Backcross Populations Research Articles

Discovery and Characterization of a Novel Tomato mlo Mutant from an EMS Mutagenized Micro-Tom Population.

In tomato (Solanum lycopersicum), there are at least three SlMLO (Mildew resistance Locus O) genes acting as susceptibility genes for the powdery mildew disease caused by Oidium neolycopersici, namely SlMLO1, SlMLO5 and SlMLO8. Of the three homologs, the SlMLO1 gene plays a major role since a natural mutant allele called ol-2 can almost completely prevent fungal penetration by formation of papillae. The ol-2 allele contains a 19-bp deletion in the coding sequence of the SlMLO1 gene, resulting in a premature stop codon within the second cytoplasmic loop of the predicted protein. In this study, we have developed a new genetic resource (M200) in the tomato cv. Micro-Tom genetic background by means of ethyl methane sulfonate (EMS) mutagenesis. The mutant M200 containing a novel allele (the m200 allele) of the tomato SlMLO1 gene showed profound resistance against powdery mildew with no fungal sporulation. Compared to the coding sequence of the SlMLO1 gene, the m200 allele carries a point mutation at T65A. The SNP results in a premature stop codon L22* located in the first transmembrane domain of the complete SlMLO1 protein. The length of the predicted protein is 21 amino acids, while the SlMLO1 full-length protein is 513 amino acids. A high-resolution melting (HRM) marker was developed to distinguish the mutated m200 allele from the SlMLO1 allele in backcross populations. The mutant allele conferred recessive resistance that was associated with papillae formation at fungal penetration sites of plant epidermal cells. A comprehensive list of known mlo mutations found in natural and artificial mutants is presented, which serves as a particularly valuable resource for powdery mildew resistance breeding.

Evaluation and Selection of Interspecific Lines of Groundnut (Arachis hypogaea L.) for Resistance to Leaf Spot Disease and for Yield Improvement.

Early and late leaf spot are two devastating diseases of peanut (Arachis hypogaea L.) worldwide. The development of a fertile, cross-compatible synthetic amphidiploid, TxAG-6 ([A. batizocoi × (A. cardenasii × A. diogoi)]4x), opened novel opportunities for the introgression of wild alleles for disease and pest resistance into commercial cultivars. Twenty-seven interspecific lines selected from prior evaluation of an advanced backcross population were evaluated for resistance to early and late leaf spot, and for yield in two locations in Ghana in 2006 and 2007. Several interspecific lines had early leaf spot scores significantly lower than the susceptible parent, indicating that resistance to leaf spot had been successfully introgressed and retained after three cycles of backcrossing. Time to appearance of early leaf spot symptoms was less in the introgression lines than in susceptible check cultivars, but the opposite was true for late leaf spot. Selected lines from families 43-08, 43-09, 50-04, and 60-02 had significantly reduced leaf spot scores, while lines from families 43-09, 44-10, and 63-06 had high pod yields. One line combined both resistance to leaf spot and high pod yield, and several other useful lines were also identified. Results suggest that it is possible to break linkage drag for low yield that accompanies resistance. However, results also suggest that resistance was diluted in many of the breeding lines, likely a result of the multigenic nature of resistance. Future QTL analysis may be useful to identify alleles for resistance and allow recombination and pyramiding of resistance alleles while reducing linkage drag.

Identification and Pyramiding of QTLs for Rice Grain Size Based on Short-Wide Grain CSSL-Z563 and Fine-Mapping of qGL3\u20132

BackgroundChromosome segment substitution lines (CSSLs) can be used to dissect complex traits, from which single-segment substitution lines (SSSLs) containing a target quantitative trait loci (QTL) can be developed, and they are thus important for functional analysis and molecular breeding.ResultsA rice line with short wide grains, CSSL-Z563, was isolated from advanced-generation backcross population (BC3F6) derived from ‘Xihui 18’ (the recipient parent) and ‘Huhan 3’ (the donor parent). Z563 carried seven segments from ‘Huhan 3’, distributed on chromosomes 3, 7, and 8, with average substitution length of 5.52 Mb. Eleven QTLs for grain size were identified using secondary F2 population of ‘Xihui 18’/Z563. The QTLs qGL3–1, qGL3–2, and qGL7 control grain length in Z563 and have additive effects to reduce grain length; qGW3–1 and qGW3–2 control grain width in Z563 and have additive effects to increase grain width. Four SSSLs, three double-segment substitution lines (D1–D3), and two triple-segment substitution lines (T1 and T2) were developed containing the target QTLs. The genetic stability of eight QTLs, including qGL3–2, qGL3–1, and qGL7, was verified by the SSSLs. D1 (containing qGL3–2 and qGL3–1), D2 (qGL3–1 and qGL7), and T1 (qGL3–2, qGL3–1, and qGL7) had positive epistatic effects on grain length, and their grain length was shorter than that of the corresponding SSSLs. The QTL qGL3–2 was fine-mapped to a 696 Kb region of chromosome 3 containing five candidate genes that differed between ‘Xihui 18’ and Z563. These results are important for functional research on qGL3–2 and molecular breeding of hybrid rice cultivars.ConclusionsThe short and wide grain of Z563 was mainly controlled by qGL3–1, qGL3–2, qGL7, qGW3–1 and qGW3–2. The major QTL qGL3–2 was fine-mapped to a 696 Kb region of chromosome 3 containing five candidate genes. Different QTLs pyramiding displayed various phenotypes. In essence, the performance after pyramiding of genes depended on the comparison between the algebraic sum of the additive and epistatic effects of QTLs in the pyramidal line and the additive effect value of the single QTL. The results lay good foundation in the functional analysis of qGL3–2 and molecular design breeding of novel hybrid rice cultivars.

Inheritance and allelic relationship of foliar blast resistance gene(s) in pearl millet

Foliar blast disease in pearl millet (Pennisetum glaucum (L.) R. Br.) caused by Magnaporthe grisea once considered as a minor disease, has become major threat for pearl millet cultivation during recent decade in almost all pearl millet growing areas. The present study is an attempt to understand the inheritance of foliar blast resistance in pearl millet against the natural inoculum of Magnaporthe grisea and also against artificial inoculum of its devastating strain PMg_DI. The experiment was conducted at ICRISAT, Hyderabad and IARI, New Delhi during 2017-19. F2 and backcross populations derived from a susceptible genotype ICMB 95444 and two resistant lines PPMI-10018 and PPMI-2464 were used. Screening of individual plant in F1s, F2s, BCP1s (susceptible parent × F1) and BCP2s (resistant parent × F1) under field and controlled conditions indicated that the resistance is governed by a single dominant gene. The test of allelism was conducted by crossing the resistant parents. No segregation for resistance was observed in F2 generation when screened against the natural inoculum of Magnaporthe grisea and its strain PMg_DI. This indicates that both the resistant parents possess the same gene.

Importance of correcting genomic relationships in single-locus QTL mapping model with an advanced backcross population.

Advanced backcross (AB) populations have been widely used to identify and utilize beneficial alleles in various crops such as rice, tomato, wheat, and barley. For the development of an AB population, a controlled crossing scheme is used and this controlled crossing along with the selection (both natural and artificial) of agronomically adapted alleles during the development of AB population may lead to unbalanced allele frequencies in the population. However, it is commonly believed that interval mapping of traits in experimental crosses such as AB populations is immune to the deviations from the expected frequencies under Mendelian segregation. Using two AB populations and simulated data sets as examples, we describe the severity of the problem caused by unbalanced allele frequencies in quantitative trait loci mapping and demonstrate how it can be corrected using the linear mixed model having a polygenic effect with the covariance structure (genomic relationship matrix) calculated from molecular markers.

An advanced lentil backcross population developed from a cross between Lens culinaris × L. ervoides for future disease resistance and genomic studies

AbstractGenetically accessible variation to some of the abiotic and biotic stresses are limited in the cultivated lentil (Lens culinaris Medik.) germplasm. Introgression of novel alleles from its wild relative species will be useful for enhancing the genetic improvement of the crop. L. ervoides, one of the wild relatives of lentil, is a proven source of disease resistance for the crop. Here we introduce a lentil advanced backcross (LABC-01) population developed in cultivar ‘CDC Redberry’ background, based on L. ervoides alleles derived from an interspecific recombinant inbred population, LR-59-81. Two-hundred and seventeen individuals of the LABC-01 population at BC2F3:4 generation were screened for the race 0 of anthracnose (Colletotrichum lentis) and stemphylium blight (Stemphylium botryosum) under controlled conditions. The population showed significant variations for both diseases and the transfer of resistance alleles into the elite cultivar was evident. It also segregated for other traits such as days to flowering, seed coat colour, seed coat pattern and flower colour. Overall, we showed that LABC-01 population can be used in breeding programmes worldwide to improve disease resistance and will be available as a valuable genetic resource for future genetic analysis of desired loci introgressed from L. ervoides.

Do fruiting habit traits affect green fruit yield and its component traits in chilli (Capsicum annuumL.)?

AbstractIn chilli, farmer preferences for fruiting habit traits, namely fruit orientation (pendant erect) and fruits node−1(solitary cluster), vary from region to region. For increased acceptability by farmers/consumers, cultivars should be bred with preferred fruiting habit traits in high green fruit yielding background. An investigation was carried out to study the influence of fruiting habit traits on green fruit yield and its component traits during the 2016 and 2017 rainy seasons. The F2, backcross populations and near-isogenic lines (NILs) derived from crosses involving parents differing for single or both the fruiting habit traits were grouped into fruiting habit classes (single and cluster fruiting; and clustered erect, clustered pendant, single erect and single pendant). Significance of differences in fruit yield and its component traits between/among different fruiting habit trait classes were examined using ‘t’/‘F’ tests. The significance of ‘t’/‘F’ tests was regarded as pieces of evidence for considerable effects of fruiting habit traits on fruit yield and its component traits. While results-based on F2and backcross generations indicated a lack of effects, those based on NILs indicated significant effects of fruiting habit traits on fruit yield and its component traits. The plants bearing pendant fruits (irrespective of whether they are clustered or single) produced a large number of heavier and longer fruits than those bearing erect fruits. The results are discussed about the strategies to develop high yielding cultivars with farmer preferred fruiting habit traits.

Final Selection of Quality Protein Popcorn Hybrids.

Quality Protein Popcorn (QPP) BC2F5 inbred lines were produced through an interpopulation breeding system between Quality Protein Maize dent (QPM) and elite popcorn germplasm. In 2019, five QPP F1 hybrids were selected for further evaluation due to superior agronomics, endosperm protein quality, and popping quality traits. Though these BC2F5 QPP hybrids were phenotypically similar to their popcorn parents, the QPP cultivars conveyed slightly inferior popping characteristics when compared to the original popcorn germplasm. The objective of this study was twofold. First, BC2F5 inbred lines were crossed to their popcorn parents and BC3F4 inbred lines were produced for hybridization to test the agronomic, protein, and popping trait effects from an additional QPP by popcorn backcross. Second, BC2- and BC3-hybrids were simultaneously evaluated alongside ConAgra Brands® elite cultivars and ranked for potential commercialization in the spring of 2020. These 10 QPP hybrids were grown alongside five ConAgra Brands® elite popcorn cultivars in three locations and agronomic, protein quality, and popping quality traits were evaluated. Significant improvements in popcorn quality traits were observed in the QPP BC3 cultivars compared to their BC2 counterparts, and yield averages were significantly lower in BC3-derived QPP hybrids compared to the BC2 population. Protein quality traits were not significantly different between QPP backcrossing populations and significantly superior to ConAgra elite popcorn varieties. Utilizing a previously published ranking system, six QPP hybrids, three from the BC2F5 population and three from the BC3F4 population, were evaluated as candidates for final selection. The successful evaluation and ranking system methodology employed is transferable to other hybrid production and testing programs. Incorporating this analysis with concurrent sensory studies, two QPP hybrids were chosen as premier cultivars for potential commercialization.

Comparative Breeding potential of two crosses for response to late wilt disease (LWD) in maize (Zea mays L.)

Plant Breeders routinely develop a large number of crosses. This poses challenge to breeders in terms of prioritizing the crosses for advancing the generations. This necessitates testing the crosses to assess the breeding potential on BC1F1 and BC2F1 generations derived from two different crosses involving parents differing for response to late wilt disease resistance was assessed for response to late wilt disease. The recurrent parent that is common for both the crosses, is a seed parent of popular public bred maize hybrid “Hema”. In the present investigation, BC1F1 and BC2F1 generations of two crosses NAI-137 × MAI-345 and NAI-137 × 97B were assessed for their breeding potential for resistance to late wilt disease. The breeding potential was assessed based on the mean, variance and frequency of transgressive segregants. The BC1F1 and BC2F1 populations derived from the cross NAI-137 × MAI-345 expressed lower mean (for response to late wilt disease), wider absolute range and standardized range, and higher phenotypic coefficient of variation and frequency of transgressive segregants. Hence, backcross populations derived from the cross NAI-137 × MAI-345 was identified as the one with better breeding potential than that derived from NAI-137 × 97B.

An analysis of simulated yield data for pepper shows how genotype × environment interaction in yield can be understood in terms of yield components and their QTLs

AbstractComplex traits like yield are those in which phenotypic variation can be modeled as a linear function of a set of quantitative trait loci (QTLs) with environment dependency. This environment dependency can be observed at a phenotypic level as genotype × environment interaction (GEI) for yield itself and at an underlying genetic level as QTL × environment interaction (QEI). We show how GEI in yield may follow from pleiotropic QTLs for yield components that themselves are not environment dependent. We generated synthetic yield data via a crop growth model and analyzed these data by common statistical models for GEI and QEI. The QTLs for yield were pleiotropic with those for yield components. Such pleiotropy offers a path for improvement of yield under GEI. As a model system we used sweet pepper (Capsicum annuum L.) and developed an eco‐physiological model for yield with seven genotype‐specific inputs or yield components. Synthetic yields were simulated for a back cross population of 500 lines across a factorial combination of four major environmental drivers. The yield components were given a simple QTL basis and produced credible amounts and patterns of GEI for yield. The QEI for yield could be interpreted from the expression of QTLs for yield components and the interaction of these components with the environmental drivers. We see the generation of synthetic yield data via crop growth models followed by an analysis with statistical models for GEI and QEI to quantify the contribution of yield components to GEI as a helpful step in the development of yield prediction models for complex traits across environments that can also serve as a basis for decisions on selection strategies of complex traits.

Genetic analysis of bacterial wilt resistance in eggplant (Solanum melongena L.)

Bacterial wilt triggered by Ralstonia solanacearum is one of the major devastating diseases causing significant yield reduction in eggplant. F1 hybrids (18 CARI-1 based F1 hybrids and 12 publicly available hybrids/varieties) were evaluated for bacterial wilt resistance, yield, and yield attributing traits. CARI-1 based F1 hybrids showed superiority in yields, however showed a varied level of resistance to bacterial wilt. Further, inheritance and gene action involved in resistance to Ralstonia solanacearum was studied. CARI-1 was crossed with two susceptible parents, Arka Neelachal Shyama and Pusa Purple Long to develop six generations for both the combinations. The genetic control of resistance to bacterial wilt was found to be polygenic in the case of the Arka Neelachal Shyama x CARI-1 derived population. While di-genic with complementary gene action in the case of Pusa Purple Long x CARI-1 F2 population, however deviation in expected ratios was observed in back cross populations. Generation mean analysis revealed the presence of epistasis. For Arka Neelachal Shyama x CARI-1 derived population, owing to the prevalence of additive × additive non-allelic interaction with a negative sign, delaying of selection to later generations, otherwise inter mating between the selected segregates accompanied by selfing for one or more generation(s) is advised for the aggregation of favorable alleles for enhancement of resistance. Similarly, for Pusa Purple Long x CARI-1 population, the simple selection can be efficient due to the prevalence of additive gene action. The inheritance details accumulated in this study would facilitate the introgression of bacterial wilt resistance into elite commercial genotypes.

Gene mapping reveals the association between tyrosine protein kinase Abl1 and the silk yield of Bombyx mori.

The Z chromosome of the silkworm contains a major gene that influences silk yield. This major locus on chromosome Z accounts for 35.10% of the phenotypic variance. The location and identification of the gene have been a focus of silkworm genetics research. Unfortunately, identification of this gene has been difficult. We used extreme phenotype subpopulations and selected from a backcross population, BC1 M, which was obtained using the high-yield strain 872B and the low-yield strain IS-Dazao as parents, for mapping the gene on the chromosome Z. The candidate region was narrowed down to 134kb at the tip of the chromosome. BmAbl1 in this region correlated with silk gland development by spatiotemporal expression analysis. This gene was differentially expressed in the posterior silk glands of the high- and low-yield strains. In BmAbl1, an insertion-deletion (indel) within the 10th exonic region and an SNP within the 6th intronic region were detected and shown to be associated with cocoon shell weight in 84 Bombyxmori strains with different yields. Nucleotide diversity analysis of BmAbl1 and its 50kb flanking regions indicated that BmAbl1 has experienced strong artificial selection during silkworm domestication. This study is the first to identify the genes controlling silk yield in the major QTL of the Z chromosome using forward genetics.

Back-cross introgression of ‘Tour’ cytoplasm from Brassica napus through in vitro embryo rescue reveals partial restoration of sterility in B. oleracea

Cytoplasmic male sterility (CMS) is the most commonly used mechanisms for developing F1 hybrids in Brassica oleracea. Ogura cytoplasm is the only source of CMS system used widely in B. oleracea and diversification of CMS system is needed to avoid any imminent epidemic. We have developed sesquidiploids and backcross progenies involving the cybrid, B. napus with B. tournefortii (Tour) cytoplasm and B. oleracea for development of novel CMS system through different approaches of in vitro embryo rescue. Maturity of the ovaries and ovules were found to play important role in recovery of inter-specific hybrids through embryo rescue. The male sterility conferred by ‘Tour’ cytoplasm was partially restored by Rf genes in the B. oleracea nuclear genome and identification of perfect maintainer is necessary in developing ‘Tour’ based CMS system. The analysis of the sesquidiploid F1 hybrids and back-cross progenies revealed frequent occurrence of A and C sub-genome aneuploids and euploids. Chromosome elimination and fragmentation of the A and C genome specific linkage groups indicated the role of autosysndesis and allosyndesis in the AnCnCo sesquidiploid. The dominance of the B. napus like gametes was also evident in the first backcross progenies. The developed back-cross population with ‘Tour’ cytoplasm will be useful in developing stable CMS system in B. oleracea as an alternative to the available Ogura based lines for commercial hybrid breeding programme.

Major QTLs, qARO1 and qARO9, Additively Regulate Adaxial Leaf Rolling in Rice.

Moderate leaf rolling is considered optimal for the ideal plant type in rice (Oryza sativa L.), as it improves photosynthetic efficiency and, consequently, grain yield. Determining the genetic basis of leaf rolling via the identification of quantitative trait loci (QTLs) could facilitate the development of high-yielding varieties. In this study, we identified three stable rice QTLs, qARO1, qARO5, and qARO9, which control adaxial leaf rolling in a recombinant inbred line (RIL) population derived from a cross between Tong 88-7 (T887) and Milyang 23 (M23), using high-density SNP markers. These QTLs controlled the rolling phenotype of both the flag leaf (FL) and secondary leaf (SL), and different allelic combinations of these QTLs led to a wide variation in the degree of leaf rolling. Additive gene actions of qARO1 and qARO9 on leaf rolling were observed in a backcross population. In addition, qARO1 (markers: 01id4854718 and 01asp4916781) and qARO9 (markers: 09id19650402 and 09id19740436) were successfully fine-mapped to approximately 60- and 90-kb intervals on chromosomes 1 and 9, respectively. Histological analysis of near-isogenic lines (NILs) revealed that qARO1 influences leaf thickness across the small vein, and qARO9 affects leaf thickness in the entire leaf and bulliform cell area, thus leading to adaxial leaf rolling. The results of this study advance our understanding of the genetic and molecular bases of adaxial leaf rolling, and this information can be used for the development of rice varieties with the ideal plant type.

Assessing the Contribution of Sli to Self-Compatibility in North American Diploid Potato Germplasm Using KASP™ Markers

Diploid hybrid potato variety development requires the introduction of reliably transmitted self-compatibility (SC) to largely self-incompatible elite diploid germplasm. The diploid Solanum chacoense clone M6 has been widely used to introgress SC into North American potato diploid breeding programs. We determined that M6 is homozygous for six DNA Kompetitive Allele Specific PCR (KASP)™ markers spanning a 224 kb region, linked to Sli in Dutch germplasm. Self-compatible Sli alleles were identified in dihaploids of the cultivars ‘Atlantic’ and ‘Superior’ and breeding clone NY148. This finding demonstrates the potential of Sli genotyping to select S. tuberosum dihaploids that will contribute to SC. We appraised the transmission of Sli in a diploid recurrent selection population and in a diploid backcross population, each designed to introgress SC while improving agronomic traits. The frequency of the homozygous self-compatible Sli genotype at the six marker loci increased over the course of four cycles of recurrent selection. The homozygous Sli self-compatible genotype at any one of five marker loci within an 80.8 kb region on chromosome 12 (58,960,090-59,040,898 bp) perfectly predicted a SC phenotype in the recurrent selection population. The heterozygous Sli genotype was found in self-compatible and self-incompatible individuals. The discrepancy between phenotype and marker genotype can be attributed in part to the difficulty of accurately phenotyping SC. We also identified self-compatible individuals with the homozygous self-incompatible Sli genotype at all tested loci. The presence of the homozygous self-incompatible Sli haplotype in self-compatible clones 1S1 and DMRH-89 and a self-compatible individual from the S. chacoense PI 133664 further suggests that other genetic components contribute to SC. This work illustrates the ability of Sli markers to predict SC in some germplasm, but it also underscores the need to identify other genomic regions critical to SC and the role of the environment in expression of genes involved in the SC reaction.

Developing partial interspecific hybrids of Momordica charantia × Momordica balsamina and their advance generations

Interspecific hybridization and introgression breeding are the major approaches employed to address climate change and food security challenges globally. The present study was conducted to trace the nature of crossing barriers and to introgress novel genes from Momordica balsamina to cultivated bitter gourd Momordica charantia. The hybridization success rate was very low between these two species with a higher rate of seedling mortality. A total of 116 accessions of Momordica charantia (female parent) were used for artificial cross-pollination with Momordica balsamina (IC-467683). Among these, only six female parents belonging to Momordica charantia (DBGS-2, NEH-4, PDMGY-201, Pusa Aushadhi, DBGS-3, and NEH-3) exhibited variable percent fruit set when crossed with Momordica balsamina. Among these interspecific crosses, only one cross combination (Pusa Aushadhi × Momordica balsamina) produced the higher percentage of normal seeds and only one seed was germinated followed by development into a full plant. The pollen-pistil interaction study confirmed the existence of post dynamic barriers in all these unsuccessful crosses. A single plant progeny of M. charantia × M. balsamina was derived and its advanced generations were studied at morphological, cytological, and molecular levels. The plant phenotype predominately resembled the female parent with variation in a few traits. The cytological analysis depicted the normal meiosis and the genomic 2C DNA content of the interspecific hybrid was higher than the female parent. The microsatellite (SSRs) markers analysis showed that amplified fragments of interspecific hybrids exhibited highly conserved similarity with fragments of female parents with a very low frequency of male fragments. The F2 and backcross generations were produced from the single partial interspecific hybrid (Pusa Aushadhi × M. balsamina). Twenty advanced generation F2 plants showed variation with majority traits resembles the female parent. The microsatellite analysis revealed that the progenies of backcross generation amplified the fragments with high similarity to both female (Pusa Aushadhi; M. charantia) and the male parent (M. balsamina). These results confirmed the partial introgression of chromosome segments of M. balsamina. But further generations could not be recovered and advanced generation was died because of chlorosis. It was the first attempt to develop an interspecific partial hybrid and its backcross population which would provide preliminary information on the crossability relationship between these two species for transferring novel gene/s or traits from M. balsamina to M. charantia.

Unraveling the Sclerotinia Basal Stalk Rot Resistance Derived From Wild Helianthus argophyllus Using a High-Density Single Nucleotide Polymorphism Linkage Map.

Basal stalk rot (BSR), caused by the fungus Sclerotinia sclerotiorum, is a serious disease of sunflower (Helianthus annuus L.) in the humid temperate growing areas of the world. BSR resistance is quantitative and conditioned by multiple genes. Our objective was to dissect the BSR resistance introduced from the wild annual species Helianthus argophyllus using a quantitative trait loci (QTL) mapping approach. An advanced backcross population (AB-QTL) with 134 lines derived from the cross of HA 89 with a H. argophyllus Torr. and Gray accession, PI 494573, was evaluated for BSR resistance in three field and one greenhouse growing seasons of 2017–2019. Highly significant genetic variations (p < 0.001) were observed for BSR disease incidence (DI) in all field screening tests and disease rating and area under the disease progress curve in the greenhouse. The AB-QTL population and its parental lines were genotyped using the genotyping-by-sequencing method. A genetic linkage map spanning 2,045.14 cM was constructed using 3,110 SNP markers mapped on 17 sunflower chromosomes. A total of 21 QTL associated with BSR resistance were detected on 11 chromosomes, each explaining a phenotypic variation ranging from 4.5 to 22.6%. Of the 21 QTL, eight were detected for BSR DI measured in the field, seven were detected for traits measured in the greenhouse, and six were detected from both field and greenhouse tests. Thirteen of the 21 QTL had favorable alleles from the H. argophyllus parent conferring increased BSR resistance.

Physical mapping and InDel marker development for the restorer gene Rf2 in cytoplasmic male sterile CMS-D8 cotton

BackgroundCytoplasmic male sterile (CMS) with cytoplasm from Gossypium Trilobum (D8) fails to produce functional pollen. It is useful for commercial hybrid cotton seed production. The restore line of CMS-D8 containing Rf2 gene can restore the fertility of the corresponding sterile line. This study combined the whole genome resequencing bulked segregant analysis (BSA) with high-throughput SNP genotyping to accelerate the physical mapping of Rf2 locus in CMS-D8 cotton.MethodsThe fertility of backcross population ((sterile line×restorer line)×maintainer line) comprising of 1623 individuals was investigated in the field. The fertile pool (100 plants with fertile phenotypes, F-pool) and the sterile pool (100 plants with sterile phenotypes, S-pool) were constructed for BSA resequencing. The selection of 24 single nucleotide polymorphisms (SNP) through high-throughput genotyping and the development insertion and deletion (InDel) markers were conducted to narrow down the candidate interval. The pentapeptide repeat (PPR) family genes and upregulated genes in restore line in the candidate interval were analysed by qRT-PCR.ResultsThe fertility investigation results showed that fertile and sterile separation ratio was consistent with 1:1. BSA resequencing technology, high-throughput SNP genotyping, and InDel markers were used to identify Rf2 locus on candidate interval of 1.48 Mb on chromosome D05. Furthermore, it was quantified in this experiment that InDel markers co-segregated with Rf2 enhanced the selection of the restorer line. The qRT-PCR analysis revealed PPR family gene Gh_D05G3391 located in candidate interval had significantly lower expression than sterile and maintainer lines. In addition, utilization of anther RNA-Seq data of CMS-D8 identified that the expression level of Gh_D05G3374 encoding NB-ARC domain-containing disease resistance protein in restorer lines was significantly higher than that in sterile and maintainer lines.ConclusionsThis study not only enabled us to precisely locate the restore gene Rf2 but also evaluated the utilization of InDel markers for marker assisted selection in the CMS-D8 Rf2 cotton breeding line. The results of this study provide an important foundation for further studies on the mapping and cloning of restorer genes.

Genetic parameters for egg production traits in crosses between local and exotic chickens estimated by Bayesian inference

Estimates of genetic parameters for economic traits are important to enable the breeder estimate the breeding value of individuals available for selection. Thus, this study was carried out to estimate genetic parameters namely heritability and genetic correlations among egg production traits in two strain crosses using bivariate animal model in Bayesian (MCMC) method. The egg production data were obtained from four generations which comprised the base population of two commercial egg strains and the local chicken, the inbred population derived from the base population, the F1 crossbred population obtained from the crossing of the local and exotic inbred chickens and the backcross population obtained from the backcrossing of the crossbred to their parents. A total number of 1,138 daughters of 62 sires and 620 dams were used for the study. The autocorrelations among samples in the MCMC chain were less than 0.1 for all lag values indicating that all samples of the posterior distribution were independent. The estimated heritability for age at first egg, body weight at first egg, hen day egg number, weight of first egg, egg weight at thirty week and egg weight at forty week were 0.62, 0.48, 0.47, 0.53, 0.54 and 0.56 for strain 1 crosses and 0.43, 0.48, 0.49, 0.52, 0.52 and 0.53 for strain 2 crosses. The corresponding highest posterior density interval ranged from 0.22 to 0.91 for strain 1 crosses and 0.07 to 0.83 for strain 2 crosses. The genetic correlations among egg production traits ranged from 0.06 to 1.97 in strain 1 and 0.06 to 2.59 in strain 2 crosses. The estimates were within the range reported in literature for egg production traits in chicken and imply that appreciable amount of additive genes exist in the strain crosses which could be used for the selection of superior birds. The magnitude of genetic correlations implies that selection of one trait could lead to correlated response to the other traits.

Agronomic and seed traits of high‐oleic soybean lines containing the DP‐305423‐1 transgene in four backcross populations

AbstractThe DP‐305423‐1 transgene elevates oleic acid concentration and reduces polyunsaturated fatty acids in soybean [Glycine max (L.) Merr.] oil, resulting in increased oxidative stability. The objective of this research was to investigate the effect of the DP‐305423‐1 transgene on agronomic and seed traits using four backcross derived soybean populations to provide further understanding of the transgene's influence across varying genetic backgrounds and environments. An equal number of high‐oleic, low‐linolenic (HOLL) and normal‐oleic, low‐linolenic (NOLL) progeny from four BC1F4:F6 populations—B (n = 30), C (n = 22), D (n = 56), and E (n = 34)—were grown across six locations in 2015. Across all locations, the high‐oleic (HO) progeny had a mean yield 77 kg ha−1 less in Population B, and 382 kg ha−1 greater in Population C compared with the normal‐oleic (NO) class. There was no significant difference in yield between HO and NO in Populations D and E. The HO progeny had a significantly lower mean oil concentration and greater protein concentration than the NO class in all populations, whereas 100‐seed weight of the HO class was, on average, greater than in the NO class. The results provide evidence that the reduction in oil concentration is associated with the HO phenotype in the progeny carrying the DP‐3054231‐1 transgene and demonstrate no consistent effect of the transgene on seed yield, suggesting that differences may be due to the genetic background of the population studied.