QTL mapping of the domestication traits pre-harvest sprouting and dormancy in wheat (<Emphasis Type="BoldItalic">Triticum aestivum L.</Emphasis>)

A set of 75 recombinant inbred lines (RILs) of the ITMI mapping population was grown under field conditions in Gatersleben. The lines were evaluated for the domestication traits pre-harvest sprouting and dormancy (germinability). Main QTLs could be localized for pre-harvest sprouting on chromosome 4AL and dormancy on chromosome 3AL. In addition, 85 Triticum aestivum cv. “Chinese Spring”-Aegilops tauschii introgression lines grown under greenhouse conditions were researched. No QTL could be found for pre-harvest sprouting but a major QTL could be detected for dormancy on chromosome 6DL.     

Microsatellite Marker Identification of a Triticum Aestivum -Aegilops Umbellulata Substitution Line with Powdery Mildew Resistance

Summary Aegilops umbellulata acc. Y39 and Triticum carthlicum acc. PS5, immune to many powdery mildew isolates, were crossed to make an amphidiploid line Am9. The powdery mildew resistance of Am9 was transferred to common wheat cultivar Laizhou953 by crossing and backcrossing. In this study, the origin of powdery mildew resistance in a BC₃F_4:5 population derived from a cross of Am9 and Laizhou953 was identified. Microsatellite markers analysis showed that markers Xgwm257, Xgwm296, and Xgwm319, co-segregated with the powdery mildew resistance, whereas markers Xgwm210, Xgwm388/140, Xgwm388/170 and Xgwm526 were related to susceptibility and linked to resistance in repulsion. Of three markers related to resistance, Xgwm257 and Xgwm319 were codominant, whereas Xgwm296 was dominant. All three markers were Ae. umbellulata-specific indicating that resistance in the test population originated from Ae. umbellulata acc. Y39. The chromosome location and mapping of these linked microsatellite markers, the chromosome numbers of derived BC₃F_4:6 families, and chromosome pairing in F₁ plants from a cross of a homozygous resistant BC₃F_4:5 plant and Laizhou953, showed that wheat chromosome 2B was substituted by Ae. umbellulata chromosome 2U. This is the first gene conferring powdery mildew resistance transferred to wheat from Ae. umbellulata, and it should be a novel resistance gene to powdery mildew. It was temporarily designated PmY39.The first two authors made equal contributions     

小麦–中间偃麦草渗入系抗白粉病基因PmCH7124的分子定位

小麦新种质CH7124由八倍体小偃麦TAI8335与高感白粉病小麦品种晋麦33杂交后代衍生而来,在苗期对白粉病菌株E09、E20、E21、E23、E26、Bg1和Bg2表现免疫或高抗,抗病表现与TAI8335及其野生亲本中间偃麦草相似。基因组原位杂交未检测到CH7124含有外源染色体信号。利用CH7124与感病亲本SY95-71和绵阳11的杂交群体接种鉴定和遗传分析证实,CH7124成株期对E09的抗性由1对显性核基因控制,暂命名为Pm CH7124。采用分离群体分组分析法(bulked segregant analysis,BSA)对SY95-71/CH7124的F6群体进行SSR标记扫描,发现抗性基因Pm CH7124与5对SSR标记连锁,与两翼邻近标记Xgwm501和Xbarc101的遗传距离分别为1.7 c M和4.5 c M。利用中国春缺体–四体和双端体材料,将Pm CH7124及其连锁标记定位在小麦2B染色体长臂上。通过分析2BL上其他抗白粉病基因的抗谱、抗性来源、物理图谱位置以及连锁标记在Pm CH7124作图群体中的多态性,认为Pm CH7124不同于2BL上已知的抗白粉病基因Pm6、Pm33、Pm JM22、Ml Zec1、Ml AB10和Ml LX99。     

Aneuploid analysis for protein content and tyrosinase activity in hexaploid wheat (Triticum aestivum L. em. Thell.)

Summary A study was conducted to locate the genes responsible for the determination of kernel protein content and tyrosinase activity in a hexaploid wheat variety UP 301 using Pb. C591 monosomic series. Genes located on chromosomes 4B, 5B, 6B, 7B, 3D and 7D of UP 301 controlled protein content of UP 301. Of these the B genome chromosomes were found to have genes for increased protein content while the D genome chromosomes were found to carry genes for low protein content. A major gene coding for tyrosinase enzyme was detected on chromosome 6B of UP 301 and a modifier on chromosome 5B. This indicated the possibility of improving these quality characters through chromosome manipulation.     

Effects of moisture stress on leaf appearance,tillering and other aspects of development in Triticum tauschii

Summary A glasshouse study was conducted to describe the dynamics of leaf and tiller appearance of four accessions of T. tauschii (Tt 04, Tt 17, Tt 65 and Tt 74) and to determine the influence of moisture stress (treatments were high and low moisture, imposed seven days after transplanting) on these and other aspects of development in this wild wheat.Under high moisture conditions, accessions differed greatly in flag leaf dimensions, culm length and seed number per spike, the values being lower in Tt 04 than in the other accessions. Low moisture strongly reduced values for these traits, with Tt 04 being least affected, but overall, there was no apparent association between the values obtained for these variables in the high moisture conditions and the effects of moisture stress. For three of the four accessions, final leaf number on the main culm was significantly lower in the low moisture treatment than in the respective control (P<0.05), but the differences between treatments (ca. 0.5 leaves or less) were very small. Maximum tiller number, on the other hand, was strongly reduced by low moisture, and initiation of tillering was inhibited until water was reapplied. There were no apparent after-effects of the moisture regime on the rate of subsequent tiller appearance.The four accessions differed in their leaf appearance rates, giving phyllochron values (117–142° Cd leaf^-1) within the range reported for hexaploid wheat. Low moisture tended to increase phyllochron, but in only one accession was this effect significant. Thus, depending on the accession, low moisture did not affect, or slightly decreased (by ca. 15–20%) the rate of leaf appearance. These effects were similar to those reported for cultivated wheat suggesting that there would be little scope for using these accessions of T. tauschii in breeding for stress tolerance.     

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em Thell.). 8. Gene Pm32 in a wheat-Aegilops speltoides translocation line

The wheat-Aegilops speltoides translocation line L501 exhibits a disease response pattern distinctive from that of documented powdery mildew genes after inoculation with differential Blumeria graminis tritici isolates. Results based on cytological C-bandings and monosomic analyses reveal that a dominant resistance gene derived from Ae. speltoides is located on a T1BL·1SS chromosome translocation in this line. The new gene is designated Pm32. This revised version was published online in July 2006 with corrections to the Cover Date.     

Microsatellite mapping of complementary genes for purple grain colour in bread wheat (Triticum aestivum) L.

Complementary genes for purple grain colour Pp1, Pp2, Pp3 (now designated Pp1, Pp3b, Pp3a, respectively) were mapped using crosses between purple-grained hexaploid wheats ‘Purple Feed’ – Pp1Pp1/Pp2Pp2 (Pp1Pp1/Pp3bPp3b), ‘Purple’ – Pp1Pp1/Pp3Pp3 (Pp1Pp1/Pp3aPp3a) with non-purple-grained cultivars ‘Novosibirskaya 67’ (‘N67’) and ‘Saratovskaya 29’ (‘S29’). The genes Pp2 (Pp3b) and Pp3 (Pp3a) were inherited as monofactorial dominant when purple-grained wheats were crossed to ‘N67’. Both were mapped in the centromeric region of the chromosome 2A. Therefore, they were suggested being different alleles at the same locus and designated Pp3a and Pp3b. In the crosses between purple-grained wheats and ‘S29’ a segregation ratio of 9 (purple) to 7 (non purple) was obtained suggesting a complementary interaction of two dominant genes, Pp1 and Pp3. To map Pp1 as a single gene, the influence of the other Pp gene was taken into consideration by determining the Pp3 genotype of the F₂ plants. The gene was mapped on chromosome 7BL, about 24 cM distal to the centromere. The Pp1gene was shown to be non allelic to the Rc-1 (red coleoptile) and Pc (purple culm) genes, contrary to what was previously suggested. The colouration caused by the Pp genes has no effect on pre-harvest sprouting.     

Assessment of genetic diversity in synthetic hexaploid wheats and their Triticum dicoccum and Aegilops tauschii parents using AFLPs and agronomic traits

Synthetic hexaploid wheats are of interest to wheat breeding programs, especially for introducing new genes that confer resistance to biotic and abiotic stresses. A group of 54 synthetic hexaploid wheats derived from crosses between emmer wheat(Triticum dicoccum, source of the A and B genomes) and goat grass (Aegilops tauschii, D genome donor) were investigated for genetic diversity. Using the AFLP technique, dendrograms revealed clear grouping according to geographical origin for the T. dicoccum parents but no clear groups for the Ae. tauschii parents. The geographical clustering of the T. dicoccum parents was also reflected in the dendrogram of their derived synthetic hexaploids. Diversity of the T. dicoccum parents and their derived synthetic hexaploids was further evaluated by measuring 18morphological and agronomic traits on the plants. Clustering based on morphological and agronomic data also reflected geographical origin. However, comparison of genetic distances obtained from AFLP and agronomic data showed no correlation between the two diversity measurements. Nevertheless, similarities among major clusters with the two systems could be identified. Based on percentage of polymorphic markers, the synthetic hexaploids had a considerably higher level of AFLP diversity (39%) than normally observed in cultivated hexaploid wheat (12–21%). This suggests that synthetic hexaploid wheats can be used to introduce new genetic diversity into the bread wheat gene pool. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular mapping of quantitative trait loci (QTLs) controlling aluminium tolerance in bread wheat

Aluminium (Al) toxicity is a major constraint to crop productivity in acidic soils. A quantitative trait locus (QTL) analysis was performed to identify the genetic basis of Al tolerance in the wheat cultivar ‘Chinese Spring’. A nutrient solution culture approach was undertaken with the root tolerance index (RTI) and hematoxylin staining method as parameters to assess the Al tolerance. Using a set of D genome introgression lines, a major Al tolerance QTL was located on chromosome arm 4DL, explaining 31% of the phenotypic variance present in the population. A doubled haploid population was used to map a second major Al tolerance QTL to chromosome arm 3BL. This major QTL (Qalt _CS .ipk-3B) in ‘Chinese Spring’ accounted for 49% of the phenotypic variation. Linkage of this latter QTL to SSR markers opens the possibility to apply marker-assisted selection (MAS) and pyramiding of this new QTL to improve the Al tolerance of wheat cultivars in breeding programmes.     

Cytological and microsatellite mapping of the genes determining liguleless phenotype in durum wheat

Liguleless phenotypes of wheat lack ligule and auricle structures on all leaves of the plant. Two recessive genes principally control the liguleless character in tetraploid wheat. The F₂ progenies of k17769 (liguleless mutant)/Triticum dicoccoides and k17769/T. dicoccum segregated in a 15:1 ratio, whereas the F₂ progenies of k17769/T. durum and k17769/T. turgidum segregated in a 3:1 ratio. A new gene, lg₃, was found on chromosome 2A. Segregation of F₂ progenies between k17769 and chromosome substitution lines for homoeologous group 2 chromosomes suggested that the liguleless genotype had occurred by mutation at the lg₃ locus on chromosome 2A, and then by mutation at the lg₁ locus on chromosome 2B, in the process of domestication of tetraploid wheat. The gene (lg₁) was linked to Tc₂ (11.9 cM), which determines phenol colour reaction of kernels, on the long arm of chromosome 2B. The distance of lg₁ to the centromere was found to be 60.4 cM, and microsatellite mapping established the gene order, centromere – Xgwm382 – Xgwm619 – Tc₂ – lg₁ on the long arm of chromosome 2B.     

Metaphase-I analysis of a Triticum aestivum x T. monococcum hybrid by the C-banding technique

Summary The meiotic pairing behaviour at metaphase I of a Triticum aestivum×Triticum monococcum hybrid has been studied by means of the C-banding technique to ascertain the homology between the chromosomes in the A genome of the two species. The technique allowed the A and B genome chromosomes and the 2D, 3D and 5D chromosomes to be identified. Differences in the level of chromosome pairing in the A genome were noted. The T. monococcum 4A chromosome did not pair with any of the T. aestivum chromosomes in any of the metaphase I cells analysed. Two reciprocal translocations between the 2B and 2D chromosomes on one side and the 2A and 3D on the other side have been identified. The usefulness of the C-banding technique in the study of chromosome homology among species related to wheat is discussed.     

Resistance to stripe rust in Triticum turgidum,T. tauschii and their synthetic hexaploids

Resistance to stripe rust (caused by Puccinia striiformis Westend.) of 34 Triticum turgidum L. var.durum, 278 T. tauschii, and 267 synthetic hexaploid wheats (T. turgidum x T. tauschii) was evaluated at the seedling stage in the greenhouse and at the adult-plant stage at two field locations. Mexican pathotype 14E14 was used in all studies. Seedling resistance, expressed as low infection type, was present in all three species. One hundred and twenty-eight (46%) accessions of T. tauschii, 8 (23%) of T. turgidum and 31 (12%) of synthetic hexaploid wheats were highly resistant as seedlings. In the field tests, resistance was evaluated by estimating area under disease progress curve (AUDPC). Synthetic hexaploid wheats showed a wide range of variability for disease responses in both greenhouse and field tests, indicating the presence of a number of genes for resistance. In general, genotypes with seedling resistance were also found to be resistant as adult plants. Genotypes, which were susceptible or intermediate as seedlings but resistant as adult plants, were present in both T. turgidum and the synthetic hexaploids. Resistances from either T. turgidum or T. tauschii or both were identified in the synthetic hexaploids in this study. These new sources of resistance could be incorporated into cultivated hexaploid wheats to increase the existing gene pool of resistance to stripe rust.     

The use of wheat/goatgrass introgression lines for the detection of gene(s) determining resistance to septoria tritici blotch (Mycosphaerella graminicola)

At the IPK Gatersleben a series of 85 bread wheat (T. aestivum)/goatgrass (Aegilops tauschii) introgression lines was developed recently. Based on the knowledge that chromosome 7D of this particular Ae. tauschii is a donor of resistance to septoria tritici blotch (Mycosphaerella graminicola), a sub-set of thirteen chromosome 7D introgression lines was investigated along with the susceptible recipient variety ‘Chinese Spring’ (CS) and the resistant donor line ‘CS (Syn 7D)’. The material was inoculated with two Argentinian isolates of the pathogen (IPO 92067 and IPO 93014) at both the seedlings (two leaf) and adult (tillering) stages at two locations over 2 years (2003, 2004). The resistance was effective against both isolates and at both developmental stages, and the resistance locus maps to the centromeric region of chromosome arm 7DS. On the basis of its relationship with the microsatellite marker Xgwm44, it is likely that the gene involved is Stb5. Stb5 is therefore apparently effective against M. graminicola isolates originating from both Europe and South America.     

The degree of similarity of backcross lines of Triticum aestivum cultivars manitou and neepawa with Aegilops speltoides accessions as donors

Summary The degree of similarity of a BC line with its recurrent parent is not related to the presence of expressions for morphological characters originating from the donor like purple coleoptile, purple anther and waxy leaf. BC lines derived from one donor do not resemble each other more than they do other BC lines. The absence of characters conditioned by dominant or co-dominant genes may be caused by the presence of inhibitor genes.     

Genetic control of long glume phenotype in tetraploid wheat derived from Triticum petropavlovskyi Udacz. et Migusch.

The Chinese wheat landrace, Xinjiang rice wheat (T. petropavlovskyi Udacz. et Migusch., 2n = 42), known as ‘Daosuimai’ or rice-head wheat is characterized by long glumes, and was found in the agricultural areas in the west part of Talimu basin, Xinjiang, China in 1948. The gene for long glume from T. petropavlovskyi was introduced into a line of spring durum wheat, LD222. The gene for long glume is located approximately46.8 cm from the cn-A1 locus, which controls the chlorinatrait. Significant deviation from a 3:1 in the F₂ of LDN7D(7A)/ANW5C confirmed that the long glume of T. petropavlovskyi can be controlled by a gene located on chromosome 7A. The gene locates approximately 12.4 ± 0.5 cM from the centromere on the long arm of 7A. It is considered that the gene for long glume from T. petropavlovskyi is an allele on the P ₁ locus, and it should be designated as P _1a. It is suggested that T. petropavlovskyi originated from either the natural hybrid between T. aestivum that has an awn-like appendage on the glume and T. polonicum or a natural point mutation of T. aestivum. This revised version was published online in August 2006 with corrections to the Cover Date.     

Development of diversity array technology (DArT) markers for assessment of population structure and diversity in Aegilops tauschii

Aegilops tauschii Coss. is the D-genome donor to hexaploid bread wheat (Triticum aestivum) and is the most promising wild species as a genetic resource for wheat breeding. To study the population structure and diversity of 81 Ae. tauschii accessions collected from various regions of its geographical distribution, the genomic representation of these lines were used to develop a diversity array technology (DArT) marker array. This Ae. tauschii array and a previously developed DArT wheat array were used to scan the genomes of the 81 accessions. Out of 7500 markers (5500 wheat and 2000 Ae. tauschii), 4449 were polymorphic (3776 wheat and 673 Ae. tauschii). Phylogenetic and population structure studies revealed that the accessions could be divided into three groups. The two Ae. tauschii subspecies could also be separately clustered, suggesting that the current taxonomy might be valid. DArT markers are effective to detect very small polymorphisms. The information obtained about Ae. tauschii in the current study could be useful for wheat breeding. In addition, the new DArT array from this Ae. tauschii population is expected to be an effective tool for hexaploid wheat studies.     

Wheat pollen dispersal under semiarid field conditions: potential outcrossing with Triticum aestivum and Triticum turgidum

Isolation distance is the main barrier to crop-to-crop gene-flow. A 3-year study assessed the maximum potential outcrossing under field conditions between two wheat cultivars (Triticum aestivum L.) and between wheat and durum wheat (Triticum turgidum L. var. durum). Outcrossing was measured by seed set on emasculated recipient plants placed at four sides with different distances from a 3 m × 3 m T. aestivum (cultivar Chinese Spring) pollen source. Frequencies of seed set at 0 m distance were 45% (37–56%) for T. aestivum cultivars and 18% (5–30%) with T. turgidum. These values agree with hybridization in non-limiting pollen conditions measured by manual crosses in greenhouse. The number of pollen grains and the outcrossing frequencies decreased at increasing distances influenced by the prevailing wind direction. Under semiarid conditions of this assay, viable pollen was found 14 m from the pollen source, with a maximum distance of 8 m at which cross-pollination decreases below 1%. Ambient conditions affect pollen viability, hybridization and pollen dispersal. Data presented in this paper emphasize the major role played by environmental conditions in outcrossing. Data obtained in one area may therefore not coincide with the prevailing situation in different locations and climates.     

Flooding tolerance of spelt (Triticum spelta L.) compared to wheat (Triticum aestivum L.) – A physiological and genetic approach

In marginal, agroclimatic zones, yield is often affected by flooding, but the effect is much less for winter spelt (Triticum spelta L.) than for winter wheat (Triticum aestivum L.). This study evaluates the reaction of a wheat x spelt population (F₅ RILs of Forno x Oberkulmer) to flooding stress in the early phase of germination. Lines with greater tolerance to 48 h flooding just after imbibition showed less electrolyte leakage (r = -0.79) indicating greater membrane integrity and better survival. Five QTL explaining 40.6% of the phenotypic variance for survival to flooding were found, and localized on the chromosomes 2B, 3B,5A, and 7S. The tolerance to 48 h flooding four days after sowing was best correlated with the mean germination time (r = 0.8), indicating that the plants with a fast coleoptile growth during flooding are less susceptible to flooding. Ten QTL were found for seedling growth index after flooding explaining 35.5% of the phenotypic variance. They were localized on chromosomes 2A, 2B, 2D, 3A, 4B, 5A, 5B, 6A, and 7S. Standard varieties of spelt and wheat showed the same tolerance characteristics. The possibility to use marker assisted selection for flooding tolerance is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Aneuploids as a key for new molecular cloning strategies: development of DNA markers by microdissection using Triticum aestivum-Aegilops markgrafii chromosome addition line B

Summary We established a chromosome specific DNA library of the Aegilops markgrafii chromosome B. Eight microdissected chromosomes B obtained from a monosomic T. aestivum-Aegilops markgrafii addition line were PCR-amplified and the DNA was cloned in Escherichia coli DH5. Clones were characterized by dot blot hybridization with total Ae. markgrafii DNA. 62% of clones represented repetitive sequences and 38% low or single copy sequences. The estimated length of excised inserts varied between less than 200 bp and more than 500 bp. The average size of inserts was 310 bp.Abbreviations bp base pairs - DOP-PCR degenerated oligonucleotide primed polymerase chain reaction     

Induction of a mutation in the male fertility gene of the preferentially transmitted Aegilops sharonensis chromosome 4S1 and its application for hybrid wheat production

Summary Wheat plants nullisomic for chromosome 4B are male sterile due to the absence of the male fertility gene Ms1. However, plants in which chromosome 4B has been substituted by the preferentially transmitted chromosome 4S¹ of Ae. sharonensis are male fertile due to the compensating effect of Ms4 on the alien chromosome. This substitution line has been mutated and three recessive mutation of Ms4 have been selected. Plants homozygous for these mutations are male sterile. The implication of these mutations for hybrid wheat production is discussed.