Mapping QTLs for pre-harvest sprouting traits in the spring wheat cross ‘RL4452/AC Domain’

Pre-harvest sprouting (PHS) in spring wheat (Triticum aestivum L.) is a major downgrading factors for grain producers and can significantly reduce end-use quality. PHS resistance is a complex trait influenced by genotype, environment and plant morphological factors. A population of 185 doubled haploid (DH) lines from the spring wheat cross ‘RL4452/AC Domain’ were used as the mapping population to detect quantitative trait loci (QTLs) associated with three PHS traits, germination index (GI), sprouting index (SI) and falling number (FN). Six major QTLs linked with PHS traits were mapped on bread wheat chromosomes 3A, 3D, 4A (2 loci), 4B and 7D. ‘AC Domain’ alleles contributed to PHS resistance on 3A, 4A (locus-2) and 4B, and ‘RL4452’ alleles contributed resistance on 3D, 4A (locus-1) and 7D. QTLs detected on chromosome 4B controlling FN (QFN.crc-4B), GI (QGI.crc-4B) and SI (QSI.crc-4B) were coincident, and explained the largest amount of phenotypic variation in FN (22%), GI (67%) and SI (26%), respectively.     

Developing standardized methods for breeding preharvest sprouting resistant wheat, challenges and successes in Canadian wheat

Preharvest sprouting (PHS) in spring wheat (Triticum aestivum L.) and durum wheat (T. turgidum L. var durum) causes significant economic losses due to a reduction in grain yield, grain functionality and viability of seed for planting. Average annual estimated losses in Canada are about $100 million. Genetic resistance to PHS reduces these losses. Development of PHS resistant cultivars is complicated by the effects of factors under genetic control, such as spike morphology, seed dormancy, environment, and kernel diseases. Resistance to PHS has been a breeding priority since the late 1960s. Development of RL4137, which is the primary source of PHS resistance in the Canada Western Red Spring market class, has led to cultivar improvements. A white-seeded derivative of RL4137 is the primary source of PHS in the Canada Prairie Spring White and Canada Western Hard White Spring wheat market classes. Procedures to select for PHS resistance vary among breeding programs, market classes and by degree of inbreeding. Methods include artificial sprouting of intact spikes, germination tests, natural weathering in field trials, artificial weathering trials, and indirect assessment of sprouting by measuring Hagberg falling number. Although many genetic loci have been attributed to preharvest sprouting resistance, application of molecular markers is currently limited due to the complex inheritance of the trait. In Canada, cultivars are characterized for their relative level of PHS resistance and the information is made available to producers.     

Isolation of mildew resistant wheat-rye translocation lines from a double substitution line

A powdery mildew resistant double disomic wheat-rye substitution line carrying rye chromosomes 1R and 2R was crossed with normal bread wheats. The F₂ generation was analysed cytologically by C-banding. Wheat-rye chromosome translocations involving both rye chromosomes 1R and 2R were frequent in F₂. Lines with translocations of 1R and 2R were harvested separately. After four generations of selfing and selection for mildew resistance and fertility, fully fertile resistant lines were selected and analysed cytologically. Lines with 1BL/1RS and 2BS/2RL translocations were identified. The resistance on chromosome 1RS could not be shown to be different from control varieties carrying the same rye segment, while the resistance on 2RL is much broader than the earlier known 2RL derived resistance in the line Transec. This revised version was published online in July 2006 with corrections to the Cover Date.     

Integration of marker-assisted selection for resistance to pre-harvest sprouting with selection for grain-filling rate in breeding of white-kernelled wheat for the Chinese environment

Few Chinese high yielding white-grained wheat cultivars possess sufficient dormancy to avoid pre-harvest sprouting (PHS). Because the field evaluation of PHS is difficult, the identification of informative molecular markers is a priority for improving the level of dormancy. In this report, the effectiveness of phenotypic and genotypic selection was compared. Four microsatellite loci Xbarc57, Xbarc294, Xbarc310 and Xbarc321, mapped on the short arm of chromosome 3A, were used for selection in white-grained wheat F₅ lines which were also selected on the basis of their grain filling rate (GFR). One of these (later designated cv. Zhongmai911) was further selected on the basis of its allelic constitution at the four SSR loci. This cultivar combines a high level of PHS resistance with high grain yield. The results suggested that rapid GFR and PHS resistance can be bred simultaneously.     

RL4137 contributes preharvest sprouting resistance to Canadian wheats

Preharvest sprouting (PHS) in spring wheat (Triticum aestivum L.) causes significant economic losses due to a reduction in grain functionality, grain yield and viability of seed for planting. Genetic resistance to PHS reduces these losses. Development of PHS resistant cultivars is complicated by the effects of genotype, environment, kernel diseases and spike morphological factors. RL4137 has consistently exhibited high levels of resistance to PHS over years and environments. The mean PHS scores of Canada Western Red Spring (CWRS) wheat cultivars with RL4137 in their ancestry are lower than that of CWRS wheat cultivars without. RL4137 has two mechanisms for PHS resistance, one associated with kernel color and the other not associated with kernel color. RL4137 was the source of PHS resistance in white wheats HY361, AC Vista, Snowbird, Kanata, and Snowstar, all of which had significantly lower PHS scores than the white-seeded check, Genesis. Known DNA markers relating to PHS were used to compare haplotypes with and without RL4137 in the ancestry. Coefficients of parentage also demonstrated the relationship. Because cultivars that have RL4137 in their ancestry were grown on about 77% of the spring wheat area for 2003–2007, RL4137 continues to contribute to protecting market grade from preharvest sprouting.     

Detection of QTLs for traits associated with pre-harvest sprouting resistance in bread wheat (Triticum aestivum L.)

Pre-harvest sprouting (PHS) is one of the serious problems for wheat production, especially in rainy regions. Although seed dormancy is the most critical trait for PHS resistance, the control of heading time should also be considered to prevent seed maturation during unfavorable conditions. In addition, awning is known to enhance water absorption by the spike, causing PHS. In this study, we conducted QTL analysis for three PHS resistant related traits, seed dormancy, heading time and awn length, by using recombinant inbred lines from ‘Zenkouji-komugi’ (high PHS resistance) × ‘Chinese Spring’ (weak PHS resistance). QTLs for seed dormancy were detected on chromosomes 1B (QDor-1B) and 4A (QDor-4A), in addition to a QTL on chromosome 3A, which was recently cloned as TaMFT-3A. In addition, the accumulation of the QTLs and their epistatic interactions contributed significantly to a higher level of dormancy. QDor-4A is co-located with the Hooded locus for awn development. Furthermore, an effective QTL, which confers early heading by the Zenkouji-komugi allele, was detected on the short arm of chromosome 7B, where the Vrn-B3 locus is located. Understanding the genetic architecture of traits associated with PHS resistance will facilitate the marker assisted selection to breed new varieties with higher PHS resistance.     

Identification of the spontaneous 7BS/7RL intergenomic translocation in one F1 multigeneric hybrid from the Triticeae tribe

The F1 AABBRH^ch hybrids studied here were produced by crosses between the Portuguese triticale cultivar 'Douro' (AABBRR) and the tritordeum line HT9 (AABBH^chH^ch). Fluorescent in situ hybridization performed with genomic DNA probes genomic in situ hybridization (GISH) from rye and Hordeum chilense allowed the unequivocal parental genomes discrimination in all hybrids. Among 55 plants, one presented a spontaneous wheat–rye translocation which was successfully detected after GISH. Recombinant chromosomes identification was made after reprobe with pTa71 and pSc119.2. Nine rDNA loci were detected by pTa71 and pSc119.2 identified the chromosome arms involved in the translocation, after comparing the observed hybridization patterns with those described by several authors. We identified the spontaneous wheat–rye translocation as being the 7BS/7RL. Many wheat–rye translocations have been found (e.g. 1BL.1RS and 1AL.1RS), but as far as we know, this is the first time that this translocation is reported. We considered it helpful for wheat breeding programmes as it could provide the transference of interesting agronomic characteristics from rye (e.g. leaf rust resistance) to wheat.     

小麦EST-SSR标记的开发和染色体定位及其在追踪黑麦染色体中的应用

根据小麦盐胁迫诱导和茎秆组织相关EST序列开发了81对EST-SSR引物, 其中67、46、18和61对分别在小麦、黑麦、簇毛麦和大麦基因组中稳定扩增, 在不同小麦和大麦品种间具有多态性的引物分别有22和23对。利用小麦缺体-四体系共定位了43对引物的81个位点, 其中A、B和D染色体组上分别有29、30和22个位点, 涉及除4B、3D和6D外的18条染色体。此外30对引物在黑麦基因组中具有特异扩增, 其中8对分别在黑麦1R、4R、5R和R7染色体上具有特异扩增, 7对在多条黑麦染色体具有相同扩增。这些新标记可有效用于小麦及其近缘物种的遗传作图与比较遗传研究。     

QTL analysis for resistance to preharvest sprouting in rice (Oryza sativa)

Preharvest sprouting (PHS) is caused by early breaking of seed dormancy. In Sichuan, a major hybrid rice seed production area of China, PHS in hybrid seeds originated from ‘G46A’ parent may lead to severe yield loss, causing serious damage to agricultural production. To detect quantitative trait loci (QTLs) governing PHS, we developed an F₂ population of 164 plants derived from ‘G46B’ and ‘K81’, a near‐isogenic introgression line of G46B, with high level of resistance to PHS. PHS was evaluated under controlled field and laboratory conditions. Using simple sequence repeat markers, we constructed a linkage map from this population and identified three QTLs for PHS, namely qPSR2, qPSR5 and qPSR8, which were located on chromosomes 2, 5 and 8, respectively. Among these QTLs, qPSR8, residing in the interval between RM447 and RM3754 on chromosome 8, was the major QTL controlling PHS, for it had a relative high logarithm of the odds (LOD) score and explained 43.04% of the phenotypic variation. These results were correspondent to those identified in extreme low germination rate plants (ELGP) using linkage and linkage disequilibrium. At all loci, ‘K81’ was responsible for enhancing the resistance to PHS.     

Comparative analysis of Australian and Canadian barleys for seed dormancy and malting quality

The association between high malting quality and pre-harvest sprouting (PHS) susceptibility is a key challenge when developing new malting barley varieties. A new malting barley variety Baudin has successfully combined high malting quality and PHS tolerance. A doubled haploid population was developed for mapping PHS tolerance and seed dormancy from a cross of Baudin?×?AC Metcalfe using 233 molecular markers. Three QTLs were mapped for seed dormancy based on the standard germination test at 24, 48 and 72?h. One major QTL was mapped to the long arm of chromosome 5H controlling seed dormancy and PHS tolerance from Baudin. Two other minor QTLs were identified from Baudin on chromosomes 3 and 7H. QTL/QTL interaction was detected for seed dormancy between chromosomes 3 and 5H. The PHS tolerance allele of the 5H QTL from Baudin contributes to higher malt yield without significant impact on diastatic power, beta-glucan content and wort viscosity. QTL from Baudin provide new sources to integrate PHS tolerance and high malting quality.     

Mapping quantitative trait loci controlling pre-harvest sprouting resistance in a red × white seeded spring wheat cross

Hard white wheat (Triticum aestivum L.) is a value-added product because of its processing advantages over red wheat; however, white wheat tends to be more susceptible to pre-harvest sprouting (PHS). To identify quantitative trait loci (QTLs) associated with PHS tolerance, we developed a doubled haploid (DH) mapping population from the cross AC Domain (red seeded) × White-RL4137 (white seeded). A genetic map was constructed using microsatellite markers located on chromosome groups 3, 4, 5 and 6. A population of 174 DH lines was characterized for important aspects of PHS including sprouting index, germination index, Hagberg falling number and seed coat colour. A total of 11 QTLs were identified on group 3 chromosomes and on chromosome 5D. Seven QTLs associated with the PHS traits were found to be co-incident with seed coat colour on chromosomes 3A, 3B and 3D. The 5D PHS QTL was notable because it is independent of seed coat colour.     

Conferring resistance to pre-harvest sprouting in durum wheat by a QTL identified in <Emphasis Type="Italic">Triticum spelta</Emphasis>

Pre-harvest sprouting (PHS) causes significant yield loss and degrade the end-use quality of wheat, especially in regions with prolonged wet weather during the harvesting season. Unfortunately, the gene pool of Triticum durum (tetraploid durum wheat) has narrow genetic base for PHS resistance. Therefore, finding out new genetic resources from other wheat species to develop PHS resistance in durum wheat is of importance. A major PHS resistance QTL, Qphs.sicau-3B.1, was mapped on chromosome 3BL in a recombinant inbred line population derived from ‘CSCR6’ (Triticum spelta), a PHS resistant hexaploid wheat and ‘Lang’, a PHS susceptible Australian hexaploid wheat cultivar. This QTL, Qphs.sicau-3B.1, is positioned between DArT marker wPt-3107 and wPt-6785. Two SCAR markers (Ph3B.1 and Ph3B.2) were developed to track this major QTL and were used to assay a BC₂F₈ tetraploid population derived from a cross between the durum wheat ‘Bellaroi’ (PHS susceptible) and ‘CSCR6’ (PHS resistant). Phenotypic assay and marker-assisted selection revealed five stable tetraploid lines were highly PHS resistant. This study has successfully established that PHS-resistance QTL from hexaploid wheat could be efficiently introgressed into tetraploid durum wheat. This tetraploid wheat germplasm could be useful in developing PHS resistant durum cultivars with higher yield and good end-use quality.     

Evaluation of genetic markers for prediction of preharvest sprouting tolerance in hard white winter wheats

Preharvest sprouting of wheat results in significant financial loss at all steps in the production and marketing chain. Due to its intermittent nature in many wheat‐growing regions, direct selection for tolerance to preharvest sprouting is difficult. DNA markers linked to genes conditioning tolerance offer a more consistent and reliable approach to genetic improvement in tolerance. This investigation assessed the value of previously identified markers linked to quantitative trait loci contributing to tolerance, across multiple genetic backgrounds. A significant contribution to tolerance was demonstrated for QPhs.pseru‐3AS, previously identified from the hard white winter wheat ‘Rio Blanco’. Marker alleles for this locus were associated with enhanced tolerance in three of four investigated populations. In addition, positive contributions of QPhs.pseru‐2B1 and QPhs.pseru‐2B2 also were documented. Simultaneous selection for putative marker alleles at two independent loci resulted in significantly higher mean tolerance scores. DNA markers linked to loci contributing to variation in preharvest sprouting tolerance offer an efficient and effective alternative to direct phenotypic selection.     

Identification of genomic regions associated with seed dormancy in white-grained wheat

Pre-harvest sprouting (PHS) in developing wheat (Triticum aestivum L.) spikes is stimulated by cool and wet weather and leads to a decline in grain quality. A low level of harvest-time seed dormancy is a major factor for PHS, which generally is a larger problem in white-grained as compared to red-grained wheat. We have in this study analyzed seed dormancy levels at the 92nd Zadok growth stage of spike development in a doubled-haploid (DH) white wheat population and associated variation for the trait with regions on the wheat genome. The phenotypic data was generated by growing the parent lines Argent (non-dormant) and W98616 (dormant) and 151 lines of the DH population in the field during 2002 and 2003, at two locations each year, followed by assessment of harvest-time seed dormancy by germination tests. A genetic map of 2681 cM was constructed for the population upon genotyping 90 DH lines using 361 SSR, 292 AFLP, 252 DArT and 10 EST markers. Single marker analysis of the 90 genotyped lines associated regions on chromosomes 1A, 2B, 3A, 4A, 5B, 6B, and 7A with seed dormancy in at least two out of the four trials. All seven putative quantitative trait loci (QTLs) were contributed by alleles of the dormant parent, W98616. The strongest QTLs positioned on chromosomes 1A, 3A, 4A and 7A were confirmed by interval mapping and markers at these loci have potential use in marker-assisted selection of PHS resistant white-grained wheat.     

RAPD markers linked with restorer genes for the C-source of cytoplasmic male sterility in rye (Secale cereale L.)

The study was aimed at the identification of random amplified polymorphic DNA markers linked to genes controlling male sterility in rye with the C‐source of sterility‐inducing cytoplasm. Markers of male sterility were distinguished using bulk segregant analysis, carried out on the two F₂ crosses between male sterile and male fertile inbred lines. Screening of polymorphisms revealed by 1000 arbitrary 10‐mer primers allowed the detection of 10 markers in the cross between 711‐cmsC and DS2 lines and seven markers in the cross between 544‐cmsC and Ot0‐20 lines. Five markers were common for the two crosses, which allowed comparative mapping to be performed. Ten markers were mapped on the 4RL chromosome arm where two linked quantitative trait loci (QTL) for male sterility were discovered. Additional QTL of minor effect on male fertility were detected between the two linked markers provisionally assigned to the 6RS chromosome arm. The effectiveness of the marker‐assisted selection (MAS) for male‐sterile genotypes was evaluated.     

Identification of seven telotrisomics of rye (Secale cereale L.)

Summary Seven monotelotrisomics emerged spontaneously from primary trisomics of rye cv. Esto. Analyses of karyotype, of chromosome pairing in meiosis and of Giemsa banding pattern were used to identify monotelotrisomics in rye as IRS, 1RL, 3RS, 4RS, 4RL, 6RS and 7RL. Vitality and fertility were better than in primary trisomics. The extra telocentrics were well transmitted through the female gamete. Transmission through the male gamete was in all cases less than trasmission through the female gamete.     

Quality effect of wheat-rye (1R) translocation in 'Pavon 76'

A growing interest exists in using wheat for producing both hard and soft wheat products. It would be desirable if 1RS translocations in hard wheat could produce flour suitable for soft wheat products. The objective of this study was to test the effects of centric translocations of chromosome 1 from different rye sources for end‐use quality. The quality influences of the 1RS and 1RL translocations and 1R substitutions from different rye sources were studied in a set of hard spring wheat ‘Pavon 76’(CIMMYT) lines in three environments in Georgia. The protein concentration of the 1RL translocations was the highest while the 1RS translocations showed no difference in protein concentration compared with that of controls. The 1RS translocations increased alkaline water retention capacity while the 1RL translocations reduced it. T1DSAE1RL was preferred for soft wheat products over other genotypes.     

以关联分析发掘小麦整穗发芽抗性基因分子标记

利用分布于小麦全基因组的181对分子标记,分析264份自然群体的基因型,采用TASSLE软件的GLM和MLM模型检测与整穗发芽抗性紧密关联的标记位点,发掘相关位点内的优异等位变异。在2012年和2013年室内整穗发芽率、2013年田间自然降雨整穗发芽率3个环境中,共关联到20个显著位点(P<0.05),分布于小麦染色体1AS、2DS、3AS、3BL、4AL、5AS、5BL、6BS、6DS、7AL和7BL上。分别位于2DS和7BL上的分子标记gwm102和barc340同时在3个环境下关联到,属于稳定的抗性位点; 另有6个标记位点同时在2个环境下关联到; 其余12个标记位点仅在1个环境下关联到。位于7BL上的barc340标记位点为一新报道位点。从重复关联的8个标记位点内共检测出10种优异等位变异。barc28-229bp和barc28-217bp对提高整穗发芽抗性效应最显著,主要分布在地方品种中(如遂宁坨坨麦等),而gwm102-142bp和barc186-199bp效应虽然相对较小,但多分布在推广品种中(如扬麦158等),有利于穗发芽抗性分子育种的直接应用。     

Vp1 expression profiles during kernel development in six genotypes of wheat, triticale and rye

During the last few decades, the physiological and genetic background of dormancy, and correlated pre-harvest sprouting (PHS) have been intensively investigated. Special attention has often been paid to genetic factors that may explain and predict PHS susceptible behaviour. A major candidate is the Vp1 gene which is involved in embryo development and maturation as well as in dormancy establishment. In this study, Vp1 gene expression during kernel development was studied in wheat, triticale and rye as a potential biomarker for selecting PHS tolerant varieties in cereal breeding programs. Plants of known PHS tolerant and PHS susceptible varieties were grown under controlled conditions from flowering until harvest ripeness. During that period, kernels were regularly harvested for RNA extraction and cDNA synthesis. Calibrated and normalized relative Vp1 expression levels were obtained in an RT-qPCR assay. During kernel development, Vp1 expression levels generally showed a typical peak during the soft dough stage, after which they decreased and remained low until harvest maturity. Differences in Vp1 expression levels could be observed between the PHS susceptible and PHS tolerant varieties of wheat, with the PHS tolerant variety showing higher levels of relative Vp1 expression compared to the PHS susceptible variety. In triticale, however, this difference was only seen once and could not be confirmed in further experiments. It seems that the Vp1 gene in triticale behaves in a similar way as in rye, in which no specific trends could be observed.     

Genetic analysis of falling number in three bi‐parental common winter wheat populations

The objective of the present study was to analyse the genetic basis of falling number in three winter wheat populations. Samples for falling number determination for each population originated from at least three test environments that were free from the occurrence of preharvest sprouting at harvest time. Quantitative trait locus (QTL) analysis employing falling number values from single environments identified eight, five and three QTL in the populations Dream/Lynx, Bussard/W332‐84 and BAUB469511/Format, respectively. A major QTL common to all three populations and consistently detected in each environment mapped to the long arm of chromosome 7B. The QTL was located to a similar genomic region as the previously described major QTL for high‐isoelectric point α‐amylase content. The T1BL.1RS wheat‐rye translocation and the dwarfing gene Rht‐D1 segregating in Dream/Lynx and BAUB469511/Format were found to be important factors of falling number variation. In both populations, the presence of Rht‐D1b or the absence of T1BL.1RS increased falling number. The results indicate that late maturity α‐amylase, responsible for low falling numbers, has now been documented in German wheat germplasm.