Indirect Effects Of Selection Research Articles

Effect of full‐sib and S2‐selection on a sweet corn population (Zea mays convar. saccharata)

AbstractSweet corn breeding goals differ from grain or silage corn. Sweet corn goals focus on marketable yield including several quality traits. This study explores the effect of a single cycle of full‐sib selection and S2 selection on improving the marketable yield of an open‐pollinated sweet corn population. The selected populations were subsequently compared in four environments for several plant‐, yield‐ and quality traits relative to the original population. Analysis of variance was used to detect selection progress and indirect effects of selection. Full‐sib and S2‐selection decreased total yield. Marketable yield was decreased more by S2‐selection than by full‐sib selection. Flowering time was changed by full‐sib selection, but not by S2‐selection. Full‐sib selection improved ear quality by increasing ear length, the diameter of the ear and the number of kernel rows. S2‐selection showed no effect or a negative effect on ear quality. The application of a single cycle of selection using either method seemed inadequate for increasing marketable yield. More cycles might be necessary to make significant improvements.

A quantitative genetic model of background selection in humans.

Across the human genome, there are large-scale fluctuations in genetic diversity caused by the indirect effects of selection. This "linked selection signal" reflects the impact of selection according to the physical placement of functional regions and recombination rates along chromosomes. Previous work has shown that purifying selection acting against the steady influx of new deleterious mutations at functional portions of the genome shapes patterns of genomic variation. To date, statistical efforts to estimate purifying selection parameters from linked selection models have relied on classic Background Selection theory, which is only applicable when new mutations are so deleterious that they cannot fix in the population. Here, we develop a statistical method based on a quantitative genetics view of linked selection, that models how polygenic additive fitness variance distributed along the genome increases the rate of stochastic allele frequency change. By jointly predicting the equilibrium fitness variance and substitution rate due to both strong and weakly deleterious mutations, we estimate the distribution of fitness effects (DFE) and mutation rate across three geographically distinct human samples. While our model can accommodate weaker selection, we find evidence of strong selection operating similarly across all human samples. Although our quantitative genetic model of linked selection fits better than previous models, substitution rates of the most constrained sites disagree with observed divergence levels. We find that a model incorporating selective interference better predicts observed divergence in conserved regions, but overall our results suggest uncertainty remains about the processes generating fitness variation in humans.

The role of recombination dynamics in shaping signatures of direct and indirect selection across the Ficedula flycatcher genome†.

Recombination is a central evolutionary process that reshuffles combinations of alleles along chromosomes, and consequently is expected to influence the efficacy of direct selection via Hill-Robertson interference. Additionally, the indirect effects of selection on neutral genetic diversity are expected to show a negative relationship with recombination rate, as background selection and genetic hitchhiking are stronger when recombination rate is low. However, owing to the limited availability of recombination rate estimates across divergent species, the impact of evolutionary changes in recombination rate on genomic signatures of selection remains largely unexplored. To address this question, we estimate recombination rate in two Ficedula flycatcher species, the taiga flycatcher (Ficedula albicilla) and collared flycatcher (Ficedula albicollis). We show that recombination rate is strongly correlated with signatures of indirect selection, and that evolutionary changes in recombination rate between species have observable impacts on this relationship. Conversely, signatures of direct selection on coding sequences show little to no relationship with recombination rate, even when restricted to genes where recombination rate is conserved between species. Thus, using measures of indirect and direct selection that bridge micro- and macro-evolutionary timescales, we demonstrate that the role of recombination rate and its dynamics varies for different signatures of selection.

Heritability and correlative variability of the conformation linear traits of first-born cows of black-and-white cattle with milk yield

An in-depth analysis the publications of domestic and foreign authors was carried out in the aspect of research on the heritability of linear traits of the conformation type and their correlative variability with milk productivity.The research authors established that the level of existing variability in the heredity of linear traits depends on many genotypic and paratypic factors. However, they argue that despite the variability of traits heritability of dairy cows conformation, their level is generally sufficient for effective selection by linear type traits. Studies on the correlation between linear traits of type and milk productivity of cows of various breeds around the world have shown a high level of this relationship. This testifies about the effectiveness of indirect selection of dairy cattle by type, which will allow obtaining not only constitutionally strong and healthy animals, but also with high milk productivity.The population-genetic aspect of determining the heritability and correlative variability of linear traits with milking of first-born Holstein cows of domestic selection and Ukrainian Black-and-White dairy in the private enterprise "Burynske" of the Podlisniv branch of the Stepaniv territorial community in Sumy district was described. The magnitudes and reliability of the heritability coefficients of group linear traits indicate that they are controlled by the genotype of animals by 24.5-42.2 % in first-born cows of the Holstein breed, and by 26.6-40.1 % in female cows of Ukrainian Black-and-White dairy breed. The final score by type of 48.2 and 45.4 %, respectively, ensures the efficiency selection of cows by genotype. Variability of descriptive traits of Holstein cows ranges from insignificant and unreliable (h2=0.084; location of front teats) to high and reliable (h2=0.484; angularity). In females of the same age of Ukrainian Black-and-White dairy breed, the variability varies from 0.077 (location of rear teats) to 0.422 (angularity).In Holstein and Ukrainian Black-and-White dairy cows, the most reliable relationship was found between the characteristics of the dairy type (0.428 and 0.387), body (0.446 and 0.439), udder (0.486 and 0.478) and, especially, the final type score (0.492 and 0.488), which gives reason to assert about the effectiveness of selection based on these traits.The highest level of reliable positive correlation with the amount of milk yield for the first lactation was found according to the scores of descriptive traits of Holstein and Ukrainian Black-and-White dairy breeds, respectively: height (r=0.363 and 0.322), body depth (r=0.468 and 0.484), angularity (r=0.477 and 0.466), back width (r=0.366 and 0.322), posture of pelvic limbs (r=0.369 and 374), attachment of front (r=0.482 and 0.426) and rear (r=0.371 and 0.351) udder parts, central ligament (r=0.364 and 0.375) and locomotion (r=0.363 and 0.322) at Р<0.001. Key words: Holstein, UkrainianBlack-and-Whitedairy, lineartypeevaluation, conformation, milkyield, first-borncows.

Genetic Variability, Correlation and Path Coefficient Analysis in Hybrid Maize (Zea mays L.)

The goal of the current investigation was to determine correlation coefficient, path analysis and genetic variability among twenty four maize hybrids for ten characters in a Randomized Block Design (RBD) with three replications at the research field of Plant Breeding Division, Regional Agricultural Research Station, Barisal, Bangladesh Agricultural Research Institute (BARI), Bangladesh during rabi season of 2014-15.
 The measured traits were Days to 50% tasseling (DT), days to 50% silking (DS), anthesis silking interval (ASI), plant height (PH), ear height (EH), days to maturity (DM), cob length (CL), cob diameter (CD), thousand seed weight (TSW) and yield(yield t/ha). Here yield was considered as dependent variable and the rest of the parameters were independent variable. The data were submitted to analysis of variance and mean values were compared by DMRT test at both 5% and 1% of probability. Positive and significant genotypic, phenotypic correlation coefficient were recorded for yield with cob diameter (rg=0.75**, rp=0.61**), cob length (rg=0.66**and rp=0.42**), plant height (rg=0.62**and rp=0.55**), ear height (rg=0.66**and rp=0.55**) and thousand seed weight (rg=0.36**and rp=0.44**). High genotypic coefficient of variation (GCV) was obtained from anthesis silking interval (17.26), yield (15.17), ear height (13.80) and thousand seed weight (9.43). The highest phenotypic coefficient of variation (PCV) were observed in anthesis silking interval (26.49) followed by yield (20.51), ear height (16.19) and the lowest in days to maturity (0.70). The difference between GCV and PCV of yield indicated that the characters had some environmental influence. The highest heritability was observed for plant height (73.78) followed by ear height (72.67), thousand seed weight (59.52) and days to maturity (55.97) but the lowest heritability identified for days to silking (18.98). The characters with higher values of GCV and heritability of the aforementioned traits were indicative for selection. The plant height had the highest positive direct effect (1.34) on yield followed by days to silking (0.75), cob diameter CD (0.46) and thousand seed weight (0.41), days to maturity (0.21) and cob length (0.20) indicating the effectiveness of direct selection. Direct negative effect on yield was shown by ear height (-1.03), days to tasseling (-0.52) and anthesis silking interval (-0.50) was indicating the effectiveness of indirect selection.

Assessment of genetic variability and trait association for yield and its components in bi-parental early segregating generation of maize

The present investigation was carried out to understand the co-efficients of variation, heritability, genetic advance, correlation co-efficient and path analysis in F2 population of maize.The study comprised of 303 F2 progeny plants, parents and F1of the cross, CM 111 × DHKN 509 evaluatedunder un-replicated trial during Rabi 2020-21. The observations were recorded for ten traits viz., days to tasseling, days to silking, anthesis-silking interval, plant height, ear height, ear girth, number of kernels per row, pith weight, shelling per cent and grain yield per plantin all the F2 progeny plants and ten plants each from parents and F1 and noticed wide variation among the traits studied in the F2 population.The extent of phenotypic and co-efficient of variation was higher than genotypic co-efficient of variation for all the traits studied. High PCV and GCV was recorded for anthesis-silking interval, number of kernels per row, pith weight and grain yield per plant. High heritability coupled with high genetic advance over mean were observed for anthesis-silking interval, number of kernels per row, pith weight and grain yield per plant suggesting that these traits are governed by additive gene action and can be improved through simple selection. Positive and significant association with grain yield was recorded with number of kernels per row, pith weight, cob girth and shelling per cent. Days to tasseling and anthesis-silking interval exhibited highest direct positive effect on grain yield per plant followed by pith weight and shelling per cent indicating the effectiveness of direct selection, whereas direct negative effects were recorded by days to silking and ear height indicating the effectiveness of indirect selection.

Predictive approach to optimize the number of visual graders for indirect selection of high-yielding Urochloa ruziziensis genotypes

Forage plant breeders often use visual scores to assess agronomic traits because of the costs associated with in-depth phenotyping in the initial stages of breeding cycles. The aim of this study was to investigate the impact of the number of graders on the effectiveness of indirect selection of high-yielding genotypes and determine an optimal number of graders in the early-stage trials of Urochloa ruziziensis. For that purpose, five graders assessed 2.219 U. ruziziensis genotypes in an augmented block design. Biomass production and vigor scores were evaluated in two cuts and were analyzed using a linear mixed model approach. Vigor scores were analyzed considering each grader's score and the combinations of two, three, four, and five graders. Genetic variance was significant for both traits. Visual evaluation was effective in identifying productive genotypes based on the statistical criteria. The optimal number of graders for indirect selection of high-yielding U. ruziziensis genotypes is three.

Direct and correlated responses to bi-directional selection on pre-adult development time in Drosophila montana

Selection experiments offer an efficient way to study the evolvability of traits that play an important role in insects’ reproduction and/or survival and to trace correlations and trade-offs between them. We have exercised bi-directional selection on Drosophila montana flies’ pre-adult development time under constant light and temperature conditions for 10 generations and traced the indirect effects of this selection on females’ diapause induction under different day lengths, as well as on the body weight and cold tolerance of both sexes. Overall, selection was successful towards slow, but not towards fast development. However, all fast selection line replicates showed at the end of selection increased variance in females’ photoperiodic diapause response and about one hour increase in the critical day (CDL), where more than 50% of emerging females enter diapause. Indirect effects of selection on flies’ body weight and cold-tolerance were less clear, as the flies of the slow selection line were significantly heavier and less cold-tolerant than the control line flies after five generations of selection, but lighter and more cold-tolerant at the end of selection. Changes in females’ diapause induction resulting from selection for fast development could be due to common metabolic pathways underlying these traits, collaboration of circadian clock and photoperiodic timer and/or by the interaction between the endocrine and circadian systems.

Genomic clustering of fitness-affecting mutations favors the evolution of chromosomal instability.

Most solid cancers are characterized by chromosomal instability (CIN)—an elevated rate of large‐scale chromosomal aberrations and ploidy changes. Chromosomal instability may arise through mutations in a range of genomic integrity loci and is commonly associated with fast disease progression, poor prognosis, and multidrug resistance. However, the evolutionary forces promoting CIN‐inducing alleles (hereafter, CIN mutators) during carcinogenesis remain poorly understood. Here, we develop a stochastic, individual‐based model of indirect selection experienced by CIN mutators via genomic associations with fitness‐affecting mutations. Because mutations associated with CIN affect large swaths of the genome and have the potential to simultaneously comprise many individual loci, we show that indirect selection on CIN mutators is critically influenced by genome organization. In particular, we find strong support for a key role played by the spatial clustering of loci with either beneficial or deleterious mutational effects. Genomic clustering of selected loci allows CIN mutators to generate favorable chromosomal changes that facilitate their rapid expansion within a neoplasm and, in turn, accelerate carcinogenesis. We then examine the distribution of oncogenic and tumor‐suppressing loci in the human genome and find both to be potentially more clustered along the chromosome than expected, leading us to speculate that human genome may be susceptible to CIN hitchhiking. More quantitative data on fitness effects of individual mutations will be necessary, though, to assess the true levels of clustering in the human genome and the effectiveness of indirect selection for CIN. Finally, we use our model to examine how therapeutic strategies that increase the deleterious burden of genetically unstable cells by raising either the rate of CIN or the cost of deleterious mutations affect CIN evolution. We find that both can inhibit CIN hitchhiking and delay carcinogenesis in some circumstances, yet, in line with earlier work, we find the latter to be considerably more effective.

Variations in Genome Size of Turnip Landraces from Two High-altitude Environments

Brassica rapa var. rapa (turnip) is considered a main source of food for the inhabitants of the Qinghai-Tibetan Plateau (QTP) and its adjacent highlands when other crops are scarce. The QTP ranges from lat. 25.59°N to 39.49°N and from long. 73.29°E to 104.40°E, whereas the Yunnan Plateau ranges from lat. 20.00°N to 29.16°N and from long. 96.00°E to 110.19°E. A comparison between the turnip landraces of two different plateau environments can provide a mechanistic insight into plant adaptation in highlands. The aim of this investigation was to understand the patterns in variation in genome size (GS) between the turnip landraces of two plateau environments. We used a well-established protocol to count chromosome number and performed propidium iodide flow cytometry to measure GS. No polyploidy was detected among the turnip landraces tested, and 15.5% variation in GS was observed between the landraces. No consistent pattern pertaining to GS variation emerged after the environmental variables were considered. Thus, we propose that such pattern may reflect the indirect effect of selection, random process, genetic drift, or some other factors on GS through interaction of life-form and phenotypic traits.

Mutation Rate Evolution in Partially Selfing and Partially Asexual Organisms.

Different factors can influence the evolution of the mutation rate of a species: costs associated with DNA replication fidelity, indirect selection caused by the mutations produced (that should generally favor lower mutation rates, given that most mutations affecting fitness are deleterious), and genetic drift, which may render selection acting on weak mutators inefficient. In this paper, we use a two-locus model to compute the strength of indirect selection acting on a modifier locus that affects the mutation rate toward a deleterious allele at a second, linked, locus, in a population undergoing partial selfing or partial clonality. The results show that uniparental reproduction increases the effect of indirect selection for lower mutation rates. Extrapolating to the case of a whole genome with many deleterious alleles, and introducing a direct cost to DNA replication fidelity, the results can be used to compute the evolutionarily stable mutation rate, U In the absence of mutational bias toward higher U, the analytical prediction fits well with individual-based, multilocus simulation results. When such a bias is added into the simulations, however, genetic drift may lead to the maintenance of higher mutation rates, and this effect may be amplified in highly selfing or highly clonal populations due to their reduced effective population size.

Selective breeding of lodgepole pine increases growth and maintains climatic adaptation

Climate change is disrupting historical patterns of adaptation in temperate and boreal tree species, causing local populations to become maladapted. Tree improvement programs typically utilise local base populations and manage adaptation using geographically defined breeding zones. As climates shift, breeding zones are no longer optimal seed deployment zones because base populations are becoming dissociated from their historical climatic optima. In response, climate-based seed transfer (CBST) policies incorporating assisted gene flow (AGF) are being adopted to pre-emptively match reforestation seedlots with future climates, but their implementation requires accurate knowledge of genetic variation in climatically adaptive traits. Here we use lodgepole pine as a case study to evaluate the effects of selective conifer breeding on adaptive traits and their climatic associations to inform CBST and AGF prescriptions.Our approach compared 105 natural stand and 20 selectively bred lodgepole pine seedlots from Alberta and British Columbia grown in a common garden of ∼2200 seedlings. The effects of selection on phenotypic variation and climatic associations among breeding zones were assessed for growth, phenology and cold hardiness. We found substantial differences between natural and selected seedlings in growth traits, but timing of growth initiation was unaffected, growth cessation was delayed slightly (average 4days, range 0.7days to 10days), and cold injury was slightly greater (average 2.5%, range −7% to 11%) in selected seedlings. Phenotypic differentiation among breeding zones and climatic clines were stronger for all traits in selected seedlings. Height gains resulted from both increased growth rate and delayed growth cessation, but negative indirect effects of selection on cold hardiness were weak.Selection, breeding and progeny testing combined have produced taller lodgepole pine seedlings that are not adaptively compromised relative to their natural seedling counterparts. Selective breeding produces genotypes that achieve increased height growth and maintain climate adaptation, rather than reconstituting genotypes similar to populations adapted to warmer climates. While CBST is needed to optimise seedlot deployment in new climates, an absence of systematic indirect selection effects on adaptive traits suggests natural and selected seedlots do not require separate AGF prescriptions.

Genetic Variability and Path Analysis Studies in Hybrid Maize (<i>Zea mays</i> L.)

The present study was carried out to access correlation coefficient, path analysis and genetic variability among twenty one locally developed maize hybrids for ten characters. Positive and significant genotypic, phenotypic correlation coefficient were recorded for yield with anthesis silking interval (rg = 1.00**, rp = 0.96**), cob diameter (rg = 0.99** and rp = 0.95**) and ear height (rg = 0.98** and rp = 0.94**). But days to 50% tasseling had moderate but significant positive correlation at both phenotypic and genotypic level. High genotypic coefficient of variation (GCV) was obtained from thousand seed weight, days to 50% silking, cob diameter and anthesis silking interval. The highest phenotypic coefficient of variation (PCV) was observed in thousand seed weight followed by days to 50% silking and cob diameter. The highest heritability (Hb) was observed for cob diameter (95.25) followed by days to 50% silking (94.15), days to maturity (93.85) and ear height (93.06). The characters with high GCV and higher values of heritability indicated high potential for selection. Anthesis silking interval (0.79) had the highest positive direct effect on yield followed by cob diameter (0.31), cob length (0.31) and plant height (0.04) indicating the effectiveness of direct selection. While some other characters such as days to 50% tasseling (-0.12), days to 50% silking (-1.78), ear height (-1.16), days to maturity (-0.64) exhibited indirect negative effect on yield indicating the effectiveness of indirect selection.

Responses to Recurrent Index Selection for Reduced Fusarium Ear Rot and Lodging and for Increased Yield in Maize

ABSTRACTFusarium ear rot, caused by the pathogen Fusarium verticillioides, damages maize (Zea mays L.) grain production and is associated with contamination of grain by fumonisin, a mycotoxin harmful to both humans and animals. Recurrent selection may be an effective way to combine improvements in resistance to Fusarium ear rot with improved grain yield and lodging resistance. To test this hypothesis, three cycles of recurrent index selection based on evaluating S0:1 lines for Fusarium ear rot, grain yield, and lodging were implemented in a genetically broad‐based population. Direct intrapopulation response to selection in the target traits was measured by comparing lines sampled from Cycle 0 and Cycle 3 populations. In addition, indirect response for fumonisin contamination was also measured along with indirect response for agronomic traits when crossed to commercial inbred tester, FR1064. Results indicate significant direct gain from selection for Fusarium ear rot, but no significant gains for yield or lodging resistance. Indirect gains were also observed for Fusarium ear rot resistance in topcrosses to an unrelated tester line and for fumonisin contamination both within the selection population and in topcrosses. Our results are the first demonstration of the indirect effect of selection against Fusarium ear rot on reduction of fumonisin contamination. Heritabilities for target traits did not decrease over generations, indicating potential for further genetic gain from selection in this population.

Recurrent Selection for Seedling Growth of Sweet Corn in Cool Temperatures

ABSTRACTEarly spring sweet corn producers would benefit from supersweet cultivars with improved seedling cold tolerance. We performed recurrent selection for improved seedling vigor and germination rates at cool temperatures in three sweet corn populations. The original populations were formed by crossing temperate sweet corn and High‐altitude Mexican germplasm. A sugary1 (su1) and a shrunken2 (sh2) population derived from Cacahuacintle Dulce germplasm were evaluated, as well as a sh2 population derived from ‘Maíz Dulce’. The most uniformly vigorous seedling lots were chosen by replicated visual selection and then intermated to form the next cycle. The direct effects of selection were measured through growth chamber germination tests at 10°C. The indirect effects of selection were assessed through replicated field trials. A positive significant linear response to selection for seedling length was present in the two sh2 populations (R2 = 0.92, P < 0.001; R2 = 0.94, P < 0.001). There was a 71% increase in seedling length over four cycles of selection in one sh2 population, and a 116% increase in the other. Significant linear decreases in the average number of dead kernels were observed in both sh2 populations (R2 = 0.91, P < 0.05; R2 = 0.89, P < 0.05). There were no significant changes in kernel carbohydrate composition in either of the sh2 populations. No linear changes were observed as a direct response to selection in the su1 population. While germination under field conditions improved for both of the sh2 populations, selection had a negative effect on several agronomic traits, including plant height, ear height, and ear weight, suggesting the possibility of inbreeding during recurrent selection.

Genetic variability, heritability and genetic advance of growth and yield components of Jatropha (Jatropha curcas Linn.) genotypes

A total of 113 Jatropha curcas clonal accessions collected from different regions of India were studied to quantify the magnitude of genetic variability present in the test population and to identify important yield-attributing characters useful for developing high-yielding Jatropha cultivars. High heritability was observed for fruits per plant, seeds per plant, 100-seed weight, seed/kernel (S/K) ratio and kernel oil percentage coupled with high genetic advance suggesting that the accessions can be considered improvement. The significant positive association of seed oil content (%) with 100-seed weight suggested the effectiveness of indirect selection for seed oil content through 100-seed weight. Accessions 76, 120, 29, 86 and 84 showed above average higher values for all yield attributes (viz. fruit and seed yield, 100-seed weight, S/K ratio and oil content) suggesting these as best out of the test accessions. Accessions showing higher values for one or the other yield attributes could be selected as parents for further improvement.

Lineage dynamics and mutation–selection balance in non-adapting asexual populations

In classical population genetics, mutation–selection balance refers to the equilibrium frequency of a deleterious allele established and maintained under two opposing forces: recurrent mutation, which tends to increase the frequency of the allele; and selection, which tends to decrease its frequency. In a haploid population, if μ denotes the per capita rate of production of the deleterious allele by mutation and s denotes the selective disadvantage of carrying the allele, then the classical mutation–selection balance frequency of the allele is approximated by μ/s. This calculation assumes that lineages carrying the mutant allele in question—the ‘focal allele’—do not accumulate deleterious mutations linked to the focal allele. In principle, indirect selection against the focal allele caused by such additional mutations can decrease the frequency of the focal allele below the classical mutation–selection balance. This effect of indirect selection will be strongest in an asexual population, in which the entire genome is in linkage. Here, we use an approach based on a multitype branching process to investigate this effect, analyzing lineage dynamics under mutation, direct selection, and indirect selection in a non-adapting asexual population. We find that the equilibrium balance between recurrent mutation to the focal allele and the forces of direct and indirect selection against the focal allele is closely approximated by γμ/(s + U) (s = 0 if the focal allele is neutral), where γ ≈ eθθ−(ω+θ)(ω + θ)(Γ(ω + θ) − Γ(ω + θ,θ)), , and ; U denotes the genomic deleterious mutation rate and denotes the geometric mean selective disadvantage of deleterious mutations elsewhere on the genome. This mutation–selection balance for asexual populations can remain surprisingly invariant over wide ranges of the mutation rate.

Recent and Ancient Signature of Balancing Selection around the S-Locus in Arabidopsis halleri and A. lyrata

Balancing selection can maintain different alleles over long evolutionary times. Beyond this direct effect on the molecular targets of selection, balancing selection is also expected to increase neutral polymorphism in linked genome regions, in inverse proportion to their genetic map distances from the selected sites. The genes controlling plant self-incompatibility are subject to one of the strongest forms of balancing selection, and they show clear signatures of balancing selection. The genome region containing those genes (the S-locus) is generally described as nonrecombining, and the physical size of the region with low recombination has recently been established in a few species. However, the size of the region showing the indirect footprints of selection due to linkage to the S-locus is only roughly known. Here, we improved estimates of this region by surveying synonymous polymorphism and estimating recombination rates at 12 flanking region loci at known physical distances from the S-locus region boundary, in two closely related self-incompatible plants Arabidopsis halleri and A. lyrata. In addition to studying more loci than previous studies and using known physical distances, we simulated an explicit demographic scenario for the divergence between the two species, to evaluate the extent of the genomic region whose diversity departs significantly from neutral expectations. At the closest flanking loci, we detected signatures of both recent and ancient indirect effects of selection on the S-locus flanking genes, finding ancestral polymorphisms shared by both species, as well as an excess of derived mutations private to either species. However, these effects are detected only in a physically small region, suggesting that recombination in the flanking regions is sufficient to quickly break up linkage disequilibrium with the S-locus. Our approach may be useful for distinguishing cases of ancient versus recently evolved balancing selection in other systems.

Selection efficiency on bones and meat yeald in pigs

Trial were conducted at 5 farms, on 5 breeds of pigs in itch farm, in a period from 2000 to 2010. To analyzed data, the MME LS model was used to correct FYS and Breed as fixed effect and Sire as random one. Genetic parameters were estimated from half siblings group. Bones had significantly smaller weight in Pietrain pigs compared to all other breeds. Furthermore, daily and life gains at the Pietrain breed were significantly smaller compared to other breeds. Heritability estimates were significantly different for three breeds, higher for bones, higher for meat yield. The pheneotipic and genetic variations were similar for all traits. Economic effect of selection can be analyzed and expected with a positive trend. Genetic correlation showed expected trend. It is possible to use the effect of indirect selection as well.

Covariation between line and testcross performance for reduced mycotoxin concentrations in European maize after silk channel inoculation of two Fusarium species

Fusarium spp. in maize can contaminate grain with mycotoxins harmful to humans and animals. Breeding and growing resistant varieties is one alternative to reduce contamination by mycotoxins. Little is known about the population parameters relevant to resistance breeding. The objectives of this study were to draw conclusions on breeding of reduced mycotoxin concentrations of deoxynivalenol, zearalenone and fumonisins, and resistance to ear rot after silk channel inoculation with F. graminearum or F. verticillioides, respectively. For that, variation and covariation of line and testcross performance and correlations between both species and between mycotoxin concentrations and ear rot resistance were calculated. Means of ear rot after infection with F. graminearum were higher than with F. verticillioides. Moderate phenotypic correlations (r = 0.46-0.65) between resistances to both Fusarium spp. implicate the need of separate testing. Analyses of variance revealed significant (P < 0.01) differences among lines in line and testcross performance for 30-60 entries per maturity group. Multi-environmental trials for accurate selection are necessary due to significant (P < 0.1) genotype × environment interactions. High genotypic correlations between ear rots and mycotoxins (r ≥ 0.90), and similar heritabilities of both traits, revealed the effectiveness of indirect selection for mycotoxin concentrations based on ear rot rating after inoculation. Moderate genotypic correlations between line and testcross performance were found (r = 0.64-0.83). The use of one moderately to highly susceptible tester is sufficient since genotypic correlations between testcrosses of different testers were high (r = 0.80-0.94). Indirect selection for testcross performance based on line performance is less effective than selection based on mycotoxin concentrations. Consequently, selection for resistance to ear rot and mycotoxin accumulation should be started among testcrosses tested first for general combining ability based on ear rot data in parallel with a negative selection for line per se performance.