Population size impacts host–pathogen coevolution

Ongoing host–pathogen interactions are characterized by rapid coevolutionary changes forcing species to continuously adapt to each other. The interacting species are often defined by finite population sizes. In theory, finite population size limits genetic diversity and compromises the efficiency of selection owing to genetic drift, in turn constraining any rapid coevolutionary responses. To date, however, experimental evidence for such constraints is scarce. The aim of our study was to assess to what extent population size influences the dynamics of host–pathogen coevolution. We used Caenorhabditus elegans and its pathogen Bacillus thuringiensis as a model for experimental coevolution in small and large host populations, as well as in host populations which were periodically forced through a bottleneck. By carefully controlling host population size for 23 host generations, we found that host adaptation was constrained in small populations and to a lesser extent in the bottlenecked populations. As a result, coevolution in large and small populations gave rise to different selection dynamics and produced different patterns of host–pathogen genotype-by-genotype interactions. Our results demonstrate a major influence of host population size on the ability of the antagonists to co-adapt to each other, thereby shaping the dynamics of antagonistic coevolution.

Molecular Characterization of Parental Lines and Validation of Snp Markers for Disease Resistance in Common Bean

The implementation of molecular tools that help the early selection of genotypes carrying target alleles increases efficiency and reduces the time and costs of breeding programs. The present study aimed the molecular characterization and validation of SNPs targeting disease resistance alleles for assisted selection. A total of 376 common bean lines with contrasting responses for anthracnose and angular leaf spot resistance were used, as well as 149 F2 plants from the cross between BRS Cometa x SEL 1308 (carrying the Anthracnose resistance gene Co-42). Seven of the ten SNP markers evaluated showed potential for assisted breeding: snpPV0025 (Phg-2), snpPV0027 (Phg-5), snpPV0079 (Phg-5), snpPV0046 (Co-u), snpPV0068 (Co-42), snpPV0070 (Co-42) and snpP8282v3-817 (Co-42). Markers snpPV0070 and snpP8282v3-817 showed high efficiency of selection (99.7 and 99.8%, respectively). These markers exhibit great potential to assist in the selection at different stages of the breeding program and may be readily incorporated into marker-assisted selection.

Variability of morphometric indicators of honey bees bred in Almaty region

One of the ways to intensify the production of beekeeping products is selection. Bee breeding is not only one of the most important methods, but also the most economically efficient way to increase the productivity of bee colonies. Thus, the selection of bees and the implementation of its achievements into production are one of the most important and most effective directions for intensifying beekeeping. Research work was carried out under the project of program-targeted financing of the Ministry of Education and Science of the Republic of Kazakhstan on the topic "Development of technologies for effective management of the selection process in beekeeping." This article examines the characteristics of the morphometric indicators of honeybees in the Almaty region of the Republic of Kazakhstan. The material for the research was the specimens of worker bees from apiaries located in the Almaty region of the Devochkin farm, Panov farm, Kalinin Individual Entrepreneur, Adilgazy Individual Entrepreneur, Kashkimbaev farm. To carry out the study according to the method of A.B. Kartashev, 35 samples of bees were worked out. Changes in the parameters of the wings, including the cubital and dumbbell index, discoidal displacement by bee species: Central Russian, Carpathian, Italian and Carniolian honey bee, are considered. It was found that in Kalinin’s apiary morphometric indicators for the cubital index, the average value was 2,787%. As a result, the morphometric indices for the cubital index in bees of the IP Kalinin bee were 2.777%. Whereas in other farms, the average value was significantly lower for all indicators. Accordingly, the percentage of the cubital index was 7.42-17.36%, the dumbbell index was 6.77-11.81%, and the discoidal displacement was 32.91-47.37%. According to all indicators, it is clear that the Kalinin Individual Entrepreneur’s bee farm is superior to other bee farms in terms of morphometric data. This is due to the isolation of the beekeeping and out of reach of other bees, thus ensuring a low level of hybridization. The considered analysis of the species belonging to the entire apiary, as well as economically useful features, can significantly increase the efficiency of selection work in beekeeping.

Core genes can have higher recombination rates than accessory genes within global microbial populations

Recombination is essential to microbial evolution, and is involved in the spread of antibiotic resistance, antigenic variation, and adaptation to the host niche. Yet quantifying the impact of homologous recombination on different gene classes, which is critical to understanding how selection acts on variation to shape species diversity and genome structure, remains challenging. This is largely due to the dynamic nature of bacterial genomes, whose high intraspecies genome content diversity and complex phylogenetic relationships present difficulties for inferring rates of recombination, particularly for rare genes. In this work, we apply a computationally efficient, non-phylogenetic approach to measure homologous recombination rates in the core and accessory genome (genes present in all strains and only a subset of strains, respectively) using >100,000 whole genome sequences from 12 microbial species. Our analysis suggests that even well-resolved sequence clusters sampled from global populations interact with overlapping gene pools, which has implications for the role of population structure in genome evolution. We show that in a majority of species, core genes have shorter coalescence times and higher recombination rates than accessory genes, and that gene frequency is often positively correlated with increased recombination. Our results provide a new line of population genomic evidence supporting the hypothesis that core genes are under strong, purifying selection, and indicate that homologous recombination may play a key role in increasing the efficiency of selection in those parts of the genome most conserved within each species.

A Validation System for Selection of Bacteriophages against Shiga Toxin-Producing Escherichia coli Contamination

Shiga toxin-producing Escherichia coli (STEC) can cause severe infections in humans, leading to serious diseases and dangerous complications, such as hemolytic-uremic syndrome. Although cattle are a major reservoir of STEC, the most commonly occurring source of human infections are food products (e.g., vegetables) contaminated with cow feces (often due to the use of natural fertilizers in agriculture). Since the use of antibiotics against STEC is controversial, other methods for protection of food against contaminations by these bacteria are required. Here, we propose a validation system for selection of bacteriophages against STEC contamination. As a model system, we have employed a STEC-specific bacteriophage vB_Eco4M-7 and the E. coli O157:H7 strain no. 86-24, bearing Shiga toxin-converting prophage ST2-8624 (Δstx2::cat gfp). When these bacteria were administered on the surface of sliced cucumber (as a model vegetable), significant decrease in number viable E. coli cells was observed after 6 h of incubation. No toxicity of vB_Eco4M-7 against mammalian cells (using the Balb/3T3 cell line as a model) was detected. A rapid decrease of optical density of STEC culture was demonstrated following addition of a vB_Eco4M-7 lysate. However, longer incubation of susceptible bacteria with this bacteriophage resulted in the appearance of phage-resistant cells which predominated in the culture after 24 h incubation. Interestingly, efficiency of selection of bacteria resistant to vB_Eco4M-7 was higher at higher multiplicity of infection (MOI); the highest efficiency was evident at MOI 10, while the lowest occurred at MOI 0.001. A similar phenomenon of selection of the phage-resistant bacteria was also observed in the experiment with the STEC-contaminated cucumber after 24 h incubation with phage lysate. On the other hand, bacteriophage vB_Eco4M-7 could efficiently develop in host bacterial cells, giving plaques at similar efficiency of plating at 37, 25 and 12 °C, indicating that it can destroy STEC cells at the range of temperatures commonly used for vegetable short-term storage. These results indicate that bacteriophage vB_Eco4M-7 may be considered for its use in food protection against STEC contamination; however, caution should be taken due to the phenomenon of the appearance of phage-resistant bacteria.

Crossover-active regions of the wheat genome are distinguished by DMC1, the chromosome axis, H3K27me3, and signatures of adaptation

The hexaploid bread wheat genome comprises over 16 gigabases of sequence across 21 chromosomes. Meiotic crossovers are highly polarized along the chromosomes, with elevation in the gene-dense distal regions and suppression in the Gypsy retrotransposon-dense centromere-proximal regions. We profiled the genomic landscapes of the meiotic recombinase DMC1 and the chromosome axis protein ASY1 in wheat and investigated their relationships with crossovers, chromatin state, and genetic diversity. DMC1 and ASY1 chromatin immunoprecipitation followed by sequencing (ChIP-seq) revealed strong co-enrichment in the distal, crossover-active regions of the wheat chromosomes. Distal ChIP-seq enrichment is consistent with spatiotemporally biased cytological immunolocalization of DMC1 and ASY1 close to the telomeres during meiotic prophase I. DMC1 and ASY1 ChIP-seq peaks show significant overlap with genes and transposable elements in the Mariner and Mutator superfamilies. However, DMC1 and ASY1 ChIP-seq peaks were detected along the length of each chromosome, including in low-crossover regions. At the fine scale, crossover elevation at DMC1 and ASY1 peaks and genes correlates with enrichment of the Polycomb histone modification H3K27me3. This indicates a role for facultative heterochromatin, coincident with high DMC1 and ASY1, in promoting crossovers in wheat and is reflected in distalized H3K27me3 enrichment observed via ChIP-seq and immunocytology. Genes with elevated crossover rates and high DMC1 and ASY1 ChIP-seq signals are overrepresented for defense-response and immunity annotations, have higher sequence polymorphism, and exhibit signatures of selection. Our findings are consistent with meiotic recombination promoting genetic diversity, shaping host–pathogen co-evolution, and accelerating adaptation by increasing the efficiency of selection.

Faster rates of molecular sequence evolution in reproduction-related genes and in species with hypodermic sperm morphologies

Sexual selection is expected to drive the evolution of many striking behaviours and morphologies, leaving signatures of selection at loci underlying these phenotypes. However, relatively few studies have contrasted molecular sequence evolution at such loci across lineages that differ in their sexual selection context. Our comparative genomics study of Macrostomum, a large genus of free-living simultaneously hermaphroditic flatworms, takes advantage of functional annotations from the model species, M. lignano, and transcriptome assemblies of 97 congeners. We compare molecular sequence evolution in species with contrasting sperm morphologies, which are strongly associated with multiple convergent shifts in the mating strategy and thus reflect the sexual selection context in Macrostomum. The sperm of most reciprocally mating species carry lateral bristles, likely functioning as anchoring mechanisms against post-copulatory sperm removal. Hypodermically mating species lack these bristles, potentially as adaptations to a different environment experienced by hypodermic sperm. We document faster molecular sequence evolution in reproduction-related, compared to ubiquitously-expressed, genes across all sperm morphologies, consistent with more intense selection acting on the former. Furthermore, we observed faster molecular sequence evolution in species with hypodermic sperm morphologies, in both reproduction-related and ubiquitously-expressed genes. These genome-wide patterns suggest that shifts to hypodermic mating reduce the efficiency of selection, possibly due to higher selfing rates in hypodermically mating species. Moreover, we find little evidence for convergent amino acid changes across species. We provide the first comprehensive comparative analysis of molecular sequence evolution in a group of simultaneously hermaphroditic animals, across well-replicated contrasts of lineages with divergent sperm morphologies.

Efficiency of selection–biotechnological system of selection for creation of breeding source material of sunflower resistant to herbicides and broomrape

The sunflower is a strategically important oil crop. Every year the area under this crop grows, and the rapid returning of sunflowers back to the fields provokes the formation of new more aggressive races of broomrape (Orobanche cumana Wallr.). Broomrape is a parasite that interferes with the normal development of sunflower and can lead to significant crop losses. For creating a sunflower hybrid (F1) it is needed to cross the parental components, which have a complex of important traits, among which there is a resistance to the herbicides and a broomrape. Considering that the creation of each of the components of the hybrid involves many years of painstaking work in the breeding process, modern approaches and methods are used to accelerate the creation of a new source material. Thus, using the technology of cultivating immature embryos in vitro culture, it is possible to reduce the time to create lines resistant to herbicides, for example. And during selection for resistance to pathogenic organisms, testing is most often used against an artificial infectious background, both in the field and in laboratory conditions, in order to differentiate the material on this basis. The aim of this work was to establish the effectiveness system when creating an initial breeding material resistant to herbicides and broomrape. As a result of testing the lines on an artificial infectious background, was identified plants which have high resistance to the G-race broomrape and were isolated from hybrid combinations resistant to tribenuron-methyl and imidazolinones. Thus, among the analyzed plants which are resistant to tribenuron‐methyl, four lines were isolated, which are highly resistant to the G-race broomrape from a hybrid combinations BH0118/SURES–2 (101/1, 101/4, 101/6, 101/7), and BH0318/SURES–2 (101/21, 101/24, 101/28, 101/30), and five lines (101/11, 101/12, 101/16, 101/17, 101/18) from a hybrid combination BH0218/SURES–2. Among imidazolinone-resistant sunflower lines – line 3 was isolated as highly resistant to the G-race broomrape.

Biological fundamentals of hardneck garlic productivity of different reproductions

Providing the population with food, agriculture with planting material, and raw materials for the processing and canning industries is an urgent problem of garlic production. Currently, not studied yet the passage and changes in the production processes of garlic plants under the influence of reproduction, which in some way constrains the industrial production of planting material and marketable products in general. Studies on the impact of reproductions on changes in physiological state, plant resistance to disease and productivity were conducted during 2017–2020 in the research field of the Department of Vegetable Growing, Uman National University of Horticulture. During the biometric measurements, a significant change in the variation of approbation traits (height of the plant and scape, number of leaves and its size, number and weight of bulbils, cloves in the bulb) of garlic plants under the influence of reproduction, ie variety testing must indicate what is this generation. There was a significant decrease in the concentration of chlorophyll and the antioxidant enzymes activity in the leaves in III–V reproductions, which significantly affected the productivity and tolerance of plants. Indicators of plant damage disease on a natural infectious background indicated a sharp decrease in the resistance of plants of the Sofiivskyi cultivar in IV–V reproductions, Prometei and Lyubasha cultivarss in III–V. It was found that in the cultivar Sofiivskyi the largest mass of the bulb was formed in the first reproduction, while in the cultivars Prometheus and Lyubasha – in the second, and its gradual decrease to 21.2 % in the fifth reproduction. Yield had a similar trend, where the maximum reduction in yield was observed at 18.2; 28.0 and 17.0 % in the cultivars Sofiivskyi, Prometei and Lyubasha. The developed scientifically substantiated provisions will allow to increase efficiency of selection process and production of seed material.

Analysis of selection for wrestling for the Olympic Games in Tokyo

Purpose: to analyze the qualification requirements for athletes to obtain Olympic licenses to participate in the XXXII Olympic Games in Tokyo in wrestling. Materials and methods of research. Research methods: theoretical analysis and generalization of literature data and the Internet, methods of mathematical statistics. The initial results of the performances are taken from the official website of the International Wrestling Federation (United World Wrestling) (https://uww.org/). MS Excel was used for statistical data processing and graphical presentation of results. Results: it is established that according to the requirements of the IOC in wrestling competitions at the Summer Olympics in Tokyo can participate no more than 288 athletes (16 wrestlers in 12 weight categories in men's competitions and 16 participants in six weight categories in women's competitions). For the right to participate in the Olympics in wrestling, a rather intense selection was carried out, which included several stages. It was found that none of the strongest «wrestling» countries in the world has obtained the maximum number of licenses (18) for the Olympics. Russia has obtained 17 licenses, the United States – 15, 12 – from Cuba and Japan, 11 – in Iran, Kazakhstan and China, 10 – in Tunisia and Ukraine. 10 or more participants will represent the 9 strongest «wrestling» states at the Olympics, which amounted to 37,85 % of all wrestlers. In total, the right to participate in the Olympics was won by representatives of 62 countries. Representatives of 14 countries obtained 52,43 % of licenses. 20 countries will be able to put only one athlete at the Olympics, despite the fact that they include countries that have a long wrestling tradition. However, small countries have also won tickets to the Olympics, which testifies to the popularization of the struggle and the expansion of its geography in the world. The largest number of tickets to the Olympics in Tokyo traditionally won the representatives of Europe – 122 licenses (42.36%), they lost to wrestlers from Asia – 84 licenses (29,17 %), much fewer licenses from the representatives of America – 44 (15,28 %), Africa and Oceania – 38 (13,19 %). Conclusions. Limiting the number of wrestlers participating in the Olympics forces wrestling experts to be in constant search of the optimal system of selection of athletes, and such selection should, firstly, ensure the participation in the Olympics of all the strongest wrestlers on the planet and, secondly, give equal rights to different countries and continents in competition for this participation. The postponement of the Summer Olympics in Tokyo to 2021 due to the coronavirus pandemic made adjustments to the qualification selection calendar and affected the results of the selection itself. All this together had a negative effect on the efficiency of selection, and a significant part of high-class wrestlers were not able to qualify for the Olympics. Keywords: selection system, Olympic license, wrestling, Olympic Games, stage, country, continent, qualifying tournament.