Expression Comparisons of Pathogenesis-Related(PR) Genes in Wheat in Response to Infection/Infestation by Fusarium, Yellow dwarf virus(YDV) Aphid-Transmitted and Hessian Fly

Expression profiles of ten pathogenesis-related （PR） genes during plant defense against Fusarium, Yellow dwarf virus （YDV） aphid-transmitted and Hessian fly （Hf） were compared temporally in both resistant and susceptible genotypes following pathogen infection or insect infestation. Quantitative real-time PCR （qRT-PCR） revealed that PR1, PR2, PR3, PR5, PR6, PR8, PR9, and PR15 appeared to be induced or suppressed independently in response to Fusarium, YDV aphid-transmitted or Hf during the interactions. The PR gene（s） essential to defense against one organism may play little or no role in defense against another pathogen or pest, suggesting the alternative mechanisms may be involved in different interactions of wheat- Fusarium, wheat-YDV aphid-transmitted and wheat-Hf. However, strong up- or down-regulation of PRl2 and PR14 encoding low molecular membrane acting protein, defensin and lipid transfer protein （LTP）, respectively, had been detected after either pathogen infection or insect infestation, therefore showed broad responses to pathogens and insects. It was postulated that low molecular proteins such as defensins and LTPs might play a role in the early stages of pathogenesis in the signaling process that informs plants about the attack from biotic stresses. In addition, a synergistic action between different PR genes might exist in plants to defense certain pathogens and insects on the basis of comprehensive expression profiling of various pathogenesis-related genes revealed by qRT-PCR in this study.

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.

Wheat breeding for Hessian fly resistance at ICARDA

Hessian fly(HF),Mayetiola destructor(Say)is an important pest of wheat in North Africa,North America,Southern Europe,Northern Kazakhstan,Northwestern China,and New Zealand.It can cause up to 30%yield losses and sometimes can result in complete crop failure if infestation coincides with young stage of the wheat crop.Studies to-date have shown the availability of genetic diversity in the wheat genetic resources(landraces,wild relatives,cultivars,etc.)for resistance to Hessian fly.About 37 resistance genes have been reported from these wheat genetic resources for resistance to Hessian fly,of which,some have been deployed singly or in combination in the breeding programs to develop high yielding varieties with resistance to HF.Deployment of resistant varieties in different agro-ecologies with other integrated management measures plays key role for the control of HF.This paper summarizes the importance,life cycle,mechanisms of resistance,gene mining,and wheat breeding efforts for HF resistance.

Relationship of Secreted Salivary Protein Variants to Virulence in Hessian Fly (<i>Mayetiola destructor</i>(Say))

Salivary proteins are the initial contact between sedentary insect pests and their host plants. It is expected that one or more salivary proteins mediate the interaction between Hessian fly and wheat, in which a feeding site is established to the benefit of the fly. A survey of 52 loci annotated as insect secreted salivary proteins was conducted in 384 individuals evenly distributed among eight biotypes of Hessian fly (B, C, D, E, GP, L, O, and vH9). Amplicons were sequenced with Illumina, and sequence reads were aligned to the reference sequences from which primers had been designed. Positions of consistent base variation (998 in all) were identified and tabulated by biotype. No varying position was associated with biotype-wide virulence to any one of wheat resistance genes H3, H5, H6, H7/H8, H9, H11, H13, and H26. The multiplate pooling strategy utilized in this study is an effective, affordable way to reveal the genotype of hundreds of individuals at tens of genetic loci.

The evolution of Hessian fly from the Old World to the New World： Evidence from molecular markers

Eighteen polymorphic microsatellite loci and 11 single-nucleotide polymor- phisms were genotyped in 1 095 individual Hessian fly specimens representing 23 popula- tions from North America, southern Europe, and southwest Asia. The genotypes were used to assess genetic diversity and interrelationship of Hessian fly populations. While phyloge- netic analysis indicates that the American populations most similar to Eurasian populations come from the east coast of the United States, genetic distance is least between （Alabama and California） and （Kazakhstan and Spain）. Allelic diversity and frequency vary across North America, but they are not correlated with distance from the historically documented point of introduction in New York City or with temperature or precipitation. Instead, the greatest allelic diversity mostly occurs in areas with Mediterranean climates. The mi- crosatellite data indicate a general deficiency for heterozygotes in Hessian fly. The North American population structure is consistent with multiple introductions, isolation by dis- tance, and human-abetted dispersal by bulk transport of puparia in infested straw or on harvesting equipment.

Genes encoding a group of related small secreted proteins from the gut of Hessian fly larvae [Mayetiola destructor （Say）]

A group of related genes has been isolated and characterized from the gut of Hessian fly larvae [Mayetiola destructor （Say）]. Members in this group appear to encode proteins with secretary signal peptides at the N-terminals. The mature putative proteins are small, acidic proteins with calculated molecular masses of 14.5 to 15.3 kDa, and isoelectric points from 4.56 to 4.88. Northern blot analysis revealed that these genes are expressed predominantly in the gut of Hessian fly larvae and pupae. Two related genes, GIOK1 and GIOK2, were isolated as tandem repeats. Both genes contain three exons and two introns. The intron/exon boundaries were conserved in terms of amino acid encoding, suggesting that they arose by gene duplication. The fact that the frequency of this group of clones in a gut cDNA library higher than that of total cDNA clones encoding digestive enzymes suggested that this group of proteins may perform an important function in the gut physiology of this insect. However, the exact functions of these proteins are as yet known since no sequence similarity could be identified between these proteins and any known sequences in public databases using standard methods.

Utilization of mechanical compression as a disinfestation technique for Hessian fly(Mayetiola destructor(say))in timothy hay:Field test

Baled timothy hay underwent testing at a hay processing plant in Canada to determine if mechanical compression(rebaling)could be used as a disinfestation protocol for Hessian fly(Mayetiola destructor(Say))puparia.Pressure sensitive films were randomly placed throughout the hay material,on the chamber walls,and in different orientations,to assess the hay compaction unit’s ability to induce the required pressure to crash a Hessian fly puparium in the hay.Attached to the pressure films were organdy cages containing wheat seedlings infested with Hessian fly puparia.The variables which were tested included the hold time(0.5 and 2.0 s),applied pressure(10.34 and 12.41 MPa),and timothy hay quality(low-moisture first cut,high-moisture first cut and high-moisture second cut hay).A total of 36 tests were conducted.For each test,10 Hessian fly cages and 10 pressure sensitive films were used.Each test cage contained approximately 168.56 Hessian fly puparia,translating into a total Hessian fly count of 60681 for the entire field test.Analysis of the pressure sensitive films showed that 100%of the hay experienced at least 200 kPa(29 psi)of pressure.Following the 75-day post experiment emergence period,0.0066%of the puparia survived,which may be due to the fact that the emerged puparia might have not been crushed and not subjected to a pressure of at least 20.6 kPa.The applied pressures affected Hessian fly emergence by considerably reducing the number of puparia that emerged.However,Hessian fly emerged from one of the cages in two tests.Most of the Hessian fly puparia were destroyed irrespective of the applied pressure,hold time or hay quality.

噻虫嗪种子处理对冬小麦黑森瘿蚊的防治效果

黑森瘿蚊（Mayetiola destructor（Say））是我国重要的检疫性害虫,近年在新疆博尔塔拉州局部暴发。田间试验了30%噻虫嗪WS拌种处理新冬18号小麦种子对黑森瘿蚊的防效及其对出苗率和产量的影响。结果表明,每100 kg种子分别用30%噻虫嗪WS 100 m L、200 m L、300 m L 3种剂量拌种处理后对黑森瘿蚊的防效分别为77.99%-78.35%、81.79%-100%、92.23%-100%;拌种处理可显著提高小麦产量,且不会降低田间出苗率,300 m L/100 kg种子处理可显著提高出苗率。建议生产中采用30%噻虫嗪WS 300 m L/100 kg种子进行处理防治黑森瘿蚊。

Hemipteran and dipteran pests: Effectors and plant host immune regulators

Hemipteran and dipteran insects have behavioral,cellular and chemical strategies for evading or coping with the host plant defenses making these insects particularly destructive pests worldwide. A critical component of a host plant＇s defense to herbivory is innate immunity. Here we review the status of our understanding of the receptors that contribute to perception of hemipteran and dipteran pests and highlight the gaps in our knowledge in these early events in immune signaling. We also highlight recent advances in identification of the effectors that activate pattern-triggered immunity and those involved in effector-triggered immunity.