Search

SUMMARY: Septoria nodorum blotch (SNB), caused by Parastagonospora nodorum, is a disease of durum and common wheat initiated by the recognition of pathogen‐produced necrotrophic effectors (NEs) by specific wheat genes. The wheat gene Snn1 was previously cloned, and it encodes a wall‐associated kinase that directly interacts with the NE SnTox1 leading to programmed cell death and ultimately the development of SNB. Here, sequence analysis of Snn1 from 114 accessions including diploid, tetraploid, and hexaploid wheat species revealed that some wheat lines possess two copies of Snn1 (designated Snn1‐B1 and Snn1‐B2) approximately 120 kb apart. Snn1‐B2 evolved relatively recently as a paralog of Snn1‐B1, and both genes have undergone diversifying selection. Three point mutations associated with the formation of the first SnTox1‐sensitive Snn1‐B1 allele from a primitive wild wheat were identified. Four subsequent and independent SNPs, three in Snn1‐B1 and one in Snn1‐B2, converted the sensitive alleles to insensitive forms. Protein modeling indicated these four mutations could abolish Snn1–SnTox1 compatibility either through destabilization of the Snn1 protein or direct disruption of the protein–protein interaction. A high‐throughput marker was developed for the absent allele of Snn1, and it was 100% accurate at predicting SnTox1‐insensitive lines in both durum and spring wheat. Results of this study increase our understanding of the evolution, diversity, and function of Snn1‐B1 and Snn1‐B2 genes and will be useful for marker‐assisted elimination of these genes for better host resistance. Significance Statement: Alleles of the wheat Snn1 gene that confer septoria nodorum blotch susceptibility through direct interaction with the pathogen‐produced necrotrophic effector SnTox1 arose through three point mutations and a gene duplication event, and four subsequent point mutations led to the formation of lack‐of‐function (resistance) alleles. Knowledge of the evolution, selection, and structural and functional nature of Snn1 alleles allowed for the development of an efficient marker‐based elimination assay for the development of disease resistant wheat. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) is a devastating fungal disease of wheat. Since early 1990s, frequent FHB epidemics in major wheat‐growing regions have caused massive economic losses. Developing FHB‐resistant varieties is key to minimize the loss caused by the disease. In durum wheat (Triticum turgidum L. ssp. durum), however, it is challenged by lack of resistant sources. Introgression of resistance genes from wild relatives and bread wheat has resulted in some durum wheat lines with moderate resistance. Due to its complex genetic nature, integrating more resistance genes with moderate and even minor effects promises to provide high and durable FHB resistance. In this study, a base population was developed using diverse resistant lines and elite durum wheat breeding lines as founders and went through three cycles of phenotypic selection from 2019 to 2022, with FHB severity decreased by 34%. Six S0:1 lines in Cycle 2 and Cycle 3 populations exhibited significantly lower FHB severity than the moderately susceptible check variety ND Riveland. The results suggested that recurrent phenotypic selection could effectively improve FHB resistance. Analysis of the founders and Cycle 2 and Cycle 3 populations with 2706 single nucleotide polymorphism markers indicated that there was little decrease in genetic variation due to selection. Genome‐wide association analysis found no markers significantly associated with FHB severity. Genomic prediction accuracies based on cross‐validation for FHB severity, plant height, and days‐to‐flowering were 0.51, 0.69, and 0.61, respectively. Recurrent genomic selection can shorten the select cycle to 4 months and therefore is promising to accelerate genetic improvement of FHB severity. Core Ideas: Recurrent phenotypic selection could effectively improve FHB resistance in durum wheat.A moderate prediction accuracy for FHB severity was found in the durum wheat recurrent selection population.Recurrent genomic selection can shorten select cycle and is promising to accelerate genetic improvement. [ABSTRACT FROM AUTHOR]

SUMMARY: Chloroplast biogenesis is critical for crop biomass and economic yield. However, chloroplast development is a very complicated process coordinated by cross‐communication between the nucleus and plastids, and the underlying mechanisms have not been fully revealed. To explore the regulatory machinery for chloroplast biogenesis, we conducted map‐based cloning of the Grandpa 1 (Gpa1) gene regulating chloroplast development in barley. The spontaneous mutation gpa1.a caused a variegation phenotype of the leaf, dwarfed growth, reduced grain yield, and increased tiller number. Genetic mapping anchored the Gpa1 gene onto 2H within a gene cluster functionally related to photosynthesis or chloroplast differentiation. One gene (HORVU.MOREX.r3.2HG0213170) in the delimited region encodes a putative plastid terminal oxidase (PTOX) in thylakoid membranes, which is homologous to IMMUTANS (IM) of Arabidopsis. The IM gene is required for chloroplast biogenesis and maintenance of functional thylakoids in Arabidopsis. Using CRISPR technology and gene transformation, we functionally validated that the PTOX‐encoding gene, HORVU.MOREX.r3.2HG0213170, is the causal gene of Gpa1. Gene expression and chemical analysis revealed that the carotenoid biosynthesis pathway is suppressed by the gpa1 mutation, rendering mutants vulnerable to photobleaching. Our results showed that the overtillering associated with the gpa1 mutation was caused by the lower accumulation of carotenoid‐derived strigolactones (SLs) in the mutant. The cloning of Gpa1 not only improves our understanding of the molecular mechanisms underlying chloroplast biosynthesis but also indicates that the PTOX activity is conserved between monocots and dicots for the establishment of the photosynthesis factory. Significance Statement: The Gpa1 gene encoding a plastid terminal oxidase is required for chloroplast biogenesis and tillering control in barley. [ABSTRACT FROM AUTHOR]

The USDA‐ARS and North Dakota State University Agricultural Experiment Station jointly released the Fusarium head blight (FHB)‐resistant spring wheat (Triticum aestivum L.) germplasm WGC002 (Reg. no. GP‐1089, PI 702949) in May 2023. WGC002 is a wheat‐Thinopyrum elongatum 7B‐7E translocation line, designated 7BS·7BL‐7EL, with the wheat chromosome 7BL terminal region replaced by the homoeologous counterpart of the Th. elongatum chromosome 7EL that contains the novel FHB resistance gene Fhb7The2. WGC002 was developed from the Chinese Spring (CS) wheat‐Th. elongatum disomic substitution line DS 7E(7B) using our genomics‐enabled chromosome engineering pipeline. The pedigree of WGC002 is DS 7E(7B)/2*CS ph1b mutant//DS 7E(7B). WGC002 has consistently exhibited resistance to FHB in inoculations of greenhouse grown plants. WGC002 does not contain the yellow flour pigment gene in the Fhb7The2 haplotype present on the terminal 7EL segment of the 7BS·7BL‐7EL translocation and has not exhibited any obvious linkage drag on the 7EL segment. Therefore, WGC002 is ready for immediate use in wheat breeding. One sequence‐tagged site (STS) and two polymerase chain reaction allelic competitive extension markers were developed specifically for Fhb7The2 and validated in different wheat genotypes. They are highly diagnostic for Fhb7The2 and extremely useful in marker‐assisted introgression of Fhb7The2 in wheat breeding. In summary, WGC002 is a new wild grass‐derived FHB‐resistant spring wheat germplasm with diagnostic DNA markers available to conduct marker‐assisted selection of Fhb7The2, that will enhance and diversify FHB resistance of wheat. Core Ideas: We developed an FHB‐resistant wheat germplasm, WGC002, which contains the wild grass‐derived resistance gene Fhb7The2.Fhb7The2 was incorporated into wheat through a 7B‐7E translocation by chromosome engineering. The chromosome 7E segment containing Fhb7The2 does not carry the gene for yellow flour pigment in WGC002.We developed the STS and PACE markers specific for Fhb7The2. [ABSTRACT FROM AUTHOR]

'ND Frohberg' (Reg. no. CV‐1200, PI 698310) is a hard‐red spring wheat (HRSW; Triticum aestivum L.) developed at North Dakota State University (NDSU) and released by the North Dakota Agricultural Experiment Station (NDAES) in 2020. ND Frohberg was selected from the cross ND709‐9/ND2902. ND709‐9 was an experimental line with the pedigree (ND 2709/3/'Grandin'*3//'Ramsey'/ND 622). ND2902 was an experimental line with the pedigree (ND674//ND2710/ND688). It was tested as experimental line NDHRS16‐13‐97 and released because of improved straw strength, yield potential, strong disease resistance and end‐use quality. ND Frohberg is highly resistant to stem rust (caused by Puccinia graminis f.sp. tritici), and moderately resistant to leaf rust (caused by Puccinia triticina), bacterial leaf streak (caused by Xanthomonas translucens pv. undulosa), and Fusarium head blight (caused by Fusarium graminearum). The name ND Frohberg was chosen to honor Dr. Richard Frohberg, hard red spring wheat breeder at NDSU for 37 years. During his tenure at NDSU, Dr. Frohberg's varieties were widely cultivated, reaching as much as 65% of the acreage in North Dakota in 2003. He was responsible for the cross that resulted in this variety. Core Ideas: ND Frohberg is a hard red spring wheat best adapted to North Dakota and the northern plains.The cultivar has good yield potential, disease resistance, and very good milling and baking quality.ND Frohberg was named in honor of D. Richard Frohberg, wheat breeder at North Dakota State University for over 37 years. [ABSTRACT FROM AUTHOR]

'MT Sidney' (Reg. no. CV‐1199; PI 699957) hard red spring wheat (Triticum aestivum L.) was released by the Montana Agricultural Experiment Station in January 2021 as a new cultivar adapted to Montana's rainfed growing environments. MT Sidney was a selection from the cross MT1274/'RB07' and was tested in Montana as experimental line MT1716 from 2018 to 2020. MT1274 is an unreleased, Montana experimental line, and RB07 was released by the University of Minnesota in 2007 for high yield, moderate Fusarium head blight (FHB) resistance, and good end‐use quality. MT Sidney was in the top‐yielding statistical group in our advanced yield trial that includes 'Vida' (PI 642366), the most widely grown cultivar in Montana. MT Sidney also has significantly higher test weight and an earlier heading date than Vida. Multiple years of FHB resistance screening indicate MT Sidney is moderately resistant to FHB. MT Sidney was released based on high yield potential, high test weight, early heading date, and moderate FHB resistance. Core Ideas: MT Sidney is a new high‐yielding hard red spring wheat cultivar adapted to Montana rainfed environments.MT Sidney has an early heading date and above‐average test weight.MT Sidney has moderate FHB resistance. [ABSTRACT FROM AUTHOR]

A spontaneous mutant in an unknown cultivar, I liguleless1 i ( I lig1 i ), is deficient in the formation of the ligule and auricle, exhibiting smaller leaf angles and a compact architecture (Figure 1a-c). A SQUAMOSA promoter binding protein-like transcription factor controls crop ideotype for high productivity in barley In cereal crops, erect leaf (small leaf angle) is a desirable trait that allows for dense planting through optimization of light capture, thus increasing photosynthesis efficiency and grain yield with a higher leaf area index. M.O.C. conducted genetic mapping, gene validation, and gene function characterization. [Extracted from the article]

SUMMARY: The resistance gene Sr13 is one of the most important genes in durum wheat for controlling stem rust caused by Puccinia graminis f. sp. tritici (Pgt). The Sr13 functional gene CNL13 has haplotypes R1, R2 and R3. The R1/R3 and R2 haplotypes were originally designated as alleles Sr13a and Sr13b, respectively. To detect additional Sr13 alleles, we developed Kompetitive allele specific PCR (KASP™) marker KASPSr13 and four semi‐thermal asymmetric reverse PCR markers, rwgsnp37–rwgsnp40, based on the CNL13 sequence. These markers were shown to detect R1, R2 and R3 haplotypes in a panel of diverse tetraploid wheat accessions. We also observed the presence of Sr13 in durum line CAT‐A1, although it lacked any of the known haplotypes. Sequence analysis revealed that CNL13 of CAT‐A1 differed from the susceptible haplotype S1 by a single nucleotide (C2200T) in the leucine‐rich repeat region and differed from the other three R haplotypes by one or two additional nucleotides, confirming that CAT‐A1 carries a new (R4) haplotype. Stem rust tests on the monogenic, transgenic and mutant lines showed that R1 differed from R3 in its susceptibility to races TCMJC and THTSC, whereas R4 differed from all other haplotypes for susceptibility to TTKSK, TPPKC and TCCJC. Based on these differences, we designate the R1, R3 and R4 haplotypes as alleles Sr13a, Sr13c and Sr13d, respectively. This study indicates that Sr13d may be the primitive functional allele originating from the S1 haplotype via a point mutation, with the other three R alleles probably being derived from Sr13d through one or two additional point mutations. Significance Statement: A new resistant haplotype (R4) of Sr13, designated as Sr13d, was identified in the genotype CAT‐A1, and based on sequencing studies this allele is hypothesized to be a primitive functional resistant allele of Sr13. We established from extensive rust tests that haplotypes R1 and R3 should be separated, and R3 was designated Sr13c and determined to be preferable to Sr13a for breeding, while Sr13d was undesirable for breeding due to susceptibility to stem rust Ug99. [ABSTRACT FROM AUTHOR]

Thinopyrum distichum (Thunb.) Á. Löve (2n = 4x = 28; J1dJ1dJ2dJ2d) inhabits harsh, dry saline coastal dunes. Its adaptive genes can be of value to cultivated cereals; therefore, single‐chromosome additions were previously developed in hexaploid triticale (×Triticosecale Wittm. ex A. Camus) and common wheat (Triticum aestivum L.); however, their homoeology to triticale and wheat chromosomes remained largely unknown. Here we used genotyping‐by‐sequencing (GBS) to supplement conventional markers and determine the synteny of the Th. distichum addition chromosomes. Twenty‐seven triticale lines with single Th. distichum addition chromosomes were analyzed. Genotyping‐by‐sequencing yielded 2.75 million unique sequences that included 134,506 Th. distichum‐specific tags absent in the wheat, durum wheat [Triticum turgidum L. subsp. Durum (Desf.) van Slageren], ×Triticosecale spp., and rye (Secale cereale L.) controls. The Th. distichum‐specific tags were then sorted into 125,262 informative, single‐pair tags (from one homoeologous group) and 9,244 uninformative, multi‐group tags associated with more than one homoeologous group. Presence–absence patterns produced by the single‐pair tags suggested the presence of 11 different Th. distichum addition chromosomes whose associated sequence tags were then aligned to the Th. elongatum (Host) D. R. Dewey and Chinese Spring (CS) genomic databases to reveal their homoeology. Five prominent translocations were detected among the 11 Th. distichum addition chromosomes and three chromosomes appeared to be extensively restructured. The extra chromosomes in 10 additions to common wheat represented five different Th. distichum chromosomes that were also represented in the triticale set. The 11 distinct Th. distichum addition chromosomes constitute a useful genetic resource for continued dissection of the Th. distichum genomes. [ABSTRACT FROM AUTHOR]

The membrane-proximal external region (MPER) of HIV gp41 is an established target of antibodies that neutralize a broad range of HIV isolates. To evaluate the role of the transmembrane (TM) domain, synthetic MPER-derived peptides were incorporated into lipid nanoparticles using natural and designed TM domains, and antibody affinity was measured using immobilized and solution-based techniques. Peptides incorporating the native HIV TM domain exhibit significantly stronger interactions with neutralizing antibodies than peptides with a monomeric TM domain. Furthermore, a peptide with a trimeric, three-helix bundle TM domain recapitulates the binding profile of the native sequence. These studies suggest that neutralizing antibodies can bind the MPER when the TM domain is a three-helix bundle and this presentation could influence the binding of neutralizing antibodies to the virus. Lipid-bilayer presentation of viral antigens in Nanodiscs is a new platform for evaluating neutralizing antibodies. [ABSTRACT FROM AUTHOR]

Summary Aegilops umbellulata serve as an important reservoir for novel biotic and abiotic stress tolerance for wheat improvement. However, chromosomal rearrangements and evolutionary trajectory of this species remain to be elucidated. Here, we present a comprehensive investigation into Ae. umbellulata genome by generating a high‐quality near telomere‐to‐telomere genome assembly of PI 554389 and resequencing 20 additional Ae. umbellulata genomes representing diverse geographical and phenotypic variations. Our analysis unveils complex chromosomal rearrangements, most prominently in 4U and 6U chromosomes, delineating a distinct evolutionary trajectory of Ae. umbellulata from wheat and its relatives. Furthermore, our data rectified the erroneous naming of chromosomes 4U and 6U in the past and highlighted multiple major evolutionary events that led to the present‐day U‐genome. Resequencing of diverse Ae. umbellulata accessions revealed high genetic diversity within the species, partitioning into three distinct evolutionary sub‐populations and supported by extensive phenotypic variability in resistance against several races/pathotypes of five major wheat diseases. Disease evaluations indicated the presence of several novel resistance genes in the resequenced lines for future studies. Resequencing also resulted in the identification of six new haplotypes for Lr9, the first resistance gene cloned from Ae. umbellulata. The extensive genomic and phenotypic resources presented in this study will expedite the future genetic exploration of Ae. umbellulata, facilitating efforts aimed at enhancing resiliency and productivity in wheat. [ABSTRACT FROM AUTHOR]