Qualitative Resistance Research Articles

QTL mapping and characterization of black spot disease resistance using two multi-parental diploid rose populations.

Black spot disease (BSD) (Diplocarpon rosae) is the most common and damaging fungal disease in garden roses (Rosa sp.). Although qualitative resistance to BSD has been extensively investigated, the research on quantitative resistance lags behind. The goal of this research was to study the genetic basis of BSD resistance in two multi-parental populations (TX2WOB and TX2WSE) through a pedigree-based analysis approach (PBA). Both populations were genotyped and evaluated for BSD incidence over five years in three locations in Texas. A total of 28 QTLs, distributed over all linkage groups (LGs), were detected across both populations. Consistent minor effect QTLs included two on LG1 and LG3 (TX2WOB and TX2WSE), two on LG4 and LG5 (TX2WSE), and one QTL on LG7 (TX2WOB). In addition, one major QTL detected in both populations was consistently mapped on LG3. This QTL was localized to an interval ranging from 18.9 to 27.8 Mbp on the Rosa chinensis genome and explained 20 and 33% of the phenotypic variation. Furthermore, haplotype analysis showed that this QTL had three distinct functional alleles. The parent PP-J14-3 was the common source of the LG3 BSD resistance in both populations. Taken together, this research presents the characterization of new SNP-tagged genetic determinants of BSD resistance, the discovery of marker-trait associations to enable parental choice based on their BSD resistance QTL haplotypes, and substrates for the development of trait-predictive DNA tests for routine use in marker-assisted breeding for BSD resistance.

Distribution, Etiology, Molecular Genetics and Management Perspectives of Northern Corn Leaf Blight of Maize (Zea mays L.)

Maize is cultivated extensively throughout the world and has the highest production among cereals. However, Northern corn leaf blight (NCLB) disease caused by <i>Exherohilum turcicum</i>, is the most devastating limiting factor of maize production. The disease causes immense losses to corn yield if it develops prior or during the tasseling and silking stages of crop development. It has a worldwide distribution and its development is favoured by cool to moderate temperatures with high relative humidity. The prevalence of the disease has increased in recent years and new races of the pathogen have been reported worldwide. The fungus <i>E. turcicum</i> is highly variable in nature. Though different management strategies have proved effective to reduce economic losses from NCLB, the development of varieties with resistance to <i>E. turcicum</i> is the most efficient and inexpensive way for disease management. Qualitative resistance for NCLB governed by Ht genes is a race-specific resistance which leads to a higher level of resistance. However, some Ht genes can easily become ineffective under the high pressure of virulent strains of the pathogen. Hence, it is imperative to understand and examine the consistency of the genomic locations of quantitative trait loci for resistance to NCLB in diverse maize populations. The breeding approaches for pyramiding resistant genes against <i>E. turcicum</i> in maize can impart NCLB resistance under high disease pressure environments. Furthermore, the genome editing approaches like CRISPR-cas9 and RNAi can also prove vital for developing NCLB resistant maize cultivars. As such this review delivers emphasis on the importance and current status of the disease, racial spectrum of the pathogen, genetic nature and breeding approaches for resistance and management strategies of the disease in a sustainable manner.

Resistance of the Wheat Cultivar 'Renan' to Septoria Leaf Blotch Explained by a Combination of Strain Specific and Strain Non-Specific QTL Mapped on an Ultra-Dense Genetic Map.

Quantitative resistance is considered more durable than qualitative resistance as it does not involve major resistance genes that can be easily overcome by pathogen populations, but rather a combination of genes with a lower individual effect. This durability means that quantitative resistance could be an interesting tool for breeding crops that would not systematically require phytosanitary products. Quantitative resistance has yet to reveal all of its intricacies. Here, we delve into the case of the wheat/Septoria tritici blotch (STB) pathosystem. Using a population resulting from a cross between French cultivar Renan, generally resistant to STB, and Chinese Spring, a cultivar susceptible to the disease, we built an ultra-dense genetic map that carries 148,820 single nucleotide polymorphism (SNP) markers. Phenotyping the interaction was done with two different Zymoseptoria tritici strains with contrasted pathogenicities on Renan. A linkage analysis led to the detection of three quantitative trait loci (QTL) related to resistance in Renan. These QTL, on chromosomes 7B, 1D, and 5D, present with an interesting diversity as that on 7B was detected with both fungal strains, while those on 1D and 5D were strain-specific. The resistance on 7B was located in the region of Stb8 and the resistance on 1D colocalized with Stb19. However, the resistance on 5D was new, so further designated Stb20q. Several wall-associated kinases (WAK), nucleotide-binding and leucine-rich repeats (NB-LRR) type, and kinase domain carrying genes were present in the QTL regions, and some of them were expressed during the infection. These results advocate for a role of Stb genes in quantitative resistance and for resistance in the wheat/STB pathosystem being as a whole quantitative and polygenic.

Winter wheat septoria blotch (&lt;i&gt;Zymoseptoria tritici&lt;/i&gt;) (literature review)

In the Southern Federal District, winter wheat is a main food crop. One of the most important factors that can destabilize gross grain yields and reduce grain crop productivity are parasitic organisms. One of the most common wheat diseases is septoria blotch (Zymoseptoria tritici). The purpose of the current study was to analyze the biological cycle of distribution, harmfulness, measures to combat septoria blotch on winter wheat. The paper has considered the importance of winter wheat septoria disease in various countries and in Russia. There was noted a leading position in distribution and harmfulness of the disease, and according to the results of study conducted by Russian and foreign researchers, it was found that this pathogen was inferior in importance only to wheat rust. There were presented three types of septoria blotch pathogens and there was established a dominant type in the Southern Federal District. Yield losses caused by septoria blotch can reach upto 30-40%, and the optimal temperature for its development and spread is from 5 to 20°C, with frequent precipitation. There have been given the technological methods under which the crop damage by pathogens increased. There have been presented the measures to combat septoria blotch and there has been described the most effective, economical and environmentally friendly method, namely the development of resistant varieties and their introduction into production. There has been considered qualitative and quantitative resistance of varieties. Currently there have been identified 21 major septoria blotch resistance genes. There has been considered longevity of stb-genes and the reasons for its loss. It has been established that the development of winter wheat varieties resistant to septoria blotch is a priority issue of breeding, since this control measure reduces yield losses and potential reserve of the pathogen in the agrocenosis.

Biology and molecular interactions of Parastagonospora nodorum blotch of wheat.

Parastagonospora nodorum is one of the important necrotrophic pathogens of wheat which causes severe economical loss to crop yield. So far, a number of effectors of Parastagonospora nodorum origin and their target interacting genes on the host plant have been characterized. Since targeting effector-sensitive gene carefully can be helpful in breeding for resistance. Therefore, constant efforts are required to further characterize the effectors, their interacting genes, and underlying biochemical pathways. Furthermore, to develop effective counter-strategies against emerging diseases, continuous efforts are required to determine the qualitative resistance that demands to screen of diverse genotypes for host resistance. Stagonospora nodorum blotch also refers to as Stagonospora glume blotch and leaf is caused by Parastagonospora nodorum. The pathogen deploys necrotrophic effectors for the establishment and development on wheat plants. The necrotrophic effectors and their interaction with host receptors lead to the establishment of infection on leaves and extensive lesions formation which either results in host cell death or suppression/activation of host defence mechanisms. The wheat Stagonospora nodorum interaction involves a set of nine host gene-necrotrophic effector interactions. Out of these, Snn1-SnTox1, Tsn1-SnToxA and Snn-SnTox3 are one of the most studied interaction, due to its role in the suppression of reactive oxygen species production, regulating the cytokinin content through ethylene-dependent wayduring initial infection stage. Further, although the molecular basis is not fully unveiled, these effectors regulate the redox state and influence the ethylene biosynthesis in infected wheat plants. Here, we have discussed the biology of the wheat pathogen Parastagonospora nodorum, role of its necrotrophic effectors and their interacting sensitivity genes on the redox state, how they hijack the resistance mechanisms, hormonal regulated immunity and other signalling pathways in susceptible wheat plants. The information generated from effectors and their corresponding sensitivity genes and other biological processes could be utilized effectively for disease management strategies.

A point mutation and large deletion at the candidate avirulence locus AvrMlp7 in the poplar rust fungus correlate with poplar RMlp7 resistance breakdown.

The deployment of plant varieties carrying resistance genes (R) exerts strong selection pressure on pathogen populations. Rapidly evolving avirulence genes (Avr) allow pathogens to escape R-mediated plant immunity through a variety of mechanisms, leading to virulence. The poplar rust fungus Melampsora larici-populina is a damaging pathogen of poplars in Europe. It underwent a major adaptive event in 1994, with the breakdown of the poplar RMlp7 resistance gene. Population genomics studies identified a locus in the genome of M. larici-populina that probably corresponds to the candidate avirulence gene AvrMlp7. Here, to further characterize this effector, we used a population genetics approach on a comprehensive set of 281 individuals recovered throughout a 28-year period encompassing the resistance breakdown event. Using two dedicated molecular tools, genotyping at the candidate locus highlighted two different alterations of a predominant allele found mainly before the resistance breakdown: a nonsynonymous mutation and a complete deletion of this locus. This results in six diploid genotypes: three genotypes related to the avirulent phenotype and three related to the virulent phenotype. The temporal survey of the candidate locus revealed that both alterations were found in association during the resistance breakdown event. They pre-existed before the breakdown in a heterozygous state with the predominant allele cited above. Altogether, these results suggest that the association of both alterations at the candidate locus AvrMlp7 drove the poplar rust adaptation to RMlp7-mediated immunity. This study demonstrates for the first time a case of adaptation from standing genetic variation in rust fungi during a qualitative resistance breakdown.

Идентичность генов устойчивости к расе G заразихи у линий подсолнечника разного происхождения

Broomrape is an obligate parasite and one of the most significant biotic factors reducing sunflower yield. The main means of controlling broomrape is breeding for sunflower resistance to it. New strategies are required to develop parasite resistant breeding germplasm, such as a stacking of key genes or a combination of qualitative and quantitative resistance mechanisms. In this regard, it is necessary to keep searching for new sources of resistance and to combine existing genes in case they are not identical. Thus, it is necessary to determine whether the genes of resistance to race G of broomrape are identical in the sunflower lines bred at the V.S. Pustovoit All-Russian Research Institute of Oil Crops. The research material was the previously developed sunflower lines RG, RGP1, RGP2, RGВ, RGL1, RGL2, and RGM – donors of resistance to race G of broomrape. The F1 hybrids from pair crossbreeding of these lines were obtained in a greenhouse. The F2 hybrids were obtained in the field by self-pollination of F1 hybrid plants. Plants were tested in a greenhouse for resistance and susceptibility to broomrape using the method of early diagnosis. Mathematical processing was performed by using the χ 2 -test. 13 combinations of crossbreeding were received to complete the test for allelism. In each F1 combination 11–33 plants were evaluated for resistance to race G of broomrape. Among the tested combinations, there was no one resistant to broomrape. Despite the differences in the number of affected plants, the affection degree was small in all hybrid combinations – from 1.0 to 1.8. All F2 hybrid combinations were also affected by broomrape. For eight combinations of F2, two phenotypic classes were found. There was no segregation in three combinations. The number of plants of two combinations was too small to perform χ 2 -test. In general, the χ 2 values were higher than the acceptable ones with a probability of 0.05, which indicates that the genes of resistance to race G of broomrape in these lines are identical.

Dissection of Quantitative Blackleg Resistance Reveals Novel Variants of Resistance Gene Rlm9 in Elite Brassica napus.

Blackleg is one of the major fungal diseases in oilseed rape/canola worldwide. Most commercial cultivars carry R gene-mediated qualitative resistances that confer a high level of race-specific protection against Leptosphaeria maculans, the causal fungus of blackleg disease. However, monogenic resistances of this kind can potentially be rapidly overcome by mutations in the pathogen’s avirulence genes. To counteract pathogen adaptation in this evolutionary arms race, there is a tremendous demand for quantitative background resistance to enhance durability and efficacy of blackleg resistance in oilseed rape. In this study, we characterized genomic regions contributing to quantitative L. maculans resistance by genome-wide association studies in a multiparental mapping population derived from six parental elite varieties exhibiting quantitative resistance, which were all crossed to one common susceptible parental elite variety. Resistance was screened using a fungal isolate with no corresponding avirulence (AvrLm) to major R genes present in the parents of the mapping population. Genome-wide association studies revealed eight significantly associated quantitative trait loci (QTL) on chromosomes A07 and A09, with small effects explaining 3–6% of the phenotypic variance. Unexpectedly, the qualitative blackleg resistance gene Rlm9 was found to be located within a resistance-associated haploblock on chromosome A07. Furthermore, long-range sequence data spanning this haploblock revealed high levels of single-nucleotide and structural variants within the Rlm9 coding sequence among the parents of the mapping population. The results suggest that novel variants of Rlm9 could play a previously unknown role in expression of quantitative disease resistance in oilseed rape.

Cross-continental experimental infections reveal distinct defence mechanisms in populations of the three-spined stickleback Gasterosteus aculeatus.

Epidemiological traits of host–parasite associations depend on the effects of the host, the parasite and their interaction. Parasites evolve mechanisms to infect and exploit their hosts, whereas hosts evolve mechanisms to prevent infection and limit detrimental effects. The reasons why and how these traits differ across populations still remain unclear. Using experimental cross-infection of three-spined stickleback Gasterosteus aculeatus and their species-specific cestode parasites Schistocephalus solidus from Alaskan and European populations, we disentangled host, parasite and interaction effects on epidemiological traits at different geographical scales. We hypothesized that host and parasite main effects would dominate both within and across continents, although interaction effects would show geographical variation of natural selection within and across continents. We found that mechanisms preventing infection (qualitative resistance) occurred only in a combination of hosts and parasites from different continents, while mechanisms limiting parasite burden (quantitative resistance) and reducing detrimental effects of infection (tolerance) were host-population specific. We conclude that evolution favours distinct defence mechanisms on different geographical scales and that it is important to distinguish concepts of qualitative resistance, quantitative resistance and tolerance in studies of macroparasite infections.

Impairment of Tomato WAT1 Enhances Resistance to Vascular Wilt Fungi Despite Severe Growth Defects.

Verticillium dahliae is a particularly notorious vascular wilt pathogen of tomato and poses a reoccurring challenge to crop protection as limited qualitative resistance is available. Therefore, alternative approaches for crop protection are pursued. One such strategy is the impairment of disease susceptibility (S) genes, which are plant genes targeted by pathogens to promote disease development. In Arabidopsis and cotton, the Walls Are Thin 1 (WAT1) gene has shown to be a S gene for V. dahliae. In this study, we identified the tomato WAT1 homolog Solyc04g080940 (SlWAT1). Transient and stable silencing of SlWAT1, based on virus-induced gene silencing (VIGS) and RNAi, respectively, did not consistently lead to reduced V. dahliae susceptibility in tomato. However, CRISPR-Cas9 tomato mutant lines carrying targeted deletions in SlWAT1 showed significantly enhanced resistance to V. dahliae, and furthermore also to Verticillium albo-atrum and Fusarium oxysporum f. sp. lycopersici (Fol). Thus, disabling the tomato WAT1 gene resulted in broad-spectrum resistance to various vascular pathogens in tomato. Unfortunately these tomato CRISPR mutant lines suffered from severe growth defects. In order to overcome the pleiotropic effect caused by the impairment of the tomato WAT1 gene, future efforts should be devoted to identifying tomato SlWAT1 mutant alleles that do not negatively impact tomato growth and development.

Qualitative and Quantitative Resistance against Early Blight Introgressed in Potato.

Simple SummaryEarly blight is a disease of potato caused by the Alternaria fungus (notably A. solani). Fungicides that are commonly used to protect potato against the disease are losing their effectiveness and an alternative control method is desired. In this research, we identified several relatives of potato from Central and South America that have a high natural resistance against early blight. Although these plants belong to other species, it was possible to cross them with cultivated potato. The resistance was inherited in offspring plants, but, interestingly, the different species seem to contain distinct types of resistance. More detailed studies will help increase our knowledge of the mechanism(s) that cause resistance. Highly resistant offspring plants can be used to develop new potato varieties with a natural resistance to early blight. Early blight is a disease of potato that is caused by Alternaria species, notably A. solani. The disease is usually controlled with fungicides. However, A. solani is developing resistance against fungicides, and potato cultivars with genetic resistance to early blight are currently not available. Here, we identify two wild potato species, which are both crossable with cultivated potato (Solanum tuberosum), that show promising resistance against early blight disease. The cross between resistant S. berthaultii and a susceptible diploid S. tuberosum gave rise to a population in which resistance was inherited quantitatively. S. commersonii subsp. malmeanum was also crossed with diploid S. tuberosum, despite a differing endosperm balance number. This cross resulted in triploid progeny in which resistance was inherited dominantly. This is somewhat surprising, as resistance against necrotrophic plant pathogens is usually a quantitative trait or inherited recessively according to the inverse-gene-for-gene model. Hybrids with high levels of resistance to early blight are present among progeny from S. berthaultii as well as S. commersonii subsp. malmeanum, which is an important step towards the development of a cultivar with natural resistance to early blight.

Multiple Sources of Introduction of North American Arabidopsis thaliana from across Eurasia.

Large-scale movement of organisms across their habitable range, or migration, is an important evolutionary process that can shape genetic diversity and influence the adaptive spread of alleles. Although human migrations have been studied in great detail with modern and ancient genomes, recent anthropogenic influence on reducing the biogeographical constraints on the migration of nonnative species has presented opportunities in several study systems to ask the questions about how repeated introductions shape genetic diversity in the introduced range. We present an extensive overview of population structure of North American Arabidopsis thaliana by studying a set of 500 whole-genome sequenced and over 2,800 RAD-seq genotyped individuals in the context of global diversity represented by Afro-Eurasian genomes. We use methods based on haplotype and rare-allele sharing as well as phylogenetic modeling to identify likely sources of introductions of extant N. American A. thaliana from the native range in Africa and Eurasia. We find evidence of admixture among the introduced lineages having increased haplotype diversity and reduced mutational load. We also detect signals of selection in immune-system-related genes that may impart qualitative disease resistance to pathogens of bacterial and oomycete origin. We conclude that multiple introductions to a nonnative range can rapidly enhance the adaptive potential of a colonizing species by increasing haplotypic diversity through admixture. Our results lay the foundation for further investigations into the functional significance of admixture.

Discovery of the REN11 Locus From Vitis aestivalis for Stable Resistance to Grapevine Powdery Mildew in a Family Segregating for Several Unstable and Tissue-Specific Quantitative Resistance Loci.

Race-specific resistance loci, whether having qualitative or quantitative effects, present plant-breeding challenges for phenotypic selection and deciding which loci to select or stack with other resistance loci for improved durability. Previously, resistance to grapevine powdery mildew (GPM, caused by Erysiphe necator) was predicted to be conferred by at least three race-specific loci in the mapping family B37-28 × C56-11 segregating for GPM resistance from Vitis aestivalis. In this study, 9 years of vineyard GPM disease severity ratings plus a greenhouse and laboratory assays were genetically mapped, using a rhAmpSeq core genome marker platform with 2,000 local haplotype markers. A new qualitative resistance locus, named REN11, on the chromosome (Chr) 15 was found to be effective in nearly all (11 of 12) vineyard environments on leaves, rachis, berries, and most of the time (7 of 12) stems. REN11 was independently validated in a pseudo-testcross with the grandparent source of resistance, “Tamiami.” Five other loci significantly predicted GPM severity on leaves in only one or two environments, which could indicate race-specific resistance or their roles in different timepoints in epidemic progress. Loci on Chr 8 and 9 reproducibly predicted disease severity on stems but not on other tissues and had additive effects with REN11 on the stems. The rhAmpSeq local haplotype sequences published in this study for REN11 and Chr 8 and 9 stem quantitative trait locus (QTL) can be used directly for marker-assisted selection or converted to SNP assays. In screening for REN11 in a diversity panel of 20,651 vines representing the diversity of Vitis, this rhAmpSeq haplotype had a false positive rate of 0.034% or less. The effects of the other foliar resistance loci detected in this study seem too unstable for genetic improvement regardless of quantitative effect size, whether due to race specificity or other environmental variables.

Fertilization integrated with microbial inoculants improves bell pepper production

ABSTRACT Increased use of fertilizers under intensive agriculture has the possibility of environmental contamination. The use of microbial inoculants may be effective in sustaining crop productivity, soil health, and supplementing chemical fertilizers. The investigation evaluated responses of arbuscular mycorrhizal (AM) fungi, Glomus mosseae (G) and Acaulospora laevis (A) and the bacterium Pseudomonas fluorescens (Pf) on bell pepper (Capsicum annuum L.) when provided superphosphate at F1 = 60 kg ha−1 (0.45 g/pot), F2 = 120 kg ha−1 (0.90 g/pot), or F3 = 240 kg ha−1 (1.80 g/pot). Plant growth, nutrient content, and yield 120 days after transplanting (DAT) were determined. Plants responded best to F1 followed by F2, while F3 produced inhibitory effects. The highest AM colonization and spore numbers were with G + A+ Pf, resulting in an increase in chlorophyll content, root phosphatase activity, shoot fresh weight, early fruit formation, number of fruit/plant, fruit size, weight, and early ripening. Inoculation with G. mosseae alone increased leaf area, photosynthesis, plant height, root freshness and dry weight. The G+ Pf commonly produced highest shoot fresh weight and fruit nutrient content. The effectiveness of these inoculants on bell pepper growth and yield was highest; 60 and 120 kg ha−1 P-fertilizer level when amended with G + A+ Pf. Use of AM or micro-inoculants may reduce fertilizer input and enhance nutrient utilization efficiency, which positively affected qualitative characteristics, nutrient uptake, and resistance to suboptimal conditions, but has few or little effect on quantitative characteristics. More work is needed to determine optimum rates of the materials tested to produce marketable size fruit.

Network organization of the plant immune system: from pathogen perception to robust defense induction.

The plant immune system has been explored essentially through the study of qualitative resistance, a simple form of immunity, and from a reductionist point of view. The recent identification of genes conferring quantitative disease resistance revealed a large array of functions, suggesting more complex mechanisms. In addition, thanks to the advent of high-throughput analyses and system approaches, our view of the immune system has become more integrative, revealing that plant immunity should rather be seen as a distributed and highly connected molecular network including diverse functions to optimize expression of plant defenses to pathogens. Here, we review the recent progress made to understand the network complexity of regulatory pathways leading to plant immunity, from pathogen perception, through signaling pathways and finally to immune responses. We also analyze the topological organization of these networks and their emergent properties, crucial to predict novel immune functions and test them experimentally. Finally, we report how these networks might be regulated by environmental clues. Although system approaches remain extremely scarce in this area of research, a growing body of evidence indicates that the plant response to combined biotic and abiotic stresses cannot be inferred from responses to individual stresses. A view of possible research avenues in this nascent biology domain is finally proposed.

Review Article: Genetics and Breeding Overview for Coffee Wilt Disease Resistance

The presence of intra- and inter specific variability in the coffee species provide a potential source of resistance to Coffee Wilt Disease (CWD). Additionally, the existence of Robusta and Arabica wilt pathogenic forms enables to design effective breeding strategies to develop resistant cultivars towards each population. The inheritance of resistance to Fussarium xylarioides in Coffea canephora suggested that resistance is controlled by polygenic. Heritability is low to moderate with low genetic gains of choosing a progeny of resistant parents as source of planting materials; so that resistant clones should be propagated vegetatively. Alternatively, in Arabica CWD resistance has been suggested that presence of certain quantitative with qualitative resistance. Moreover, Arabica coffee was lacking or low heterosis for resistance, predominance of additive over non additive genetic effects and estimated of high heritability coupled with genetic advance as percent of mean (GAM) for resistance and incubation period; indicated that selection and hybridization are important to improve population and to obtain segregating generation, respectively. The resistant Arabica coffee genotypes were also significantly associated with extended incubation period, leaf area, stem diameter and minimum number of defoliated leaves than the susceptible genotypes. For further screening, promising resistant Arabica coffee genotypes were planted and also under evaluation for other major diseases, yield and quality traits at sick plot of Gera agricultural Research Sub Center, Ethiopia. Generally, CWD symptoms, source of resistance, host-pathogen interaction, resistance screening techniques, genotypes evaluation, inheritance of resistance, hybridization and resistant variety development approaches were comprehensively discussed. Keywords: Coffee Wilt Disease, Coffea Arabica , Coffea canephora , Resistance DOI: 10.7176/JEES/11-9-01 Publication date: September 30 th 2021

Avian blood parasite richness decreases with major histocompatibility complex class I loci number.

Major histocompatibility complex (MHC) genes are among the most polymorphic in the vertebrate genome. The high allele diversity is believed to be maintained primarily by sexual and pathogen-mediated balancing selection. The number of MHC loci also varies greatly across vertebrates, most notably across birds. MHC proteins play key roles in presenting antigens on the cell surface for recognition by T cells, with class I proteins specifically targeting intracellular pathogens. Here, we explore the hypothesis that MHC class I diversity (measured as loci number) coevolves with haemosporidian parasite burden of the host. Using data on 54 bird species, we demonstrate that high-MHC class I diversity is associated with significantly lower richness of Plasmodium, Haemoproteus as well as overall haemosporidian parasite lineages, the former thus indicating more efficient protection against intracellular pathogens. Nonetheless, the latter associations were only detected when MHC diversity was assessed using cloning and not 454 pyrosequencing-based studies, nor across all genotyping methods combined. Our results indicate that high-MHC class I diversity might play a key role in providing qualitative resistance against diverse haemosporidian parasites in birds, but further clarification is needed for the origin of contrasting results when using different genotyping methods for MHC loci quantification.

Genome-Wide Association Mapping and Gene Expression Analysis Reveal the Negative Role of OsMYB21 in Regulating Bacterial Blight Resistance in Rice

BackgroundBacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most devastating diseases in rice all over the world. Due to the diversity and rapid evolution of Xoo, identification and use of the non-race specific quantitative resistance QTLs has been considered the preferred strategy for effective control of this disease. Although numerous QTLs for BB resistance have been identified, they haven’t been effectively used for improvement of BB resistance in rice due to their small effects and lack of knowledge on the function of genes underlying the QTLs.ResultsIn the present study, a genome-wide association study of BB resistance was performed in a rice core collection from South China. A total of 17 QTLs were identified to be associated with BB resistance. Among them, 13 QTLs were newly identified in the present study and the other 4 QTLs were co-localized with the previously reported QTLs or Xa genes that confer qualitative resistance to Xoo strains. Particularly, the qBBR11–4 on chromosome 11 explained the largest phenotypic variation in this study and was co-localized with the previously identified QTLs for BB and bacterial leaf streak (BLS) resistance against diverse strains in three studies, suggesting its broad-spectrum resistance and potential value in rice breeding. Through combined analysis of differential expression and annotations of the predicted genes within qBBR11–4 between two sets of rice accessions selected based on haplotypes and disease phenotypes, we identified the transcription factor OsMYB21 as the candidate gene for qBBR11–4. The OsMYB21 overexpressing plants exhibited decreased resistance to bacterial blight, accompanied with down-regulation of several defense-related genes compared with the wild-type plants.ConclusionThe results suggest that OsMYB21 negatively regulates bacterial blight resistance in rice, and this gene can be a promising target in rice breeding by using the gene editing method. In addition, the potential candidate genes for the 13 novel QTLs for BB resistance were also analyzed in this study, providing a new source for cloning of genes associated with BB resistance and molecular breeding in rice.

Quantitative resistance linked to late effectors.

Quantitative resistance linked to late effectors.

EFFICIENCY OF THE USE THE CROSSBREEDING OF UKRAINIAN BLACK-AND-WHITE DAIRY AND SWISS CATTLE IN THE STATE STUD FARM "PASICHNA"

Goal. To study the influence of intermediate crossing on the level of dairy productivity, qualitative milk indicators, exterior features and resistance of the body of pureorgain and local animals. Methods. Selection and genetic analysis, comparative, statistical. The results. Scientific and production studies were conducted on the basis of a tribal factory of the State Enterprise "Pasichnya" IKSGP NAAN "of the StarosinyaVsky district of the Khmelnytsky region in the chains of distinct animals of the Podilsky factory type of Ukrainian Black-and-White dairy (UCHRMP) and local animals derived from the crossing of the BPRMP cows with Bojabs of the Shvitsky breed. According to the results of experimental studies, it has been found that local cows-first-bristles are somewhat inferior to the purest animals of the Ukrainian Black-and-White dairy breed by the magnitude of the NADA (93.8 kg), but it is compensated by milk quality (fat +0.26%, protein +0.19%), where in the general yield of dairy fat (+9.5 kg) and protein (+6.4 kg), they are favorably different from its purgatory rior. The analysis of the results of the reproductive capacity of cows shows that local animals were first fruitfully inseminated at the age of 545 days and the duration of fertility was 283 days, at that time, purely meters were inserted at the age of 567 days, and the duration of the sharing was 281.5 days. Service-period in the cows-first-born of genotypes, respectively, amounted to 97 and 112 days. The obtained data for the morphological and functional properties of the cow-first-prints show that the assessed number of both groups meets the needs of target standards on technological features and have high indicators of the studied functional properties. Comparative analysis of exterior valuation indicators between the studied groups shows that local cows have higher rates over latitudinal gates, in particular, by breast width and width in the ice, at that time inferior to the children's rior in the rectors of height in the racing, in the area of the torso. and hammer. In the study of natural resistance in the studied cows it has been established that the estimated animal groups are characterized by a sufficiently high level of protective functions of the body and adaptation capacity to technological conditions, which creates good opportunities for further effective selection. The general assessment of the natural resistance of cows-firstbody by morphological and biochemical parameters of blood, phagocytic, bactericidal and lysozymic activity showed that local cows according to Method VE Chumachenko and others. (1990) have a natural resistance to 3 points (61) higher than in their pure-breeding rior (58 points). Conclusions. Results of analysis of dairy performance of local cows-first-birthsters derived from the crossing of Ukrainian Black-and-White breeds with bulls of the Shvitskaya breed showed that the data of the animal though inferior to the christening rior of the Ukrainian Black-and-White dairy breed by the magnitude of the NADA but this difference is compensated by the quality of milk, where The total output of dairy fat and protein, they are favorably different from pureoral analogues. By indicators of reproducible ability, it has been found that local animals were first crazy at the age of 823 days that on 21 days earlier than puredom and 15 days they have a smaller service period. An analysis of the results of the estimation of morphological and physiological properties of the elder showed that there are no significant differences in the investigated groups of primary differences. All animals correspond to technological requirements. The exterior evaluation of the investigated groups of the firstborn showed that purely cows, having higher rates in the elevation in the roll, in the height in the ice and a contrary length of the trunk and the intensity, but inferior to the latitude gauge: the width of the breast, width in the machaches and width in the machaches and width in the machach. Animal estimation according to natural resistance indicators found that animals of both groups have a sufficiently high level of protective functions of the body and adaptation capacity to technological conditions that creates good opportunities for further effective selection.