Effect of parental genotypes and colchicine treatment on the androgenic response of wheat F1 hybrids

The effect of the parental genotypes and colchicine treatment on the androgenic response of wheat (Triticum aestivum L.) F1 hybrids was studied. For this, anthers from three F1 hybrids and their parents were cultured on W14 initiation medium and W14 supplemented with 0.03% colchicine. The number of responding anthers, microspore‐derived structures/100 anthers, green plants/embryos cultured, green plants/100 anthers and albino plants/100 anthers were recorded. It was observed that embryo formation and plant regeneration ability were genetically controlled and genotype dependent. In both treatments the variety Kavkaz had a significantly higher percentage of responding anthers, microspore‐derived structures and green plants/100 anthers than the other genotypes. On the other hand, the variety Myconos also demonstrated high microspore‐derived structure production and green plant regeneration when treated with colchicine. The good response observed in these two varieties indicates the importance of colchicine treatment only for certain genotypes. Green plant production capacity of the hybrids was intermediate to that of the parental varieties. As one parent with a high or even an intermediate response to anther culture could lead to the production of sufficient (for breeding purposes) green plants from the F₁ hybrids, it was concluded that screening the inbred lines for the response to anther culture with and without colchicine treatment could contribute to utilization of breeding material with a low response to anther culture via the proper hybrid combinations.     

Chromosomal regions associated with green plant regeneration in wheat (Triticum aestivum L.) anther culture

Genetic capacity for green plant regeneration in anther culture were mapped in a population comprising 50 doubled haploid lines from a cross between two wheat varieties ‘Ciano’ and ‘Walter’ with widely different capacity for green plant regeneration. Bulked segregant analysis with AFLP markers and composite interval mapping detected four QTLs for green plant percentage on chromosomes 2AL (QGpp.kvl-2A), 2BL (QGpp.kvl-2B.1 and QGpp.kvl-2B.2) and 5BL (QGpp.kvl-5B).The three QTLs detected on chromosome 2AL and 2BL all derived their alleles favouring green plant formation from the responsive parent ‘Ciano’.The remaining QTL on chromosome 5BL had the allele favouring green plants from the low responding parent ‘Walter’. In a multiple regression analysis the four QTLs could explain a total of 80% of the genotypic variation for green plant percentage. None of the chromosomal regions with QTLs for green plant percentage showed significant influence on either embryo formation or regeneration frequencies from the anther culture. The three major QTLs located on group two chromosomes were fixed in a second DH population derived from two parents ‘Ciano’ and ‘Benoist’,both with high capacity to produce green plants. A QTL explaining31.5% of the genetic variation for green plant formation were detected on chromosome 5BL in this cross as well. This revised version was published online in July 2006 with corrections to the Cover Date.     

Anther and isolated microspore culture response of wheat lines from northwestern and eastern Europe

Hexaploid wheat genotypes from north-western Europe show low responses to current anther culture techniques. This phenomenon was investigated on 145 north-western European wheat lines. Twenty-seven lines from eastern Europe were included to observe the response pattern of wheat from an area, where the technique has been used successfully. On average, eastern European wheat lines produced 3.6 green plants per 111 anthers, while only 1.4 green plants per 111 anthers were obtained in north-western European lines. This difference was due to the high capacity for embryo formation among the eastern European lines, while the ability to regenerate green plants was widespread in both germplasm groups. Isolated wheat microspore culture performed on 85 of these wheat lines gave an average 3.7-fold increase in green plants per anther compared with the anther culture response. The increased recovery of green plants was due to improved plant regeneration and increased green plant percentage from embryos derived from isolated microspore culture.     

The Effect of the "D" Genome from Synthetic Wheat Lines in Anther Culture Responses

Synthetic lines of wheat were compared in order to determine the effect of the “D” genome on embryo induction and plant regeneration from anther culture. The experiments were performed using 6 genotypes of wheat in a randomized block design with 4 replications. In all cases except one, addition of the “D” genome from T. tauschii increased the efficiency of embryo formation and green plantlet production. This positive effect of the “D” genome does not exclude the existence of possible interactions between the three genomes (A, B and D) and/or the effect of each genome separately.     

Mapping of the Vrn-B1 gene in Triticum aestivum using microsatellite markers

An F₂ population segregating for the dominant gene Vrn‐B1 was developed from the cross of the substitution line ‘Diamant/'Miro‐novskaya 808 5A’ and the winter wheat cultivar ‘Bezostaya 1′. Microsatellite markers (Xgwm and Xbarc) with known map locations on chromosome 5B of common wheat were used for mapping the gene Vrn‐B1. Polymorphism between parental varieties was observed for 28 out of 34 microsatellite markers (82%). Applying the quantitative trait loci mapping approach, the target gene was mapped on the long arm of chromosome 5B, closely linked to Xgwm408. The map position of Vrn‐B1 suggests that the gene is homoeologous to other vernalization response genes located on the homoeologous group 5 chromosomes of wheat, rye and barley.     

Genetics of androgenesis in winter and spring wheat genotypes

Androgenetic response and its inheritance was studied in nine winter type and two spring type wheat genotypes by crossing them in line × tester fashion. The 18 F₁ and 11 parental genotypes were raised in completely randomized block design with three replications and subjected to anther culture. Data were recorded with respect to per cent calli induction, percent regeneration and per cent green plant development. Analysis of variance revealed considerable genetic variation for all the three component traits of androgenesis. Both additive and non-additive genetic variances were involved in the androgenetic response with the preponderance of non-additive gene action in case of calli induction and additive gene action for regeneration and green plant development. Low estimates of heritability (narrow sense) for calli induction and moderate for regeneration and green plantlet development were obtained. The genotypes, Henies VII, Pnfjoumee, Saptdhara, Sentry, Purthi of winter wheat and HPW147 of spring wheat were identified as good general combiners for almost all the androgenetic parameters and have potential use in future haploidy breeding programmes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Optimization of culture conditions for improved plant regeneration efficiency from wheat microspore culture

The production of haploid plants through microspore culture is a very important tool for plant breeding. However, progress in microspore culture for many species has been hampered by a number of factors that have resulted in low recovery of regenerated green plants. In this study, a series of experiments were conducted to increase the regeneration of haploid green plants from isolated wheat microspores. The use of different basal media and variations in media components resulted in the increased recovery (approximately double) of regenerated haploid wheat plants. Our findings demonstrate that CHB medium, in combination with 2,4-d, was a better medium for embryoids induction and plant regeneration than medium MC17 with either 2,4-d or PAA growth hormones. Wheat microspores cultured without ovary co-cultivation did not respond. Furthermore, high efficiency of microspore derived embryoids (up to 296 MDEs per 100 anthers) and green plant regeneration (up to 71 green plants per 100 anthers) were achieved by the use of gelrite instead of agarose as a gelling agent, and by the addition of media additives such as spent medium or MET.     

Marker‐assisted backcross breeding for improvement of drought tolerance in bread wheat (Triticum aestivum L. em Thell)

Drought stress is presently a major productivity limiting factor in wheat. This study developed five wheat lines with inbuilt tolerance to drought stress using marker‐assisted backcross breeding (MABB) approach employing three linked quantitative trait loci (QTLs) in an initial population of 516 BC₁F₁ plants. The high‐yielding wheat cultivar ‘HD2733’ grown over last few years extensively in the eastern plains of India is largely sensitive to drought and is used as the recurrent parent. ‘HI1500’ released for water‐limiting conditions and carrying drought‐tolerant QTLs was used as donor parent. MABB lines were advanced using foreground and background selection, coupled with stringent phenotyping. We identified 29 lines that were homozygous for targeted QTLs in different combinations with background recovery range of 89.2%–95.4%. Further evaluation of selected lines for physiological traits and distinctness, uniformity and stability (DUS) characters under rainfed condition identified five potential varieties for national varietal evaluation programme in the zone. The report is first of its kind in implementing known QTLs for the development of drought‐tolerant wheat lines through MABB approach.     

Mapping of quantitative trait loci for resistance to race 1 of Pyrenophora tritici‐repentis in synthetic hexaploid wheat

Tan spot, caused by a necrotrophic fungus Pyrenophora tritici‐repentis (Ptr), has become an important foliar disease of wheat worldwide. Effective control of tan spot can be achieved by deployment of resistant wheat cultivars. An F_2:3 population derived from a cross between synthetic hexaploid wheat (SHW), TA4161‐L1 (moderately resistant) and susceptible winter wheat cultivar, ‘TAM105’ was evaluated with race 1 of Ptr under controlled conditions. The population was genotyped using Diversity Arrays Technology (DArT). Presence of transgressive segregants indicated contribution of positive alleles from both parents. Two major QTLs were located on the short arm of chromosomes 1A and 6A and designated as QTs.ksu‐1A and QTs.ksu‐6A, respectively. Two additional QTLs were identified on chromosome 7A. Resistant alleles of all the QTLs were contributed by TA4161‐L1. Novel QTLs on 6A and 7A can be a valuable addition to known resistance genes and utilized in breeding programmes to produce highly resistant cultivars.     

QTL analysis of quality traits in the spring wheat cross RL4452 × 'AC Domain'

Wheat grain quality is a complex group of traits of tremendous importance to wheat producers, end‐users and breeders. Quantitative trait locus (QTL) analysis studied the genetics of milling, mixograph, farinograph, baking, starch and noodle colour traits in the spring wheat population RL4452/‘AC Domain’. Forty‐seven traits were measured on the population and 99 QTLs were detected over 18 chromosomes for 41 quality traits. Forty‐four of these QTLs mapped to three major QTL clusters on chromosomes 1B, 4D, and 7D. Fourteen QTLs mapped near Glu‐B1, 20 QTLs mapped near a major plant height QTL on chromosome 4D, and 10 QTLs mapped near a major time to maturity QTL on chromosome 7D. Large QTLs were detected for grain and flour protein content, farinograph absorption, mixograph parameters, and dietary fibre on chromosome 2BS. QTLs for yellow alkaline noodle colour parameter L* mapped to chromosomes 5B and 5D, while the largest QTL for the b* parameter mapped to 7AL.     

我国部分主推小麦品种组织培养再生能力评价

小麦细胞工程育种和基因工程育种存在强烈的基因型特异性, 从目前推广的优良小麦品种中筛选不同外植体再生能力强的基因型, 对于提高小麦生物技术育种效率和加速育成品种的生产应用具有重要意义。本研究以全国大面积推广的24个优良小麦品种和抗白粉病优良品系CB037为材料, 连续2年进行花药培养、幼胚培养和成熟胚培养, 统计愈伤组织诱导率、愈伤组织分化率和植株再生率, 分析、评价这些小麦品种(系) 3种外植体的组织培养再生性能。结果表明, 25个小麦品种(系)花药、幼胚、成熟胚的植株再生率分别为0~41.75%、2.25%~531.92%和3.24%~84.34%, 基因型差异显著; 组织培养再生能力以幼胚最强(119.79%), 成熟胚其次(36.23%), 花药最弱(4.91%)。CB037的3种外植体组织培养再生效率均最高, 轮选987、扬麦16、内麦836、科农199、新春6号、郑麦366、郑麦9023、新冬20、烟农19和川麦42幼胚培养植株再生能力表现较强, 新春6号、京冬8号、石麦4185、科农199和轮选987成熟胚培养植株再生率较高, 石麦4185和邯6172花药培养绿苗诱导率较高。小麦组织培养效率与基因型和外植体类型密切相关, 不同品种同一外植体再生能力差异显著, 同一品种不同外植体再生能力也存在显著差异, 并且3种外植体的组织培养再生能力不存在相关性。本研究筛选到不同外植体再生能力较好的优良小麦基因型, 可进一步用于小麦转基因育种和单倍体育种。     

Relative efficiency of different Gramineae genera for haploid induction in triticale and triticale x wheat hybrids through the chromosome elimination technique

The study was undertaken to evaluate the relative efficiency of different Gramineae genera for haploid induction in triticale (x Triticosecale) and triticale × wheat (Triticum aestivum) hybrids through the chromosome elimination (wheat × maize, Zea mays) system. Eight intergenotypic triticale and 15 triticale x wheat crosses were subjected to hybridization with nine different Gramineae genera viz., Z. mays, Sorghum bicolor, Pennisetum americanum, Setaria italica, Festuca arundinacea, Imperata cylindrica, Cynodon dactylon, Lolium temulentum and Phalaris minor in two separate experiments. This was followed by in vivo auxin treatment of the crossed spikes and subsequent rescue of the haploid embryos to regenerate green haploid plantlets. All the triticale and triticale x wheat crosses resulted in seed set in variable frequencies when hybridized with maize, I. cylindrica, pearl millet and sorghum. Seed set was also obtained with S. italica, F. arundinacea and P. minor in a few crosses in both groups. In general, all the triticale x wheat crosses, except for one in each case, resulted in embryo formation and green haploid plantlet regeneration when hybridizations were carried out with maize and I. cylindrica. However, the latter outperformed the former in embryo formation (25.48% vs. 20.0%) and regeneration (34.17% vs. 15.10%) frequencies, the differences being significant for regeneration frequencies. In the case of triticale hybrids, no significant differences between maize and I. cylindrica were observed for the three parameters of haploid induction. Embryo formation and regeneration were also observed in some of the triticale as well as triticale × wheat F₁ hybrids when hybridized with sorghum and pearl millet.     

Differential contribution of two Ppd-1 homoeoalleles to early-flowering phenotype in Nepalese and Japanese varieties of common wheat

Wheat landraces carry abundant genetic variation in heading and flowering times. Here, we studied flowering-related traits of two Nepalese varieties, KU-4770 and KU-180 and a Japanese wheat cultivar, Shiroganekomugi (SGK). These three wheat varieties showed similar flowering time in a common garden experiment. In total, five significant quantitative trait loci (QTLs) for three examined traits, the heading, flowering and maturation times, were detected using an F₂ population of SGK/KU-4770. The QTLs were found at the Ppd-1 loci on chromosomes 2B and 2D and the 2B QTL was also confirmed in another F₂ population of SGK/KU-180. The Ppd-D1 allele from SGK and the Ppd-B1 alleles from the two Nepalese varieties might be causal for early-flowering phenotype. The SGK Ppd-D1 allele contained a 2-kb deletion in the 5′ upstream region, indicating a photoperiod-insensitive Ppd-D1a allele. Real-time PCR analysis estimating the Ppd-B1 copy number revealed that the two Nepalese varieties included two intact Ppd-B1 copies, putatively resulting in photoperiod insensitivity and an early-flowering phenotype. The two photoperiod-insensitive Ppd-1 homoeoalleles could independently contribute to segregation of early-flowering individuals in the two F₂ populations. Therefore, wheat landraces are genetic resources for discovery of alleles useful for improving wheat heading or flowering times.     

Regeneration of fertile doubled haploid plants from colchicine-supplemented media in wheat anther culture

The effect of colchicine added to induction medium for the production of fertile doubled haploid plants after in‐vitro anther culture was studied in wheat, Triticum aestivum L. For this, one winter and two spring wheat varieties were used. Anther cultures of the three genotypes were treated with 0.03% colchicine for 3 days at the beginning of microspore induction. Colchicine had no significant effect on anther response and embryoid production of the genotypes examined. However, in the winter wheat genotype ‘Mv Szigma’, colchicine caused a significant reduction in microspore‐derived structures. A significant decrease was also observed in plant regeneration ability of two genotypes (‘Vergina’ and ‘Acheloos’) after colchicine treatment. In addition, a significant reduction of the albinos produced was observed in all genotypes after olchicine treatment. In contrast, the regenerants obtained from the colchicine‐supplemented induction media produced significantly higher percentages of fertile plants in all genotypes. However, the level of fertility, was significantly different among the fertile plants obtained. This, together with the observation that in the case of the winter wheat variety the colchicine treatment resulted in 100% completely fertile plants with a high seed‐setting ability indicate that there is space for further improvement of the method when it is applied to spring cultivars. Finally, the increased number of seeds per 100 plated anthers obtained from all three genotypes after colchicine treatment, clearly demonstrates that the addition of colchicine to induction medium was superior to the conventional anther culture method and it could therefore be introduced into wheat breeding programmes.     

Plant regeneration through callus initiation from mature embryo of Triticum

The behaviour of diverse Triticum genotypes in the tissue culture response of mature embryo callus was compared, and factors affecting tissue culture response were studied in this paper. Significant differences were detected in callus induction, embryogenic callus differentiation, plantlet regeneration and culture efficiency when mature embryos of 31 plants of different Triticum species were compared. These were the main wheat cultivars of the Chinese northern winter‐type wheat region and breeding lines (Triticum aestivum L.), durum wheat (Triticum durum Desf.), cultivable emmer wheat (Triticumdicoccum Schuble) and the common wheat progenitors Triticum dicoccoides and Triticum aegilopides. The genotype dependency was particularly high in tissue culture of mature embryos of these Triticum genotypes. The efficiency of induction, differentiation and regeneration of mature embryos callus was high in genotypes selected out. Mature embryo‐derived callus of HB341, TS021, SN2618, T. dicoccum, HB188, and T9817 showed better tissue culture response than the other genotypes. Plantlets can be regenerated from mature embryo‐derived callus of 31 genotypes, saving on growth facility resources and time required for the collection of other explants, and providing a solid basis for the genetic transformation and molecular plant breeding of Triticum plants.     

Mapping boron efficiency gene(s) in Brassica napus using RFLP and AFLP markers

Soil boron (B) deficiency, a world‐wide problem in agriculture, exists for more than 33 million hectares of cultivated land in China. Genetic variation exists for B‐efficiency among different Brassica napus germplasms. To identify genes controlling B efficiency, an F₂ population of B. napus was constructed from a cross between a high B‐efficiency cultivar, ‘Qingyou 10’, and a low B‐efficiency cultivar, ‘Bakow’, and then evaluated for seed yield, bolting date and maturity date under B‐deficient conditions. The ratio of high B‐efficiency to low B‐efficiency individuals fitted the expected ratio of 3:1, indicating a major gene controlling the B‐efficiency trait. The major gene was mapped in the ninth linkage group of B. napus. Genome‐wide quantitative trait loci (QTL) analyses detected one major locus near the major gene, which explained 64.0% of the phenotypic variance. At the same time, three minor loci in three linkage groups were also detected, and these minor loci individually explained 39.2%, 32.5% and 36.9%, respectively, of the phenotypic variance. A total of 11 QTLs were detected for bolting date and maturity date, some of which were associated with B‐efficiency.     

Detection of QTLs for bread‐making quality in wheat using a recombinant inbred line population

Whereas gluten fraction accounts for 30–60% of the variation in wheat bread‐making quality, there remains substantial variation determined by non‐gluten factors. The objective of this study was to detect new loci for wheat quality. The genetics of sodium dodecyl sulphate‐sedimentation volume (Ssd), grain hardness (GH), grain protein content, wet gluten content (WGC) and water absorption (Abs) in a set of 198 recombinant inbred lines derived from two commercial varieties was studied by quantitative trait loci (QTL) analysis. A genetic map based on 255 marker loci, consisting of 250 simple sequence repeat markers and five glutenin loci, Glu‐A1, Glu‐B1, Glu‐D1, Glu‐B3 and Glu‐D3, was constructed. A total of 73 QTLs were detected for all traits. A major QTL for GH was detected on chromosome 1B and its relative contribution to phenotypic variation was 27.7%. A major QTL for Abs on chromosome 5D explained more than 30% of the phenotypic variation. Variations in Ssd were explained by four kinds of genes. Some QTLs for correlated traits mapped to the same regions forming QTL clusters or indicated pleiotropic effects.     

Inheritance and QTL mapping of leaf rust resistance in the European winter wheat cultivar ‘Beaver’

Genetic studies were conducted on an European winter wheat cultivar, Beaver, to determine the mode of inheritance of leaf rust resistance at seedling and adult plant growth stages using a recombinant doubled haploid population, Beaver/Soissons. Greenhouse studies indicated the involvement of genes Lr13 and Lr26 in governing leaf rust resistance at seedling growth stages, whereas, adult plant resistance (APR) in the field with pathotypes carrying virulence individually for Lr13 and Lr26 showed trigenic inheritance for the population. Marker regression analysis of adult plant field data indicated the involvement of six significant QTLs (chromosomes 1B, 3B, 3D, 4B, 4D and 5A) in year 2005, four QTLs (1B, 3B, 4B and 5A) in 2006, and six QTLs (1A, 1B, 3B, 4A, 4B and 5A) in 2007 for reducing leaf rust severity. QTLs on chromosomes 1B, 4B and 5A were considered the most important because of their detection across years, whereas QTLs on chromosomes 1A, 3B, 3D and 4A were either inconsistent or non-significant and unexplained. Based on an association of closely linked markers with phenotypic data, putative single gene stocks were identified for each consistent QTL and crossing was initiated to develop populations segregating for each to permit fine mapping of the identified regions.     

Identification of a novel QTL for the number of spikelets per panicle using a cross between indica‐ and japonica‐type high‐yielding rice cultivars in Japan

Yield is a complex trait. To improve it, the accumulation of the favourable alleles of valuable genes is required for each yield‐related trait. In this study, we used two high‐yielding rice cultivars developed in Japan, indica‐type ‘Takanari’ and japonica‐type ‘Momiroman’, for a genetic analysis of the sink capacity‐related traits. An F₂ population showed transgressive segregation for the number of spikelets per panicle. Quantitative trait locus (QTL) analysis detected four QTLs for the trait. Two of the QTLs were most likely identical to previously cloned GN1a and APO1, and their Takanari alleles had positive effects. The Momiroman alleles of the other two QTLs had positive effects, and one of these QTLs was most likely identical to SPIKE/GPS. The QTL on the long arm of chromosome 3 appeared to be novel; it clustered with QTLs for grain length and days‐to‐heading. Substitution mapping revealed that the close linkage of QTLs caused the clustering. These results suggest that the combination of the favourable alleles of detected QTLs could lead to greater sink capacity than that of the parental cultivars.     

Mapping and validation of the quantitative trait loci for leaf stay‐green‐associated parameters in maize

Functional stay‐green is generally regarded as a desirable trait of varieties in major crops including maize. In this study, we used an F_3:4 recombinant inbred line population with 165 lines from a cross between a stay‐green inbred line (Zheng58) and a model inbred line (B73) using 211 polymorphic simple sequence repeat markers to map quantitative trait loci for three stay‐green‐associated parameters, chlorophyll content, photosystem II photochemical efficiency and stay‐green area, at maturity stage, detected a total of 23 quantitative trait loci (QTL) on nine chromosomes. Single QTL explained 3.7–13.5% of the phenotypic variance. Additionally, we validated some important stay‐green QTL using a heterogeneous inbred family approach and found that the stay‐green‐associated parameters were significantly correlated with the plant yield. This study may contribute to a better insight into the regulatory mechanism behind leaf stay‐green in maize and a novel development of elite maize varieties with delayed leaf senescence through molecular marker‐assisted selection.