Creating large EMS populations for functional genomics and breeding in wheat

Wheat germplasm is a fundamental resource for basic research,applied studies,and wheat breeding,which can be enriched normally by several paths,such as collecting natural lines,accumulating breeding lines,and introducing mutagenesis materials.Ethyl methane sulfonate(EMS)is an alkylating agent that can effectively introduce genetic variations in a wide variety of plant species.In this study,we created a million-scale EMS population(MEP)that started with the Chinese wheat cultivars‘Luyan 128’,‘Jimai 38’,‘Jimai 44’,and‘Shannong 30’.In the M1 generation,the MEP had numerous phenotypical variations,such as>3,000 chlorophyll-deficient mutants,2,519 compact spikes,and 1,692 male sterile spikes.There were also rare mutations,including 30 independent tillers each with double heads.Some M1 variations of chlorophyll-deficiency and compact spikes were inheritable,appearing in the M2 or M3 generations.To advance the entire MEP to higher generations,we adopted a single-seed descendent(SSD)approach.All other seed composites of M2 were used to screen other agronomically important traits,such as the tolerance to herbicide quizalofop-P-methyl.The MEP is available for collaborative projects,and provides a valuable toolbox for wheat genetics and breeding for sustainable agriculture.

Mapping the glaucousness suppressor Iw1 from wild emmer wheat “PI 481521”

Many species of Triticeae display a glaucous phenotype. In wheat, glaucousness/waxiness on spikes, leaves and shoots is controlled by wax production genes(W loci) and epistatic inhibitors(Iw loci). In this study, a suppressor of glaucousness from wild emmer wheat(Triticum turgidum ssp. dicoccoides) accession "PI 481521" was investigated in a pair of durum(T. turgidum ssp. durum cv. "Langdon", LDN)—wild emmer wheat chromosome substitution lines, LDN and "LDNDIC521-2B". Genetic analysis revealed that the non-glaucous phenotype of LDNDIC521-2Bwas controlled by the dominant glaucous suppressor Iw1 on the short arm of chromosome 2B. In total, 371 2B-specific marker differences were identified between LDN and LDNDIC521-2B. The location of the Iw1 gene was mapped using an F2 population that stemmed from LDN and LDNDIC521-2B, generating a partial linkage map that included 19 simple sequence repeats(SSR) and ten gene-based markers. On the current map, the Iw1 gene was located within the Xgwm614–BE498111 interval, and cosegregated with BQ788707,CD893659, CD927782, CD938589, and Xbarc35. Mapping of Iw1 in LDNDIC521-2B, a publically accessible and widely distributed line, will provide valuable information for marker-assisted selection of the agronomically important trait of glaucousness.

WheatOmics:A platform combining multiple omics data to accelerate functional genomics studies in wheat

Dear Editor,Mold-breaking progress in whole-genome sequencing and rapid accumulation of multi-omics data have revolutionized the research strategies of functional genomics in wheat(Wang et al.,2018).However,how to access these vast multi-omics data and to extract key information on genes of in-terest,is still challenging for most wet-lab or field wheat re-searchers who have little bioinformatic experiences and cannot access the expensive computational resources.Here,we pre-sent WheatOmics(http://wheatomics.sdau.edu.cn/,previously designated as Triticeae Multi-omics Center,http://202.194.139.32/),a free,web-accessible,and user-friendly platform.WheatOmics not only empowers the effective access to the visualized multi-omics data of user-interested genes but also offers several distinctive and practical toolkits that can ease almost every aspect of wheat functional genomics studies(Figure 1A).

ZmMS1/ZmLBD30-orchestrated transcriptional regulatory networks precisely control pollen exine development

Because of its significance for plant male fertility and,hence,direct impact on crop yield,pollen exine development has inspired decades of scientific inquiry.However,the molecularmechanismunderlying exine formation and thickness remains elusive.In this study,we identified that a previously unrecognized repressor,ZmMS1/ZmLBD30,controls proper pollen exine development in maize.Using an ms1 mutant with aberrantly thickened exine,we cloned a male-sterility gene,ZmMs1,which encodes a tapetum-specific lateral organ boundary domain transcription factor,ZmLBD30.Weshowed thatZmMs1/ZmLBD30 is initially turned on by a transcriptional activation cascade of ZmbHLH51-ZmMYB84-ZmMS7,and then it serves as a repressor to shut down this cascade via feedback repression to ensure timely tapetal degeneration and proper level of exine.This activation-feedback repression loop regulating male fertility is conserved in maize and sorghum,and similar regulatory mechanism may also exist in other flowering plants such as rice and Arabidopsis.Collectively,these findings reveal a novel regulatory mechanism of pollen exine development by which a long-sought master repressor of upstream activators prevents excessive exine formation.

Distribution,Frequency and Variation of Stripe Rust Resistance Loci Yr10,Lr34/Yr18 and Yr36 in Chinese Wheat Cultivars

Wheat stripe rust is a devastating disease in many regions of the world. In wheat, 49 resistance genes for stripe rust have been officially documented, but only three genes are cloned, including the race-specific resistance YrlO candidate gene （YrlOca） and slow-rusting genes Lr34/Yr18 （hereafter designated as Yrl8） and Fr36. In this study, we developed gene-specific markers for these genes and used them to screen a collection of 659 wheat accessions, including 485 Chinese cultivars. Thirteen percent and eleven percent of the tested Chinese cultivars were positive for the markers for YrlOca and Yr18nn （the resistant haplotype of YrlS）, respectively, but none were positive for the Yr36 marker. Since there is a limited use of the YrlO gene in Chinese wheat, the relatively high frequency of wheat varieties with the YrlOcG marker suggests that the identity of the YrlO gene is unknown. With regards to the Yr18 gene, 29% of the tested cultivars that are used in the Middle and Lower Yangtze Valleys＇ winter wheat zone were positive for Yrl8RH markers. A non-functional allele of Yrl8Rn was identified in ＇Mingxian 169＇, a commonly used susceptible check for studying stripe rust. The data presented here will provide useful information for marker-assisted selection for wheat stripe rust resistance.