Identification of two genes for resistance to Triticum isolates of Magnaporthe oryzae in wheat.

A screening of common wheat cultivars revealed that Triticum aestivum 'Thatcher' was resistant to Triticum isolates of Magnaporthe oryzae, whereas T. aestivum 'Chinese Spring' was susceptible. When F2 seedlings from a cross between 'Thatcher' and 'Chinese Spring' were inoculated with the Triticum isolates, resistant and susceptible seedlings segregated in a 15:1 ratio, suggesting that the resistance of 'Thatcher' was conditioned by two major genes. An inoculation test of 'Chinese Spring' substitution lines carrying individual chromosomes from 'Thatcher' indicated that these genes, designated Rmg2 and Rmg3, were located on chromosomes 7A and 6B.     

普通小麦99-2439 中的白粉病抗性遗传

普通冬小麦品系99-2439在郑州连续4年对田间白粉菌(Blumeria graminis sp. tritici)表现高抗,但其抗性基因来源不清。通过染色体C-分带和1RS染色体特异性SCAR标记鉴定, 表明它是一个小麦-黑麦(Triticum aestivum - Secale cereale)1BL/1RS异易位系。通过对中国春×99-2439杂交F2代分离群 体抗性鉴定和1RS染色体臂检测结果分析, 证明该抗病基因不在1RS染色体臂上。用单孢小麦白粉菌分离株对其抗性遗传进行研究, 结果表明, 99-2439的白粉病抗性由一对小种专化、隐性抗病基因控制。由于携带Pm5a的Hope/8Cc对中国的21个小麦白粉菌分离菌株均高度感病, 而99-2439高抗混和白粉菌和5个单孢分离菌株, 所以, 99-2439所携带的抗白粉病基因不同于Pm5a。     

Identification of RFLP markers for resistance to wheat spindle streak mosaic bymovirus (WSSMV) disease.

Wheat spindle streak mosaic bymovirus (WSSMV) causes an economically important disease of winter wheat in Europe and North America. Artificial inoculation with this virus to identify resistant wheat genotypes is difficult. This study was conducted to identify restriction fragment length polymorphism (RFLP) markers associated with resistance to this disease. A population, consisting of 104 F5 recombinant inbred lines from a cross between hexaploid Triticum aestivum cultivars 'Geneva' (resistant) and 'Augusta' (susceptible), was evaluated for WSSMV symptoms under field conditions for four years. Two linked markers on the long arm of chromosome 2D, Xbcd1095 and Xcdo373, were determined to be associated with WSSMV resistance by bulked segregant analysis of the 10 most resistant and 10 most susceptible lines. Marker Xcdo373 accounted for 79% and Xbcd1095 for 73% of the phenotypic variation. Our results suggest that resistance to WSSMV in this population is qualitative in nature and is controlled by few genes. These markers should be useful in the development of wheat cultivars resistant to WSSMV and perhaps also to wheat yellow mosaic bymovirus (WYMV).     

普通小麦99-2439中的白粉病抗性遗传

普通冬小麦品系99-2439在郑州连续4年对田间白粉菌(Blumeria graminis sp.tritici)表现高抗,但其抗性基因来源不清.通过染色体C-分带和IRS染色体特异性SCAR标记鉴定,表明它是一个小麦-黑麦(Triticum aestivum-Secale cereale)lBL/1RS异易位系.通过对中国春×99-2439杂交F2代分离群体抗性鉴定和1RS染色体臂检测结果分析,证明该抗病基因不在1RS染色体臂上.用单孢小麦白粉菌分离株对其抗性遗传进行研究,结果表明,99-2439的白粉病抗性由一对小种专化、隐性抗病基因控制.由于携带Pm5a的Hope/8Cc对中国的21个小麦白粉菌分离菌株均高度感病,而99-2439高抗混和白粉菌和5个单孢分离菌株,所以,99-2439所携带的抗白粉病基因不同于Pm5a.     

Identification of quantitative trait loci (QTL) for resistance to Fusarium crown rot (Fusarium pseudograminearum) in multiple assay environments in the Pacific Northwestern US

Fusarium crown rot (FCR), caused by Fusarium pseudograminearum and F. culmorum, reduces wheat (Triticum aestivum L.) yields in the Pacific Northwest (PNW) of the US by as much as 35%. Resistance to FCR has not yet been discovered in currently grown PNW wheat cultivars. Several significant quantitative trait loci (QTL) for FCR resistance have been documented on chromosomes 1A, 1D, 2B, 3B, and 4B in resistant Australian cultivars. Our objective was to identify QTL and tightly linked SSR markers for FCR resistance in the partially resistant Australian spring wheat cultivar Sunco using PNW isolates of F. pseudograminerarum in greenhouse and field based screening nurseries. A second objective was to compare heritabilities of FCR resistance in multiple types of disease assaying environments (seedling, terrace, and field) using multiple disease rating methods. Two recombinant inbred line (RIL) mapping populations were derived from crosses between Sunco and PNW spring wheat cultivars Macon and Otis. The Sunco/Macon population comprised 219 F(6):F(7) lines and the Sunco/Otis population comprised 151 F(5):F(6) lines. Plants were inoculated with a single PNW F. pseudograminearum isolate (006-13) in growth room (seedling), outdoor terrace (adult) and field (adult) assays conducted from 2008 through 2010. Crown and lower stem tissues of seedling and adult plants were rated for disease severity on several different scales, but mainly on a numeric scale from 0 to 10 where 0?=?no discoloration and 10?=?severe disease. Significant QTL were identified on chromosomes 2B, 3B, 4B, 4D, and 7A with LOD scores ranging from 3 to 22. The most significant and consistent QTL across screening environments was located on chromosome 3BL, inherited from the PNW cultivars Macon and Otis, with maximum LOD scores of 22 and 9 explaining 36 and 23% of the variation, respectively for the Sunco/Macon and Sunco/Otis populations. The SSR markers Xgwm247 and Xgwm299 flank these QTL and are being validated for use in marker-assisted selection for FCR resistance. This is the first report of QTL associated with FCR resistance in the US.     

Molecular mapping of novel genes controlling Fusarium head blight resistance and deoxynivalenol accumulation in spring wheat.

Fusarium head blight of wheat is an extremely damaging disease, causing severe losses in seed yield and quality. The objective of the current study was to examine and characterize alternate sources of resistance to Fusarium head blight (FHB). Ninety-one F1-derived doubled haploid lines from the cross Triticum aestivum 'Wuhan-1' x Triticum aestivum 'Maringa' were examined for disease reaction to Fusarium graminearum by single-floret injection in replicated greenhouse trials and by spray inoculation in replicated field trials. Field and greenhouse experiments were also used to collect agronomic and spike morphology characteristics. Seed samples from field plots were used for deoxynivalenol (DON) determination. A total of 328 polymorphic microsatellite loci were used to construct a genetic linkage map in this population and together these data were used to identify QTL controlling FHB resistance, accumulation of DON, and agronomic and spike morphology traits. The analysis identified QTL for different types of FHB resistance in four intervals on chromosomes 2DL, 3BS, and 4B. The QTLs on 4B and 3BS proximal to the centromere are novel and not reported elsewhere. QTL controlling accumulation of DON independent of FHB resistance were located on chromosomes 2DS and 5AS. Lines carrying FHB resistance alleles on 2DL and 3BS showed a 32% decrease in disease spread after single-floret injection. Lines carrying FHB resistance alleles on 3BS and 4B showed a 27% decrease from the mean in field infection. Finally, lines carrying favourable alleles on 3BS and 5AS, showed a 17% reduction in DON accumulation. The results support a polygenic and quantitative mode of inheritance and report novel FHB resistance loci. The data also suggest that resistance to FHB infection and DON accumulation may be controlled, in part, by independent loci and (or) genes.     

Chromosomal location of a Triticum timopheevii--derived powdery mildew resistance gene transferred to common wheat.

A dominant powdery mildew resistance gene introduced from Triticum timopheevii in line 146-155-T of common wheat, Triticum aestivum, was located on chromosome 6B by monosomic analysis. Restriction fragment length polymorphism (RFLP) and microsatellite analyses detected the presence of a T. timopheevii segment, translocated to chromosome 6B, with breakpoints between the loci Xpsr8/Xpsr964 on 6BS and Xpsr154/Xpsr546 on 6BL. The novel powdery mildew resistance gene, which has been designated Pm27, was shown to cosegregate with the microsatellite locus Xpsp3131, which is located on the introgressed T. timopheevii segment. The molecular data confirm the location of Pm27 on the translocated 6B chromosome.     

Interval mapping of genes for quantitative resistance of maize to Setosphaeria turcica,cause of northern leaf blight,in a tropical environment

Quantitative trait loci (QTL) involved in the resistance of maize to Setosphaeria turcica, the causal agent of northern leaf blight, were located by interval mapping analysis of 121 F_2:3 lines derived from a cross between Mo17 (moderately resistant) and B52 (susceptible). A linkage map spanning 112 RFLP loci with 15 cM mean interval length was constructed, based on marker data recorded in a previous study. Field tests with artificial inoculation were conducted at three sites in tropical mid- to high-altitude regions of Kenya, East Africa. Host-plant response was measured in terms of incubation period, disease severity (five scoring dates), and the area under the disease progress curve (AUDPC). Heritability of all traits was high (around 0.75). QTL associated with the incubation period were located on chromosomes 2S and 8L. For disease severity and AUDPC, significant QTL were detected in the putative centromeric region of chromosome 1 and on 2S, 3L, 5S, 6L, 7L, 8L and 9S. On 2S the same marker interval which carried a gene enhancing latent period was also associated with reduced disease severity of juvenile plants. QTL on chromosomes 3L, 5S, 7L and 8L were significant across environments but all other QTL were affected by a large genotype x environment interaction. Partially dominant gene action for resistance as well as for susceptibility was prevailing. Single QTL explained 10 to 38% of the phenotypic variation of the traits. All but the QTL on chromosomes 1, 6 and 9 were contributed by the resistant parent Mo17. On chromosome 8L a QTL mapped to the same region as the major race-specific gene Ht2, supporting the hypothesis that some qualitative and quantitative resistance genes may be allelic.Abbreviations AUDPC area under the disease progress curve - CIMMYT International Maize and Wheat Improvement Center - KARI Kenya Agricultural Research Institute - NCLB northern corn leaf blight - QTL quantitative trait locus/loci     

Introgression and characterization of barley yellow dwarf virus resistance from Thinopyrum intermedium into wheat.

Wheatgrasses (species of Agropyron complex) have previously been reported to be resistant to barley yellow dwarf virus (BYDV). To introgress this resistance into wheat, Triticum aestivum x Thinopyrum (Agropyron) intermedium hybrids were advanced through a backcrossing program and reaction to BYDV, as determined by enzyme-linked immunosorbent assay (ELISA), is reported for the first time in backcross populations of wide hybrids between wheat and wheatgrasses. ELISA values revealed highly resistant to highly susceptible segregants in backcrosses. BYDV resistance was expressed in some backcross derivatives. Continued selection, based on cytology and ELISA in each generation, eliminated most of the unwanted wheatgrass chromosomes and produced self-fertile BYDV resistant wheat lines. The BYDV resistant lines with 2n = 42 had normal chromosome pairing similar to wheat, and their F1 hybrids with wheat had two univalents. DNA analyses showed that the source of alien chromatin in these BYDV resistant wheat lines is distinguishable from that in other Th. intermedium derived BYDV resistant wheat lines. Chromosome pairing and restriction fragment length polymorphism analyses indicated that the 42 chromosome resistant Purdue wheat lines are substitution lines in which chromosome 7D was replaced by a chromosome from Th. intermedium that was carrying gene(s) for BYDV resistance.     

Seedling and adult plant resistance to Sitobion avenae (Hemiptera: Aphididae) in Triticum monococcum (Poaceae), an ancestor of wheat

Cereal aphids are important pests of wheat, Triticum aestivum L. and Triticum durum Desf. Crop resistance is a desirable method for managing cereal aphids in central North America, where the dominant crop, spring-sown wheat, has a low value per unit area. A diploid ancestor of wheat, Triticum monococcum L., is reported to be partially resistant to Sitobion avenae (Fabricius), the most damaging cereal aphid in the region. To identify potential sources of resistance, 42 accessions of T. monococcum and three cultivated wheats were infested with aphids, seedlings for six days and adult plants for 21 days. Overall resistance was estimated by the biomass loss of foliage and spikes in relation to uninfested control plants. Antibiosis was estimated by the gain in biomass of aphids during infestation, and tolerance was estimated as a biomass conversion ratio, overall resistance divided by antibiosis. A few T. monococcum accessions exhibited partial resistance. No relationship was found between seedling and adult plant resistance: the former exhibited primarily antibiosis and the latter primarily tolerance. Two accessions with antibiosis reduced aphid biomass by 60% compared with commercial wheats. Tolerance was correlated with growth potential, and was useful only in accessions with high growth potential. Four accessions exhibited tolerance levels at least 30% greater than commercial wheats. Highly susceptible accessions also were identified, which would be useful for investigating the inheritance of antibiosis and tolerance.     

Inheritance of field resistance to Stagonospora nodorum leaf and glume blotch and correlations with other morphological traits in hexaploid wheat (Triticum aestivum L.)

Breeding for wheat varieties resistant to Stagonospora nodorum blotch (SNB) is the most sustainable strategy for controlling the disease. In order to map quantitative trait loci (QTLs) for SNB resistance we analysed 204 recombinant inbred lines of the cross between the winter wheat (Triticum aestivum L.) variety Forno and the winter spelt (Triticum spelta L.) variety Oberkulmer. We determined the level of resistance of adult plants to leaf blotch (SNL) and glume blotch (SNG) as well as morphological traits for 2 years after artificial inoculation with S. nodorum. Using composite interval mapping and LOD > 3.7, we detected ten QTLs for SNG blotch resistance (six inherited from the susceptible parent Forno) and 11 QTLs for SNL resistance (four inherited from Forno) across 2 years. Both resistance traits were moderately correlated (r = 0.52) and had only one common QTL. For SNL resistance, seven QTLs were not associated with QTLs for morphological traits. Among them, QSnl.eth-2D, QSnl.eth-4B and QSnl.eth-7B3 had major effects (R(2) > 13%) and were potential candidates for marker-assisted selection. For SNG, the major QTL on chromosome 5A, explaining 36% of the phenotypic variance for resistance, was associated with the q locus conferring the spelt morphology (long lax ear, long culm and hard glumes). Only QSng.eth-1BS, which explained 7% of the variance for resistance to SNG blotch, was not associated with QTLs for morphological traits. The consequences for breeding programmes are discussed.     

Detection of Fusarium head blight resistance QTL in a wheat population using bulked segregant analysis

A population of 218 recombinant inbred lines (RILs) was developed from the cross of two wheat (Triticum aestivum L.) cultivars, 'Ning 894037' and 'Alondra'. Ning 894037 has resistance to Fusarium head blight (FHB) and Alondra is moderately susceptible. Response of the RILs and their parental lines to FHB infection was evaluated with point inoculation in four experiments both in greenhouse and in field conditions. Distribution of disease severity in the population is continuous, indicating quantitative inheritance of resistance to FHB. Bulked segregant analysis and QTL mapping based on simple sequence repeat (SSR) markers revealed three chromosome regions that are responsible for FHB resistance. A chromosome region on 3BS accounted for 42.5% of the phenotypic variation for FHB resistance. Additional QTLs were located on chromosomes 2D and 6B. These three QTLs jointly accounted for 51.6% of the phenotypic variation. SSR markers linked to the QTLs influencing resistance to FHB have potential for use in breeding programs.     

Molecular analysis of leaf-rust resistant introgression lines obtained by crossing hexaploid wheat Triticum aestivum with tetraploid wheat Triticum timopheevii

Twenty-four Triticum eastivum x T. timopheevii hybrid lines developed on the basis of five varieties of common wheat and resistant to leaf rust were analyzed by the use of microsatellite markers specific for hexaploid common wheat T. aestivum. Investigation of intervarietal polymorphism of the markers showed that the number of alleles per locus ranged from 1 to 4, depending on the marker (2.5 on average). In T. timopheevii, amplification fragments are produced by 80, 55, and 30% of primers specific to the A, B, and D common wheat genomes, respectively. Microsatellite analysis revealed two major areas of introgression of the T. timopheevii genome: chromosomes of homoeological groups 2 and 5. Translocations were detected in the 2A and 2B chromosomes simultaneously in 11 lines of 24. The length of the translocated fragment in the 2B chromosome was virtually identical in all hybrid lines and did not depend on the parental wheat variety. In 15 lines developed on the basis of the Saratovskaya 29, Irtyshanka, and Tselinnaya 20, changes occurred in the telomeric region of the long arm of the 5A chromosome. Analysis with markers specific to the D genome suggested that introgressions of the T. timopheevii genome occurred in chromosomes of the D genome. However, the location of these markers on T. timopheevii chromosomes is unknown. Our data suggest that the genes for leaf-rust resistance transferred from T. timopheevii to T. aestivum are located chromosomes of homoeological group 2.     

Components of quantitative resistance in sunflower to Alternaria helianthi

Components of quantitative resistance, spore production, incubation period, infection frequency and mean lesion size were measured in 17 sunflower accessions inoculated with conidia of Alternuria helianthi under controlled conditions. The same accessions were also rated for disease reaction in the field in 1994 and 1995 using a generated epidemic and varied in their disease reactions from highly susceptible to highly resistant. Spearman's ranking of accessions was highly correlated (r = 0.9) for both years; however, the ranking of components measured under controlled conditions with field severity was generally poor. Regression analysis of components with field severity ratings of the accessions showed that mean lesion size was highly correlated (r = O.74) and infection frequency was moderately correlated (r = 0.58) with the field severity ratings taken over the two years. Infection frequency was also well correlated (r = 0.75) with mean lesion size. Spore production and incubation period were poorly correlated with the field severity ratings for both years. An index based on infection frequency and mean lesion size gave a better correlation with the 1995 field severity ratings than either component alone, but in 1994 the index was not as well correlated with field severity as mean lesion size alone. It is suggested that mean lesion size, determined from plants 7–9 days after inoculation could be used to select for resistance to A. helianthi in the greenhouse. Infection frequency could also be used as a predictor of resistance, but to a lesser degree.     

小麦硫代硫酸硫转移酶类似基因的克隆与定位

小麦-簇毛麦6VS/6AL易位系92R137含有抗白粉病基因Pm21。为了研究该易位系的抗病机理,应用mRNA差异显示和快速扩增cDNA未端（Rapid Amplification of cDNAEnd,RACE)技术对在白粉菌诱导后表达增强的基因进行了克隆,分离到1个命名为TaTST的全长cDNA序列。Northern杂交分析表明,TaTST基因在白粉菌诱导后表达明显增强,24h达到峰值,氨基酸序列同源性分析表明,TaTST与Datisca glomerata的硫代硫酸硫转移酶基因（rho-danese,EC,2.8.1.1)序列有64%相同,80%相似,用中国春缺体/四体系和端体系Southern杂交和基因特异性引物扩增（gene specific primer-PCR)将TaTST基因定位在小麦6B染色体短臂上,Southern杂交表明,该基因为单拷贝基因,由于在杨麦5号和6VS/6AL易位系间存在明显多态,可以推测在6VS上有TaTST的同源基因,TaTST是从小麦中分离的新基因。白粉菌诱导后的表达变化提示;TaTST与小麦抗白粉病反应有关。     

Molecular mapping of resistance to<Emphasis Type="Italic"> Fusarium</Emphasis> head blight in the spring wheat cultivar Frontana

Fusarium head blight (FHB) is a destructive disease of wheat. The objective of this study was to characterise the FHB resistance of the Brazilian spring wheat cultivar Frontana through molecular mapping. A population of 210 doubled-haploid lines from a cross of Frontana (partially resistant) and Remus (susceptible) was evaluated for FHB resistance during three seasons. Spray and single-spikelet inoculations were applied. The severity, incidence and spread of the disease were assessed by visual scoring. The population was genotyped with 566 DNA markers. The major QTL effect associated with FHB resistance mapped to chromosome 3A near the centromere, explaining 16% of the phenotypic variation for disease severity over 3 years. The most likely position is in the Xgwm720–Xdupw227 interval. The genomic region on 3A was significantly associated with FHB severity and incidence in all years evaluated, but not with FHB spread, indicating the prominent contribution of this QTL to resistance against initial infection. The map interval Xgwm129–Xbarc197 on chromosome 5A also showed consistent association with FHB severity and accounted for 9% of the phenotypic variation. In addition, smaller effects for FHB severity were identified on chromosomes 1B, 2A, 2B, 4B, 5A and 6B in single years. Individual QTLs for resistance to FHB spread accounted for less than 10% of the variation in trait expression. The present study indicates that FHB resistance of Frontana primarily inhibits fungal penetration (type I resistance), but has a minor effect on fungal spread after infection (type II resistance).Communicated by H.C. Becker     

Field evaluation of emmer wheat-derived synthetic hexaploid wheat for resistance to Russian wheat aphid (Homoptera: Aphididae)

Broadening the genetic base for resistance to Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera: Aphididae), in bread wheat, Triticum aestivum L., is desirable. To date, identified Russian wheat aphid resistance genes are either located to the D chromosomes or to rye translocation of wheat, and resistance derived from the A or B genomes of tetraploid Triticum spp. would therefore be highly beneficial. Fifty-eight synthetic hexaploid wheat, derived from interspecific crosses of Triticum dicoccum Schrank. and Aegilops tauschii (Coss.) Schmal. and their parents were evaluated for resistance to Russian wheat aphid under field conditions. Plots infested with aphids were compared with plots protected with insecticides. The T. dicoccum parents were highly resistant to Russian wheat aphids, whereas the Ae. tauschii parents were susceptible. Resistance levels observed in the synthetic hexaploids were slightly below the levels of their T. dicoccum parents when a visual damage scale was used. but no major resistance suppression was observed among the synthetics. Russian wheat aphid infestation on average reduced plant height and kernel weight at harvest in the synthetic hexaploids and the T. dicoccum parents by 3-4%, whereas the susceptible control 'Seri M82' suffered losses of above 20%. Because resistance in the synthetic hexaploid wheat is derived from their T. dicoccum parent, resistance gene(s) must be located on the A and/or B genomes. They must therefore be different from previously identified Russian wheat aphid resistance genes, which have all been located on the D genome of wheat or on translocated segments.     

Disomic Thinopyrum intermedium addition lines in wheat with barley yellow dwarf virus resistance and with rust resistances.

Zhong 5 is a partial amphiploid (2n = 56) between Triticum aestivum (2n = 42) and Thinopyrum intermedium (2n = 42) carrying all the chromosomes of wheat and seven pairs of chromosomes from Th. intermedium. Following further backcrossing to wheat, six independent stable 2n = 44 lines were obtained representing 4 disomic chromosome addition lines. One chromosome confers barley yellow dwarf virus (BYDV) resistance, whereas two other chromosomes carry leaf and stem rust resistance; one of the latter also confers stripe rust resistance. Using RFLP and isozyme markers we have shown that the extra chromosome in the Zhong 5-derived BYDV resistant disomic addition lines (Z1, Z2, or Z6) belongs to the homoeologous group 2. It therefore carries a different locus to the BYDV resistant group 7 addition, L1, described previously. The leaf, stem, and stripe rust resistant line (Z4) carries an added group 7 chromosome. The line Z3 has neither BYDV nor rust resistance, is not a group 2 or group 7 addition, and is probably a group 1 addition. The line Z5 is leaf and stem rust resistant, is not stripe rust resistant, and its homoeology remains unknown.     

Genome-wide identification of QTL conferring high-temperature adult-plant (HTAP) resistance to stripe rust (<Emphasis Type="Italic">Puccinia striiformis</Emphasis> f. sp<Emphasis Type="Italic">. tritici</Emphasis>) in wheat

High-temperature adult-plant (HTAP) resistance to stripe rust (caused by Puccinia striiformis f. sp. tritici) is a durable type of resistance in wheat (Triticum aestivum L.). This study identified quantitative trait loci (QTL) conferring HTAP resistance to stripe rust in a population consisting of 169 F_8:10 recombinant inbred lines (RILs) derived from a cross between a susceptible cultivar Rio Blanco and a resistant germplasm IDO444. HTAP resistance was evaluated for both disease severity and infection type under natural infection over two years at two locations. The genetic linkage maps had an average density of 6.7 cM per marker across the genome and were constructed using 484 markers including 96 wheat microsatellite (SSR), 632 Diversity Arrays Technology (DArT) polymorphisms, two sequence-tagged-site (STS) from semi-dwarf genes Rht1 and Rht2, and two markers for low molecular-weight glutenin gene subunits. QTL analysis detected a total of eight QTL significantly associated with HTAP resistance to stripe rust with two on chromosome 2B, two on 3B and one on each of 1A, 4A, 4B and 5B. QTL on chromosomes 2B and 4A were the major loci derived from IDO444 and explained up to 47 and 42% of the phenotypic variation for disease severity and infection type, respectively. The remaining five QTL accounted for 7–10% of the trait variation. Of these minor QTL, the resistant alleles at the two QTL QYrrb.ui-3B.1 and QYrrb.ui-4B derived from Rio Blanco and reduced infection type only, while the resistant alleles at the other three QTL, QYrid.ui-1A, QYrid.ui-3B.2 and QYrid.ui-5B, all derived from IDO444 and reduced either infection type or disease severity. Markers linked to 2B and 4A QTL should be useful for selection of HTAP resistance to stripe rust.     

Identification of AFLP markers on the satellite region of chromosome 1BS in wheat.

The satellite region on the short arm of chromosome 1B in wheat (Triticum aestivum L., 2n = 6x = 42) carries many agronomically important genes; i.e., genes conferring fungal disease resistance, seed storage proteins, and fertility restoration. To find molecular markers located on the satellite region, we applied the fluorescent AFLP (amplified fragment length polymorphism) technique to aneuploids and deletion stocks of the cultivar T. aestivum 'Chinese Spring'. Out of 6017 fragments amplified with 80 primer combinations in normal 'Chinese Spring', 24 were assigned to 1BS. Twelve of them clustered within a small region of the satellite known to be rich in RFLP (restriction fragment length polymorphism) markers. AFLPs in 1BS and in the whole genome were calculated between 'Chinese Spring' and T. spelta var. duhamelianum. The polymorphism rates in the satellite region (58.3%) and in the 1BS arm (45.8%) were much higher than the average rate for the whole genome (10.7%). Seven of the 12 AFLP markers in the satellite region were revealed to be specific to 'Chinese Spring' and could potentially be useful for genetic mapping in a segregation population of 'Chinese Spring' x T. spelta.