Inheritance and molecular mapping of new greenbug resistance genes in wheat germplasms derived from Aegilops tauschii

Molecular mapping of genes for crop resistance to the greenbug, Schizaphis graminum Rondani, will facilitate selection of greenbug resistance in breeding through marker-assisted selection and provide information for map-based gene cloning. In the present study, microsatellite marker and deletion line analyses were used to map greenbug resistance genes in five newly identified wheat germplasms derived from Aegilops tauschii. Our results indicate that the Gb genes in these germplasms are inherited as single dominant traits. Microsatellite markers Xwmc157 and Xgdm150 flank Gbx1 at 2.7 and 3.3 cM, respectively. Xwmc671 is proximately linked to Gba, Gbb, Gbc and Gbd at 34.3, 5.4, 13.7, 7.9 cM, respectively. Xbarc53 is linked distally to Gba and Gbb at 20.7 and 20.2 cM, respectively. Xgdm150 is distal to Gbc at 17.9 cM, and Xwmc157 is distal to Gbd at 1.9 cM. Gbx1, Gba, Gbb, Gbc, Gbd and the previously characterized Gbz are located in the distal 18% region of wheat chromosome 7DL. Gbd appears to be a new greenbug resistance gene different from Gbx1 or Gbz. Gbx1, Gbz Gba, Gbb, Gbc and Gbd are either allelic or linked to Gb3.     

Microsatellite markers linked to six Russian wheat aphid resistance genes in wheat

The Russian wheat aphid (RWA), Diuraphis noxia Mordvilko, is a serious economic pest of wheat and barley in North America, South America, and South Africa. Using aphid-resistant cultivars has proven to be a viable tactic for RWA management. Several dominant resistance genes have been identified in wheat, Triticum aestivum, including Dn1 in PI 137739, Dn2 in PI 262660, and at least three resistance genes (Dn5+) in PI 294994. The identification of RWA-resistant genes and the development of resistant cultivars may be accelerated through the use of molecular markers. DNA of wheat from near-isogenic lines and segregating F₂ populations was amplified with microsatellite primers via PCR. Results revealed that the locus for wheat microsatellite GWM111 (Xgwm111), located on wheat chromosome 7DS (short arm), is tightly linked to Dn1, Dn2 and Dn5, as well as Dnx in PI 220127. Segregation data indicate RWA resistance in wheat PI 220127 is also conferred by a single dominant resistance gene (Dnx). These results confirm that Dn1, Dn2 and Dn5 are tightly linked to each other, and provide new information about their location, being 7DS, near the centromere, instead of as previously reported on 7DL. Xgwm635 (near the distal end of 7DS) clearly marked the location of the previously suggested resistance gene in PI 294994, here designated as Dn8. Xgwm642 (located on 1DL) marked and identified another new gene Dn9, which is located in a defense gene-rich region of wheat chromosome 1DL. The locations of markers and the linked genes were confirmed by di-telosomic and nulli-tetrasomic analyses. Genetic linkage maps of the above RWA resistance genes and markers have been constructed for wheat chromosomes 1D and 7D. These markers will be useful in marker-assisted breeding for RWA-resistant wheat. Received: 17 May 2000 / Accepted: 13 June 2000     

Categories of resistance to greenbug (Homoptera: Aphididae) biotype K in wheat lines containing Aegilops tauschii genes

The wheat lines (cultivars) 'Largo', 'TAM110', 'KS89WGRC4', and 'KSU97-85-3' conferring resistance to greenbug, Schizaphis graminum (Rondani), biotypes E, I, and K were evaluated to determine the categories of resistance in each line to greenbug biotype K. Our results indicated that Largo, TAM110, KS89WGRC4, and KSU97-85-3 expressed both antibiosis and tolerance to biotype K. Largo, KS89WGRC4, and KSU97-85-3, which express antixenosis to biotype I, did not demonstrate antixenosis to biotype K. The results indicate that the same wheat lines may possess different categories of resistance to different greenbug biotypes. A new cage procedure for measuring greenbug intrinsic rate of increase (r(m)) was developed, by using both drinking straw and petri dish cages, to improve the efficiency and accuracy of r(m)-based antibiosis measurements.     

Biochemical markers associated with two Mv chromosomes from Aegilops ventricosa in wheat-Aegilops addition lines

Summary The distribution of three biochemical markers, U-1, CM-4 and Aph_v-a, -b, among wheat-Aegilops addition lines carrying M^v chromosomes from Aegilops ventricosa (genomes D^vM^v) has been investigated. Addition lines which had been previously grouped together on the basis of common non-biochemical characters carried marker U-1, a protein component from the 2M urea extract. The added chromosome, in the appropriate genetic background, seems to confer a high level of resistance to the eyespot disease, caused by the fungus Cercosporella herpotrichoides. The other two markers were concomitantly associated with another similarly formed group of addition lines. Both CM-4, a protein component from the chloroform:methanol extract, and Aph_v-a, -b, alkaline phosphate isozymes, have been previously shown to be associated with homoeologous chromosome group 4, which suggests that the added chromosome in the second group of addition lines is 4M^v.     

Mapping and validation of quantitative trait loci associated with wheat yellow mosaic bymovirus resistance in bread wheat

Wheat yellow mosaic (WYM) caused by wheat yellow mosaic bymovirus (WYMV) has been growing as one of the most serious diseases affecting wheat production in China. In this study, the association of quantitative trait loci (QTLs) governing WYMV resistance with molecular markers was established using 164 recombinant inbred lines (RILs) derived from 'Xifeng Wheat' (highly resistant)?×?'Zhen 9523' (highly susceptible). Phenotypic data of WYMV resistance of the RILs were collected from 4-year, two-location replicated field trials. A molecular marker-based linkage map, which was comprised of 273 non-redundant loci and represented all the 21 wheat chromosomes, was constructed with the JoinMap 4.0 software. Using the Windows QTL Cartographer V2.5 software, three QTLs associated with WYMV resistance, QYm.njau-3B.1, QYm.njau-5A.1 and QYm.njau-7B.1, were detected on chromosomes 3BS, 5AL, and 7BS, respectively. The favorable allele effects were all contributed by 'Xifeng Wheat'. Among the three QTLs, QYm.njau-3B.1 and QYm.njau-5A.1 were detected in all the four trials and the overall mean, and could explain 3.3-10.2% and 25.9-53.7% of the phenotypic variation, respectively, while QYm.njau-7B.1 was detected in one trial and the overall mean and explained 4.9 and 3.3% of the phenotypic variation, respectively. A large portion of the variability for WYMV response was explained by a major QTL, QYm.njau-5A.1. The relationship of the molecular markers linked with QYm.njau-5A.1 and the WYMV resistance was further validated using a secondary F(2) population. The results showed that three markers, i.e., Xwmc415.1, CINAU152, and CINAU153, were closely linked to QYm.njau-5A.1 with the genetic distances of 0.0, 0.0, and 0.1?cM, respectively, indicating they should be useful in marker-assisted selection (MAS) wheat breeding for WYMV resistance. A panel of germplasm collection consisting of 46 wheat varieties with known WYMV response phenotypes was further used to validate the presence and effects of QYm.njau-5A.1 and the above three markers. It was found that QYm.njau-5A.1 was present in 12 of the 34 WYMV-resistant varieties.     

Conversion of AFLP markers associated with FHB resistance in wheat into STS markers with an extension-AFLP method.

Amplified fragment length polymorphism (AFLP) has proven a powerful tool for tagging genes or quantitative trait loci (QTLs) of interest in plants. However, conversion of AFLP markers into sequence-tagged site (STS) markers is technically challenging in wheat owing to the complicated nature of its genome. In this study, we developed an "extension-AFLP" method to convert AFLP markers associated with Fusarium head blight (FHB) resistance into STS markers. When an AFLP marker of interest was detected with an EcoRI+3-MseI+4-selective primer combination, the PCR product was used as a template for an additional selective amplification with four primer pairs, in which one additional selective base (either A, C, G, or T) was added to the 3' end of one of the two primers. The extended primer pair that produced the targeted band was further extended by adding each of the four selective nucleotide bases for the next round of selective amplification. Extension selective amplification was performed until the target bands became clear enough for subsequent cloning and sequencing. By using the extension-AFLP method, we successfully converted two AFLP markers located on chromosome 3BS and associated with FHB resistance into STS markers. Our results indicated that the extension-AFLP method is an efficient approach for converting AFLP markers into STS markers in wheat. The developed STS markers might be used for marker-assisted selection (MAS) for FHB resistance in wheat breeding programs.     

Categories of resistance to greenbug (Homoptera: Aphididae) biotype I in Aegilops tauschii germplasm

Categories of resistance to greenbug, Schizaphisgraminum (Rondani), biotype I, were determined in goatgrass, Aegilops tauschii (Coss.) Schmal., accession 1675 (resistant donor parent), 'Wichita' wheat, Triticum aestivum L., (susceptible parent), and an Ae. tauschii-derived resistant line, '97-85-3'. Antibiosis was assessed using the intrinsic rate of increase (rm) of greenbugs confined to each of the three genotypes. Neither parent nor the resistant progeny expressed antibiosis. Mean rm values for greenbug I on Wichita (0.0956), and Ae. tauschii (0.10543) were not significantly different. Mean rm values for Wichita and 97-85-3 were also not significantly different. Antixenosis was determined by allowing aphids a choice to feed on plants of each of the three genotypes. Ae. tauschii 1675 exhibited antixenosis, but this resistance was not inherited and expressed in '97-85-3'. In experiments comparing Wichita and Ae. tauschii 1675, greenbug I population distributions were not significantly different on Wichita at 24 h, but were shifted toward Wichita at 48 h. In the second antixenosis experiment, there were no significant differences in greenbug I population distributions on 97-85-3 or Wichita at 24 or 48 h. When all three lines were compared, there were no significant differences in greenbug biotype I populations at 24 or 48 h after infestation. Comparisons of proportional dry plant weight loss (DWT) and SPAD meter readings were used to determine tolerance to greenbug I feeding. Ae. tauschii 1675 and 97-85-3 were highly tolerant compared with Wichita. Infested and uninfested Ae. tauschii 1675 DWT was nonsignificant, and infested Wichita plants weighed significantly less than uninfested plants. When Wichita and 97-85-3 were contrasted, DWT of infested and uninfested Wichita plants were significantly different, but those of 97-85-3 were not. Mean percent leaf chlorophyll losses for the three genotypes, as measured by the SPAD chlorophyll meter, were as follows: Wichita = 65%; Ae. tauschii 1675 = 25%; and 97-85-3 = 39%. Percent leaf chlorophyll losses caused by greenbug feeding was significantly different in comparisons between Wichita and Ae. tauschii 1675, and comparisons between Wichita and 97-85-3, although feeding damage was not significantly different in comparisons between Ae. tauschii 1675 and 97-85-3. These data provided further evidence of the expression of tolerance to greenbug feeding in Ae. tauschii 1675 and 97-85-3.     

Microsatellite markers associated with quantitative trait loci controlling antibody response to Escherichia coli and Salmonella enteritidis in young broilers

A unique resource population was produced to facilitate detection of microsatellite markers associated with quantitative trait loci controlling antibody (Ab) response in broiler chickens. Three F1 males were produced by mating two lines divergently selected on Ab response to Escherichia coli vaccination. Each F1 male was mated with females from four genetic backgrounds: F1, high-Ab line (HH), low-Ab line and commercial line, producing three resource families, each with four progeny types. About 1700 chicks were immunized with E. coli and Salmonella enteritidis vaccines. Selective genotyping was conducted on the individuals with highest or lowest average Ab to E. coli and S. enteritidis within each progeny type in each sire family. Twelve markers were significantly associated with Ab to E. coli and six of them were also associated with Ab to S. enteritidis, mostly exhibiting a similar low effect (approximately 0.35 phenotypic SD) in all progeny types. Four markers exhibited a highly significant and much larger effect (approximately 1.7 SD), but only in progeny of females from the HH, suggesting that a backcross to the high parental line should be preferred over the commonly used F2 population. Results from two markers suggested a quantitative trait locus on chromosome 2 around 400 cM. The marker MCW0083, significant in two sire families, is closely linked to the bone morphogenetic protein 2 (BMP2) gene, known to be associated with the control of T-cell transformation in humans.     

Broad-spectrum resistance loci for three quantitatively inherited diseases in two winter wheat populations

Septoria tritici blotch (STB), caused by S. tritici, Stagonospora glume blotch (SGB), caused by S. nodorum, and Fusarium head blight (FHB), caused by F. graminearum and F. culmorum, are the most important diseases of wheat (Triticum aestivum L.) in temperate growing areas. The main goals of this study were to detect (1) new quantitative trait loci (QTL) for STB resistance in two adapted European biparental populations (Arina/Forno, History/Rubens) and (2) QTL regions for broad-spectrum resistance (BSR) to the above-mentioned diseases during the adult-plant stage in the field. The three resistances were phenotyped across 4–7 field environments and phenotypic data revealed significant (P < 0.01) genotypic differentiation in all cases. Entry-mean heritabilities (h2) ranged from 0.73 to 0.93. For STB resistance, correlations between disease ratings and heading date were significant (P < 0.01), but moderate (r = −0.23 to −0.30) in both populations. Correlations between STB and plant height were higher in Arina/Forno (r = −0.45) and History/Rubens (r = −0.55), the latter population segregating at the Rht-D1 locus. During the initial QTL analysis, 5 QTL were detected for STB resistance in each of the populations, amounting to an explained genotypic variance of 45–63%, thus, showing the same ranges as FHB and SGB resistances in Arina/Forno and FHB resistance in History/Rubens. In total, 7 BSR QTL were found in the meta-analysis with the raw data, including the QTL on chromosome 4D at the Rht-D1 locus. A BSR QTL for all three diseases was not found but several BSR QTL for combinations with two diseases were detected. Combining the BSR QTL detected in the present breeding material by applying marker-assisted selection seems a promising approach.     

Efficacy of pyramiding greenbug (Homoptera: Aphididae) resistance genes in wheat

Durable resistance to greenbug, Schizaphis graminum (Rondani), in wheat is a goal of wheat improvement teams, and one that has been complicated by the regular occurrence of damaging biotypes. Simulation modeling studies suggest that pyramiding resistance genes, i.e., combining more than one resistance gene in a single cultivar or hybrid, may provide more durable resistance than sequential releases of single genes. We examined this theory by pyramiding resistance genes in wheat and testing a series of greenbug biotypes. Resistance genes Gb2, Gb3, and Gb6, and pyramided genes Gb2/Gb3, Gb2/Gb6, and Gb3/Gb6 were tested for effectiveness against biotypes E, F, G, H, and I. By comparing reactions of plants with pyramided genes to those with single resistance genes, we found that pyramiding provided no additional protection over that conferred by the single resistance genes. Based on the results of this test, we concluded that the sequential release of single resistance genes, combined with careful monitoring of greenbug population biotypes, is the most effective gene deployment strategy for greenbug resistance in wheat.     

Mapping and validation of powdery mildew resistance loci from spring wheat cv. Naxos with SNP markers

Powdery mildew, caused by Blumeria graminis f.sp. tritici, is a major wheat disease in maritime and temperate climates. Breeding for race-non-specific or partial resistance is a cost-effective and environmentally friendly disease control strategy. The German spring wheat cultivar Naxos has proven to be a good source for partial resistance to powdery mildew. The objectives of the present study were to map the resistance loci in Naxos with use of high-density SNP markers in the Shanghai3/Catbird x Naxos inbred line population and validate the results in a different genetic background; Soru#1 x Naxos. Both populations were genotyped with the Illumina iSelect 90K wheat chip, and integrated linkage maps developed by inclusion of previously genotyped SSR and DArT markers. With the new linkage maps, we detected a total of 12 QTL for powdery mildew resistance in Shanghai3/Catbird x Naxos, of which eight were derived from Naxos. Previously reported QTL on chromosome arms 1AS and 2BL were more precisely mapped and the SNP markers enabled discovery of new QTL on 1AL, 2AL, 5AS and 5AL. In the Soru#1 x Naxos population, four QTL for powdery mildew resistance were detected, of which three had resistance from Naxos. This mapping verified the 1AS and 2AL QTL detected in Shanghai3/Catbird x Naxos, and identified a new QTL from Naxos on 2BL. In conclusion, the improved linkage maps with SNP markers enabled discovery of new resistance QTL and more precise mapping of previously known QTL. Moreover, the results were validated in an independent genetic background.     

Identification of genetic loci associated with ear-emergence in bread wheat

A doubled haploid population constructed from a cross between the South Australian wheat cultivars ‘Trident’ and ‘Molineux’ was grown under winter field conditions, under field conditions over summer and under artificial light both with and without vernalisation. The duration from planting to ear-emergence was recorded and QTL associated with heading date were detected using a previously constructed genetic linkage map. Associations were shown with chromosomal regions syntenous to previously identified photoperiod (Ppd-B1) and vernalisation (Vrn-A1) sensitive loci. Additional QTL associated with time to heading were also identified on chromosomes 1A, 2A, 2B, 6D, 7A and 7B. Comparisons between the genetic associations observed under the different growing conditions allowed the majority of these loci to be classified as having either photoperiod-sensitive, vernalisation-sensitive or earliness per se actions. The identification of a photoperiod-sensitive QTL on chromosome 1A provides evidence for a wheat gene possibly homoeologous to Ppd-H2 previously identified on chromosome 1H of barley. The occurrence of a putative major gene for photoperiod sensitivity observed on chromosome 7A is presented. The combined additive effects at these loci accounted for more than half the phenotypic variance in the duration from planting to ear-emergence in this population. The possible role of these loci on the adaptation of wheat in Australia is discussed.     

Microsatellite loci for Ponto-Caspian gobies: markers for assessing exotic invasions

We developed and tested eight polymorphic microsatellite loci for Ponto‐Caspian ‘neogobiin’ gobies, many of which are invasive in Eurasia and North America, whose study will aid understanding of the population genetics underlying their success. We tested samples from one to two locations from 12 taxa in the recently revised genera Babka, Benthophilus, Mesogobius, Neogobius = Apollonia, Ponticola and Proterorhinus; including the bighead, Caspian, knout, monkey, racer, round, tadpole and tubenose gobies; and taxa from introduced vs. native populations, those diverging between fresh and marine waters, and those differentiated between the Black and Caspian Seas. Populations conformed to Hardy–Weinberg equilibrium expectations, averaging five to 15 alleles per locus and 0.11 to 0.67 mean heterozygosity. Allelic variation significantly differentiated among all taxa and populations.     

Single-strand conformational polymorphism markers associated with a major QTL for fusarium head blight resistance in wheat

A major quantitative trait locus (QTL) associated with resistance to Fusarium head blight (FHB) was identified on chromosome 3BS between simple sequence repeat (SSR) markers Xgwm389 and Xgwm493 in wheat “Ning 7840”, a derivative from “Sumai 3”. However, the marker density of SSR in the QTL region was much lower than that required for marker-assisted selection (MAS) and map-based cloning. The objective of this study was to exploit new markers to increase marker density in this QTL region by using single-strand conformational polymorphism (SSCP) markers developed from wheat-expressed sequence tags (ESTs) on 3BS bin 8-0.78-1.0. Sixty-nine out of 85 SSCP primer pairs amplified PCR (polymerase chain reaction) products from the genomic DNA of “Chinese Spring”. Thirty-four primer pairs amplified PCR products that could form clear ssDNA (single strand DNA) bands through denaturation treatment. Ten SSCP markers had polymorphisms between Ning 7840 and “Clark”. Five of the ten polymorphic SSCP markers were located on chromosome 3B by nullitetrasomic analysis. Three SSCP markers (Xsscp6, Xsscp20, and Xsscp21) were mapped into the region between Xgwm493 and Xgwm533 and possessed a higher coefficient of determination (R²) than Xgwm493 and Xgwm533. The SSCP markers, Xsscp6, Xsscp20, and Xsscp21, can be used for map-based cloning of the QTL and for marker-assisted selection in FHB resistance breeding.     

Identification of molecular markers linked to Pm13, an Aegilops longissima gene conferring resistance to powdery mildew in wheat

 RFLP, RAPD, STS and DDRT-PCR techniques were applied to find molecular markers linked to Pm13, an Aegilops longissima gene conferring resistance to powdery mildew in wheat. The experimental strategy was based on the differential comparison of DNAs from common wheat and from common wheat/Ae. longissima recombinant lines carrying short segments of the 3S ^l S chromosome arm containing the Pm13 gene. Sixteen RFLP clones that detect loci previously located in the short arms of group-3 wheat chromosomes were screened for their ability to hybridise to Ae. longissima restriction fragments derived from the 3S ^l S segments introgressed into the recombinant lines. Eight RFLP clones and one STS marker detected 3S ^l S-specific fragments whose location relative to the wheat-alien chromatin breakage point of the recombinant lines was determined. Four amplification products were identified through the screening of about 200 RAPD primers. Their polymorphism was associated with the introgression of the alien DNA. One of the differential fragments was derived from the 3S ^l S DNA segment, while the remaining three corresponded to the replaced 3DS DNA. Further analyses carried out using 40 combinations of DDRT-PCR primers detected an additional reproducible polymorphism associated with the presence of 3S ^l S DNA. In view of their possible utilisation in Pm13 marker-assisted selection, differentially amplified RAPD and DDRT-PCR fragments were cloned, transformed into RFLP markers and converted into STS markers. Received: 23 March 1998 / Accepted: 5 August 1998     

Mapping resistance to the bird cherry-oat aphid and the greenbug in wheat using sequence-based genotyping

Key message

Identification of novel resistance QTL against wheat aphids. First QTL-resistance report for R. padi in wheat and chromosome 2DL for S. graminum . These sources have potential use in wheat breeding.

Abstract

The aphids Rhopalosiphum padi and Schizaphis graminum are important pests of common wheat (Triticum aestivum L.). Characterization of the genetic bases of resistance sources is crucial to facilitate the development of resistant wheat cultivars to these insects. We examined 140 recombinant inbred lines (RILs) from the cross of Seri M82 wheat (susceptible) with the synthetic hexaploid wheat CWI76364 (resistant). RILs were phenotyped for R. padi antibiosis and tolerance traits. Phenotyping of S. graminum resistance was based on leaf chlorosis in a greenhouse screening and the number of S. graminum/tiller in the field. RILs were also scored for pubescence. Using a sequence-based genotyping method, we located genomic regions associated with these resistance traits. A quantitative trait locus (QTL) for R. padi antibiosis (QRp.slu.4BL) that explained 10.2 % of phenotypic variation was found in chromosome 4BL and located 14.6 cM apart from the pubescence locus. We found no association between plant pubescence and the resistance traits. We found two QTLs for R. padi tolerance (QRp.slu.5AL and QRp.slu.5BL) in chromosomes 5AL and 5BL, with an epistatic interaction between a locus in chromosome 3AL (EnQRp.slu.5AL) and QRp.slu.5AL. These genomic regions explained about 35 % of the phenotypic variation. We re-mapped a previously reported gene for S. graminum resistance (putatively Gba) in 7DL and found a novel QTL associated with the number of aphids/tiller (QGb.slu-2DL) in chromosome 2DL. This is the first report on the genetic mapping of R. padi resistance in wheat and the first report where chromosome 2DL is shown to be associated with S. graminum resistance.     

Quantitative trait loci associated with agronomic traits and stripe rust in winter wheat mapping population using single nucleotide polymorphic markers

Heavy rain during the wheat seedling stage, drought in the flowering stage, and high temperatures with high humidity prior to harvest all contribute to substantial reductions in overall wheat yields in the Chinese province of Sichuan. In this study, we explored the effects of Rht-B1 and Yr18 in Chuannong16 (CN16) and a population derived from breeding line 30481. The population of 188 recombinant inbred lines was genotyped using an iSelect 90,000 single nucleotide polymorphism array and two functional markers for Rht-B1 and Yr18, and was phenotyped over 2 years in replicated trials. Grain yield was highly correlated with leaf color, plant height, and thousand kernel weights, and was negatively correlated with sedimentation. Plant height was positively correlated with grain yield and leaf color and negatively correlated with the number of tillers, thousand kernel weight, and sedimentation volume. In addition, sedimentation was negatively correlated with all five of the other traits (plant height, leaf color, tillers per square meter, grain yield, and thousand kernel weight) using both genetic and phenotypic correlation. The semi-dwarf allele Rht-B1b reduced plant height, grain yield, and thousand kernel weight. Yr18 did not affect stripe rust or other agronomic traits in the population examined. A total of 15 quantitative trait locii (QTLs) were identified for seven traits over 2 years, except for grain yield. One pleiotropic QTL on chromosome 4B was significantly associated with leaf color, thousand kernel weight, and plant height, but it was in different scaffolds with Rht-B1 on the physical map. We found a co-segregation SNP marker with Yr18 in our population; they were not in the same region on the physical map. This may be due to the relatively small population size and limited recombinant events in the population.     

Quantitative trait loci of stripe rust resistance in wheat

Key message

Over 140 QTLs for resistance to stripe rust in wheat have been published and through mapping flanking markers on consensus maps, 49 chromosomal regions are identified.

Abstract

Over thirty publications during the last 10 years have identified more than 140 QTLs for stripe rust resistance in wheat. It is likely that many of these QTLs are identical genes that have been spread through plant breeding into diverse backgrounds through phenotypic selection under stripe rust epidemics. Allelism testing can be used to differentiate genes in similar locations but in different genetic backgrounds; however, this is problematic for QTL studies where multiple loci segregate from any one parent. This review utilizes consensus maps to illustrate important genomic regions that have had effects against stripe rust in wheat, and although this methodology cannot distinguish alleles from closely linked genes, it does highlight the extent of genetic diversity for this trait and identifies the most valuable loci and the parents possessing them for utilization in breeding programs. With the advent of cheaper, high throughput genotyping technologies, it is envisioned that there will be many more publications in the near future describing ever more QTLs. This review sets the scene for the coming influx of data and will quickly enable researchers to identify new loci in their given populations.