Breeding Schemes Research Articles

Supply Chain Perspectives on Breeding for Legume-Cereal Intercrops.

Compared to sole crops, intercropping—especially of legumes and cereals—has great potential to improve crop yield and resource use efficiency, and can provide many other ecosystem services. However, the beneficial effects of intercrops are often greatly dependent on the end use as well as the specific species and genotypes being co-cultivated. In addition, intercropping imposes added complexity at different levels of the supply chain. While the need for developing crop genotypes for intercropping has long been recognized, most cultivars on the market are optimized for sole cropping and may not necessarily perform well in intercrops. This paper aims to place breeding targets for intercrop-adapted genotypes in a supply chain perspective. Three case studies of legumes and cereals intercropped for human consumption are used to identify desirable intercrop traits for actors across the supply chains, many of which are not targeted by traditional breeding for sole crops, including certain seed attributes, and some of which do not fit traditional breeding schemes, such as breeding for synchronized maturity and species synergies. Incorporating these traits into intercrop breeding could significantly reduce complexity along the supply chain. It is concluded that the widespread adoption and integration of intercrops will only be successful through the inclusion and collaboration of all supply chain actors, the application of breeding approaches that take into account the complexity of intercrop supply chains, and the implementation of diversification strategies in every process from field to fork.

Novel insights into heat tolerance using metabolomic and high-throughput sequencing analysis in dairy cows rumen fluid

Heat stress influences rumen fermentative processes with effects on the physiology and production of dairy cows. However, the underlying relationship between rumen microbiota and its associated metabolism with heat tolerance in cows have not been extensively described yet. Therefore, the main objective of this study was to investigate differential heat resistance in Holstein cows using rumen bacterial and metabolome analyses. We performed both principal component analysis and membership function analysis to select seven heat-tolerant (HT) and seven heat-sensitive (HS) cows. Under heat stress conditions, the HT cows had a significantly (P < 0.05) higher propionic acid content than the HS cows; while measures of the respiratory rate, acetic, and butyric acid in the HT cows were significantly (P < 0.05) lower compared with the HS cows. Also, the HT cows showed lower (P < 0.01) rectal temperature and acetic acid to propionic acid ratio than the HS group of cows. Omics sequencing revealed that the relative abundances of Muribaculaceae, Rikenellaceae, Acidaminococcaceae, Christensenellaceae, Rikenellaceae_RC9_gut_group, Succiniclasticum, Ruminococcaceae_NK4A214_group and Christensenellaceae_R-7_group were significantly (P < 0.01) higher in the HT cows; whereas Prevotellaceae, Prevotella_1, Ruminococcaceae_UCG-014, and Shuttleworthia were significantly (P < 0.01) lower in HT cows compared to HS cows. Substances mainly involved in carbohydrate metabolism, including glycerol, mannitol, and maltose, showed significantly higher content in the HT cows (P < 0.05) compared to that in the HS cows. Simultaneously, distinct metabolites were significantly correlated with differential bacteria, suggesting that glycerol, mannitol, and maltose could serve as potential biomarkers for determining heat resistance that require further study. Overall, distinct changes in the rumen microbiota and metabolomics in the HT cows may be associated with a better adaptability to heat stress. These findings suggest their use as diagnostic tools of heat tolerance in dairy cattle breeding schemes.

The development of effective ruminant breeding programmes in Ireland from science to practice

A genetic improvement programme is a sustainable, cumulative and permanent approach to achieving year-on-year performance gains. Its success is predicated not only on an efficient and effective breeding programme but also on a vision of the traits of importance in the future. A single, industry-owned, centralised database for cattle and sheep has been the foundation for genetic improvement programmes in Ireland. While DNA information has been heralded as a breakthrough for accelerating genetic gain, the basic principles of a successful animal breeding programme still remain the same: (1) a pertinent breeding goal, (2) the appropriate breeding objective to deliver on the breeding goal, (3) an accurate genetic evaluation system, (4) an efficient and effective breeding scheme, and (5) a system to disseminate the elite germplasm to the end user; also of importance is a system for validating the underlying procedures and principles. The constituent traits and their relative emphasis within breeding objectives will continue to be contentious. Traits that will need to be considered more in future ruminant breeding objectives include environmental impact, product quality and animal well-being, including health; while not always explicitly included in Irish breeding objectives for cattle and sheep, indirect improvements for many are expected via the genetic improvement in traits like reproductive performance and survival as well as macro measures of quality such as milk fat and protein concentration and carcass merit. Crucial for the future sustainability of ruminant production systems is the co-evolution of management systems and breeding programmes so that the animal of the future is suited to the most sustainably efficient production system.

Manipulation of Meiotic Recombination to Hasten Crop Improvement.

Simple SummaryHarnessing the natural and induced diversity existing in plant genetic resources is fundamental for building future crops more sober in fertilizers, water, and pesticides that can cope with climate instability while yielding healthier and more nutritious products. The essence of plant breeding is to combine favorable traits in crossing parental varieties to select novel performing associations amongst the progenies. These associations are the product of recombination between the parental chromosomes occurring during meiosis, mainly by a reciprocal DNA exchange called Cross Over (CO). However, recombination does not occur randomly along the chromosomes, and COs are limited in number often hampering the desired associations of favorable traits. This review surveys the recent advances in methods for achieving a stimulation and/or a redistribution of meiotic COs along the parental chromosomes and targeting COs specifically at desired chromosomal sites.Reciprocal (cross-overs = COs) and non-reciprocal (gene conversion) DNA exchanges between the parental chromosomes (the homologs) during meiotic recombination are, together with mutation, the drivers for the evolution and adaptation of species. In plant breeding, recombination combines alleles from genetically diverse accessions to generate new haplotypes on which selection can act. In recent years, a spectacular progress has been accomplished in the understanding of the mechanisms underlying meiotic recombination in both model and crop plants as well as in the modulation of meiotic recombination using different strategies. The latter includes the stimulation and redistribution of COs by either modifying environmental conditions (e.g., T°), harnessing particular genomic situations (e.g., triploidy in Brassicaceae), or inactivating/over-expressing meiotic genes, notably some involved in the DNA double-strand break (DSB) repair pathways. These tools could be particularly useful for shuffling diversity in pre-breeding generations. Furthermore, thanks to the site-specific properties of genome editing technologies the targeting of meiotic recombination at specific chromosomal regions nowadays appears an attainable goal. Directing COs at desired chromosomal positions would allow breaking linkage situations existing between favorable and unfavorable alleles, the so-called linkage drag, and accelerate genetic gain. This review surveys the recent achievements in the manipulation of meiotic recombination in plants that could be integrated into breeding schemes to meet the challenges of deploying crops that are more resilient to climate instability, resistant to pathogens and pests, and sparing in their input requirements.

Truncated dopamine transporter's epigenetics: Heterozigosity of the grandmother rat temperates the vulnerable phenotype in second-generation offspring.

Behavioral phenotype differs among epigenotypes of dopamine-transporter heterozygous (DAT-HET) rats. Epigenetic regulations act through transgenerational effects, referring to phenotypic variations emerging at second or third generation. To investigate transgenerational influences exerted by maternal grandmothers, we developed breeding schemes where only the genotype of maternal grandmothers varied. HET females, to serve as MAT vs. MIX mothers, were generated, respectively, from WT × KO = MAT and MAT × KO = MIX breeding, with KO males acting as grandfather. The HET experimental groups, generated from either MAT or MIX mothers, were called MIX-by-MAT and MIX2 (male-fathers KO; asset-M: wild/healthy-allele from dam) or SOT and SIX (male-fathers WT; asset-P: mutated-allele from dam). Thus, sequelae of first encounter between wild/healthy and mutated DAT alleles (in maternal-lineage) were compared at first- (MAT-dam, WT-grandmother) vs. at second- (MIX-dam, HET-grandmother) generation. We characterized, within these epigenotypes, (1) circadian home-cage activity and (2) preference for social stimuli. Marked alterations of circadian activity appeared in MIX-by-MAT HETs, offspring of MAT-dams, compared with MIX2 HET (offspring of MIX-dams); The latter, in turn, were undistinguishable from WT-controls. A clear-cut social preference by WT rats was expressed towards SIX compared with SOT stimulus rats, confirming that the latter elicited reduced social motivations. In conclusion, significant epigenetic modulations took place in DAT-HET rats, as a function of maternal grandmother's genotype.

A survey on the performance and status of disseminated elite N’Dama cattle breeding bulls at the multiplier tier of an Open Nucleus Breeding Scheme in The Gambia for the period 2011 to 2019

The objectives of this survey conducted in 2020 were to profile Multiplier farmers, assess the performance of disseminated N’ breeding bulls at the multiplier cattle herds, and inquire about cattle health and production challenges. Thirty-three farmers living in 33 villages in 5 regions of The Gambia who received 52 elite N’ breeding bulls from the West Africa Livestock Innovation Centre (WALIC) Nucleus tier were interviewed.&#x0D; &#x0D; The results showed that the disseminated bulls’ performance is generally satisfactorily as asserted by 28 respondents. Twenty-eight respondents reported that the bulls were healthier, 31 ascribed these bulls with stronger libido, 20 asserted that female offspring from these bulls produced more milk, and 26 claimed that offspring had a faster growth rate. A total of 473 calves have been sired by these bulls thus far. However, only 19 bulls are currently present at the multiplier herds due to the exit of 33 bulls arising from various causes. Cattle production challenges reported by farmers included decreasing grazing lands, rampant bush fires, and inadequate watering points; whilst listed health constraints included inadequate access to veterinary drugs and disease prevalence. The multiplication of the disseminated breeding bulls at the Multiplier tier has progressed well in terms of sired offspring, but further transfer to the Commercial Farmer tier is slow. This situation calls for more sensitization of farmers, increased visibility of the breeding programme, and utilization of other reproductive techniques such as artificial insemination to reach more cows for enhanced genetic improvement and productivity.

Genotypic characterization of meat-type lambs expressing the callipyge gene in Turkey: II. Effect on body indexes

This study is set out to examine the relationship between the callipyge (CLPG) gene, attributed to sheep affecting growth and meat quality, and body indexes of meat-type sheep breeds to assess its feasibility in using it genomic selection programs. For this purpose, blood samples were collected from 177 lambs (66 male, 111 female) of five different sheep breeds (Kivircik, Karacabey Merino, Ramlic, German Black-Head Mutton × Kivircik, Hampshire Down × Merino) to identify M (mutant) and N (normal) alleles and genotypes. Live weight (LW) and morphometric measurements were taken on the 90th, 180th, and 360th day of the study. The principal component analysis results show that four morphometric measurements (body length, BL; chest circumference, CC; chest width, CW; withers height, WH) and two body indexes (index of body weight, IBF; Baron-Crevat index, BCI) with LW could be used to the morphometric characterization. It was found that the cannon bone perimeter (CBP) was the differentiation point of CLPG genotypes. While a lower to moderate correlation was observed between CBP to CC, LW, CW, chest depth (CD), and rump width (RW) in the NN genotype, no significant correlation was observed in the MN genotype. This investigation also revealed that BCI and IBF were the two body indexes that should be adopted into breeding schemes as a performance and etiological comparison of animals, especially in marker-assisted selection schemes due to well-reflecting animal current status.

Exploiting genetic variability in the trajectory of lactation yield and somatic cell score with each progressing parity

The inclusion of reproductive performance in dairy cow breeding schemes has resulted in a cumulative improvement in genetic merit for reproductive performance; this improvement should manifest in longer productive lives through a reduced requirement for involuntary culling. Nonetheless, the average length of dairy cow productive life has not changed in most populations, suggesting that risk factors for culling, especially in older cows, are possibly more associated with lower yield or high somatic cell score (SCS) than compromised reproductive performance. The objective of the present study was to understand the dynamics of lactation yields and SCS in dairy cows across parities and, in doing so, quantify the potential to alter this trajectory through breeding. After edits, 3,470,520 305-d milk, fat, and protein yields, as well as milk fat and protein percentage and somatic cell count records from 1,162,473 dairy cows were available for analysis. Random regression animal models were used to identify the parity in which individual cows reached their maximum lactation yields, and highest average milk composition and SCS; also estimated from these models were the (co)variance components for yield, composition, and SCS per parity across parities. Estimated breeding values for all traits per parity were calculated for cows reaching ≥fifth parity. Of the cows included in the analyses, 91.0%, 92.2%, and 83.4% reached maximum milk, fat, and protein yield in fifth parity, respectively. Conversely, 95.9% of cows reached their highest average fat percentage in first parity and 62.9% of cows reached their highest average protein percentage in third parity. In contrast to both milk yield and composition traits, 98.4% of cows reached their highest average SCS in eighth parity. Individual parity estimates of heritability for milk yield traits, milk composition, and SCS ranged from 0.28 to 0.44, 0.47 to 0.69, and 0.13 to 0.23, respectively. The strength of the genetic correlations per trait among parities was inversely related to the interval between the parities compared; the weakest genetic correlation was 0.67 (standard error = 0.02) between milk yield in parities 1 and 8. Eigenvalues and eigenfunctions of the additive genetic covariance matrices for all investigated traits revealed potential to alter the trajectory of parity profiles for milk yield, milk composition, and SCS. This was further demonstrated when evaluating the trajectories of animal estimated breeding values per parity.

Microsatellite analysis of genetic diversity in wild and cultivated Portunus trituberculatus in Bohai Bay.

Previous studies have revealed a reduction in the genetic diversity of P. trituberculatus in Bohai Sea. However, because swimming crabs have been released into this area for some time, it is unclear whether the release of cultured populations from the national breeding farms of swimming crabs in Bohai Bay have affected the population genetics of wild populations of P. trituberculatus. In this study, the genetic diversity and population structure of 120 P. trituberculatus specimens in Bohai Bay were investigated using six microsatellite loci, including one wild population and one cultivated population. A total of 132 alleles were identified for all loci. The mean expected (He) and observed heterozygosity (Ho) were 0.8185 and 0.7759, respectively, thus indicating high levels of genetic diversity for these two populations. Molecular variance analysis (AMOVA) (FST = 0.0180), genetic distance (D = 0.1168) and similarity (S = 0.8898) indicated that these two populations could not be distinguished genetically. Structural analysis, phylogenetic tree construction, and principal component analysis, showed no significant distinction between the wild and cultivated populations. Finally, we investigated genetic exchange between the two populations by analyzing migration rate (M) and gene flow (Nm), thus demonstrating significant flow of genetic information. These findings contribute information for further breeding schemes for P. trituberculatus, evaluation of its genetic potential and programs for the protection of wild resources.

Breeding Schemes: What Are They, How to Formalize Them, and How to Improve Them?

Formalized breeding schemes are a key component of breeding program design and a gateway to conducting plant breeding as a quantitative process. Unfortunately, breeding schemes are rarely defined, expressed in a quantifiable format, or stored in a database. Furthermore, the continuous review and improvement of breeding schemes is not routinely conducted in many breeding programs. Given the rapid development of novel breeding methodologies, it is important to adopt a philosophy of continuous improvement regarding breeding scheme design. Here, we discuss terms and definitions that are relevant to formalizing breeding pipelines, market segments and breeding schemes, and we present a software tool, Breeding Pipeline Manager, that can be used to formalize and continuously improve breeding schemes. In addition, we detail the use of continuous improvement methods and tools such as genetic simulation through a case study in the International Institute of Tropical Agriculture (IITA) Cassava east-Africa pipeline. We successfully deploy these tools and methods to optimize the program size as well as allocation of resources to the number of parents used, number of crosses made, and number of progeny produced. We propose a structured approach to improve breeding schemes which will help to sustain the rates of response to selection and help to deliver better products to farmers and consumers.

Genetic and economic evaluation of alternative breeding schemes for two indigenous goat populations of Ethiopia

ABSTRACT In this study, breeding objective traits were identified, and alternative breeding schemes were simulated and evaluated for two goat populations. The traits were as follows: body size, twinning ability and kidding interval (KI) for Arab goats and body size, twinning ability and mothering ability for Oromo goats. The selection criteria were six-month weight (6mw, kg), litter size at birth (LSB), litter size at weaning (LSW) and KI (days). The schemes were as follows: (1) Scheme 1: 2 years of buck use and 10% selection proportion, (2) Scheme 2: 2 years of buck use and 15% selection proportion, (3) Scheme 3: 3 years of buck use and 10% selection proportion, and (4) Scheme 4: 3 years of buck use and 15% selection proportion. The predicted annual genetic gain (PAGG) for 6mw ranged from 0.29 to 0.32 kg for Arab goats while it varied from 0.34 to 0.38 kg for Oromo goats. On the contrary, the PAGGs for LSB and LSW for both populations were considerably small regardless of the different schemes. The economic return (Euro/doe) ranged from 0.99 to 1.15 for Arab goats and from 0.60 to 0.70 for Oromo goats. SCM2 is recommended over other schemes.

Single-step genomic evaluation of milk production traits in Canadian Alpine and Saanen dairy goats

Genomic evaluations are routine in most plant and livestock breeding programs but are used infrequently in dairy goat breeding schemes. In this context, the purpose of this study was to investigate the use of the single-step genomic BLUP method for predicting genomic breeding values for milk production traits (milk, protein, and fat yields; protein and fat percentages) in Canadian Alpine and Saanen dairy goats. There were 6,409 and 12,236 Alpine records and 3,434 and 5,008 Saanen records for each trait in first and later lactations, respectively, and a total of 1,707 genotyped animals (833 Alpine and 874 Saanen). Two validation approaches were used, forward validation (i.e., animals born after 2013 with an average estimated breeding value accuracy from the full data set ≥0.50) and forward cross-validation (i.e., subsets of all animals included in the forward validation were used in successive replications). The forward cross-validation approach resulted in similar validation accuracies (0.55 to 0.66 versus 0.54 to 0.61) and biases (-0.01 to -0.07 versus -0.03 to 0.11) to the forward validation when averaged across traits. Additionally, both single and multiple-breed analyses were compared, and similar average accuracies and biases were observed across traits. However, there was a small gain in accuracy from the use of multiple-breed models for the Saanen breed. A small gain in validation accuracy for genomically enhanced estimated breeding values (GEBV) relative to pedigree-based estimated breeding values (EBV) was observed across traits for the Alpine breed, but not for the Saanen breed, possibly due to limitations in the validation design, heritability of the traits evaluated, and size of the training populations. Trait-specific gains in theoretical accuracy of GEBV relative to EBV for the validation animals ranged from 17 to 31% in Alpine and 35 to 55% in Saanen, using the cross-validation approach. The GEBV predicted from the full data set were 12 to 16% more accurate than EBV for genotyped animals, but no gains were observed for nongenotyped animals. The largest gains were found for does without lactation records (35-41%) and bucks without daughter records (46-54%), and consequently, the implementation of genomic selection in the Canadian dairy goat population would be expected to increase selection accuracy for young breeding candidates. Overall, this study represents the first step toward implementation of genomic selection in Canadian dairy goat populations.

Construction of Genetic Linkage Maps From a Hybrid Family of Large Yellow Croaker (Larimichthys crocea).

Consensus and sex-specific genetic linkage maps for large yellow croaker (Larimichthys crocea) were constructed using samples from an F1 family produced by crossing a Daiqu female and a Mindong male. A total of 20,147 single nucleotide polymorphisms (SNPs) by restriction site associated DNA sequencing were assigned to 24 linkage groups (LGs). The total length of the consensus map was 1757.4 centimorgan (cM) with an average marker interval of 0.09 cM. The total length of female and male linkage map was 1533.1 cM and 1279.2 cM, respectively. The average female-to-male map length ratio was 1.2 ± 0.23. Collapsed markers in the genetic maps were re-ordered according to their relative positions in the ASM435267v1 genome assembly to produce integrated genetic linkage maps with 9885 SNPs distributed across the 24 LGs. The recombination pattern of most LGs showed sigmoidal patterns of recombination, with higher recombination in the middle and suppressed recombination at both ends, which corresponds with the presence of sub-telocentric and acrocentric chromosomes in the species. The average recombination rate in the integrated female and male maps was respectively 3.55 cM/Mb and 3.05 cM/Mb. In most LGs, higher recombination rates were found in the integrated female map, compared to the male map, except in LG12, LG16, LG21, LG22, and LG24. Recombination rate profiles within each LG differed between the male and the female, with distinct regions indicating potential recombination hotspots. Separate quantitative trait loci (QTL) and association analyses for growth related traits in 6 months fish were performed, however, no significant QTL was detected. The study indicates that there may be genetic differences between the two strains, which may have implications for the application of DNA-information in the further breeding schemes.

Analyzing the Economic Effectiveness of Genomic Selection Relative to Conventional Breeding Approaches.

Comparing the economic efficiency of alternative strategies for breeding requires to compare the genetic gain obtained with breeding schemes that represent the same total investment. In this chapter, we present a generic method to assess this economic efficiency for alternative breeding schemes. After presenting the baseline framework and the necessity of comparing breeding schemes with equivalent total investment, we propose one illustrative example on wheat breeding. In this application, we compare the use of conventional breeding and genomic selection. With this example, we explain the requirements and the different steps to implement this method. At last, we discuss several extensions of the baseline model.

Genomic Prediction Methods Accounting for Nonadditive Genetic Effects.

The use of genomic information for prediction of future phenotypes or breeding values for the candidates to selection has become a standard over the last decade. However, most procedures for genomic prediction only consider the additive (or substitution) effects associated with polymorphic markers. Nevertheless, the implementation of models that consider nonadditive genetic variation may be interesting because they (1) may increase the ability of prediction, (2) can be used to define mate allocation procedures in plant and animal breeding schemes, and (3) can be used to benefit from nonadditive genetic variation in crossbreeding or purebred breeding schemes. This study reviews the available methods for incorporating nonadditive effects into genomic prediction procedures and their potential applications in predicting future phenotypic performance, mate allocation, and crossbred and purebred selection. Finally, a brief outline of some future research lines is also proposed.

Rootstock-Mediated Genetic Variance in Cadmium Uptake by Juvenile Cacao (Theobroma cacao L.) Genotypes, and Its Effect on Growth and Physiology.

Grafting typically offers a shortcut to breed tree orchards throughout a multidimensional space of traits. Despite an overwhelming spectrum of rootstock-mediated effects on scion traits observed across several species, the exact nature and mechanisms underlying the rootstock-mediated effects on scion traits in cacao (Theobroma cacao L.) plants often remain overlooked. Therefore, we aimed to explicitly quantify rootstock-mediated genetic contributions in recombinant juvenile cacao plants across target traits, specifically cadmium (Cd) uptake, and its correlation with growth and physiological traits. Content of chloroplast pigments, fluorescence of chlorophyll a, leaf gas exchange, nutrient uptake, and plant biomass were examined across ungrafted saplings and target rootstock × scion combinations in soils with contrasting levels of Cd. This panel considered a total of 320 progenies from open-pollinated half-sib families and reciprocal full-sib progenies (derived from controlled crosses between the reference genotypes IMC67 and PA121). Both family types were used as rootstocks in grafts with two commercial clones (ICS95 and CCN51) commonly grown in Colombia. A pedigree-based best linear unbiased prediction (A-BLUP) mixed model was implemented to quantify rootstock-mediated narrow-sense heritability (h2) for target traits. A Cd effect measured on rootstocks before grafting was observed in plant biomass, nutrient uptake, and content of chloroplast pigments. After grafting, damage to the Photosystem II (PSII) was also evident in some rootstock × scion combinations. Differences in the specific combining ability for Cd uptake were mostly detected in ungrafted rootstocks, or 2 months after grafting with the clonal CCN51 scion. Moderate rootstock effects (h2> 0.1) were detected before grafting for five growth traits, four nutrient uptake properties, and chlorophylls and carotenoids content (h2 = 0.19, 95% CI 0.05–0.61, r = 0.7). Such rootstock effects faded (h2< 0.1) when rootstock genotypes were examined in soils without Cd, or 4 months after grafting. These results suggest a pervasive genetic conflict between the rootstock and the scion genotypes, involving the triple rootstock × scion × soil interaction when it refers to Cd and nutrient uptake, early growth, and photosynthetic process in juvenile cacao plants. Overall, deepening on these findings will harness early breeding schemes of cacao rootstock genotypes compatible with commercial clonal scions and adapted to soils enriched with toxic levels of Cd.

Breeding goals for conservation and active Polish dairy cattle breeds derived with a bio-economic model

The aim of the study was to calculate economic values (EV) of breeding traits (production, reproduction, direct health, calving and survival traits) for the Polish dairy cattle breeds Polish Holstein (PH) and Polish Red (PR). EV are key elements in setting up economically based breeding goals for dairy cattle and they are crucial for optimizing breeding schemes. For deriving EV, a stochastic bio-economic model was used, which estimates EVs based on population-specific biological and economic characteristics. Because the bio-economic model considers correlations between different traits, a multiple regression approach was used to correct for any double counting of effects. The results showed that EVs for direct health traits and fertility differed between breeds. The biggest difference was observed for lameness (PH -1.44 €, PR -1.09 € per cow-year), ketosis (PH -0.94 €, PR -0.58 € per cow-year) and for cow conception rate (PH 1.94 €, PR 0.84 € per cow-year). The relative economic weights for production traits were estimated as 37.00 % (PH) and 34.30 % for (PR) and for fertility traits 15.10 % (PH and for 16.10 % (PR). Major economic differences between the relative weights were observed for cow mortality (22.70 % PH, 16.90 % PR). The results of our study showed that breeding the PH brings higher economic profit than breeding the PR. Total income per PR cow was equal to 1,623 € and for PH 2,970 €.

Genetic Variability, Population Structure, and Relatedness Analysis of Meagre Stocks as an Informative Basis for New Breeding Schemes

This study evaluates the genetic diversity of different meagre broodstocks sampled in Greece. A multiplex of twelve microsatellite markers was used to genotype 946 fish from eleven stocks and batches used for broodstock selection, and the genetic data was used to calculate genetic population parameters as well as to investigate the genetic differentiation between stocks. The results from a relatedness analysis were used as the guiding lines for a fine-tuned and overall evaluation of the genetic distance between stocks, and the choice of candidate breeders from some of them. The approach implemented in this study uses well-established population genetics methods to evaluate the selection of breeder candidates in aquaculture commercial conditions utilizing a descriptive genetic data set based on microsatellite analyses, and to outline an efficient methodology for establishing the basis of new breeding schemes.

Screening cassava for time of maturity to respond to various market needs: Case study in African sub‐tropical zones

BACKGROUNDCassava evaluation trials are mostly harvested at 12 months after planting (MAP) irrespective of their actual maturity date, which includes the maximum accumulation of dry matter in tuberous roots. Depending on the market needs, some producers prefer to keep their crops up to 24 MAP and harvest sequentially when needed. Such varieties should mature early at 12 MAP and maintain or enhance their root dry matter rather than losing it. A modified breeding scheme has been suggested to evaluate selected lines from 12 to 24 MAP. In a harvest scheme such as this, many of the improved varieties lose their dry yield as starch is converted to sugar. Hence the breeding program in DR Congo started screening both early and late bulking varieties to identify those that can bulk early and keep their economically profitable dry root yield until late in the growing cycle. Six varieties and one local variety were subjected to several harvest dates ranging from 9 to 24 MAP.RESULTSIn general, the best harvests occurred at 15 MAP. Variety Zizila continued to increase its dry root yield from 15 t ha−1 at 15 MAP to 20 t ha−1 at 24 MAP. However, the varieties Butamu and Disanka both with dry yields of 15 t ha−1 at 15 MAP reduced their dry root yields to 5 t ha−1 at 24 MAP, thus limiting themselves to early maturing varieties.CONCLUSIONBy assessing early generation populations in the clonal trials, study results revealed that breeders may lose around 15% of superior clones with good dry root yield from 12 to 24 MAP when limiting the selection at 12 MAP. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Discovery and Validation of a Recessively Inherited Major-Effect QTL Conferring Resistance to Maize Lethal Necrosis (MLN) Disease.

Maize lethal necrosis (MLN) is a viral disease with a devastating effect on maize production. Developing and deploying improved varieties with resistance to the disease is important to effectively control MLN; however, little is known about the causal genes and molecular mechanism(s) underlying MLN resistance. Screening thousands of maize inbred lines revealed KS23-5 and KS23-6 as two of the most promising donors of MLN resistance alleles. KS23-5 and KS23-6 lines were earlier developed at the University of Hawaii, United States, on the basis of a source population constituted using germplasm from Kasetsart University, Thailand. Both linkage mapping and association mapping approaches were used to discover and validate genomic regions associated with MLN resistance. Selective genotyping of resistant and susceptible individuals within large F2 populations coupled with genome-wide association study identified a major-effect QTL (qMLN06_157) on chromosome 6 for MLN disease severity score and area under the disease progress curve values in all three F2 populations involving one of the KS23 lines as a parent. The major-effect QTL (qMLN06_157) is recessively inherited and explained 55%–70% of the phenotypic variation with an approximately 6 Mb confidence interval. Linkage mapping in three F3 populations and three F2 populations involving KS23-5 or KS23-6 as one of the parents confirmed the presence of this major-effect QTL on chromosome 6, demonstrating the efficacy of the KS23 allele at qMLN06.157 in varying populations. This QTL could not be identified in population that was not derived using KS23 lines. Validation of this QTL in six F2 populations with 20 SNPs closely linked with qMLN06.157 was further confirmed its consistent expression across populations and its recessive nature of inheritance. On the basis of the consistent and effective resistance afforded by the KS23 allele at qMLN06.157, the QTL can be used in both marker-assisted forward breeding and marker-assisted backcrossing schemes to improve MLN resistance of breeding populations and key lines for eastern Africa.