Fine mapping and characterization of stripe rust resistance gene YrAYH in near-isogenic lines derived from a cross involving wheat landrace Anyuehong

Stripe rust,caused by Puccinia striiformis f.sp.tritici(Pst),is a devastating disease in wheat worldwide.Discovering and characterizing new resistance genes/QTL is crucial for wheat breeding programs.In this study,we fine-mapped and characterized a stripe rust resistance gene,YRAYH,on chromosome arm 5BL in the Chinese wheat landrace Anyuehong(AYH).Evaluations of stripe rust response to prevalent Chinese Pst races in near-isogenic lines derived from a cross of Anyuehong and Taichung 29 showed that YrAYH conferred a high level of resistance at all growth stages.Fine mapping using a large segregating population of 9748 plants,narrowed the YRAYH locus to a 3.7 Mb interval on chromosome arm 5BL that included 61 annotated genes.Transcriptome analysis of two NIL pairs identified 64 upregulated differentially expressed genes(DEGs)in the resistant NILs(NILs-R).Annotations indicated that many of these genes have roles in plant disease resistance pathways.Through a combined approach of fine-mapping and transcriptome sequencing,we identified a serine/threonine-protein kinase SRPK as a candidate gene underlying YrAYH.A unique 25 bp insertion was identified in the NILs-R compared to the NILs-S and previously published wheat genomes.An InDel marker was developed and co-segregated with YrAYH.Agronomic trait evaluation of the NILs suggested that YrAYH not only reduces the impact of stripe rust but was also associated with a gene that increases plant height and spike length.

Fine mapping and transcriptome sequencing reveal candidate genes conferring all-stage resistance to stripe rust on chromosome arm 1AL in Chinese wheat landrace AS1676

Stripe rust, caused by Puccinia striiformis f. sp. tritici(Pst), threatens wheat production worldwide, and resistant varieties tend to become susceptible after a period of cultivation owing to the variation of pathogen races. In this study, a new resistance gene against Pst race CYR34 was identified and predicted using the descendants of a cross between AS1676, a highly resistant Chinese landrace, and Avocet S, a susceptible cultivar. From a heterozygous plant from a F7recombinant inbred line(RIL) population lacking the Yr18 gene, a near-isogenic line(NIL) population was developed to map the resistance gene. An allstage resistance gene, YrAS1676, was identified on chromosome arm 1AL via bulked-segregant exomecapture sequencing. By analyzing a large NIL population consisting of 6537 plants, the gene was further mapped to the marker interval between KA1A_485.36 and KA1A_490.13, spanning 485.36–490.13 Mb on1AL. A total of 66 annotated genes have been reported in this region. To characterize and predict the candidate gene(s), an RNA-seq was performed using NIL-R and NIL-S seedlings 3 days after CYR34 inoculation. Compared to NIL-S plants, NIL-R plants showed stronger immune reaction and higher expression levels of genes encoding pathogenesis-associated proteins. These differences may help to explain why NIL-R plants were more resistant to Pst race CYR34 than NIL-S plants. By combining fine-mapping and transcriptome sequencing, a calcium-dependent protein kinase gene was finally predicted as the potential candidate gene of YrAS1676. This gene contained a single-nucleotide polymorphism. The candidate gene was more highly expressed in NIL-R than in NIL-S plants. In field experiments with Pst challenge,the YrAS1676 genotype showed mitigation of disease damage and yield loss without adverse effects on tested agronomic traits. These results suggest that YrAS1676 has potential use in wheat stripe rust resistance breeding.

A major vernalization-independent QTL for tiller angle on chromosome arm 2BL in bread wheat

Tiller angle(TA)strongly influences plant architecture and grain yield in cereals.However,the genetic basis of TA in wheat is largely unknown.We identified three TA-related quantitative trait loci(QTL).One of them was QTa.sau-2 B-769,a major QTL localized on chromosome arm 2 BL.QTa.sau-2 B-769 was detected in seven environments,explaining 18.1%–51.1%of phenotypic variance.We developed a linked Kompetitive Allele-Specific Polymerase chain reaction(KASP)marker,KASP-AX-108792274,to further validate this locus in three additional populations in multiple environments.QTa.sau-2 B-769 increased TA by up to 24.9%in these populations.There were significant and positive correlations between TA and flag leaf angle(FLANG).However,TA was not correlated with plant height or anthesis date,suggesting that expression of QTa.sau-2 B-769 is independent of vernalization.Traes CS2 B01 G583800,a gene known to be involved in leaf angle regulation,was identified as the most likely candidate gene for QTa.sau-2 B-769.These results enrich our understanding of the mechanisms regulating wheat TA at maturity and may support precise mapping and cloning of gene(s)underlying QTa.sau-2 B-769.

Mapping a stable adult-plant stripe rust resistance QTL on chromosome 6AL in Chinese wheat landrace Yibinzhuermai

Stripe rust,caused by Puccinia striiformis f.sp.tritici(Pst),is one of the most important diseases threatening the yield and stability of wheat production in China and many other countries.Identification and utilization of new genes for durable stripe rust resistance are important for ongoing control of this disease.The objectives of this study were to identify quantitative trait loci(QTL)associated with adult-plant stripe rust resistance in the Chinese wheat landrace Yibinzhuermai(YBZR)and to provide wheat breeders with new sources of potentially durable resistance.A total of 117 recombinant inbred lines(RILs)(F5:8)derived from a cross between YBZR and highly susceptible cultivar Taichung 29(TC29)were assessed for stripe rust severity in field experiments at Wenjiang in 2016 and 2017 and Chongzhou in 2016,2017,2018,and 2019 in Sichuan following inoculation with a mixture of current Pst races.The RILs were genotyped using the Wheat55K single nucleotide polymorphism(SNP)array.Three QTL were identified on chromosome arms 6AL,5BL and 7DS.QYr.YBZR-6AL and QYr.YBZR-7DS conferred major effects in all field environments,explaining 10.6%to 14.7%and 11.5%to 21.2%of phenotypic variation,respectively.The QTL on 5BL and 7DS likely correspond to previously known QTL,whereas QYr.YBZR-6AL is probably novel.Haplotype analysis revealed that the resistance allele at QYr.YBZR-6AL was present in 2.8%of 324 Chinese wheat landraces.SNP markers closely linked with QYr.YBZR-6AL were converted to kompetitive allele-specific PCR markers and validated in the RIL population and a subset of 92 wheat cultivars.QYr.YBZR-6AL and its markers should be useful in breeding programs to improve the level and durability of stripe rust resistance.

Transcriptomic Analysis of the Tolerance Response to Dehydration and Rehydration in Wheat Seedlings

Drought is the main abiotic stress that restricts wheat production.The rapid development of sequencing technology and its widespread application to various fields have revealed the structural characteristics and regulation of related genes through gene expression analysis.Here,we studied responses of wheat plants under drought and rewatering conditions,using morphological and physiological indicators.Moreover,a transcriptome analysis was conducted on Jingmai 12,a drought-resistant wheat strain,to explore the mechanism underlying the response of drought-resistant wheat seedlings to drought stress at the transcriptome level.Drought stress caused morphological and physiological changes in both drought-resistant and-sensitive varieties,but to a greater extent in the drought-sensitive specimen.After re-watering,the drought-resistant wheat showed greater ability to recover than the drought-sensitive wheat.Transcriptome sequencing of Jingmai 12 revealed 97,422 genes,including 80,373 known genes and 17,049 newly predicted genes.The observed upregulation of genes was mostly involved in hormone and signal transduction,carbon metabolism,amino acid synthesis,small molecule production,transmembrane transport,ROS detoxification and defense,drought response protein,and protective enzyme activity.Downregulated genes were mostly involved in photosynthesis,lipid metabolism,signaling,and auxin response.Upon rehydration,these genes and metabolic pathways returned to normal.Our results suggest that all these changes are adaptations to drought stress.Through morphological adaptation,physiological regulation,and the expression of drought-induced genes,normal growth of drought-resistant varieties under drought stress can be promoted.These results increase our understanding of the transcriptomic changes taking place in drought-resistant wheat seedlings under drought stress,and provide a direction for future investigations.

Delineating a locus conferring Fusarium crown rot resistance on chromosome arm 1HL in barley by developing and analysing a large population derived from near isogenic lines

Fusarium crown rot(FCR),a chronic and severe disease caused by various Fusarium species,is prevalent in semi-arid cropping regions worldwide.One of the major QTL conferring FCR resistance was detected on chromosome arm 1 HL(Qcrs.cpi-1 H)in barley.To develop markers that can be reliably used to incorporate the resistance locus into breeding programs,we developed and assessed a near-isogenic line-derived population consisting of1180 recombinant inbred lines targeting the locus.Using this population,we delineated Qcrs.cpi-1 H into an interval of 0.4 c M covering a physical length of about 487 kb.Six markers co-segregating with this locus were generated.Co-linearity for genes located in this interval between the genome of barley and those of either rice or Brachypodium distachyon is poor.Three genes with non-synonymous variations between the resistant and susceptible lines were identified within the interval.The results reported in this study not only provide markers for integrating Qcrs.cpi-1 H into breeding programs,but also form a solid foundation for cloning the causal gene(s)underlying this locus.

MOTIVIC VIRTUAL SIGNED EULER CHARACTERISTICS AND THEIR APPLICATIONS TO VAFA-WITTEN INVARIANTS

For any scheme M with a perfect obstruction theory,Jiang and Thomas associated a scheme N with a symmetric perfect obstruction theory.The scheme N is a cone over M given by the dual of the obstruction sheaf of M,and contains M as its zero section.Locally,N is the critical locus of a regular function.In this note we prove that N is a d-critical scheme in the sense of Joyce.There exists a global motive for N locally given by the motive of the vanishing cycle of the local regular function.We prove a motivic localization formula under the good and circle compact C*-action for N.When taking the Euler characteristic,the weighted Euler characteristic of N weighted by the Behrend function is the signed Euler characteristic of M by motivic method.As applications,using the main theorem we study the motivic generating series of the motivic Vafa-Witten invariants for K3 surfaces.

基于被动同步的宽调谐中红外差频技术研究

实验搭建了基于同步脉冲泵浦的非线性差频中红外光源,利用主-从注入式全光调制技术实现了保偏掺饵和掺镱锁模光纤激光器的被动同步输出,结合高非线性光纤光谱展宽和宽带可调谐滤波器,获得了2940~3260 nm宽波段可调谐的中红外皮秒激光,平均功率为580~926 mW,最大泵浦光转换效率为41%。实验发现,小功率的同步诱导脉冲注入可以大幅降低中红外参量产生的泵浦阈值,从而放宽了高效率中红外产生对高功率泵浦光场的要求。

A pedagogical review on solvable irrelevant deformations of 2D quantum field theory

This is a pedagogical review on TT^(-)deformation of two dimensional quantum field theories.It is based on three lectures which the author gave at ITP-CAS in December 2018.This review consists of four parts.The first part is a general introduction to TT^(-)deformation.Special emphasises are put on the deformed classical Lagrangian and the exact solvability of the spectrum.The second part focuses on the torus partition sum of the TT^(-)/JT^(-)deformed conformal field theories and modular invariance/covariance.In the third part,different perspectives of TT^(-)deformation are presented,including its relation to random geometry,2D topological gravity and holography.We summarize more recent developments until January 2021 in the last part.