Major Locus Research Articles

Identification of RppSLN from an Elite Landrace: A Major Locus Conferring Resistance to Southern Corn Rust in Maize (Zea mays L.)

Southern corn rust (SCR) is one of the most destructive foliar diseases in maize (Zea mays L.), resulting in significant yield losses. Therefore, the continuous identification of disease-resistant germplasm and the deployment of resistant hybrids is essential for durably controlling SCR. The objective of this research was to identify and characterize resistance loci against SCR in maize to expand disease management strategies. Here, we identified a maize landrace with high resistance to SCR ‘Silunuo’ (SLN) approaching complete immunity. We backcrossed it with a susceptible inbred line, N531, to generate a stable SCR-resistant introgression line N531_R. By crossing it with F35 (a susceptible inbred line), we created a large F2 segregating population and mapped a major SCR-resistant locus on chromosome 10, known as RppSLN. Based on the genome assembly and annotation, we found that RppSLN harbors two NBS-LRR (nucleotide binding site–leucine-rich repeat) genes, namely Zmays10G000430 and Zmays10G000440. These NBS-LRR genes were significantly induced during artificial inoculation with Puccinia polysora, suggesting that they might be candidate genes collectively contributing to the resistance level at this locus. In conclusion, this study identified a major SCR resistance locus directly isolated from a landrace, providing valuable support and information for expanding new disease-resistant germplasms and promoting the utilization of landraces.

Fine mapping and candidate gene mining of QSc/Sl.cib-7H for spike compactness and length and its pleiotropic effects on yield-related traits in barley (Hordeum vulgare L.).

A major locus for spike compactness and length was mapped on chromosome 7H and its pleiotropic effects, candidate genes and transcriptional regulatory network were analyzed. Spike compactness (SC) and length (SL) are important traits of barley (Hordeum vulgare L.) due to their close association with grain yield. In this study, a major SC and SL locus QSc/Sl.cib-7H was primarily identified on chromosome 7H by bulked segregant analysis, and further fine mapped to a recombination cold spot expanding 244.36-388.09Mb by developing a secondary population using residual heterozygous lines. This region is much more accurate than previously reported spike compactness loci on chromosome 7H.The strong effects of QSc/Sl.cib-7H on SL and SC were validated in two pair of near isogenic lines (NILs) and diverse genetic backgrounds. QSc/Sl.cib-7H exhibited pleiotropic effects on plant height (PH), thousand grain weight and grain length, and did not significantly influence the spikelet number of main spike (SMS) and grain width. Transcriptome analysis based on NILs showed that regulation of SC and SL might be related to the plant circadian rhythm pathway. The candidate genes were mined by analyzing variants and expression patterns of genes in the target region employing multiple genome and transcriptome data. This study takes a further step towards cloning of QSc/Sl.cib-7H, and the data obtained and the developed molecular markers will facilitate its utilization in barley breeding.

Cotranscriptional splicing is required in the cold to produce COOLAIR isoforms that repress Arabidopsis FLC

Plants use seasonal cold to time the transition to reproductive development. Short- and long-term cold exposure is registered via parallel transcriptional shutdown and Polycomb-dependent epigenetic silencing of the Arabidopsis thaliana major flowering repressor locus FLOWERING LOCUS C (FLC). The cold-induced antisense transcripts (COOLAIR) determine the dynamics of FLC transcriptional shutdown, but the thermosensory mechanisms are still unresolved. Here, through a forward genetic screen, we identify a mutation that perturbs cold-induced COOLAIR expression and FLC repression. The mutation is a hypomorphic allele of SUPPRESSORS OF MEC-8 AND UNC-52 1 (SMU1), a conserved subunit of the spliceosomal B complex. SMU1 interacts in vivo with the proximal region of nascent COOLAIR and RNA 3' processing/cotranscriptional regulators and enhances COOLAIR proximal intron splicing to promote specific COOLAIR isoforms. SMU1 also interacts with ELF7, an RNA Polymerase II Associated Factor (Paf1) component and limits COOLAIR transcription. Cold thus changes cotranscriptional splicing/RNA Pol II functionality in an SMU1-dependent mechanism to promote two different isoforms of COOLAIR that lead to reduced FLC transcription. Such cotranscriptional mechanisms are emerging as important regulators underlying plasticity in gene expression.

Identification of a novel locus qGW12/OsPUB23 regulating grain shape and weight in rice (Oryza sativa L.).

Key message A major quantitative trait locus (qGW12) for grain shape and weight has been isolated in rice, corresponding to LOC_Os12g17900/OsPUB23, and its encoded protein interacts with OsMADS1. Grain shape in rice is an important trait that influences both yield and quality. The primary determinants of grain shape are quantitative trait loci (QTLs) inherited from natural variation in crops. In recent years, much attention has been paid to the molecular role of QTLs in regulating grain shape and weight. In this study, we report the cloning and characterization of qGW12, a major QTL regulating grain shape and weight in rice, using a series of chromosome fragment substitution lines (CSSLs) derived from Oryza sativa indica cultivar 9311 (acceptor) and Oryza rufipogon Griff (donor). One CSSL line, Q187, harboring the introgression of qGW12, exhibited a significant decrease in grain-shape-related traits (including grain length and width) and thousand-grain weight compared to the cultivar 9311. Subsequent backcrossing of Q187 with 9311 resulted in the generation of secondary segregating populations, which were used to fine-map qGW12 to a 24-kb region between markers Seq-44 and Seq-48. Our data indicated that qGW12 encodes a previously unreported U-box type E3 ubiquitin ligase, designated OsPUB23, which exhibited E3 ubiquitin ligase activity. Overexpression of OsPUB23 in rice resulted in higher plant yield than the wild type due to an increase in grain size and weight. Conversely, loss of OsPUB23 function resulted in the opposite tendency. Yeast two-hybrid screening and split luciferase complementation assays revealed that OsPUB23 interacts with OsMADS1. The functional characterization of OsPUB23 provides new genetic resources for improving of grain yield and quality in crops.

Evolutionary history written in tandem arrays – satellite repeats in the Lagoseris lineage of Crepis sensu lato (Asteraceae)

Abstract Satellite DNA families are excellent markers in evolutionary studies of plant karyotypes. Together with phylogenetic background, they can provide additonal information on different scenarios accompanying the speciation and diversification of related species. The Lagoseris lineage of Crepis sensu lato constitutes an interesting model in such studies, mainly due to: (i) the presence of large chromosomes; (ii) several base chromosome numbers; and (iii) variation in genome sizes. We aimed to characterize the satellite families and compare their genomic and chromosomal organization to better understand the evolutionary pathways that shaped the genomes of the Lagoseris lineage. Eight different families of satellite repeats were identified in Crepis palaestina based on RepeatExplorer raw Illumina read analyses. Most of these satellites were present in five species studied from the Lagoseris lineage and organized in tandem arrays. If the particular repeat was present in the genome of the related species, its genomic organization showed similarity to the one observed in C. palaestina. This similar genomic organization was not often reflected at the chromosomal level, where many distinct distribution patterns were shown, from several major loci to numerous minor ones spread throughout the chromosomal arms. The evolution of satellite repeats is discussed in phylogenetic context.

Binding of PtoRAP2.12 to demethylated and accessible chromatin regions in the PtoGntK promoter stimulates growth of poplar.

DNA methylation is an essential epigenetic modification for gene regulation in plant growth and development. However, the precise mechanisms of DNA methylation remain poorly understood, especially in woody plants. We employed whole-genome bisulfite sequencing (WGBS), assays for transposase-accessible chromatin using sequencing (ATAC-seq), and RNA-Seq to investigate epigenetic regulatory relationships in Populus tomentosa treated with DNA methylation inhibitor 5-azacitidine. Expression-quantitative trait methylation analysis (eQTM), epigenome-wide association study (EWAS), and joint linkage-linkage disequilibrium mapping were used to explore the epigenetic regulatory genes, and using CRISPR/Cas9 to identify the role of candidate genes. Plant developmental abnormalities occurred when DNA methylation levels were substantially reduced. DNA methylation regulated 112 expressed genes via chromatin accessibility, of which 61 genes were significantly influenced by DNA methylation variation at the population level. One DNA methylation-regulated gene, PtoGntK, was located in a major quantitative trait locus (QTL) for poplar growth. Overexpression and CRISPR/Cas9 of PtoGntK revealed it affected poplar height and stem diameter. The PtoRAP2.12 was found to bind to the demethylated accessible region in the PtoGntK promoter, thereby promoting growth in poplar. This study identified key genes with epigenetic regulation for plant growth and provides insights into epigenetic regulation mechanisms in woody plants.

Artificial selection of two antagonistic E3 ubiquitin ligases finetunes soybean photoperiod adaptation and grain yield

The precise control of flowering time is of utmost importance for crop adaptation to varying environmental conditions and consequently determines grain yield and plant fitness. Soybean E2, the homolog of Arabidopsis GIGANTEA, is a major locus contributing to high-latitude adaptation and is involved in photoperiod sensitivity. However, due to major effects of E2, additional genetic loci controlling soybean flowering and adaptation have historically been masked and difficult to identify. Here, by eliminating the effect of E2, we identified a Tof9 locus controlling flowering in which ZEITLUPE 2 (ZTL2) is the causal gene. ZTL2 encodes an F-box E3 ubiquitin ligase with homology to Arabidopsis ZEITLUPE and is shown to play a key role in the soybean photoperiodic flowering pathway. ZTL2 physically interacts with E2 to mediate its degradation. Intriguingly, ZTL2 and FKF1, both belong to the F-box-type E3 ubiquitin-ligase family, exhibit opposite roles in regulating soybean flowering. ZTL2 degrades E2, leading to early flowering, while FKF1 stabilizes E2, resulting in delayed flowering. The balance between ZTL2-mediated degradation and FKF1-mediated stabilization enables soybeans to finetune flowering time and maximize grain yield. Field-grown ztl2 mutants are taller, flower late, and have increased yield parameters. ZTL2 and FKF1b bear contrasting artificial-selection patterns to adapt to different latitudes. This antagonistic regulation is crucial for soybean adaptation to diverse ecological settings and allows plants to fine-tune their flowering time in response to photoperiod and latitudinal changes.

Discover QTLs for the level of blood components in Shaoxing duck using GWAS and haplotype sharing analysis

Blood composition is indicative of health-related traits such as immunity and metabolism. The use of molecular genetics to investigate alterations in these attributes in laying ducks is a novel approach. Our objective was to employ genome − wide association studies (GWAS) and haplotype − sharing analysis to identify genomic regions and potential genes associated with 11 blood components in Shaoxing ducks. Our findings revealed 35 SNPs and 1 SNP associated with low-density lipoprotein cholesterol (LDL) and globulin (GLB), respectively. We identified 36 putative candidate genes for the LDL trait in close proximity to major QTLs and key loci. Based on their biochemical and physiological properties, TRA2A, NPY, ARHGEF26, DHX36, and AADAC are the strongest putative candidate genes. Through linkage disequilibrium analysis and haplotype sharing analysis, we identified three haplotypes and one haplotype, respectively, that were significantly linked with LDL and GLB. These haplotypes could be selected as potential candidate haplotypes for molecular breeding of Shaoxing ducks. Additionally, we utilized a bootstrap test to verify the reliability of GWAS with small experimental samples. The test can be accessed at https://github.com/xuwenwu24/Bootstrap-test.

COLD6-OSM1 module senses chilling for cold tolerance via 2′,3′-cAMP signaling in rice

While it is known that temperature sensors trigger calcium (Ca2+) signaling to confer cold tolerance in cells, less is known about sensors that couple with other secondary messengers. Here, we identify a cold sensor complex of CHILLING-TOLERANCE DIVERGENCE 6 (COLD6) and osmotin-like 1 (OSM1), which triggers 2',3'-cyclic adenosine monophosphate (2',3'-cAMP) production to enhance cold tolerance in rice. COLD6, which is encoded by a major quantitative trait locus (QTL) gene, interacts with the rice G protein α subunit (RGA1) at the plasma membrane under normal conditions. Upon exposure to chilling, cold-induced OSM1 binds to COLD6, kicking out RGA1 from interaction. This triggers an elevation of 2',3'-cAMP levels for enhancing chilling tolerance. Genetic data show that COLD6 negatively regulates cold tolerance and functionally depends on OSM1 in chilling stress. COLD6 alleles were selected during rice domestication. Knockout and natural variation of COLD6 in hybrid rice enhanced chilling tolerance, hinting design potential for breeding. This highlighted a module triggering 2',3'-cAMP to improve chilling tolerance in crops.

Lactuca super-pangenome reduces bias towards reference genes in lettuce research

BackgroundBreeding of lettuce (Lactuca sativa L.), the most important leafy vegetable worldwide, for enhanced disease resistance and resilience relies on multiple wild relatives to provide the necessary genetic diversity. In this study, we constructed a super-pangenome based on four Lactuca species (representing the primary, secondary and tertiary gene pools) and comprising 474 accessions. We include 68 newly sequenced accessions to improve cultivar coverage and add important foundational breeding lines.ResultsWith the super-pangenome we find substantial presence/absence variation (PAV) and copy-number variation (CNV). Functional enrichment analyses of core and variable genes show that transcriptional regulators are conserved whereas disease resistance genes are variable. PAV-genome-wide association studies (GWAS) and CNV-GWAS are largely congruent with single-nucleotide polymorphism (SNP)-GWAS. Importantly, they also identify several major novel quantitative trait loci (QTL) for resistance against Bremia lactucae in variable regions not present in the reference lettuce genome. The usability of the super-pangenome is demonstrated by identifying the likely origin of non-reference resistance loci from the wild relatives Lactuca serriola, Lactuca saligna and Lactuca virosa.ConclusionsThe super-pangenome offers a broader view on the gene repertoire of lettuce, revealing relevant loci that are not in the reference genome(s). The provided methodology and data provide a strong basis for research into PAVs, CNVs and other variation underlying important biological traits of lettuce and other crops.

Continuous integration of heading and goal directions guides steering.

Navigating animals must integrate a diverse array of sensory cues into a single locomotor decision. Insects perform intricate navigational feats using a brain region termed the central complex in which an animal's heading direction is transformed through several layers of circuitry to elicit goal-directed locomotion. These transformations occur mostly in the fan-shaped body (FB), a major locus of multi-sensory integration in the central complex. Key aspects of these sensorimotor computations have been extensively characterized by functional studies, leveraging the genetic tools available in the fruit fly. However, our understanding of how neuronal activity in the FB dictates locomotor behaviors during navigation remains enigmatic. Here, we manipulate the activity of two key neuronal populations that input into the FB-the PFN a and PFN d neurons-used to encode the direction of two complex navigational cues: wind plumes and optic flow, respectively. We find that flies presented with unidirectional optic flow steer along curved walking trajectories, but silencing PFN d neurons abolishes this curvature. We next use optogenetic activation to introduce a fictive heading signal in the PFNs to establish the causal relationship between their activity and steering behavior. Our studies reveal that the central complex guides locomotion by summing the PFN-borne directional signals and shifting movement trajectories left or right accordingly. Based on these results, we propose a model of central complex-mediated locomotion wherein the fly achieves fine-grained control of sensory-guided steering by continuously integrating its heading and goal directions over time.

Machine vision-assisted genomic prediction and genome-wide association of spleen-related traits in large yellow croaker infected with visceral white-nodules disease

High-resolution and high-throughput genotype-to-phenotype studies in fish are rapidly advancing, driven by innovative technologies that aim to address the challenges of modern breeding models. In recent years, machine vision and deep learning techniques, particularly convolutional neural networks (CNNs), have achieved significant success in image recognition and segmentation. Moreover, qualitative and quantitative analysis of disease resistance has always been a crucial field of research in genetics. This motivation has led us to investigate the potential of large yellow croaker visceral white-nodules disease (VWND) in encoding information on disease resistance for the task of accession classification. In this study, we proposed an image segmentation framework for the feature extraction of the spleen after VWND infection based on machine vision. We utilized deep CNNs and threshold segmentation for automatic feature learning and object segmentation. This approach eliminates subjectivity and enhances work efficiency compared to using hand-crafted features. Additionally, we employed spleen-related traits to conduct genome-wide association analysis (GWAS), which led to the identification of 24 significant SNPs and 10 major quantitative trait loci. The results of function enrichment analysis on candidate genes also indicated potential relationships with immune regulation mechanisms. Furthermore, we explored the use of genomic selection (GS) technology for phenotype prediction of extreme individuals, which further supports the predictability of spleen-related phenotypes for VWND resistance in large yellow croakers. Our findings demonstrate that artificial intelligence (AI)-based phenotyping approaches can deliver state-of-the-art performance for genetics research. We hope this work will provide a paradigm for applying deep learning and machine vision to phenotyping in aquaculture species.

Localization of Genetic Factors that Determine the Economically-Useful Traits of the PEAR (<i>Pyrus</i>) and Methods of Marker-Assisted Selection

DNA markers are an alternative method for accelerated identification of interested genes and loci at the early stages of ontogenesis, and, consequently, DNA markers are able to intensify the breeding process. This article represents overview of research on the localization of economically useful traits in the pear genome and the development and use of marker-assisted selection (MAS) techniques. At the moment, several traits have been localized in the pear genome, i.e.: resistance to scab European (V. pirina Aderh) and Asian (V. nashicola), black spot (Alternaria alternata (Fr.) Keissler), brown spot (Stemphylium vesicarium), fire blight (Erwinia amylovora), pear psylla (Cacopsylla pyri), pear sawfly (Caliroa cerasi), pear blister mite (Eriophyes pyri), self-incompatibility, dwarf trait. Major genes and loci of quantitative traits (QTLs) of fruits characteristics have also been identified, namely: skin color and rustiness of the fruit, size and weight of the fruit, taste, level of ethylene production, harvest time etc. It should be noted that currently Russian research is limited to the validation and use of MAS methods developed abroad. According to the experience of Japanese scientists, the use of MAS for several key traits has made it possible to triple the efficiency of the breeding process. Despite the currently limited list of MBC methods for pears, the high speed of genomic technologies development promises rapid development of new MAS methods in the future. In combination with new breeding technologies (New Breeding Techniques) based on accelerated flowering, the use of MAS for pears is a promising direction of breeding.

7448 Endogenous ACTH But Not Intermittent Cosyntropin Prevents Dexamethasone-Induced Adrenal Suppression In Mice

Abstract Disclosure: L.S. Gaston: None. H.R. Friedman: None. J.A. Majzoub: None. Background: Iatrogenic adrenal insufficiency (IAI) can persist for up to a year after withdrawal of long-term glucocorticoids (GC) by unknown mechanisms. We developed a mouse model of IAI in which 8 weeks of dexamethasone (DEX) induced protracted adrenocortical dysfunction despite early ACTH recovery. We then asked if 1) adrenal secretory dysfunction after GC withdrawal exceeded the cellular defect, and 2) ongoing trophic ACTH signaling while on DEX (either exogenous cosyntropin [COS] or endogenous ACTH) prevented IAI. Methods: Adult, male, wild-type C56BL/6J (n=3-6) mice were treated for 8 weeks (long-term) or 4-days (short-term) with DEX ± daily, intraperitoneal COS. At 1-2-week intervals after DEX±COS withdrawal, basal and stimulated ACTH and CORT were measured (mean±SEM) followed by necroscopy for morphometric analysis of immunostained, equatorial adrenal sections. Experiments were repeated in mice with irrepressible, endogenous ACTH due to selective loss of the hypothalamic GC receptor (Sim1-Cre:GR fl/fl, or SGR) and their Cre-negative (WT) littermates. Results: Stimulated corticosterone (CORT) required 8 weeks to normalize after stopping long-term DEX. Notably, both basal (811±220 vs. 216±24 pg/mL) and stimulated (1708±85 vs. 876±44) ACTH increased above controls by 1-week post-withdrawal (p<0.001 for both). Adrenal weights (1±0.1 vs. 2.5±0.1 mg) and cortical areas (480±9 vs. 1290±222 mm2) were significantly lower in DEX-treated glands vs. controls (p≤ 0.0001 for both) but recovered by 1-week post-withdrawal. Paucicellular, lipofuscin-rich accumulations were present in DEX-treated glands and persisted through 8 weeks post-withdrawal. In a linear regression of cortical area minus these inclusions (functional cortical area) vs. stimulated CORT (r2=0.43), predicted CORT was >2x higher (10 and 11 mg/dL) than measured CORT (5 for both) at 1- and 2-weeks post-DEX. In subsequent experiments, short-term COS inhibited DEX-induced adrenocortical apoptosis (200±85 vs 1170±481 TUNEL+ cells/HPF, p<0.01). However, CORT recovered more slowly in mice treated with long-term DEX+COS vs. DEX alone (doubling time=5.2 vs. 2.5 weeks), and glands were atrophic with lipofuscin-rich inclusions. Meanwhile, SGR mice maintained normal ACTH levels on long-term DEX. At the time of DEX withdrawal, SGR basal (14±4 vs.1.5±1.7 mcg/dL, p<0.05) and stimulated CORT responses (33±9.6 vs. 1.1±1.1, p<0.001), adrenal weights (2.3±0.2 vs. 1.1±0.06 mg, p≤ 0.001), and functional cortical area (1249±45 vs. 324±102 mm2, p≤ 0.001) were all greater than WT littermates, and lipofuscin-rich inclusions were absent in DEX-treated SGR glands. Conclusions: The adrenal is the major anatomic locus of post-withdrawal IAI in mice, which may involve early defects in both cortical size and secretory function. Novel therapies that mimic endogenous ACTH signaling during the period of GC exposure may prevent IAI. Presentation: 6/2/2024

Complete sequencing of ape genomes.

We present haplotype-resolved reference genomes and comparative analyses of six ape species, namely: chimpanzee, bonobo, gorilla, Bornean orangutan, Sumatran orangutan, and siamang. We achieve chromosome-level contiguity with unparalleled sequence accuracy (<1 error in 500,000 base pairs), completely sequencing 215 gapless chromosomes telomere-to-telomere. We resolve challenging regions, such as the major histocompatibility complex and immunoglobulin loci, providing more in-depth evolutionary insights. Comparative analyses, including human, allow us to investigate the evolution and diversity of regions previously uncharacterized or incompletely studied without bias from mapping to the human reference. This includes newly minted gene families within lineage-specific segmental duplications, centromeric DNA, acrocentric chromosomes, and subterminal heterochromatin. This resource should serve as a definitive baseline for all future evolutionary studies of humans and our closest living ape relatives.

Cy-1, a major QTL for tomato leaf curl New Delhi virus resistance, harbors a gene encoding a DFDGD-Class RNA-dependent RNA polymerase in cucumber (Cucumis sativus)

BackgroundTomato leaf curl New Delhi virus (ToLCNDV) (family Geminiviridae, genus Begomovirus) is a significant threat to cucumber (Cucumis sativus) production in many regions. Previous studies have reported the genetic mapping of loci related to ToLCNDV resistance, but no resistance genes have been identified.ResultsWe conducted map-based cloning of the ToLCNDV resistance gene in cucumber accession No.44. Agroinfiltration and graft-inoculation analyses confirmed the resistance of No.44 to ToLCNDV isolates from the Mediterranean and Asian countries. Initial mapping involving two rounds of phenotyping with two independent F2 populations generated by crossing the begomovirus-susceptible cultivar SHF and No.44 consistently detected major quantitative trait loci (QTLs) on chromosomes 1 and 2 that confer resistance to ToLCNDV. Fine-mapping of Cy-1, the dominant QTL on chromosome 1, using F3 populations narrowed the candidate region to a 209-kb genomic segment harboring 24 predicted genes. Among these genes, DFDGD-class RNA-dependent RNA polymerase (CsRDR3), an ortholog of Ty-1/Ty-3 of tomato and Pepy-2 of capsicum, was found to be a strong candidate conferring ToLCNDV resistance. The CsRDR3 sequence of No.44 contained multiple amino acid substitutions; the promoter region of CsRDR3 in No.44 had a large deletion; and the CsRDR3 transcript levels were greater in No.44 than in SHF. Virus-induced gene silencing (VIGS) of CsRDR3 using two chromosome segment substitution lines harboring chromosome 1 segments derived from No.44 compromised resistance to ToLCNDV.ConclusionsForward and reverse genetic approaches identified CsRDR3, which encodes a DFDGD-class RNA-dependent RNA polymerase, as the gene responsible for ToLCNDV resistance at the major QTL Cy-1 on chromosome 1 in cucumber. Marker-assisted breeding of ToLCNDV resistance in cucumber will be expedited by using No.44 and the DNA markers developed in this study.

Genome-Wide Association Analyses Defined the Interplay between Two Major Loci Controlling the Fruit Texture Performance in a Norwegian Apple Collection (Malus × domestica Borkh.)

Increasing consumption of apples (Malus domestica Borkh.) produced in Norway requires the availability of superior cultivars and extended marketability. Favorable texture and slow softening are important traits for consumer appreciation and postharvest performance. Apple texture has been well characterized using both sensory evaluation and instrumental assessments, and major quantitative trait loci (QTL) have been detected. With texture being targeted as an important trait and markers being publicly available, marker-assisted selection has already been implemented into several breeding programs. When focusing solely on a limited set of markers linked to well-investigated major QTLs, most minor-effect QTLs are normally excluded. To find novel potential SNP markers suitable to assist in selection processes, we selected a subset of accessions from a larger apple collection established in Norway based on the favorable alleles of two markers previously associated with texture, enabling the investigation of a minor part of the variance initially masked by the effect of major loci. The subset was employed to conduct a genome-wide association study aiming to search for associations with texture dynamics and retainability. QTL regions related to texture at harvest, postharvest, and for the storage index were identified on chromosomes 3, 12, and 16. Specifically, the SNPs located on chromosome 12 were shown to be potential novel markers for selection of crispness retention during storage, a valuable storability trait. These newly detected QTLs and underlying SNPs will represent a potential set of markers for the selection of the most favorable accessions characterized by superior fruit texture properties in ongoing breeding programs.

Identification of quantitative trait loci for lodging and related agronomic traits in soybean (Glycine max [L.] Merr.)

BackgroundLodging, a crucial agronomic trait linked to soybean yield, poses a significant challenge in soybean production. Nevertheless, there has been less research on soybean lodging compared to other important agronomic traits, hindering progress in breeding high-yield soybeans. Our goals were to investigate lodging, pinpoint quantitative trait loci (QTL) linked to lodging, and forecast potential candidate genes linked to this trait. To achieve this, we employed a recombinant inbred line (RIL) population derived from a cross between Guizao 1 and B13 (GB) across various environments.ResultsThe lodging score of the RIL population was found to be significantly positively correlated with flowering time, maturity time, plant height, number of main stem nodes, stem diameter, and internode length, with correlation coefficients ranging from 0.457 to 0.783. A total of 84 QTLs associated with soybean lodging and related traits were identified using the GB population. The contribution of phenotypic variance ranged from 1.26 to 66.87%, with LOD scores ranging from 2.52 to 69.22. Additionally, within these QTLs, a stable major QTL associated with lodging was newly discovered in the GB population. Out of the ten major QTLs associated with other related traits, nine of them were situated within the qLD-4-1 interval of the major lodging score locus, displaying phenotypic variations ranging from 12.10 to 66.87%. Specific alterations in gene expression were revealed through the analysis of resequencing data from the two parental lines, potentially indicating their significant roles in lodging. Subsequently, it was determined through qRT-PCR that four genes are likely to be the major genes controlling soybean lodging.ConclusionsThis study’s findings offer valuable insights into the genetic underpinnings of soybean lodging resistance traits. By comprehending the potential genetic factors associated with lodging, this research lays the groundwork for breeding high-yield soybeans with improved lodging resistance.

SlJMJ14, identified via QTL‑seq and fine mapping, controls flowering time in tomatoes.

A major QTL, qLF2.1, for flowering time in tomatoes, was fine mapped to chromosome 2 within a 51.37-kb interval, and the SlJMJ14 gene was verified as the causal gene by knockout. Tomato flowering time is an important agronomic trait that affects yield, fruit quality, and environmental adaptation. In this study, the high-generation inbred line 19108 with a late-flowering phenotype was selected for the mapping of the gene that causes late flowering. In the F2 population derived from 19108 (late flowering) × MM (early flowering), we identified a major late-flowering time quantitative trait locus (QTL) using QTL-seq, designated qLF2.1. This QTL was fine mapped to a 51.37-kb genomic interval using recombinant analysis. Through functional analysis of homologous genes, Solyc02g082400 (SlJMJ14), encoding a histone demethylase, was determined to be the most promising candidate gene. Knocking out SlJMJ14 in MM resulted in a flowering time approximately 5-6days later than that in the wild-type plants. These results suggest that mutational SlJMJ14 is the major QTL for the late-flowering phenotype of the 19108 parental line.

Rpv10.2: A Haplotype Variant of Locus Rpv10 Enables New Combinations for Pyramiding Downy Mildew Resistance Traits in Grapevine.

In viticulture, pathogens like the oomycete Plasmopara viticola, the causal agent of downy mildew, can cause severe yield loss and require extensive application of plant protection chemicals. Breeders are generating pathogen-resistant varieties exploiting American and Asian wild Vitis germplasm as sources of resistance. Several loci mediating resistance to P. viticola have been identified in the past but may be overcome by specifically adapted strains of the pathogen. Aiming to find and characterize novel loci, a cross population with Vitis amurensis ancestry was investigated searching for resistance-correlated quantitative trait loci (QTL). As a prerequisite, a genetic map was generated by analyzing the 244 F1 individuals derived from a cross of the downy mildew susceptible Vitis vinifera cultivar 'Tigvoasa' and the resistant V. amurensis pBC1 breeding line We 90-06-12. This genetic map is based on the information from 627 molecular markers including 56 simple sequence repeats and 571 rhAmpSeq markers. A phenotypic characterization of the progeny showed a clear segregation of the resistance traits in the F1 population after an experimental inoculation of leaf discs with downy mildew. Combining genetic and phenotypic data, an analysis for QTL revealed a major locus on linkage Group 9 that correlates strongly with the resistance to downy mildew. The locus was mapped to a region of about 80 kb on the PN40024 (12x.V2) grapevine reference genome. This genomic region co-localizes with the formerly identified locus Rpv10 from the grapevine cultivar 'Solaris'. As we found different allele sizes of the locus-linked SSR markers than those characterizing the known Rpv10 locus and differences in the sequence of a candidate gene, it was regarded as a haplotype variant and named Rpv10.2.