Photoperiod and vernalization gene effects in southern Australian wheat
H. A. EaglesKaren CaneHaydn KuchelG. J. HollambyNeil VallanceR. F. EastwoodN. N. GororoPeter J. Martin
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Abstract:
Photoperiod and vernalization genes are important for the optimal adaptation of wheat to different environments. Diagnostic markers are now available for Vrn-A1, Vrn-B1, Vrn-D1 and Ppd-D1, with all four genes variable in southern Australian wheat-breeding programs. To estimate the effects of these genes on days to heading we used data from 128 field experiments spanning 24 years. From an analysis of 1085 homozygous cultivars and breeding lines, allelic variation for these four genes accounted for ~45% of the genotypic variance for days to heading. In the presence of the photoperiod-insensitive allele of Ppd-D1, differences between the winter genotype and genotypes with a spring allele at one of the genes ranged from 3.5 days for Vrn-B1 to 4.9 days for Vrn-D1. Smaller differences occurred between genotypes with a spring allele at one of the Vrn genes and those with spring alleles at two of the three genes. The shortest time to heading occurred for genotypes with spring alleles at both Vrn-A1 and Vrn-D1. Differences between the photoperiod-sensitive and insensitive alleles of Ppd-D1 depended on the genotype of the vernalization genes, being greatest when three spring alleles were present (11.8 days) and least when the only spring allele was at Vrn-B1 (3.7 days). Because of these epistatic interactions, for the practical purposes of using these genes for cross prediction and marker-assisted selection we concluded that using combinations of alleles of genes simultaneously would be preferable to summing effects of individual genes. The spring alleles of the vernalization genes responded differently to the accumulation of vernalizing temperatures, with the common spring allele of Vrn-A1 showing the least response, and the spring allele of Vrn-D1 showing a response that was similar to, but less than, a winter genotype.Keywords:
Vernalization
Epistasis
Monogastric
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Flowering of Arabidopsis thaliana (L.) HEYNH., var. “Stockholm”, plants, raised from vernalized seeds, may be modified by the photoperiodic conditions or a short (1 week) exposure to high temperature (32°C) following vernalization, depending on the duration of the cold treatment. When vernalization is partial (1 to 4 weeks at 4°C), both short days (8hr light) and high temperature have a devernalizing effect, but when the cold requirement has been fully satisfied, after 5 to 6 weeks at 4°C, devernalization is no longer possible. There is no interaction between photoperiod and high temperature. Fully vernalized plant flower in both long and short days, although flowering is delayed in short days. This delay is not a photoperiodic effect, however, but may be ascribed to the decreased radiant energy available in an 8-hr photoperiod. Thus, fully vernalized Arabidopsis plants are day-neutral.
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SummarySummaryTo control the bolting of Japanese bunching onion (Allium fistulosum L.) photoperiodically, the effect of photoperiods before, during and after vernalization on flower initiation and development and the varietal differences were investigated using the two mid-season flowering cvs Kincho and Asagi-kujo, and a late-season flowering cv. Cho-etsu. A long-day photoperiod (LD, 16 h) given before vernalization inhibited flower initiation. Especially, the bolting rate of ‘Asagi-kujo’ decreased by about a half, compared with the short-day photoperiod (SD, 8 h). The interaction between the effect of night temperature (3°C, 7°C, 11°C or 15°C) and the effect of the photoperiod (SD and LD) during vernalization was also investigated. In ‘Kincho’, LD did not affect flower initiation at 3°C, but inhibited flower initiation at 7°C, 11°C and 15°C. In ‘Asagi-kujo’, flower initiation was significantly inhibited by LD under all temperature conditions. This inhibitory effect was stronger at 11°C and 15°C than at 3°C and 7°C. In ‘Cho- etsu’, LD significantly inhibited flower initiation at 3°C and 7°C, and flower initiation rarely occurred at 11°C and 15°C. In this study, generally, LD during vernalization inhibited flower initiation in all cultivars. Thus Japanese bunching onion required a short-day photoperiod in flower initiation, which was stronger in ‘Asagi-kujo’ and ‘Cho-etsu’ than in ‘Kincho’. From these results, we conclude that low temperature and a short-day photoperiod complementarily induce flower initiation in Japanese bunching onion. Varietal differences exist in the requirement of low temperature and a short-day photoperiod: the primary requirement in ‘Kincho’ is low temperature and that in ‘Asagi-kujo’ is a short-day. After flower initiation, the early stage of flower development is day-neutral, and after the floret formation stage, a long-day photoperiod promotes flower development and elongation of the seedstalk.
Vernalization
Allium fistulosum
Bolting
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We have compared the flowering response to vernalization, photoperiod, and far-red (FR) light of the Columbia (Col) and Landsberg erecta (Ler) ecotypes of Arabidopsis into which the flowering-time locus FRIGIDA (FRI) has been introgressed with that of the wild types Col, Ler, and San Feliu-2 (Sf-2). In the early-flowering parental ecotypes, Col and Ler, a large decrease in flowering time in response to vernalization was observed only under short-day conditions. However, Sf-2 and the Ler and Col genotypes containing FRI showed a strong response to vernalization when grown in either long days or short days. Although vernalization reduced the responsiveness to photoperiod, plants vernalized for more than 80 d still showed a slight photoperiod response. The effect of FRI on flowering was eliminated by 30 to 40 d of vernalization; subsequently, the response to vernalization in both long days and short days was the same in Col and Ler with or without FRI. FR-light enrichment accelerated flowering in all ecotypes and introgressed lines. However, the FR-light effect was most conspicuous in the FRI-containing plants. Saturation of the vernalization effect eliminated the effect of FR light on flowering, although vernalization did not eliminate the increase of petiole length in FR light.
Vernalization
Ecotype
Bolting
Petiole (insect anatomy)
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Influences of vernalization duration, photoperiod, forcing temperature, and plant growth regulators (PGRs) on growth and development of Oenothera fruticosa L. `Youngii-lapsley' (`Youngii-lapsley' sundrops) were determined. Young plants were vernalized at 5 °C for 0, 3, 6, 9, 12, or 15 weeks under a 9-hour photoperiod and subsequently forced in a 20 °C greenhouse under a 16-hour photoperiod. Only one plant in 2 years flowered without vernalization, while all plants flowered after receiving a vernalization treatment, regardless of its duration. Thus, O. fruticosa had a nearly obligate vernalization requirement. Time to visible bud and flower decreased by ≈1 week as vernalization duration increased from 3 to 15 weeks. All plants flowered under 10-, 12-, 13-, 14-, 16-, or 24-hour photoperiods or a 4-hour night interruption (NI) in a 20 °C greenhouse following 15-weeks vernalization at 5 °C. Time to flower decreased by ≈2 weeks, flower number decreased, and plant height increased as photoperiod increased from 10 to 16 hours. Days to flower, number of new nodes, and flower number under 24 hour and NI were similar to that of plants grown under a 16-hour photoperiod. In a separate study, plants were vernalized for 15 weeks and then forced under a 16-h photoperiod at 15.2, 18.2, 20.6, 23.8, 26.8, or 29.8 °C (average daily temperatures). Plants flowered 35 days faster at 29.8 °C but were 18 cm shorter than those grown at 15.2 °C. In addition, plants grown at 29.8 °C produced only one-sixth the number of flowers (with diameters that were 3.0 cm smaller) than plants grown at 15.2 °C. Days to visible bud and flowering were converted to rates, and base temperature (T b ) and thermal time to flowering (degree-days) were calculated as 4.4 °C and 606 °days, respectively. Effects of foliar applications of ancymidol (100 mg·L -1 ), chlormequat (1500 mg·L -1 ), paclobutrazol (30 mg·L -1 ), daminozide (5000 mg·L -1 ), and uniconazole (15 mg·L -1 ) were determined on plants vernalized for 19 weeks and then forced at 20 °C under a 16-h photoperiod. Three spray applications of uniconazole reduced plant height at first flower by 31% compared with that of nontreated controls. All other PGRs did not affect plant growth. Chemical names used: α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); (2-chloroethyl) trimethylammonium chloride (chlormequat); butanedioic acid mono-(2,2-dimethyl hydrazide) (daminozide); (2 R, 3 R+ 2 S ,3 S ) - 1-(4-chlorophenyl-4,4-dimethyl-2-[1,2,4-triazol-1-yl]) (paclobutrazol); ( E )-( S )-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ene-3-ol (uniconazole).
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Day treatment
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The interactions between vernalization and photoperiodic effects on the flowering of 12 turnip varieties were examined under controlled environment. Seedlings of all varieties bolted and flowered under a long-day condition of 24 h day-length (LD) when the germinated seeds had been pre-exposed to low temperature at 3 °C (LT) for 30 days. Under the LD condition, the ratio of flower formation of all the varieties except for 'Tennoji' significantly decreased as the duration of LT treatment was shortened to less than 7 days. With LT treatment of more than 14 days, 80 to 100% of plants in all varieties formed flower buds under LD. When the seedlings were subjected to either LT and subsequently grown under a short-day condition of 8 h day-length (SD) or LD without LT treatment, the number of plants that formed flower buds substantially decreased. Furthermore, the effect of seed vernalization was counteracted by subsequent SD conditions under which the vernalized seedlings were grown throughout the experiment. Namely, flower formation and bolting of the vernalized seedlings were significantly inhibited when the LT-treated seedlings were subsequently grown under SD. These flowering responses of turnip plants to temperature and photoperiod significantly differed among the varieties used. We have classified the turnip varieties into five groups. 'Tennoji', 'Shogoin', and 'Hakatasuwari' strongly responded to the single treatment of either LD or LT, resulting in a high ratio of flower formation (Type I), whereas either treatment hardly induced the formation of flower bud in 'Yorii', 'Hinona', 'Ohnobeni', and 'Kanamachi' (Type II). 'Ohyabu', 'Ohmi', and 'Atsumi' showed an intermediate degree of flowering ratio between the Type I and II in repsonse to either LD or LT treatment (Type III). In 'Yamauchi', LD itself did not induce flower formation of non-vernalized plants, but the LT caused a high ratio of flower formation even under SD (Type IV). By contrast, 'Narusawana' showed a substantial ratio of flower formation due to LD without LT treatment, while the seedlings treated with LT did not flower under the following SD in this variety (Type V). Thus, the flowering of turnip plants is dramatically influenced by photoperiod as well as by temperature, and the responses to the two factors significantly differ among the varieties.
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Bolting
Long day
Day treatment
Flower induction
Day length
Bud
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Coreopsis grandiflora `Sunray' has been reported to flower under long days (LD) following vernalization or short days (SD). The objectives of this study were to characterize the effective duration of vernalization and SD and to determine if photoperiod during vernalization influences flowering. Vegetative cuttings taken from stockplants developed from one seedling were rooted for 2 weeks and grown for 5 weeks. Plants were provided with a 9-hour photoperiod for 2, 4, 6, or 8 weeks or were vernalized at 5 °C under a 16-hour photoperiod for 2, 4, 6 or 8 weeks or under a 9-hour photoperiod for 2 or 8 weeks. Following treatments, plants were grown in a greenhouse at 20 °C under a 16-hour photoperiod. Control plants were grown under constant 9- or 16-hour photoperiod. Leaf development, days to first visible bud (DVB), days to first open flower (DFLW), and height and total number of flower buds at FLW were recorded. No plants flowered under continuous SD. Under continuous LD, two plants flowered on axillary shoots but only after 95 days. All vernalized and SD-treated plants flowered on both terminal and axillary shoots. Photoperiod during vernalization did not affect subsequent flowering. DFLW decreased from 56 to 42 and from 50 to 42 after 2 to 8 weeks of vernalization and SD treatments, respectively. Following 2, 4, 6, and 8 weeks of vernalization, plants had 116, 116, 132, and 204 flower buds, respectively. Plant height at FLW of all SD-treated and vernalized plants was similar. Thus, 2 weeks of 9-hour SD or vernalization at 5 °C followed by LD was sufficient for flowering of our clone of C. `Sunray', although longer durations hastened flowering and increased flower bud number.
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Herbaceous plant
Cutting
Flower induction
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Vernalization
Growing season
Vegetative reproduction
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Controlled environment studies of the effects of vernalization, photoperiod, and growing period temperatures were carried out on selected cultivars of four annual Lupinus species. All responded to both vernalization and photoperiod to varying degrees, and in at least two there were indications of an additional effect of growing period temperatures specifically on flower initiation. Flower initiation in L. angustifolius was found to be controlled mainly by its vernalization requirement, with subsidiary control by photoperiod. In L. cosentini vernalization, photoperiod, and an acceleration of initiation by high temperatures all appeared to play important roles, with critical control by photoperiod under short days. L. luteus responded strongly to both vernalization and photoperiod, but long days were able to substitute for vernalization to a marked degree. The results are discussed in the context of the ecology of lupins and the breeding of new crop cultivars.
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Miltoniopsis orchids have appealing potted-plant characteristics, including large, fragrant, and showy pansylike flowers that range from white and yellow to shades of red and purple. Scheduling orchid hybrids to flower on specific dates requires knowledge of how light and temperature regulate the flowering process. We performed experiments to determine whether a 9- or 16-h photoperiod [short day (SD) or long day (LD)] before vernalization and vernalization temperatures of 8, 11, 14, 17, 20, or 23 °C under SD or LD regulate flowering of potted Miltoniopsis orchids. Flowering of Miltoniopsis Augres `Trinity' was promoted most when plants were exposed to SD and then vernalized at 11 or 14 °C. Additional experiments were performed to determine how durations of prevernalization SD and vernalization at 14 °C influenced flowering of Miltoniopsis Augres `Trinity' and Eastern Bay `Russian'. Plants were placed under SD or LD at 20 °C for 0, 4, 8, 12, or 16 weeks and then transferred to 14 °C under SD for 8 weeks. Another set of plants was placed under SD or LD at 20 °C for 8 weeks and then transferred to 14 °C with SD for 0, 3, 6, 9, or 12 weeks. After treatments, plants were grown in a common environment at 20 °C with LD. Flowering of Miltoniopsis Augres `Trinity' was most complete and uniform (≥90%) when plants were exposed to SD for 4 or 8 weeks before 8 weeks of vernalization at 14 °C. Flowering percentage of Miltoniopsis Eastern Bay `Russian' was ≥80 regardless of prevernalization photoperiod or duration. This information could be used by greenhouse growers and orchid hobbyists to more reliably induce flowering of potted Miltoniopsis orchids.
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Long day
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