Isolation and Characterization of NBS-LRR Class Resistance Homologous Gene from Wheat

One resistance gene analog fragment named RGA-CIN14 was isolated from TcLr19 wheat,which contains kinase-2,kinase-3a,and the GLPL motif of the NBS-spanning region,using degenerated primers according to the nucleotide binding site （NBS） conserved domain.Based on the RGA-CIN14,a full-length cDNA,CIN14,which was 2 987 bp encoding 880 amino acids,was obtained by using the method of the rapid amplification cDNA ends （RACE）.Bioinformatics analysis showed that the deduced amino acids of CIN14 protein consisted of a NB-ARC conserved domain and many leucine-rich repeats （LRR） domains.The phylogenetic tree analysis indicated a considerable identity of the protein encoded by CIN14 with that of wheat leaf rust resistance gene Lr1,but a lower similarity with Lr21.The expression profile of the CIN14 gene detected by semi-quantitative RT-PCR showed that the CIN14 gene was not induced by Puccinia triticina and it was a constitutive gene with low abundance in the wheat leaf tissue.The resistance homology sequence was successfully obtained,which provides the shortcut for cloning of the resistance gene in TcLr19 wheat.

Rapid Identification for Drought Resistance of Wheat Using Near-infrared Diffuse Reflectance Spectroscopy

[Objective] This study aimed to establish an identification system for drought-resistance in wheat by using near-infrared diffuse reflectance spectroscopy. [Method] In 2006-2007, 36 wheat varieties with different drought resistance were selected and were classified according to their drought resistance grades determined by the Technical Specification of Identification and Evaluation for Drought Resistance in Wheat （GB/T 21127-2007）. In addition, the harvested wheat seed samples were spectrally analyzed with FOSS NIRSystems5000 near-infrared spectrum analyzer for grain quality （full spectrum analyzer） and then the forecasted regression equations were established. [Result] After the establishment of a database and validation, dis- criminated functions were obtained. The determination coefficient （RSQ） and coeffi- cients of determination for cross validation （1-VR） in the discriminant function built with seed samples from water stress area were 0.846 0 and 0.781 8, respectively, which indicated that the consistency between drought resistance and spectral charac- teristics in wheat varieties was good, and there was high correlation between the near-infrared diffuse reflectance spectra of seeds and the drought resistance in wheat. [Conclusiou] Under water stress condition, it is feasible to establish a conve- nient, rapid and no-damage identification system for the drought resistance in wheat by using the near-infrared diffuse reflectance spectrum technique to scan wheat seeds.

Identification of a major QTL for Hessian fly resistance in wheat cultivar‘Chokwang’

The Hessian fly(HF,Mayetiola destructor)is one of the destructive pests of wheat(Triticum aestivum L.)worldwide.Resistant cultivars can effectively minimize wheat damage due to this insect pest.To identify new quantitative trait loci(QTL)for HF resistance,a population of recombinant inbred lines(RILs)was developed from a cross between the HF-resistant wheat cultivar‘Chokwang’and susceptible wheat‘Ning 7840’,and phenotyped for responses to HF attack.A linkage map was constructed using 1147 single nucleotide polymorphism(SNP)markers generated from genotyping-by-sequencing(GBS).One major QTL,QHf.hwwg-6 BS,for HF-resistance was identified on chromosome arm 6 BS,which explained up to84.0%of the phenotypic variation and was contributed by Chokwang.Two RILs showed recombination in the candidate interval of QHf.hwwg-6 BS,which delimited QHf.hwwg-6 BS to a 4.75 Mb physical interval between 6,028,601 bp and 10,779,424 bp on chromosome arm 6 BS of IWGSC Chinese Spring reference genome Ref Seq v2.0.Seven GBS-SNPs in the candidate interval were converted into Kompetitive allele specific polymerase chain reaction(KASP)markers.Two of them,KASP-6 B112698 and KASP-6 B7901215,were validated in a U.S.winter wheat panel.KASP-6 B112698 was nearly diagnostic,thus can be used to screen QHf.hwwg-6 BS and pyramid it with other resistance genes in breeding programs.

Can effectoromics and loss-of-susceptibility be exploited for improving Fusarium head blight resistance in wheat?

Bread wheat(Triticum aestiuum L.),which provides about 20%of daily calorie intake,is the most widely cultivated crop in the world,in terms of total area devoted to its cultivation.Therefore,even small increases in wheat yield can translate into large gains.Reducing the gap between actual and potential grain yield in wheat is a crucial task to feed the increasing world population.Fusarium head blight(FHB)caused by the pathogenic fungus Fusaium graminearum and related Fusarium species is one of the most devastating wheat diseases throughout the world.This disease reduces not only the yield but also the quality by contaminating the grain with mycotoxins harmful for humans,animals and the environment.In recent years,remarkable achievements attained in omics"technologies have not only provided new insights into understanding of processes involved in pathogenesis but also helped develop effective new tools for practical plant breeding.Sequencing of the genomes of various wheat patho gens,including F.graminearum,as well as those of bread and durum wheat and their wild relatives,together with advances made in transcriptomics and bioinformatics,has allowed the identification of candidate pathogen effectors and corresponding host resistance(R)and susceptibility(S)genes.However,so far,FHB effectors and wheat susceptibility genes/factors have been poorly studied.In this paper,we first briefly highlighted recent examples of improving resistance against pathogens via new techniques in different host species.We then propose effective strategies towards developing wheat cultivars with improved resistance to FHB.We hope that the article will spur discussions and interest among researchers about novel approaches with great potential for improving wheat against FHB.

Evaluation of Wheat Stripe Rust Resistance in Sichuan Province

Wheat stripe rust,caused by Puccinia striiformis Westend. f. sp. tritici Erikss.（ Pst）,is one of the most destructive diseases of wheat（ Triticum aestivum L.） worldwide. Sichuan province plays an important role in stripe rust epidemic in China. To identify and evaluate wheat stripe rust resistance in Sichuan Province,134 wheat cultivars（ lines） were inoculated with seven Pst races at seedling stage and adult stage. The results indicated that the resistance frequencies of wheat cultivars（ lines） against seven races CYR31,Su11-7,CYR29,Su11-4,CYR32,CYR33 and V26 were 92. 4%,92. 5%,89. 3%,89. 4%,87. 3%,85. 0% and 82. 8%,respectively. Among 134 materials,76（ 56. 0%） performed resistance against all tested races both in seedling and adult stages. The virulence of new pathogenic type V26 of Pst on wheat cultivars（ lines） was stronger than the dominant races CYR32 and CYR33. All wheat cultivars（ lines） were classified into three types according to analysis of resistance spectrum; 66. 4% of cultivars（ lines） showed all-stage resistance,17. 9% were adult-plant resistance,and 15. 7% were susceptible. This indicated that although the overall resistance level of wheat cultivars（ lines） in Sichuan Province was very high,the resistance type was simple. Therefore,it is important to identify new resistance genes and enhance resistance gene diversity. Meanwhile,pyramiding breeding of all-stage resistance gene and adult-plant resistance gene could be gradually developed,to achieve durable resistance of wheat cultivars（lines） against stripe rust in Sichuan Province.

Genetic Analysis of Major and Minor Gene(s) Resistant to Stripe Rust in Important Resource Wheat Line Jinghe891-1

Inheritance of line Jinghe891-l resistant to pathotype of Puccinia striiformis in two patterns of temperature (Normal: day 18℃ /night 10℃ , High: day 24℃ /night 15℃ )was studied in this paper. The results showed that there were at least two pairs of dominant major genes and one pair of recessive minor genes in Jinghe 891-1. The two pairs of major genes that conferred resistance to CY31 were allelic or linked closely with resistance gene in Jubilejna Ⅱ , Kangyin655 and T. spelta Album. They were novel resistance genes and were inherited in a repeated or independent mode. The minor genes, which could modify the major genes, were sensitive to temperature and conferred resistance to all pathotypes of Puccinia striiformis in China. It is recommended that this line can be used as an important resource stock.

Resistance in Barley (<i>Hordeum vulgare</i>L.) to New Invasive Aphid, Hedgehog Grain Aphid (<i>Sipha maydis</i>, Passerini) (Hemiptera: Aphididae)

Sipha maydis Passerini (Hemiptera: Aphididae) is a pest of cereals in many regions of the world and was identified as an invasive pest of the US in 2007. Regional surveys from 2015-2017 revealed this pest was broadly distributed throughout many of the western Great Plains states where it is a potential threat to cereal production. The common name hedgehog grain aphid, HGA, has been associated with Sipha maydis in the US. Cross-resistance where a plant is resistant to one aphid species and is also resistant to another species that is known to occur. Six barleys were evaluated for cross-resistance to HGA: Russian wheat aphid, RWA, resistant germplasms STARS 9301B and STARS 9577B and cultivar “Mesa”;greenbug, GB, resistant germplasm STARS 1501B and cultivar “Post 90”;and RWA and GB resistant experimental line 00BX 11-115. Cultivars “Morex” and “Schuyler” were susceptible controls. Antixenosis was measured 5 days after infestation by HGA. Seedling damage ratings and reductions in seedling growth were recorded after 17 days of infestation. Intrinsic rate of increase, rm, of HGA was determined by following the development of newborn aphids to adulthood and reproduction. 00BX 11-115 and Post 90 had significantly greater antixenosis (fewer aphids/seedling), significantly lower plant damage ratings, and significantly lower intrinsic rates of increase than other entries. Differences in seedling growth were not significant. 00BX 11-115 and Post 90 were the only entries with the Rsg1 greenbug resistance gene. Rsg1 greenbug resistance confers cross-resistance to HGA in the seedling stage.

Genetic Analysis of Stripe Rust Resistance of Xikemai 6 at Adult Plant Stage

To confirm resistance and genetic rules of Xikemai 6 against physiological races of wheat stripe rust,physiological races CYR31,CYR32 and CYR33,Su11-4 and V26 were inoculated in Xikemai 6 and Mingxian 169 and their hybrid progenies F_1,F_2 and F_3 at adult plant stage on March 2015. The results showed that the resistance of Xikemai 6 against CYR31 was controlled by 2 pairs of dominant genes and a pair of recessive genes; the resistance against CYR32 was controlled by three pairs of dominant resistant genes（ two pairs of genes performed cumulative effect）; the resistance against CYR33 was controlled by a pair of dominant genes and a pair of recessive genes; the resistance against Su11-4 was controlled by a pair of dominant genes and a pair of recessive genes independently or collaboratively; the resistance against V26 was controlled by a pair of dominant genes independently. Due to good performance of Xikemai 6 in test and production,as well as years of resistance identification and genetic analysis,Xikemai 6 was proved to be an excellent cultivar with good resistance against stripe rust,and the inheritance of its resistance was stable,so Xikemai 6 could be used as a germplasm resource and resistance material with excellent comprehensive character. Molecular marker and localization could be further studied,to provide new resistance parents for disease-resistant breeding of wheat.

Characterization of Three Novel Wheat LThinopyrum intermedium Addition Lines with Novel Storage Protein Subunits and Resistance to Both Powdery Mildew and Stripe Rust

Wide hybridization is an effective approach for enhancing the resistance of bread wheat （Triticum aestivum L.） to biotic and abiotic stresses by introducing favorable alien genes （Sepsi et al., 2008）. Wheatgrass, Thinopyrum intermedium （Host） Barkworth ＆ D.R. Dewey or Agropyron intermedium （Host） Beauvoir （2n = 42; genome formula JJjSjSstst）, is a perennial species in the tribe Triticeae and an important source of wheat improvement for biotic and abiotic stress resistance and quality-related traits, such as high grain protein concentration （Chen et al., 1998; 2001; 2003; Han et al., 2004; Li and Wang, 2009）. In addition, the ready crossing ability of wheatgrass with various Triticum species has made it popular in germ- plasm development.