more frequent in manure-fertilized soils than in inorganic-fertilized soils. Manure application drove this coexistence by not only directly introducing resistance genes but also increasing co-selection through antibiotics and metals, and stimulating their potential common hosts, including species of Actinobacterium WWH12, Bacillus, Geobacter, Solirubrobacter, Acidobacteriales, Bacillales, Chloroflexi, Methyloligellaceae and Xanthobacteraceae. Soil antibiotic resistance was significantly predicted by the coexistence of major multidrug efflux genes (mfs, mex, abc, mate and smr) and MRGs. The coexistence between MDRGs and MRGs explained 18% of the increase in soil antibiotic resistance. Such coexistence is nonnegligible and permits the promotion of soil antibiotic resistance, thus posing a potential threat to both agroecosystems and humans.

Selective concentrations for trimethoprim resistance in aquatic environments

Antibiotic resistance presents a serious and still growing threat to human health. Environmental exposure levels required to select for resistance are unknown for most antibiotics. Here, we evaluated different experimental approaches and ways to interpret effect measures, in order to identify what concentration of trimethoprim that are likely to select for resistance in aquatic environments. When grown in complex biofilms, selection for resistant E. coli increased at 100 µg/L, whereas there was only a non-significant trend with regards to changes in taxonomic composition within the tested range (0–100 µg/L). Planktonic co-culturing of 149 different E. coli strains isolated from sewage again confirmed selection at 100 µg/L. Finally, pairwise competition experiments were performed with engineered E. coli strains carrying different trimethoprim resistance genes (dfr) and their sensitive counterparts. While strains with introduced resistance genes grew slower than the sensitive ones at 0 and 10 µg/L, a significant reduction in cost was found already at 10 µg/L. Defining lowest effect concentrations by comparing proportion of resistant strains to sensitive ones at the same time point, rather than to their initial ratios, will reflect the advantage a resistance factor can bring, while ignoring exposure-independent fitness costs. As costs are likely to be highly dependent on the specific environmental and genetic contexts, the former approach might be more suitable as a basis for defining exposure limits with the intention to prevent selection for resistance. Based on the present and other studies, we propose that 1 µg/L would be a reasonably protective exposure limit for trimethoprim in aquatic environments.

Engineering bacteriocin-mediated resistance against the plant pathogen Pseudomonas syringae.

SummaryThe plant pathogen, Pseudomonas syringae (Ps), together with related Ps species, infects and attacks a wide range of agronomically important crops, including tomato, kiwifruit, pepper, olive and soybean, causing economic losses. Currently, chemicals and introduced resistance genes are used to protect plants against these pathogens but have limited success and may have adverse environmental impacts. Consequently, there is a pressing need to develop alternative strategies to combat bacterial disease in crops. One such strategy involves using narrow‐spectrum protein antibiotics (so‐called bacteriocins), which diverse bacteria use to compete against closely related species. Here, we demonstrate that one bacteriocin, putidacin L1 (PL1), can be expressed in an active form at high levels in Arabidopsis and in Nicotiana benthamiana in planta to provide effective resistance against diverse pathovars of Ps. Furthermore, we find that Ps strains that mutate to acquire tolerance to PL1 lose their O‐antigen, exhibit reduced motility and still cannot induce disease symptoms in PL1‐transgenic Arabidopsis. Our results provide proof‐of‐principle that the transgene‐mediated expression of a bacteriocin in planta can provide effective disease resistance to bacterial pathogens. Thus, the expression of bacteriocins in crops might offer an effective strategy for managing bacterial disease, in the same way that the genetic modification of crops to express insecticidal proteins has proven to be an extremely successful strategy for pest management. Crucially, nearly all genera of bacteria, including many plant pathogenic species, produce bacteriocins, providing an extensive source of these antimicrobial agents.

Pyramiding of 3-resistant-gene to improve rice blast resistance of a restorer line, Fuhui 673

To improve the blast resistance of elite rice restorer line Fuhui 673, 3 blast resistance genes Pi-1, Pi-9 and Pi-kh were introduced into Fuhui 673 from a good-quality restorer line Jinhui 1059 through 3 successive backcrosses followed by one selfing using the technique of marker-assisted selection. Ten near-isogenic lines (NILs) of Fuhui 673 carrying the 3 introduced resistance genes were created. Genotype analysis using 68 SSR markers evenly distributed in the genome indicated that 92.96%-98.59% of the NILs' genetic background had been recovered to Fuhui 673. Both indoor and field resistance tests indicated that the NILs and their hybrids with sterile line Yixiang A were all resistant to rice blast, with resistance levels significantly higher than those of controls Fuhui 673 and hybrid Yiyou 673 (Yixiang A  Fuhui 673). In addition, among the 10 hybrids between the NILs and Yixiang A, 2 showed significantly higher yield than and 4 displayed similar yield to that of control Yiyou 673, suggesting that most of the NILs retained the elite characteristics of Fuhui 673. Two new hybrid rice cultivars Liangyou 7283 and Jintaiyou 683 from NIL Line 9 showed high yield, good resistance to blast and moderate growth period in regional trial, suggesting that the NIL Line 9 has a good prospect for application.

Supplanting resistance of the Mi gene by root-knot nematode in industrial tomato in the Cerrado in Goiás State of Brazil

ABSTRACT: Problems with root-knot nematodes, caused by genus Meloidogyne, can be controlled through the introduction of resistance genes in commercial varieties of tomatoes. However, plants of the hybrid ‘Heinz 9992’ for industrial processing, carrying the Mi gene, were reported with their roots severely infected in experimental cultivation in Goiás State of Brazil with symptoms typical of galls caused by Meloidogyne spp. After dissecting the galls present in the root samples, the females of the nematodes were removed and afterwards, performed the analysis of the perineal pattern and the biochemical characterization by electrophoresis of isoenzymes, besides the pathogenicity test. The pathogen analyzed was identified as Meloidogyne incognita. The pathogenicity test confirmed the supplanting resistance of the tomato hybrid with the Mi gene by this virulent population of M. incognita.

Improving blast resistance of the rice restorer line, Hui 316, by introducing Pi9 or Pi2 with marker-assisted selection

Introducing resistance (R) genes into a susceptible rice cultivar is an effective strategy to achieve broad-spectrum and durable disease resistance. During the breeding process, marker-assisted selection (MAS) provides an efficient approach for direct screening of the progeny containing the R gene in a population. In this study, we designed an optimized polymerase chain reaction marker, Pi9/2, targeting the same polymorphic region of our previously developed Pi9-Pro and demonstrated that Pi9/2 is more specific than Pi9-Pro for the blast resistance genes Pi9 and Pi2 in MAS. With the assistance of Pi9/2, Pi9 and Pi2, from donor lines 75-1-127 and C101A51, respectively, were separately introgressed into the strong rice restorer line, Hui 316, by backcrossing. The two improved representative Hui 316 lines, Hui 316-Pi9 and Hui 316-Pi2, displayed similar agronomic traits to Hui 316. Inoculation tests for blast resistance revealed that Hui 316-Pi9 and Hui 316-Pi2 showed markedly enhanced resistance to blast fungi compared with Hui 316. Investigation of agronomic traits for yield and rice quality indicated that the hybrid combinations from Hui 316-Pi9 or Hui 316-Pi2 crossed with male sterility lines were similar to those derived from Hui 316. Therefore, introgression of Pi9 or Pi2 into with Hui 316 could improve its resistance to blast with little influence on its restoring ability, which will facilitate the application of Hui 316 in rice production. These results also indicate that the optimized marker, Pi9/2, is effective in introducing Pi9 or Pi2 by MAS to improve blast resistance of rice cultivars.

ГЕНЕТИЧЕСКИЕ РЕСУРСЫ В СЕЛЕКЦИИ ПШЕНИЦЫ НА УСТОЙЧИВОСТЬ К ТВЕРДОЙ ГОЛОВНЕ

Common bunt (Tilletia caries (D.C.) Tul. & C. Tul. (syn. Tilletia tritici (Bjerk.) G. Winter) and T. laevis J.G. Kuhn (syn. T. foetida (Wallr.) Liro) is one of the most devastating diseases of wheat in many wheat-producing countries. Contamination of wheat with common bunt spores leads to significant (up to 40%) yield losses. Most varieties currently cultivated are susceptible to one or more common bunt races. The search for new sources of sustainability is needed. Most sources of bunt resistance have poor agronomic indicators. The challenge is to introduce resistance genes, while simultaneously eliminating bad agronomic traits. The purpose of research was the screening of bread wheat genetic resources of Kazakhstan and world breeding for resistance to common bunt and productivity in conditions of the foothill zone of Zailiysky Alatau (48° N, 77° E and 740 m above sea level). The assessment of resistance to common bunt of a wide range of bread wheat materials of local (79 varieties) and 70 accessions world breeding (СИММИТ - CBUNT-RN 2015-2016) in the foothill zone of the Zailiysky Alatau shows an ambiguous level of resistance depending on the climatic conditions of the year of research. To adapt to the needs of organic farming, CB-resistant breeding lines and registered varieties must be assessment by using spores with a certain virulence.