Breeding Science 60: 286–292 (2010)

Note

Differential effects of tauschii genotypes on maturing-time in synthetic hexaploid

Yuki Fujiwara1), Sanae Shimada1), Shigeo Takumi2) and Koji Murai*1)

1) Department of Bioscience, Fukui Prefectural University, 4-1-1 Matsuoka-Kenjojima, Eiheiji, Yoshida, Fukui 910-1195, Japan 2) Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, Hyogo 657-8501, Japan

Bread (Triticum aestivum) is a hexaploid species with A, B and D . Therefore, most bread wheat genes are present in the as triplicated homoeologous genes (homoeologs) derived from the an- cestral A, B, and D genome diploid species. Maturing-time, which is associated with flowering-time and the grain-filling period, is one of the most important agronomic traits for wheat breeding. Here, the effects of homoeologs derived from D genome diploid species on maturing-time in bread wheat were examined in syn- thetic hexaploid wheats obtained by crossing tetraploid durum wheat T. turgidum ssp. durum cv. Langdon and three accessions of the D genome diploid species (Aegilops tauschii). After vernalization, the synthetic hexaploid wheat derived from an early-flowering D genome donor showed an early-flowering phenotype among the synthetic hexaploids, whereas the synthetic wheat derived from a late-flowering D genome donor was late-flowering among the synthetic hexaploids. This suggests that the early-flowering phenotype in hexaploid wheat is affected by the homoeolog for early-flowering in the D genome donor. In contrast, maturing-time and grain-filling period in the synthetic hexaploids did not correspond with those of the D genome donors, suggesting that these traits are controlled by the interaction between homoeologs on the A, B and D genomes in hexaploid wheat.

Key Words: maturing-time, grain-filling period, hexaploid, wheat, Triticum aestivum, Aegilops tauschii, homoeolog.

Introduction and Vrn-D1, have been shown to be located on chromo- somes 5A, 5B and 5D, respectively, of bread wheat. The A In crops such as wheat and barley, maturing-time, genome of hexaploid bread wheat came from T. urartu, the which includes flowering-time and the grain-filling period, B genome from Aegilops speltoides or another species is an important character because of its influence on adapt- classified in the Sitopsis section, and the D genome from ability to different environmental conditions. Bread wheat Ae. tauschii (Feldman 2001). As a consequence of its (Triticum aestivum, 2n = 6x = 42, genome constitution origin, the hexaploid wheat genome contains triplicated AABBDD) is grown in a wide range of environments all homoeologous genes (homoeologs) derived from the ances- over the world, and its wide adaptability results from the tral diploid species. Vrn-A1, Vrn-B1 and Vrn-D1 are the variation in maturing-time among cultivars (reviewed in homoeologs of the Vrn-1 gene. Vrn-A1 of the diploid Worland and Snape 2001). einkorn wheat T. monococcum (2n = 2x = 14, AmAm) has Many genetic studies have been performed to investigate been identified as a homolog of APETALA1/FRUITFULL of the genetic control of heading/flowering-time in wheat and Arabidopsis (Yan et al. 2003). The Vrn-1 genes of hexaploid three component factors have been identified: vernalization wheat have been identified as either WAP1 (wheat AP1) requirement, photoperiod sensitivity, and narrow-sense (Murai et al. 2003, Trevaskis et al. 2003) or TaVRT-1 earliness (earliness per se) (Yasuda and Shimoyama 1965, (Triticum aestivum vegetative to reproductive transition-1) reviewed in Murai et al. 2005). Vernalization requirement is (Danyluk et al. 2003) that are now uniformly called VRN1. concerned with the sensitivity of the to cold tempera- The photoperiod (long-day) response in wheat is determined ture for accelerating spike primordium formation. The ver- by the dominant genes Ppd-A1, Ppd-B1 and Ppd-D1, which nalization insensitivity (spring habit) genes, Vrn-A1, Vrn-B1 control sensitivity to day length and are located on chromo- somes 2A, 2B and 2D, respectively. Wheat is a quantitative Communicated by T. Komatsuda long-day plant, and short day conditions delay the heading Received May 28, 2010. Accepted August 4, 2010. time. Ppd acts to reduce the delay in heading under short day *Corresponding author (e-mail: [email protected]) conditions (Murai et al. 2003). Ppd-H1 of barley (Hordeum Diploid donor genotype affects maturing-time in hexaploid wheat 287 vulgare, 2n = 2x = 14, HH) was identified as a pseudo- sions PI476874, CGN10768, and AT80, respectively, and response regulator (PRR) that showed most similarity to the were selected for use in this study. Syn 6256 was described Arabidopsis circadian clock-associated gene, PRR7 (Turner in our previous report (Takumi et al. 2009), but the other two et al. 2005). Orthologous PRR genes were identified in the lines are unpublished. The synthetic hexaploids contain the A, B and D genomes of hexaploid wheat (Beales et al. A and B genomes from the female parent Langdon and the D 2007). Narrow-sense earliness, which corresponds to the au- genome from the respective Ae. tauschii male parents. All tonomous flowering pathway in Arabidopsis, is defined as hexaploid lines have the normal chromosome set, 2n = 42 earliness in flowering of fully vernalized grown under (data not shown), and grow normally (described here). long-day conditions. Several QTLs have been identified in barley and wheat for this characteristic (reviewed in Evaluation of agronomic characters including maturing- Cockram et al. 2007), and a major locus, Eps-1, was reported time in the field in wheat (Faricelli et al. 2009). In contrast our understanding The three synthetic hexaploid wheat lines and Langdon of the genetics of heading/flowering-time, little is known of were grown in season 2008–2009 at Fukui, Japan (latitude that for maturing-time or grain-filling period. 36N, longitude 136E). Seeds were sown on 23 Oct. 2008 in Ae. tauschii is widely distributed in , ranging from the experimental field of Fukui Prefectural University. The Turkey to China, and shows considerable genetic variation plants were thinly distributed with 10 cm spacing in a single (Dvorak et al. 1998, Matsuoka et al. 2005, Mizuno et al. row. Seven characters were observed: heading date, matur- 2010). The birthplace of hexaploid wheat is believed to lie ing date, plant height (cm), ear length (cm), spikelet number within the area comprising Transcaucasia and the southern per ear, fertility (%), and grain number per spikelet. With the coastal region of the Caspian Sea. This indicates that the exception of fertility and maturing time, these characters Ae. tauschii populations involved in the origin of hexaploid were measured on the main shoot and ear of each plant, and wheat would have had a narrow range of genetic variation averages of three plants were used for statistical analyses. compared to that present in the species as a whole. Thus, this Analyses of variance were used to identify significant differ- diploid species contains a large amount of genetic diversity ences among lines. Fertility (%) was estimated by the seed that is not represented in hexaploid wheat, and, therefore, setting rate of the first and second florets of all spikelets. offers agronomic potential for improving modern varieties of Heading date was the day when 50% of the ears of five hexaploid wheat. In this study, synthetic hexaploid wheats plants had appeared from flag leaf. Maturing date was the obtained by crossing tetraploid durum wheat and a D ge- day when 80% of the ears of five plants had turned yellow. nome diploid species (Ae. tauschii) (Takumi et al. 2009, and unpublished lines) were examined to investigate the effect of Evaluation of heading, flowering, and maturing-times using homoeologs derived from the D genome diploid species on a growth chamber maturing-time in bread wheat. This analysis showed that Seeds that sprouted after being soaked on wet filter paper maturing-time and grain-filling period in hexaploid wheat is at 20°C were sown in small soil-filled containers at a spac- affected by the D genome genotype of the diploid species. ing of 2 cm, and then vernalized at 4°C (24 h light condition) for 35 days. After vernalization, they were placed in a Materials and Methods growth chamber under a 16 h/8 h light/dark regime at 20°C (12,000 lux light intensity). For non-vernalization experi- Plant materials ment, sprouted seeds were place in a growth chamber under Three Aegilops tauschii accessions, PI476874, the same long-day condition as the vernalization experi- CGN10768 and AT80, were used as the D genome donor in ments. Three to seven plants comprised the experimental the construction of the synthetic hexaploid wheats. The sample group for each genotype. The first leaf unfolded dur- PI476874, CGN10768 and AT80 accessions originated in ing the 35 day vernalization treatment. Therefore, the num- Afghanistan, Pakistan and China, respectively. They all ber of days from unfolding of the second leaf to heading have a winter habit, and carry recessive alleles of VRN1 (DH) of the main tiller was scored for each plant. Similarly, (Vrn1) (data not shown). When grown under either vernal- the number of days from unfolding of the second leaf to ized or non-vernalized conditions, PI476874 is an early- flowering (DF) was scored for each plant. For experiments maturing accession while AT80 is late-maturing (shown in in the growth chamber, maturing-times (dates) were deter- this study). CGN10768 has an intermediate maturing-time mined in two ways. One maturing date was defined as the (shown in this study). The tetraploid durum wheat Triticum day when the ear neck of the main shoot turned yellow (ma- turgidum ssp. durum cv. Langdon was used as the AB ge- turing date 1). A second maturing date was defined as the nome donor for construction of the synthetic hexaploid day when whole ear of main shoot turned yellow (maturing wheat lines. Langdon is a spring durum wheat cultivar and is date 2). The number of days from unfolding of the second known to carry the vernalization-insensitive (spring habit) leaf to maturing date 1 (DM-1) or maturing date 2 (DM-2) gene, VRN-A1, in the A genome. Three F3 lines of synthetic were scored for each plant. Grain-filling period was defined hexaploids, Syn 6256, Syn 6277, and Syn 6239, were de- as the number of days from flowering date to maturing date rived from crosses between Langdon and Ae. tauschii acces- 1 (GF-1) or to maturing date 2 (GF-2). Differences between 288 Fujiwara, Shimada, Takumi and Murai

Table 1. Agronomic characters of three synthetic hexaploid wheat lines and the parental tetraploid cultivar Langdon grown under field condi- tionsa Grain number/ Line Heading dated Maturing dated Plant height (cm) Ear length (cm) Spikelet no./ear Fertility (%) spikelet Langdon 9, May 22, Jun 147.7 ± 1.9 8.8 ± 0.3 28.2 ± 0.6 84.5 ± 1.3 1.92 ± 0.08 Syn 6256 7, May 18, Jun 105.3 ± 0.3 ** 13.3 ± 0.4 ** 20.7 ± 0.9 ** 82.4 ± 2.4 1.70 ± 0.08 Syn 6277 7, May 18, Jun 106.0 ± 2.5 ** 13.0 ± 0.4 ** 21.0 ± 0.6 ** 79.2 ± 4.7 1.58 ± 0.09 * Syn 6239 8, May 20, Jun 103.3 ± 2.4 ** 13.3 ± 0.5 ** 21.7 ± 0.7 ** 77.0 ± 0.8 * 1.68 ± 0.02 Total F-valueb – – 117.13 ** 39.15 ** 32.87 ** 2.20 3.78 * Syn F-valuec – – 0.47 0.22 0.50 0.78 0.72 a Means and standard errors are indicated in the table. * and ** indicate significance at the 5% and 1% level, respectively, compared with Langdon. b F-test using synthetic hexaploids together with Langdon. * and ** indicate significance at the 5% and 1% level, respectively. c F-test using three synthetic hexaploids. * and ** indicate significance at the 5% and 1% level, respectively. d Field data obtained in 2009. Sowing date was 22, October, 2008. these characters among the three lines were evaluated sta- tistically using Fisher’s LSD test. The effect of vernaliza- tion was estimated as the percentage decrease in DH after treatment.

Results

Agronomic characters of synthetic hexaploid wheat lines in the field The agronomic characters of the synthetic hexaploid lines and the tetraploid parental line, Triticum turgidum ssp. durum cv. Langdon (Langdon), were examined in the field (Table 1). All of the synthetic hexaploids were significantly shorter in plant height than Langdon. Ear length in the syn- thetic hexaploids was longer than in Langdon, but spikelet number per ear was lower. Overall, grain number per spike- let in the synthetic hexaploids tended to be lower than in Langdon. The synthetic hexaploids had a speltoid-ear pheno- type (Fig. 1), indicating that the ear morphology of the tetraploid wheat was greatly altered by the addition of a D genome. There were no significant differences among the Fig.1. Ears of synthetic hexaploid wheats (Syn6256, Syn6277, and Syn6239) together with tetraploid Langdon and D genome donors hexaploid lines for these agronomic characters. However, (PI476874, CGN10768, and AT80). Bar = 5cm maturing-time (flowering-time + grain-filling period) varied in the different synthetic hexaploids: Syn 6239 matured two days later than Syn 6256 and Syn 6277. This suggests that (DH = 56.3). Under these conditions, however, the diploid the D genome from the different Ae. tauschii accessions parents were late-heading (DH = 120.8–182.2). Langdon have different effects on maturing-time in synthetic hexa- carries the spring habit gene, VRN-A1, in the A genome, and ploid wheats. shows early-heading without vernalization. In contrast, the three diploid Ae. tauschii lines do not carry a VRN dominant Heading, flowering, and maturing-time of synthetic hexa- allele (data not shown), and they show late-heading in the ploid wheat lines grown in a growth chamber absence of vernalization. Although DH in the diploid parent Table 2 shows the heading (DH), flowering (DF), and ranged from 120.8 to 182.2 days, all of the synthetic hexa- maturing (DM-1 and DM-2) times in the synthetic hexa- ploids showed early-heading, indicating that the VRN-A1 ploids and their parental lines in a growth chamber under allele derived from Langdon functioned in the synthetic long-day conditions. When the plants were not vernalized, hexaploids. Flowering times (DF) were comparable to DH in all of the synthetic hexaploids showed early-heading all of the synthetic hexaploids, but maturing-times (DM-1 (DH = 52.7–58.5), similar to the tetraploid Langdon parent and DM-2) differed. For Syn 6277, a DF of 60.0 was Diploid donor genotype affects maturing-time in hexaploid wheat 289 obtained; this was six days later than Syn 6256 with DF hills, steppe, wastelands, roadsides and humid temperate for- = 54.0. However, the timing of DM-1 and DM-2 in Syn 6277 ests (Van Slageren 1994), indicating that it has a high level (DM-1 = 96.8 and DM-2 = 105.0) were similar to those in of genetic diversity with regard to environmental responses. Syn 6256 (DM-1 = 96.0 and DM-2 = 104.3). Furthermore, in Ae. tauschii has been reported to show wide variability in Syn 6239, the DF of 55.4 was earlier than that of Syn 6277 biotic (Innes and Kerber 1994, Malik et al. 2003) and abiotic (DF = 60.0), but DM-1 and DM-2 (DM-1 = 103.4 and DM-2 stress tolerance (Gororo et al. 2002, Kurahashi et al. 2009). = 107.2) were later (Syn 6277, DM-1 = 96.8 and DM-2 Previously, our group reported that extensive flowering- = 105.0). The grain-filling periods (GF-1 and GF-2) from time variation was present among Ae. tauschii accessions flowering to maturing in Syn 6277 (GF-1 = 36.8 and GF-2 (Matsuoka et al. 2008). Early-flowering Ae. tauschii acces- = 45.2) were significantly earlier than those in the other syn- sions are widespread in the eastern part of the species range thetic hexaploids (Table 2 and Fig. 2A). This indicates that and are particularly common in the Afghanistan-Pakistan maturing-time and grain-filling period were differentially border area, indicating that the early-flowering phenotype is affected by the D genome genotype from the diploid parents. well adapted to the continental Asian climate. Ae. tauschii After vernalization for 35 days at 4°C, all lines headed has agronomic potential for improving modern varieties of earlier than those grown under non-vernalizing conditions. , but, to date, the diversity in flowering/ The relative requirement for vernalization in the different maturing-time among Ae. tauschii accessions has not been lines can be estimated from the percentage decrease in DH applied to breeding of commercial wheat varieties. For the after treatment (Table 2). A wide range of vernalization re- genetic diversity in flowering/maturing-time in Ae. tauschii quirements was found in the diploid parents (33.4–74.8%), to be of use for hexaploid wheat breeding, it is vital that the while Ae. tauschii accession PI476874 showed a strong ver- introgressed Ae. tauschii genes are expressed in the wheat nalization requirement (74.8%). However, the vernalization genome. Therefore, it is important to understand how the ge- requirement of the synthetic hexaploids ranged only from netic background of Ae. tauschii affects flowering/maturing- 41.2 to 49.1%. Although the spring habit gene VRN-A1 de- time in hexaploid wheat. rived from Langdon is assumed to function in the synthetic Previously, our group reported on the production of 27 hexaploids, the latter lines showed a higher percent decrease synthetic hexaploid wheat lines derived from interspecific in DH after vernalization than Langdon. This may be caused hybrids between T. turgidum ssp. durum cv Langdon and by the following factors: the narrow-sense earliness was Ae. tauschii accessions (Takumi et al. 2009). The synthetic shortened and the effect of VRN-A1 was depressed by the ad- hexaploid wheat lines had the same A and B genomes, ditional D genome in the synthetic hexaploids. Days to flow- which were derived from Langdon as the female parent, ering (DF), days to maturing (DM-1 and DM-2), and grain- and had a genetically variable D genome derived from an filling period (GF-1 and GF-2) were significantly different Ae. tauschii accession as the pollen parent. The synthetic among the synthetic hexaploids (Table 2 and Fig. 2B), indi- wheat lines headed and flowered on average 20–30 days cating that these characteristics were differentially affected earlier than their corresponding Ae. tauschii parents. The by the D genome genotype from the diploid parents. DF wide variations in heading and flowering-times observed ranged from 32.3 to 35.4 in the synthetic hexaploids. How- in Ae. tauschii were maintained to some extent in the hexa- ever, DM-1 ranged from 68.0 to 76.4, and DM-2 ranged ploid backgrounds of the synthetic wheat lines, although no from 70.8 to 77.0. As a result, GF-1 and GF-2 in Syn 6277 significant correlations were found between the diploid and were significantly shorter than in Syn 6239. AT80, the dip- hexaploid backgrounds (Takumi et al. 2009). In this study, loid parent of Syn 6239, showed the shortest GF-1 and GF-2 we examined heading/flowering-times in three synthetic of the three Ae. tauschii accessions, although GF-1 and GF- hexaploids together with their tetraploid and diploid parents 2 in Syn 6239 were the longest of the synthetic hexaploids. under artificial conditions and with or without vernalization These results indicate that there was no correlation between treatment (Table 2). Our results indicate that early-heading/ GF in a diploid parent and its synthetic hexaploid, suggest- flowering in synthetic hexaploids resulted from a decreased ing that GF is controlled by the interaction between ho- vernalization requirement, which was probably due to the moeologs on the A, B, and D genomes in hexaploid wheat. It effect of VRN-A1 from the tetraploid Langdon parent. Fur- is interesting that GF in the vernalized synthetic hexaploids thermore, the early-heading/flowering in synthetic hexa- was shorter than that in the non-vernalized plants, suggest- ploids are also associated with a shortened narrow-sense ing that vernalization treatment affected grain filling after earliness caused by the additional D genome. flowering by an as yet unknown mechanism. Early-maturity is one of the most important objectives of wheat breeding in Japan in order to allow harvesting before Discussion the rainy season. Maturing-time is determined by flowering- time and grain-filling period. The present study indicated Aegilops tauschii is a wild diploid wheat species that is that flowering-time in diploid Ae. tauschii is comparable to widely distributed in central Eurasia, from northern Syria that in synthetic hexaploids (Table 2). After vernalization, and Turkey to western China. It is adapted to diverse environ- the synthetic hexaploid wheat that contained a D genome ments including sandy seashore, margins of deserts, stony from an early-flowering donor showed the early-flowering 290 Fujiwara, Shimada, Takumi and Murai e 100 × (NV-V)/NV Days to heading (HD) 0.0* 49.1 0.5** 74.8 0.9** 33.4 0.9* 44.4 0.9 41.2 0.9 21.3 2.5** 60.0 ± ± ± ± ± ± ± n under long-day conditions (16 h 0.3 38.0 0.5 36.6 1.4** 27.2 1.1 38.8 1.3 41.6 1.2 42.0 2.5 37.0 ± ± ± ± ± ± ± 0.3* 35.3 1.5** 36.6 5.4** 25.2 1.7* 38.0 1.3 41.0 2.3 37.5 13.0 37.0 ± ± ± ± ± ± ± their parental cultivars grow 0.0* 70.8 1.5* 67.8 4.7** 152.8 1.9* 71.0 1.2 77.0 2.5 88.0 13.0 96.7 ared with Langdon. ± ± ± ± ± ± el, respectively. ± 0.3 68.0 1.1* 67.8 5.9** 150.8 0.9 70.3 1.0 76.4 1.4 83.5 15.1 96.7 ± ± ± ± ± ± ± the 5% and 1% lev hexaploid wheat lines with ** 55.54** 58.63** 56.50** 25.05** 24.22** 0.3* 32.8 1.2* 31.2 5.9** 125.6 0.9* 32.3 1.4 35.4 1.4 46.0 14.5 59.7 ± ± ± ± ± ± 60.31** 61.04** 59.42** 56.63** 19.08** 28.67** ± d 1% level, respectively, comp 0.5** 29.8 0.3** 30.4 1.1** 121.4 0.7 29.3 0.7 32.2 1.5 44.3 1.0** 57.7 dicate significance at ± ± ± ± ± ± ±

d 1% level, respectively. a and 1% level, respectively. ng period in three synthetic 1.7** 45.2 1.2** 30.8 1.3** 27.2 2.5 50.0 1.9 51.8 3.0 51.0 1.2** 29.9 ± ± ± ± ± ± ± dicate significance at the 5% an V) Vernalization (V) vernalization treatment 2.4 36.8 3.0** 28.5 5.3** 26.2 1.8 42.0 1.0 48.0 1.8 45.8 2.6** 27.0 n requirement). ± ± ± ± ± ± ± significance at the 5% an dicate significance at the 5% , and length of the grain-filli 3.1 105.0 3.1** 154.5 5.4** 213.0 3.5 104.3 2.2 107.2 3.3 108.5 2.8** 177.3 xaploids, and diploid parent). * ** in ± ± ± ± ± ± ± C with or without ° Non-Vernalization (N n (relative vernalizatio 2.7 96.8 2.8** 152.3 4.5** 212.0 1.0 96.0 0.5 103.4 0.5 103.3 2.9** 174.4 indicated in the table. * and ** ± ± ± ± ± ± ± 1.9 60.0 3.5** 123.8 4.7** 185.8 1.5 54.0 0.7 55.4 0.8 57.5 3.0** 147.4 4.37* 3.34 2.26 0.79 8.94** 29.37** 2.37 4.30* 11.70** 8.40** 7.59** 6.38* ± ± ± ± ± ± ± 60.12** 68.19** 53.58** 54.44** 0.72 3.10 53.59 DH DF DM-1 DM-2 GF-1 GF-2 DH DF DM-1 DM-2 GF-1 GF-2 325.80** 363.50** 174.78** 206.68** 28.94** 139.52** Days to heading, flowering, and maturing b c d 2.

Means and standard errors are F-test using all lines (Langdon, synthetic he F-test using three synthetic hexaploids. * and ** indicate F-test using three diploid parental lines. * and ** in Representing effects of vernalizatio F-value F-value F-value Syn6277 58.5 Total PI476874 120.8 AT80 182.2 Syn6256 52.7 Syn6239 54.8 Syn Langdon 56.3 Table Line CGN10768 144.1 a b c d e Diploid light/8 h dark) in a growth chamber at 20 Diploid donor genotype affects maturing-time in hexaploid wheat 291

observed for most morphological traits in synthetic hexa- ploid wheats (Takumi et al. 2009). In this study, we similarly observed no significant differences in agronomic characters in the synthetic hexaploids (Table 1), indicating that the ex- pression of D genome variation was masked. By contrast, maturing-time varied with the identity of the D genome donor. This suggests that the variation in maturing-time (flowering-time + grain-filling period) in the synthetic hexa- ploids is not caused by suppressive or buffering effects of the A and B genome from the durum parent but might result from new interactions between the A, B, and D homoeologs that occur following hexaploidization. It has been reported that gene expression patterns are stochastically and epigenet- ically altered during the generation of allopolyploid plants (reviewed in Chen 2007). In order to elucidate the causes of the variation in maturing-time and grain-filling period, it will be necessary to determine the molecular mechanisms that control these traits. In conclusion, the present findings indicate that diploid parents have differential effects on maturing-time and grain- filling period in synthetic hexaploid wheat (Fig. 2), suggest- ing that Ae. tauschii variation for these traits will be useful for hexaploid wheat breeding.

Acknowledgements

Fig. 2. Days to flowering (DF) and grain-filling period (GF-1) in three This work was supported by a Grant-in-Aid from the synthetic hexaploid wheat lines, Syn 6256, Syn 6277 and Syn 6239, Ministry of Agriculture, Forestry and Fisheries of Japan and the tetraploid parental line (Langdon) under non-vernalized (A) or (Genomics for Agricultural Innovation, TRC-1003), and vernalized conditions (B). Days to maturing (DM-1) was estimated as from the Fukui Prefectural Government. DF plus GF-1. Literature Cited phenotype among synthetic hexaploids. By contrast, syn- thetic wheat that contained a D genome from a late- Beales, J., A. Turner, S. Griffiths, J.W. Snape and D.A. Laurie (2007) flowering donor showed late-flowering among synthetic A Pseudo-Response Regulator is misexpressed in the photoperiod hexaploids. This suggests that the flowering-time genes of insensitive Ppd-D1a mutant of wheat (Triticum aestivum L.). Ae. tauschii function in the hexaploid background and affect Theor. Appl. Genet. 115: 721–733. flowering-time. Our next step will be to study the expression Chen,Z.J. (2007) Genetic and epigenetic mechanisms for gene expres- patterns in synthetic wheats of flowering-time genes, such as sion and phenotypic variation in plant polyploids. Ann. Rev. Plant Biol. 58: 377–406. VRN1 and Wheat FLOWERING LOCUS T (Shimada et al. Cockram, J., H. Jones, F.J. Leigh, D. O’Sullivan, W. Powell, D.A. Laurie 2009, ortholog of VRN3 in diploid wheat and barley reported and A.J. Greenland (2007) Control of flowering time in temperate by Yan et al. (2006)), derived from Ae. tauschii. : genes, domestication, and sustainable productivity. J. Exp. In contrast to flowering-time, maturing-time (flowering- Bot. 58: 1231–1244. time + grain-filling period) as well as grain-filling period in Danyluk, J., N.A. Kane, G. Breton, A.E. Limin, D.B. Fowler and F. the synthetic hexaploids were not correlated with those in Sarhan (2003) TaVRT-1, a putative transcription factor associated Ae. tauschii accessions (Table 2). For example, Ae. tauschii with vegetative to reproductive transition in cereals. Plant Physiol. accession AT80 has a short grain-filling period, but the syn- 132: 1849–1860. thetic line Syn 6239 derived from AT80 showed the longest Dvorak, J., M.C. Luo, Z.L. Yang and H.B. Zhang (1998) The structure grain-filling period of the synthetic hexaploids. Unlike of the Aegilops tauschii genepool and the evolution of hexaploid flowering-time, grain-filling period in the synthetic hexa- wheat. Theor. Appl. Genet. 97: 657–670. Faricelli, M.E., M. Valárik and J. Dubcovsky (2009) Control of flower- ploids was not related to that of the D genome donors, sug- ing time and spike development in cereals: the earliness per se gesting that grain-filling period is controlled by a different Eps-1 region in wheat, rice, and Brachypodium. Funct. Integr. genetic system to that of flowering-time determination, Genomics 10: 293–306. probably some interaction between homoeologs on the A, B, Feldman, M. (2001) Origin of cultivated wheat. In: Bonjean, A.P. and and D genomes. W.J. Angus (eds.) The World Wheat Book, A History of Wheat Repression of D genome variation has been commonly Breeding, Lavoisier Publishing, Paris, pp. 3–56. 292 Fujiwara, Shimada, Takumi and Murai

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