Substitution Lines Research Articles

Mapping of Quantitative Trait Loci Underlying Nodule Traits in Soybean (Glycine max (L.) Merr.) and Identification of Genes Whose Expression Is Affected by the Sinorhizobium fredii HH103 Effector Proteins NopL and NopT

Symbiotic nitrogen fixation provides most of the nitrogen required for soybean growth. Rhizobial nodulation outer proteins (Nops) have been reported to influence host specificity during symbiosis establishment. However, the host proteins that interact with Nops remain unknown. In this study, we generated Sinorhizobium fredii HH103 mutants (HH103ΩNopL, HH103ΩNopT, and HH103ΩNopLΩNopT) and analysed the nodule number (NN) and nodule dry weight (NDW) of 12 soybean germplasms after inoculation with wild-type S. fredii HH103 or the mutant strains. The analysis of chromosome segment substitution lines revealed quantitative trait loci (QTLs) associated with NopL and NopT interactions. A total of 22 QTLs for the 2 nodule traits were detected and mapped to 12 different chromosomes in the soybean genome. Eight and fifteen QTLs were found to be associated with NN and NDW, respectively. Furthermore, 17 candidate genes were selected for further analyses. Considering the results of reverse-transcription quantitative PCR, we propose that the protein products of these 17 candidate genes interact with NopL and NopT.

Detection of QTLs for Plant Height Architecture Traits in Rice (Oryza sativa L.) by Association Mapping and the RSTEP-LRT Method.

Plant height (PH) and its component traits are critical determinants of lodging resistance and strongly influence yield in rice. The genetic architecture of PH and its component traits were mined in two mapping populations. In the natural population composed of 504 accessions, a total of forty simple sequence repeat (SSR) markers associated with PH and its component traits were detected across two environments via association mapping. Allele RM305-210 bp on chromosome 5 for PH had the largest phenotypic effect value (PEV) (−51.42 cm) with a reducing effect. Allele RM3533-220 bp on chromosome 9 for panicle length and allele RM264-120 bp on chromosome 8 for the length of upper first elongated internode (1IN) showed the highest positive PEV. Among the elongated internodes with negative effects being desirable, the allele RM348-130 bp showed the largest PEV (−7.48 cm) for the length of upper second elongated internode. In the chromosome segment substitution line population consisting of 53 lines, a total of nine QTLs were detected across two environments, with the phenotypic variance explained (PVE) ranging 10.07–28.42%. Among the detected QTLs, q1IN-7 explained the largest PVE (28.42%) for the 1IN, with an additive of 5.31 cm. The favorable allele RM257-125 bp on chromosome 9 for the 1IN increasing was detected in both populations. The favorable alleles provided here could be used to shape PH architecture against lodging.

An Integration of MicroRNA and Transcriptome Sequencing Analysis Reveal Regulatory Roles of miRNAs in Response to Chilling Stress in Wild Rice.

A chromosome single segment substitution line (CSSL) DC90, which was generated by introgressing CTS-12, a locus derived from common wild rice (Oryza rufipogon Griff.), into the 9311 (Oryza sativa L. ssp. indica) background, exhibits a chilling tolerance phenotype under chilling stress. Here, an integration of microRNA (miRNA) deep sequencing and transcriptomic sequencing analysis was performed to explore the expression profiles of miRNAs and their target genes mediated by CTS-12 under chilling stress, and to reveal the possible regulatory mechanisms of miRNAs that are involved in chilling tolerance. Integration analysis revealed that a number of differentially expressed miRNAs (DEMs) and putative target genes with different expression patterns and levels were identified in 9311 and DC90 under chilling stress. KEGG enrichment analysis revealed that the target genes that are regulated by chilling-induced miRNAs are involved in the regulation of various biological processes/pathways, including protein biosynthesis, redox process, photosynthetic process, and chloroplast development in two genotypes. CRISPR/Cas9 editing of the target genes of the key DEMs in a chilling tolerant rice variety Zhonghua 11 (ZH11) found that LOC_Os11g48020 (OsGL1-11), one of the putative target genes of osa-miR1846a/b-5p and encoding a wax synthesis protein, is correlated with a chilling stress tolerance phenotype, implying osa-miR1846a/b-5p/OsGL1-11 plays an important role in CTS-12-mediated chilling stress tolerance regulatory pathway(s). Therefore, we speculate that the CTS-12 may regulate the key miRNA target genes in response to chilling stress by differential regulation of miRNAs in wild rice, thereby resulting in the variation of chilling tolerance phenotype between 9311 and DC90.

Dynamic analysis of QTLs on plant height with single segment substitution lines in rice

Dynamic regulation of QTLs remains mysterious. Single segment substitution lines (SSSLs) and conditional QTL mapping and functional QTL mappings are ideal materials and methods to explore dynamics of QTLs for complex traits. This paper analyzed the dynamics of QTLs on plant height with SSSLs in rice. Five SSSLs were verified with plant height QTLs first. All five QTLs had significant positive effects at one or more developmental stages except QTL1. They interacted each other, with negative effects before 49 d after transplanting and positive effects since then. The five QTLs selectively expressed in specific periods, mainly in the periods from 35 to 42 d and from 49 to 56 d after transplanting. Expressions of epistasis were dispersedly in various periods, negative effects appearing mainly before 35 d. The five QTLs brought the inflexion point ahead of schedule, accelerated growth and degradation, and changed the peak plant height, while their interactions had the opposite effects. The information will be helpful to understand the genetic mechanism for developmental traits.

Fine Mapping of Two Interacting Loci for Transmission Ratio Distortion in Rice (Oryza sativa L.)

Transmission ratio distortion (TRD) denotes the observed allelic or genotypic frequency deviation from the expected Mendelian segregation ratios in the offspring of a heterozygote. TRD can severely hamper gene flow between and within rice species. Here, we report the fine mapping and characterization of two loci (TRD4.1 and TRD4.2) for TRD using large F2 segregating populations, which are derived from rice chromosome segment substitution lines, each containing a particular genomic segment introduced from the japonica cultivar Nipponbare (NIP) into the indica cultivar Zhenshan (ZS97). The two loci exhibited a preferential transmission of ZS97 alleles in the derived progeny. Reciprocal crossing experiments using near-isogenic lines harboring three different alleles at TRD4.1 suggest that the gene causes male gametic selection. Moreover, the transmission bias of TRD4.2 was diminished in heterozygotes when they carried homozygous TRD4.1ZS97. This indicates an epistatic interaction between these two loci. TRD4.2 was mapped into a 35-kb region encompassing one candidate gene that is specifically expressed in the reproductive organs in rice. These findings broaden the understanding of the genetic mechanisms of TRD and offer an approach to overcome the barrier of gene flow between the subspecies in rice, thus facilitating rice improvement by introgression breeding.

Genetic Effects of Indica Lineage Introgression on Amylopectin Chain Length Distribution in Japonica Milled Rice

The fine structure of amylopectin affects rice quality; in particular, the amylopectin chain length distribution (ACLD) in milled rice differs between subspecies of Oryza sativa L. However, the correlation between ACLD and quality trait factors, and the genetic basis of ACLD phenotypic variation, are still unknown. Here, the correlations of ACLD with cooking and eating quality and with the rapid viscosity analysis (RVA) index were studied using chromosome segment substitution lines (CSSLs). Clear variations in ACLD were observed in introgression lines: introgression of indica segments of chromosome 3 and 7 increased the proportion of amylopectin Fa, and another segment of chromosome 3 reduced the proportion of amylopectin Fb2. A segment of chromosome 11 decreased the proportion of amylopectin Fa but increased that of Fb3. Correlation analysis with the RVA index further showed that the breakdown viscosity (BDV) was negatively correlated with the proportion of amylopectin Fb1, Fb2, and Fb3 chains, and positively correlated with Fa. Consistency viscosity (CSV) values were negatively correlated with the proportion of amylopectin Fb1, Fb2, and Fb3 chains. We thus clarified the quality trait factors determined by variation in ACLD, and provide key information for pyramiding inter-subspecific genetic superiority in molecular design breeding for rice quality.

Integrated transcriptomic and proteomic characterization of a chromosome segment substitution line reveals a new regulatory network controlling the seed storage profile of soybean

AbstractSoybean is a major crop that provides oil and protein worldwide. Soybean products have been consumed for centuries in many different kinds of food. The regulatory network that controls the accumulation of fatty acids (FAs) and storage proteins (SSPs) in seeds is poorly understood. To gain new insights into the molecular mechanisms that contribute to high‐quality seeds, seed FA and SSP contents were analyzed for the effects of chromosome segment substitution in a wild soybean line (CSSL). High‐throughput transcriptomics and tandem mass tag (TMT)‐based quantitative proteomics were performed on the dry seeds of the CSSL and parent lines. In total, 665 differentially expressed genes (DEGs) and 83 differentially accumulated proteins (DAPs) were identified. Of these 27 DEGs and 23 DAPs were found to regulate the seed storage profile. These genes encode proteins involved in photosynthesis, protein processing, protein sorting, and storage protein accumulation. Data are presented showing that FA synthesis was decreased by the regulation of SSP‐accumulation‐related genes and proteins. Taken together, the results provide new insights into the regulation network involved in the accumulation of seed storage compounds involving both source and sink processes that may be used as markers in future soybean breeding programs.

Molecular cytogenetics and development of St-chromosome-specific molecular markers of novel stripe rust resistant wheat\u2013Thinopyrum intermedium and wheat\u2013Thinopyrum ponticum substitution lines

BackgroundOwing to their excellent resistance to abiotic and biotic stress, Thinopyrum intermedium (2n = 6x = 42, JJJsJsStSt) and Th. ponticum (2n = 10x = 70) are both widely utilized in wheat germplasm innovation programs. Disomic substitution lines (DSLs) carrying one pair of alien chromosomes are valuable bridge materials for transmission of novel genes, fluorescence in situ hybridization (FISH) karyotype construction and specific molecular marker development.ResultsSix wheat–Thinopyrum DSLs derived from crosses between Abbondanza nullisomic lines (2n = 40) and two octoploid Trititrigia lines (2n = 8x = 56), were characterized by sequential FISH–genome in situ hybridization (GISH), multicolor GISH (mc-GISH), and an analysis of the wheat 15 K SNP array combined with molecular marker selection. ES-9 (DS2St (2A)) and ES-10 (DS3St (3D)) are wheat–Th. ponticum DSLs, while ES-23 (DS2St (2A)), ES-24 (DS3St (3D)), ES-25(DS2St (2B)), and ES-26 (DS2St (2D)) are wheat–Th. intermedium DSLs. ES-9, ES-23, ES-25 and ES-26 conferred high thousand-kernel weight and stripe rust resistance at adult stages, while ES-10 and ES-24 were highly resistant to stripe rust at all stages. Furthermore, cytological analysis showed that the alien chromosomes belonging to the same homoeologous group (2 or 3) derived from different donors carried the same FISH karyotype and could form a bivalent. Based on specific-locus amplified fragment sequencing (SLAF-seq), two 2St-chromosome-specific markers (PTH-005 and PTH-013) and two 3St-chromosome-specific markers (PTH-113 and PTH-135) were developed.ConclusionsThe six wheat–Thinopyrum DSLs conferring stripe rust resistance can be used as bridging parents for transmission of valuable resistance genes. The utility of PTH-113 and PTH-135 in a BC1F2 population showed that the newly developed markers could be useful tools for efficient identification of St chromosomes in a common wheat background.

Development and Identification of a Novel Wheat-Thinopyrum scirpeum 4E (4D) Chromosomal Substitution Line with Stripe Rust and Powdery Mildew Resistance.

Stripe rust caused by Puccinia striiformis f. sp. tritici and powdery mildew caused by Blumeria graminis f. sp. tritici are devastating diseases of wheat worldwide. Exploration of new disease-resistant genes from cultivated wheat and wild relatives are the most effective means of reducing the amounts of fungicides applied to combat these diseases. Thinopyrum scirpeum (2n = 4x = 28, EEEE) is an important promising reservoir of useful genes, including stripe rust and powdery mildew resistance, and may be useful for increasing wheat disease resistance. Here, we characterize a novel wheat-Th. scirpeum disomic substitution line, K16-730-3, and chromosome-specific markers were developed that can be used to trace the Th. scirpeum chromosome or chromosome segments transferred into wheat. Genomic in situ hybridization and fluorescence in situ hybridization analyses indicated that K16-730-3 is a new 4E (4D) chromosomal substitution line. Evaluation of seedling and adult disease responses revealed that K16-730-3 is resistant to stripe rust and powdery mildew. In addition, no obvious difference in grain yield was observed between K16-730-3 and its wheat parents. Genotyping-by-sequencing analyses indicated that 74 PCR-based markers can accurately trace chromosome 4E, which were linked to the disease resistance genes in the wheat background. Further marker validation analyses revealed that 13 specific markers can distinguish between the E-genome chromosomes of Th. scirpeum and the chromosomes of other wheat-related species. The new substitution line K16-730-3 carrying the stripe rust and powdery mildew resistance genes will be useful as novel germplasm in breeding for disease resistance. The markers developed in this study can be used in marker-assisted selection for increasing disease resistance in wheat.

Identification and Evaluation of Wheat-Aegilops bicornis Lines with Resistance to Powdery Mildew and Stripe Rust.

Wheat pathogens, especially those causing powdery mildew and stripe rust, seriously threaten yield worldwide. Utilizing newly identified disease resistance genes from wheat relatives is an effective strategy to minimize disease damage. In this study, chromosome-specific molecular markers for the 3Sb and 7Sb chromosomes of Aegilops bicornis were developed using PCR-based landmark unique gene primers for screening wheat-A. bicornis progenies. Fluorescence in situ hybridization (FISH) was performed to further identify wheat-A. bicornis progenies using oligonucleotides probes Oligo-pSc119.2-1, Oligo-pTa535-1, and Oligo-(GAA)8. After establishing A. bicornis 3Sb and 7Sb chromosome-specific FISH markers, Holdfast (common wheat)-A. bicornis 3Sb addition, 7Sb addition, 3Sb(3A) substitution, 3Sb(3B) substitution, 3Sb(3D) substitution, 7Sb(7A) substitution, and 7Sb(7B) substitution lines were identified by the molecular and cytological markers. Stripe rust and powdery mildew resistance, along with agronomic traits, were investigated to evaluate the breeding potential of these lines. Holdfast and Holdfast-A. bicornis progenies were all highly resistant to stripe rust, indicating that the stripe rust resistance might derive from Holdfast. However, Holdfast-A. bicornis 3Sb addition, 3Sb(3A) substitution, 3Sb(3B) substitution, and 3Sb(3D) substitution lines showed high resistance to powdery mildew while Holdfast was highly susceptible, indicating that chromosome 3Sb of A. bicornis carries previously unknown powdery mildew resistance gene(s). Additionally, the transfer of the 3Sb chromosome from A. bicornis to wheat significantly increased tiller number, but chromosome 7Sb has a negative effect on agronomic traits. Therefore, wheat germplasm containing A. bicornis chromosome 3Sb has potential to contribute to improving powdery mildew resistance and tiller number during wheat breeding.

Genomic compatibility and inheritance of hexaploid-derived Fusarium head blight resistance genes in durum wheat.

Hexaploid-derived resistance genes exhibit complex inheritance and expression patterns in tetraploid backgrounds. This study aimed to characterize the inheritance patterns and genomic compatibilities of hexaploid-derived Fusarium head blight (FHB) resistance genes in tetraploid durum wheat (Triticum durumDesf.). Evaluation of FHB resistance for F1 hybrids of hexaploid 'Sumai 3' crossed with tetraploid and hexaploid wheats indicated that Sumai 3-derived FHB resistance genes exhibit a dominant phenotypic effect seen only in hexaploid hybrids. Alternately, the hexaploid-derived FHB resistance genes from PI 277012 exhibited complete dominance in the crosses with both tetraploid and hexaploid wheat. FHB evaluation of the F1 hybrids of Sumai 3 and PI 277012 crossed with 'Langdon' (LDN)-'Chinese Spring' D-genome substitution lines suggested that chromosomes 2B, 3B, 4B, 5B, 6B, 3A, 4A, 6A, and 7A contain genes that suppress expression of the Sumai 3-derived FHB resistance, whereas chromosomes 4A, 6A, and 6B contain genes required for expression of PI 277012-derived FHB resistance. A wide range of segregation for FHB severity (10-90%) was observed in the F2 generation of Sumai 3 crossed with durum cultivars LDN and 'Divide', but the distribution of F3 families derived from the most resistant F2 segregants was skewed towards susceptibility. Similar segregation trends were observed in the crosses of PI 277012 with other durum wheats, whereby FHB resistance became slightly diluted over successive generations. These results suggest tetraploid durum wheat contains the unique alleles at multiple gene loci on different chromosomes that positively and/or negatively regulate the expression of hexaploid-derived FHB resistance genes, which complicate efforts to deploy these genes in durum breeding programs.

Assembly of yield heterosis of an elite rice hybrid is promising by manipulating dominant quantitative trait loci.

In the past, rice hybrids with strong heterosis have been obtained empirically, by developing and testing thousands of combinations. Here, we aimed to determine whether heterosis of an elite hybrid could be achieved by manipulating major quantitative trait loci. We used 202 chromosome segment substitution lines from the elite hybrid Shanyou 63 to evaluate single segment heterosis (SSH) of yield per plant and identify heterotic loci. All nine detected heterotic loci acted in a dominant fashion, and no SSH exhibited overdominance. Functional alleles of key yield-related genes Ghd7, Ghd7.1, Hd1, and GS3 were dispersed in both parents. No functional alleles of three investigated genes were expressed at higher levels in the hybrids than in the more desirable parents. A hybrid pyramiding eight heterotic loci in the female parent Zhenshan 97 background had a comparable yield to Shanyou 63 and much higher yield than Zhenshan 97. Five hybrids pyramiding eight or nine heterotic loci in the combined parental genome background showed similar yield performance to that of Shanyou 63. These results suggest that dominance underlying functional complementation is an important contributor to yield heterosis and that heterosis assembly might be successfully promised by manipulating several major dominant heterotic loci.

Identification and DNA Marker Development for a Wheat-Leymus mollis 2Ns (2D) Disomic Chromosome Substitution.

Leymus mollis (2n = 4x = 28, NsNsXmXm), a wild relative of common wheat (Triticum aestivum L.), carries numerous loci which could potentially be used in wheat improvement. In this study, line 17DM48 was isolated from the progeny of a wheat and L. mollis hybrid. This line has 42 chromosomes forming 21 bivalents at meiotic metaphase I. Genomic in situ hybridization (GISH) demonstrated the presence of a pair chromosomes from the Ns genome of L. mollis. This pair substituted for wheat chromosome 2D, as shown by fluorescence in situ hybridization (FISH), DNA marker analysis, and hybridization to wheat 55K SNP array. Therefore, 17DM48 is a wheat-L. mollis 2Ns (2D) disomic substitution line. It shows longer spike and a high level of stripe rust resistance. Using specific-locus amplified fragment sequencing (SLAF-seq), 13 DNA markers were developed to identify and trace chromosome 2Ns of L. mollis in wheat background. This line provides a potential bridge germplasm for genetic improvement of wheat stripe rust resistance.

QTL mapping and candidate gene prediction for fiber yield and quality traits in a high-generation cotton chromosome substitution line with Gossypium barbadense segments.

Gossypium provides the foremost natural fiber for supporting the rapid development of the textile industry. Quantitative trait locus (QTL) mapping of fiber yield and quality traits is, thus, of great significance for providing a foundation for the genetic improvement of key target traits in cotton production. In this study, a superior chromosome segment substitution line (CSSL), MBI8255, with high yield and premium fiber quality characteristics was cultivated from the BC5F3:5 lineage derived from G. barbadense Hai1 and G. hirsutum CCRI36, and was chosen to construct a segregation population containing 123 F2 individuals with CCRI36. A total of 71 polymorphic SSR (simple sequence repeat) markers were identified based on a previous high-density linkage map, and 17 QTLs distributed on five chromosomes were detected, of which 10 QTLs for cotton yield explained 0.26-15.41% of phenotypic variations, while 7 QTLs for fiber quality explained 0.84-9.38% of phenotypic variations, separately containing four and one stable QTLs detected from over two environments. Among three identified QTL clusters, only the Chr19 QTL cluster harbored two stable and one unstable QTL for three different traits, and hence this significant region, which included 1546 genes, was subjected to functional enrichment and transcriptome expression analyses, ultimately screening eight candidate genes relevant to fiber development. This study not only provides useful information for the further fine-mapping and functional verification of candidate genes, but also offers a solid foundation for revealing the molecular mechanisms of fiber formation.

Features of Chromosome Introgression from Gossypium barbadense L. into G. hirsutum L. during the Development of Alien Substitution Lines.

The creation of G. barbadense L./G. hirsutum L. chromosome-substitution lines is an important method to transfer agronomically valuable traits from G. barbadense into G. hirsutum. In this study, 30 monosomic lines of G. hirsutum from the Cytogenetic Collection of Uzbekistan, created in the genotypic background of line L-458, were used in crosses with the G. barbadense line Pima 3-79 to create substitution lines. In the course of this work, new monosomic lines were identified for chromosome 12 and monotelodisome 6 of the Atsubgenome and for chromosomes 17, 21, and 22 of the Dtsubgenome using chromosome-specific SSR markers and a well-defined tester set of cotton translocation lines (USA). Compared to those in the F1 hybrids, a strong decrease in the crossing and setting rates was found in the BC1F1 backcross lines, with the substitution of chromosomes 2, 4, 6, 7, and 12 of the Atsubgenome and 17, 18, 21, and 22 of the Dtsubgenome. The F1 and BC1F1 offspring from interspecific crosses differed in their transmission of univalents. Despite the regular pairing of chromosomes and the high meiotic index, interspecific aneuploid hybrids were characterized by a decrease in pollen fertility, which may indicate hidden structural variability in these genomes that did not affect meiotic division. The identification of chromosomes using chromosome-specific SSR markers in the early stages of plant development has greatly accelerated the detection of monosomic plants. The analysis of morphobiological traits revealed that monosomic F1 hybrids were more similar to the donor line, while BC1F1 hybrids were more similar to the recurrent parent but also showed previously undetected traits.

Gene mining of 100‐grain weight and the number of four‐seed pods in soybean (Glycine max)

AbstractThe number of four‐seed pods and 100‐grain weight are important yield components in soybean. Typically, they are negatively correlated traits. Generally, soybean varieties with a high 100‐grain weight and a higher number of three‐ or four‐seed pods are more likely to obtain a high yield. It is difficult to select for double‐excellent traits that meet the needs of farmers and the market using conventional breeding methods. The purpose of this study was to mine genes associated with the number of four‐seed pods and 100‐grain weight in soybean. Whole‐transcriptome sequencing was performed on four specific chromosome segment substitution lines (HWMN, HWFN, LWMN and LWFN) combined with the distribution of blocks imported from wild soybean DNA fragments and gene annotation. The material was sampled in each of the eight development stages. Among them, globular embryo formation, heart embryo formation, and cotyledon primordium formation were used to mine differentially expressed genes (DEGs). A total of 3792 DEGs were identified, and 25 expression patterns were obtained by the K‐means rapid clustering method. GO enrichment analysis of DEGs was performed by Agrigo, and a total of 43 GO terms were enriched. Through annotation analysis, 126 DEGs associated with seed size and number were obtained. Combined with analysis of the introduced DNA fragments of wild soybean ZYD00006, 19 genes that eventually aligned on those blocks were obtained. Six representative genes were selected as candidate genes, namely, Glyma.07G218200, Glyma.05G162100, Glyma.19G240800, Glyma.04G180300, Glyma.05G214400 and Glyma.12G146700. They may regulate the formation of 100‐grain weight and the number of four‐seed pods, which will provide reference information for the genetic improvement of agronomic traits, such as seed number per pod and 100‐grain weight of soybean, in the future and will enrich the theoretical basis of high yield in soybean.

LncRNA7 and lncRNA2 modulate cell wall defense genes to regulate cotton resistance to Verticillium wilt.

In plants, long noncoding RNAs (lncRNAs) regulate disease resistance against fungi and other pathogens. However, the specific mechanism behind this regulation remains unclear. In this study, we identified disease resistance-related lncRNAs as well as their regulating genes and assessed their functions by infection of cotton (Gossypium) chromosome segment substitution lines with Verticillium dahliae. Our results demonstrated that lncRNA7 and its regulating gene Pectin methylesterase inhibitor 13 (GbPMEI13) positively regulated disease resistance via the silencing approach, while ectopic overexpression of GbPMEI13 in Arabidopsis (Arabidopsis thaliana) promoted growth and enhanced resistance to V. dahliae. In contrast, lncRNA2 and its regulating gene Polygalacturonase 12 (GbPG12) negatively regulated resistance to V. dahliae. We further found that fungal disease-related agents, including the pectin-derived oligogalacturonide (OG), could downregulate the expression of lncRNA2 and GbPG12, leading to pectin accumulation. Conversely, OG upregulated the expression of lncRNA7, which encodes a plant peptide phytosulfokine (PSK-α), which was confirmed by lncRNA7 overexpression and Ultra Performance Liquid Chromatography Tandem Mass Spectrometry (UPLC-MS)experiments. We showed that PSK-α promoted 3-Indoleacetic acid (IAA)accumulation and activated GbPMEI13 expression through Auxin Response Factor 5. Since it is an inhibitor of pectin methylesterase (PME), GbPMEI13 promotes pectin methylation and therefore increases the resistance to V. dahliae. Consistently, we also demonstrated that GbPMEI13 inhibits the mycelial growth and spore germination of V. dahliae in vitro. In this study, we demonstrated that lncRNA7, lncRNA2, and their regulating genes modulate cell wall defense against V. dahliae via auxin-mediated signaling, providing a strategy for cotton breeding.

小麦-中间偃麦草2A/6St代换系014-459的分子细胞遗传学鉴定

<p id="C3"><italic>Thinopyrum intermedium </italic>is a valuable resource for wheat genetic improvement, and numerous wheat-<italic>Th. intermedium </italic>chromosome addition and substitution lines and partial amphiploids have been developed. Zhong 4 is a wheat-<italic>Th. intermedium </italic>partial amphidiploid, which can easily hybridize with wheat and is extensively utilized for wheat improvement. The strain 014-459 was a progeny of partial amphidiploid Zhong 4 descendant of wheat and <italic>Th. intermedium </italic>with some special characteristics such as high crude protein and wet gluten content and partial F₁ of common wheat cultivars and strain 014-459 were sterility while a few others were fertility despite reciprocal cross. Molecular cytogenetic identification of strain 014-459 were detected for speculated contained fragment of <italic>Th. intermedium </italic>chromosomes based on its special characters. Genomic composition of strain 014-459 was detected by FISH, GISH, and PLUG (polymerase chain reaction-based landmark unique gene) marker analysis. Combined FISH/GISH analysis confirmed that a pair of wheat 2A chromosomes in strain 014-459 of the hybrid progeny between wheat-<italic>Thinopyrum intermedium</italic> partial amphidiploid Zhong 4 and wheat was replaced by a pair of St chromosomes from <italic>Thinopyrum intermedium</italic>. PLUG marker analysis verified that this pair belonged to the sixth homologous group. The special characters of strain 014-459 might be attributable to the substitution of <italic>Th. intermedium</italic> St chromosome into wheat. The study of molecular cytogenetic identification of strain 014-459 was probably beneficial to quality improvement and utilization of 6St chromosome of <italic>Th. intermedium</italic> in wheat breeding.

Whole-Genome Sequencing of 117 Chromosome Segment Substitution Lines for Genetic Analyses of Complex Traits in Rice

Rice is one of the most important food crops in Asia. Genetic analyses of complex traits and molecular breeding studies in rice greatly rely on the construction of various genetic populations. Chromosome segment substitution lines (CSSLs) serve as a powerful genetic population for quantitative trait locus (QTL) mapping in rice. Moreover, CSSLs containing target genomic regions can be used as improved varieties in rice breeding. In this study, we developed a set of CSSLs consisting of 117 lines derived from the recipient ‘Huanghuazhan’ (HHZ) and the donor ‘Basmati Surkb 89–15’ (BAS). The 117 lines were extensively genotyped by whole-genome resequencing, and a high-density genotype map was constructed for the CSSL population. The 117 CSSLs covered 99.78% of the BAS genome. Each line contained a single segment, and the average segment length was 6.02 Mb. Using the CSSL population, we investigated three agronomic traits in Shanghai and Hangzhou, China, and a total of 25 QTLs were detected in both environments. Among those QTLs, we found that RFT1 was the causal gene for heading date variance between HHZ and BAS. RFT1 from BAS was found to contain a loss-of-function allele based on yeast two-hybrid assay, and its causal variation was a P to S change in the 94th amino acid of the RFT1 protein. The combination of high-throughput genotyping and marker-assisted selection (MAS) is a highly efficient way to construct CSSLs in rice, and extensively genotyped CSSLs will be a powerful tool for the genetic mapping of agronomic traits and molecular breeding for target QTLs/genes.

Identification of resistance to Fusarium head blight and molecular cytogenetics of interspecific derivatives between wheat and Psathyrostachys huashanica.

Psathyrostachys huashanica is a relative of wheat (Triticum aestivum L.) with many disease resistance genes that can be used to improve wheat disease resistance. In order to enrich the germplasm resources available in wheat genetics and breeding, we assessed Fusarium head blight (FHB) resistance in 45 interspecific derivatives between wheat and Psathyrostachys huashanica during two years from 2017-2018. Two interspecific derivatives comprising, H-34-8-2-6-1 and H-24-3-1-5-19-1 were identified as FHB resistant lines. These two lines were examined based on their morphology and cytogenetics, as well as by genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), molecular markers, and 660K genotyping array to determine their genetic construction. The results confirmed H-34-8-2-6-1 as a wheat-P. huashanica 1Ns long arm ditelosomic addition line and H-24-3-1-5-19-1 as a wheat-P. huashanica 2Ns substitution line. Assessments of the agronomic traits showed that H-34-8-2-6 had significantly higher kernel number per spike and self-fertility rate than parent 7182. In addition, compared with 7182, H-24-3-1-5-19-1 had a much lower plant height while the other agronomic traits were relatively similar. The two new lines are valuable germplasm materials for breeding FHB resistance in wheat.