Vernalization Treatment Research Articles

Errata

The Plant JournalVolume 37, Issue 3 p. 459-460 Free Access Errata First published: 20 January 2004 https://doi.org/10.1111/j.0960-7412.2004.02021.xAboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume 36, Number 4, November 2003, pages 500–509, Logan et al. In the above article the incorrect year was given for the Fields et al. reference. It was stated as being published in 2003 when in fact it was published in 2002. The correct reference is as follows: Fields, S.D., Arana, Q., Heuser, J. and Clarke, M. (2002) Mitochondrial membrane dynamics are altered in cluA− mutants of Dictyostelium. J. Muscle Res. Cell Motil.23, 829–838. The authors apologize for this error. Volume 35, Number 5, September 2003, pages 613–623, Moon et al. In the above article Figure 7 was printed incorrectly. Below is a corrected version of the figure. The modification made is an inversion of the positions of (c) and (d). The Figure legends were also corrected. Figure 7Open in figure viewerPowerPoint Effect of vernalization on expression of FLC and SOC1 in plants containing ga1-3. (a) RNA gel blot analysis of FLC and SOC1 transcript in FRI FLC and ga1-3 FRI FLC grown under long days after 0, 2, 4, and 6 weeks of vernalization treatment. Plants were harvested for total RNA extraction when four rosette leaves were produced. (b) RNA gel blot analysis of FLC and SOC1 transcript in FRI FLC and ga1-3 FRI FLC grown under short days after 0, 2, 4, and 6 weeks of vernalization treatment. Plants were harvested for total RNA extraction when 10 rosette leaves were produced. TUB2 probe was used as a loading control. (c) Effect of vernalization on the flowering time of FRI FLC and ga1-3 FRI FLC grown under long (left) and short (right) days. Gray bars represent the plants without vernalization treatment and white bars represent the plants with vernalization. Flowering time was measured as the number of total leaves produced before flowering. Values represent the mean ± SD of at least 12 plants. (*) indicates that plants were unable to flower. (d) RNA gel blot analysis of SOC1 transcript in Ler and ga1-3 plants grown under short days after 0, 3, 6, and 9 weeks of vernalization treatment. Total RNA was isolated when 10 rosette leaves were produced. (e) Flowering time of Ler (black bar) and ga1-3 (white bar) plants grown under short days after 0, 3, 6, and 9 weeks of vernalization treatment. The authors apologize for this error. Volume 35, Number 4, August 2003, pages 465–475, Grelon et al. In the above article the authors names were inverted with the first names appearing after the surnames. Below are the author names as they should have appeared: Mathilde Grelon, Ghislaine Gendrot, Daniel Vezon, Georges Pelletier The authors and publisher apologize for this error References Logan, D.C., Scott, I. and Tobin, A.K. (2003) The genetic control of plant mitochondrial morphology and dynamics. Plant J. 34, 500– 509. Moon, J., Suh, S.-S., Lee, H., Choi, K.-R., Bong Hong, C., Paek, N.-C., Kim, S.-G. and Lee, I. (2003) The SOC1 MADS-box gene integrates vernalization and gibberellin signals for flowering in Arabidopsis. Plant J. 35, 613– 623. Mathilde, G., Ghislaine G., Daniel, V. and Georges, P. (2003) The Arabidopsis MEI1 gene encodes a protein with five BRCT domains that is involved in meiosis-specific DNA repair events independent of SPO11-induced DSBs. Plant J. 35, 465– 475. Volume37, Issue3February 2004Pages 459-460 FiguresReferencesRelatedInformation

Dwarfing effect associated with the threshability gene Q on wheat chromosome 5A

AbstractA dwarfing effect of the 44.1 cM chromosomal region between the threshability gene Q and Xfba068 on the long arm of hexaploid wheat chromosome 5A has been reported. To clarify whether Q or its adjacent region is responsible for regulating culm elongation, two precise genetic stocks of near‐isogenic lines (NIL), a single chromosome substitution line, ‘Chinese Spring’ (CS; ‘Cappelle‐Desprez’ 5A) (NIL‐Q) and a single chromosome recombinant substitution line (NIL‐q) were used. The target segment of NIL‐q included the q allele and QEet.ocs‐5A.1, an earlinessper se gene, from spelt wheat in the CS genetic background. They were grown under 16‐h day length with and/ or without vernalization treatment. Being independent of heading date, NIL‐Q showed shorter elongation in lower internodes and decreased internode differentiation in comparison with NIL‐q. The culm‐length reduction associated with Q was confirmed in the recombinant F5 population derived from the cross between NIL‐Q and NIL‐q. Vernalization promotion had a tendency to reduce this dwarfing effect.

MADS box genes control vernalization-induced flowering in cereals.

By comparing expression levels of MADS box transcription factor genes between near-isogenic winter and spring lines of bread wheat, Triticum aestivum, we have identified WAP1 as the probable candidate for the Vrn-1 gene, the major locus controlling the vernalization flowering response in wheat. WAP1 is strongly expressed in spring wheats and moderately expressed in semispring wheats, but is not expressed in winter wheat plants that have not been exposed to vernalization treatment. Vernalization promotes flowering in winter wheats and strongly induces expression of WAP1. WAP1 is located on chromosome 5 in wheat and, by synteny with other cereal genomes, is likely to be collocated with Vrn-1. These results in hexaploid bread wheat cultivars extend the conclusion made by Yan et al. [Yan, L., Loukoianov, A., Tranquilli, G., Helguera, M., Fahima, T. & Dubcovsky, J. (2003) Proc. Natl. Acad. Sci. USA 100, 6263-6268] in the diploid wheat progenitor Triticum monococcum that WAP1 (TmAP1) corresponds to the Vrn-1 gene. The barley homologue of WAP1, BM5, shows a similar pattern of expression to WAP1 and TmAP1. BM5 is not expressed in winter barleys that have not been vernalized, but as with WAP1, expression of BM5 is strongly induced by vernalization treatment. In spring barleys, the level of BM5 expression is determined by interactions between the Vrn-H1 locus and a second locus for spring habit, Vrn-H2. There is now evidence that AP1-like genes determine the time of flowering in a range of cereal and grass species.

Effect of vernalisation and 5-azacytidine on the methylation level of DNA in wheat ( Triticum aestivum L., cv. Martonvásár 15)

The aim of the research was to examine the changes occurring during vernalisation in the 5-methylcytosine (5-meC) content of the DNA in a winter wheat variety Mv 15 with a short vernalisation requirement after treatment with 5-azacytidine (5-azaC), and to determine the correlation between the quantity of 5-meC and flowering. The results indicated that both vernalisation treatment and 5-azaC, a compound causing demethylation, reduced the methylation of the DNA in the winter wheat variety. The data also proved that although the 5-azaC treatment reduced the methylation of the DNA in unvernalised plants, this in itself was not sufficient to induce flowering.

Grain and floret number in response to photoperiod during stem elongation in fully and slightly vernalized wheats

The manipulation of photoperiod sensitivity during stem elongation (terminal spikelet initiation—anthesis) has been suggested as a means to increase wheat yield potential. Nevertheless, photoperiod sensitivity and the interaction with vernalization during that phase have not been previously explored under field conditions. Thus, a field study was carried out (i) to assess whether duration of stem elongation is sensitive to photoperiod experienced only during that phase, and if so (ii) to evaluate whether vernalization interacts with this photoperiod response and (iii) to determine if altering duration of stem elongation may influence wheat yield and its components. The experiment was a factorial combination of two vernalization treatments (15 (V 15) or 50 (V 50) days at 4±1 °C and 8 h photoperiod), two photoperiod regimes during stem elongation (natural daylength in the field (NP+0) and one daylength extension of 6 h (NP+6)) and three cultivars (Buck Manantial (BM), Eureka Ferrocarril Sur (EFS), and ProINTA Puntal (PP)). The stem elongation phase responded to the actual photoperiod experienced during that phase in the three cultivars, increasing its duration with shorter photoperiod. In the vernalization-sensitive cultivars EFS and PP, plants vernalized 50 days showed greater response to photoperiod than those vernalized 15 days. In the most photoperiod-sensitive cultivar (BM), as duration of stem elongation lengthened by exposure to less inductive photoperiod, a higher number of fertile florets at anthesis was achieved leading to an increased grain number and thereby to a higher wheat yield. These results reinforce the idea that a longer duration of stem elongation may offer an alternative avenue to improve yield potential in wheat.

A VERNALIZATION MODEL IN ONION (Allium cepa L.)

Vernalization is a process required for certain plant species, among them onion (Allium cepa L.), to enter the reproductive stage, through an exposure to low, non-freezing temperatures. Currently, there is a lack of a realistic vernalization model in onion, which provides a rationale for this effort. The objective of this study was to develop a vernalization model that describes the response of development to vernalizing temperatures and to the duration of the vernalization period in onion. The temperature response of vernalization was described by a nonlinear beta function that has three coefficients (the cardinal temperatures), which were defined as 0, 10, and 16°C. The response to the duration of the vernalization period was described by a nonlinear MMF function with four coefficients (the response of unvernalized plants, the response of fully vernalized plants, the duration of the vernalization treatment when plants are half fully vernalized and a shape coefficient), which were defined as 0, 1, 30 vernalization days, and 5, respectively. The vernalization model successfully described the response of development to vernalizing temperatures and to the duration of the vernalization period of several American, European, Japanese, and Brazilian onion cultivars published in the literature, which were independent data sets.

Segregation analysis of heading traits in hexaploid wheat utilizing recombinant inbred lines.

The purpose of this study was to analyze the genetic segregation of heading traits in wheat using recombinant inbred lines (RILs) of hexaploid wheat, derived from Triticum aestivum cv. Chinese Spring and T. spelta var. duhameliamum. The population was examined under controlled environmental conditions as well as in the field. This strategy differentiated the effect of three genetic factors (vernalization requirement, photoperiod sensitivity and narrow-sense earliness) and identified their interactions. Correlation analysis showed that photoperiod sensitivity and narrow-sense earliness are critical for heading time in the field. Single-marker analysis using 322 molecular markers segregating among RIL detected a total of 38 linked markers for each genetic factor and heading in the field. In interval analysis, two Vrn genes (Vrn-B1 and Vrn-D1) and Ppd-B1 were mapped on chromosomes 5B, 5D and 2B, respectively. It was noticed that Vrn-B1 on 5B from the spelt wheat conferred a strong-spring habit equivalent to the homologous Vrn-A1. Quantitative trait locus analysis also showed that Ppd-B1 was not detected under the short-day condition without vernalization treatment, and that there were two types of genes for photoperiod sensitivity, dependent on and independent of vernalization treatment.

A Generalized Vernalization Response Function for Winter Wheat

Vernalization is a process required for certain plant species to enter the reproductive stage through an exposure to low, nonfreezing temperatures. These plant species include some fall‐planted cereals, among them winter wheat (Triticum aestivum L.). A three‐stage linear function is currently used in wheat simulation models to describe the developmental response to the duration of the vernalization treatment, expressed as effective vernalization days (VD). This function lacks generality because the value of its coefficients varies with genotype. The objective of this study was to develop a generalized nonlinear vernalization response function for winter wheat. The nonlinear vernalization function developed in this study has coefficients with biological meaning. Data of final leaf number at different VD treatments in 12 winter wheat cultivars from 19 trials, which are from published research and from a growth chamber experiment conducted as part of this study, were used as independent data for evaluating the nonlinear vernalization function. These data sets represent a wide range of winter wheat cultivars developed in different parts of the world. The generalized nonlinear vernalization function described the developmental response to VD better (RMSE = 0.032) than the three‐stage linear functions (RMSE = 0.060 for cultivar Karl 92 and RMSE = 0.129 for cultivar Arapahoe). It is concluded that the vernalization response of winter wheat can be described by a general vernalization function. This conclusion implies that a reduction in the input data requirements is possible for winter wheat simulation models.

Vernalization Response of Some Winter Wheat Cultivars (Triticum aestivum L.)

For 17 cultivars of winter wheat (Triticum aestivum L.) different vernalization and photoperiod responses were detected. The effect of photoperiod sensitivity was not significantly changed by vernalization; different vernalization responses were probably due to the presence of multiple alleles at Vrn loci. The delay in heading depended on the vernalization deficit exponentially: y = Parameter (1) + (y0 – Parameter (1)) × EXP (Parameter (2) × (x – x0)). The dependence was shown to be general and significant for the given model in all the studied cultivars. Individual regressions characterised responses of cultivars to a deficit of vernalization treatment. Cluster analysis according to the characterisation obtained (full vernalization requirement, minimum vernalization requirement, insufficient vernalization and parameters of the dependence) showed the relationships between cultivars and enabled their grouping by similar profiles of vernalization, and, possibly, of photoperiod response. In individual cultivars, an attempt was made to use the model to predict performance for some agronomic traits.

Temperature and photoperiod response of vernalization in near-isogenic lines of wheat

Vernalization, a requirement for plants to experience a period of cool conditions to accelerate flowering, is an important determinant of flowering date in winter wheat. Although recent work has provided much better quantitative descriptions of the process, questions remain about the temperature response of vernalization, and how vernalization and daylength responses interact. Hence, controlled environment studies were carried out to quantify the response of vernalization rate to temperature for two near-isogenic lines of the wheat cultivar Batten, and to determine the effects of photoperiod during vernalization. The lines differed in vernalization-sensitivity, with Spring Batten (SB) being essentially vernalization-insensitive and Winter Batten (WB) being strongly vernalization responsive. Vernalization treatments were 1 °C (in darkness), and 5, 8, and 11 °C under both 16 and 8 h photoperiods for treatment durations of up to 12 weeks. A 25/20 °C, 8 h photoperiod treatment was included to test for short day vernalization. Post-treatment conditions for all treatments were 25/20 °C with 16 h photoperiod. Plants were sampled for dissection at intervals during the treatment and post-treatment period, recording leaf stage and cumulative primordium number until the flag leaf could be distinguished. Unvernalized WB flowered with 19 leaves, reducing to a minimum of 8.1 leaves when fully vernalized by the 5 °C/16 h treatment. The progress of vernalization was monitored through both changes in the pattern of primordium initiation at the shoot apex and changes in the final number of leaves initiated. Based on the duration to saturation of the vernalization response, the rate of vernalization under 16 h photoperiods increased linearly from 1 to 8 °C then declined again to a projected zero rate at 16 °C. The vernalization rate under 8 h photoperiods was greater than the rate at 16 h photoperiods for all temperatures, with a maximum rate at 8 °C. The existence of a short day vernalization response at 25/20 °C meant that the vernalization rate under 8 h photoperiods declined only slightly between 8 and 22 °C. In all cases, a significant lag period preceded any response to vernalization, ranging from 6 days in the 25/20 °C, 8 h treatment to 45 days in the 1 °C treatment. The work reported here suggests that the recently developed framework for describing vernalization is sound, but the details may need modification.

Plant regeneration from embryogenic cell suspension cultures of Lolium temulentum

Lolium temulentum L. (Darnel ryegrass) is a self-fertile and diploid grass species with a relatively short life cycle. We propose to use L. temulentum as a model system for genetic manipulation studies in forage and turf grasses, since most of the important grasses are outcrossing, require vernalization to flower, and in some cases are polyploid. As the first step to develop an efficient regeneration and transformation system, we performed a large-scale genotype screening for tissue culture responses using 46 L. temulentum accessions. Embryogenic callus formation frequency ranged from <1% to 11% across all accessions tested. Embryogenic calluses of a few responsive accessions were used to establish cell suspension cultures. The regeneration frequency of green plantlets from the established cell suspension ranged from 15% to 39%. After transferring the regenerants to the greenhouse, fertile plants were readily obtained without any vernalization treatment. This efficient plant regeneration system is being used for genetic transformation studies. With the development of genomics approaches for the improvement of forage and turf grasses, L. temulentum could serve as a model system for testing gene functions.

Mapping of a thermo-sensitive earliness per se gene on Triticum monococcum chromosome 1A(m).

An earliness per se gene, designated Eps-A(m) 1, was mapped in diploid wheat in F(2) and single-seed descent mapping populations from the cross between cultivated (DV92) and wild (G3116) Triticum monococcum accessions. A QTL with a peak on RFLP loci Xcdo393 and Xwg241, the most distal markers on the long arm of chromosome 1A(m), explained 47% of the variation in heading date (LOD score 8.3). Progeny tests for the two F(2:3) families with critical recombination events between Xcdo393 and Xwg241 showed that the gene was distal to Xcdo393 and linked to Xwg241. Progeny tests and replicated experiments with line #3 suggested that Eps-A(m) 1 was distal to Xwg241. This gene showed a large effect on heading date in the controlled environment experiments, and a smaller, but significant, effect under natural conditions. Eps-A(m) 1 showed significant epistatic interactions with photoperiod and vernalization treatments, suggesting that the different classes of genes affecting heading date interact as part of a complex network that controls the timing of flowering induction. Besides its interactions with other genes affecting heading date, Eps-A(m) 1 showed a significant interaction with temperature. The effect of temperature was larger in plants carrying the DV92 allele for late flowering than in those carrying the G3116 allele for early flowering. Average differences in heading date between the experiments performed at 16 degrees C and 23 degrees C were approximately 11 days ( P < 0.001) for the lines carrying the Eps-A(m) 1 allele for early flowering but approximately 50 days ( P < 0.0001) for the lines carrying the allele for late flowering. The large differences in heading time (average 80 days) observed between plants carrying the G3116 and DV92 alleles when grown at 16 degrees C, suggest that it would be possible to produce very detailed maps for this gene to facilitate its future positional cloning.

Vernalization, photoperiod and GA3 interact to affect flowering of Japanese radish (Raphanus sativus Chinese Radish Jumbo Scarlet)

Raphanus sativus L. Chinese Radish Jumbo Scarlet has characteristics that make it an excellent plant model for vernalization studies. This study further characterizes flower induction of R. sativus Chinese Radish Jumbo Scarlet. Seed were imbibed in distilled water containing 0, 10-5 M or 10-3 M GA3 for 24 h and were then exposed to 6 +/- 0.5 degrees C (vernalized) for 0, 2, 4, 6, or 8 days. Seedlings were then grown under a short- (8 h) or long-day photoperiod (8 h with or without a 4-h night interruption; 2200-0200 h). Of unvernalized plants grown under long- and short-day conditions, 45 and 3% flowered, respectively. Saturation of the vernalization response occurred after a 4- or 8-day vernalization treatment when plants were placed under long- or short-days, respectively. Basal leaf number and days to anthesis decreased when seeds were cooled for 2 or 4 days and were imbibed with 10-3 M GA3 compared to distilled water only. These data indicate that R. sativus Chinese Jumbo Scarlet has principally an obligate vernalization requirement when grown under short-days. GA3 application only facilitated flowering when the length of the vernalization treatment was marginal. Taken together, these data support the use of this plant as a model plant for identifying vernalization responses under short-day conditions.

Genomic regions controlling vernalization and photoperiod responses in oat.

Oat genotypes vary for photoperiod and vernalization responses. Vernalization often promotes earlier flowering in fall-sown but not spring-sown cultivars. Longer photoperiods also promote earlier flowering, and the response to longer photoperiods tends to be greater in cultivars from higher latitudes. To investigate the genetic basis of photoperiod and vernalization responses in oat, we mapped QTLs for flowering time under four combinations of photoperiod and vernalization treatments in the Ogle x TAM O-301 mapping population in growth chambers. We also mapped QTLs for flowering time in early spring and late-spring field plantings to determine the genetic basis of response to early spring planting in oat. Three major flowering-time QTLs (on linkage groups OT8, OT31 and OT32) were detected in most conditions. QTLs with smaller effects on flowering were less-consistently observed among treatments. Both vernalization-sensitive and insensitive QTLs were discovered. Longer photoperiod or vernalization alone tended to decrease the effects of flowering-time QTLs. Applied together, longer photoperiod and vernalization interacted synergistically, often on the same genomic regions. Earlier spring planting conferred an attenuated vernalization treatment on seeds. The major flowering-time QTLs mapped in this study matched those mapped previously in the Kanota x Ogle oat mapping population. Between these two studies, we found a concordance of flowering-time QTLs, segregation distortion, and complex genetic linkages. These effects may all be related to chromosomal rearrangements in hexaploid oat. Comparative mapping between oat and other grasses will facilitate molecular analysis of vernalization response in oat.

Genes responding to vernalization in hexaploid wheat.

Genotype-specific gene expression in response to vernalization in common wheat was examined by the differential display method. Two near-isogenic lines of Vrn-A1 ( Vrn-A1 for the spring type and vrn-A1 for the winter type) were treated by vernalization of developing embryos in detached-ear cultures. This treatment was effective to promote vrn-A1 genotypes to head at a time equivalent to that of Vrn-A1. Differential cDNA fragments were isolated by the RT-PCR method from embryos subjected to vernalization treatments for 2- and 4-weeks at DAP10 and DAP20 stages, respectively. Among 110 differential cDNA fragments isolated, 48 were examined for their chromosomal locations and designated as wec ( wheat- embryo cold treatment) genes. Seven wec genes showed genotype-specific expression in response to vernalization. The statistical analysis utilizing two recombinant inbred lines showed that four wec genes were significantly associated with heading factors.

Vernalization and photoperiod responses in wheat pre-flowering reproductive phases

It has been established that photoperiod influences the rate of wheat development well beyond the end of the vegetative phase. Conversely, vernalization effects are still assumed to be mainly during the vegetative phase. The aim of the study was to assess the effects of different combinations of vernalization and photoperiods on the developmental characteristics of wheat pre-flowering reproductive phases under field conditions. For this purpose, three high yielding cultivars (ProINTA Puntal, ProINTA Super and Klein Pegaso) were subjected to two vernalization treatments (unvernalized (V 0) and vernalized during 56 days in a cool chamber (V 56)) and four photoperiod regimes. The photoperiod treatments consisted of the natural photoperiod of the season (NP+0) and daylength extensions over that of 2 (NP+2), 4 (NP+4), and 6 (NP+6) hours. Photoperiod influenced the duration of early (collar—first node detectable) and late (first node detectable—heading) pre-flowering reproductive phases, reducing their durations as photoperiod increased. When cultivars with strong vernalization response (ProINTA Puntal and ProINTA Super) were not vernalized, duration of the early and late pre-flowering reproductive phases increased and the rate of spikelet initiation decreased. Thus, when vernalization requirements were not satisfied, the spikelet initiation rate was even slower than the leaf initiation rate (both expressed in a thermal time base). Results showed significant interactions between photoperiod and vernalization (vegetative phase), or clear, though non-significant, trends to interactive effects (late pre-flowering reproductive phase). Thus, the length of vegetative and late pre-flowering reproductive phases changed in response to photoperiod depending on the level of satisfaction of the vernalization requirements. The relationship between the cumulative number of leaves on the main stem and thermal time fitted a bi-linear model whenever the final leaf number (LN f) was large, e.g. when photoperiod was not extended or vernalization requirements not satisfied. Thus, responses during the pre-flowering reproductive phases were accompanied by an increased phyllochron for leaves emerging after the first 7–8 leaves. This study demonstrated with field grown plants that the length of the late pre-flowering reproductive phase in wheat is sensitive to photoperiod and that the response to this environmental factor could be changed by the level of satisfaction of the vernalization requirements.

Existence of homologous sequences corresponding to cDNA of the ver gene in diverse higher plant species.

The presence of DNA homologues corresponding to verc203 (vernalization-related cDNA clone) was investigated by molecular hybridization techniques. The genes were detected in 16 plant species that cover 12 subclasses of the Takhtajan system of angiosperms classification including diverse model species. The results of Southern blot analysis showed a low copy number of this gene existed in rice, wheat, barley and Arabidopsis. The hybridization result of PCR products demonstrated the conservation of the gene corresponding to ver203 in diverse plants. The phylogenetic tree of the ver203 gene in tested plants was supported by evolution relationship of species. The ver203 gene expressed in a vernalized plumule winter wheat, instead of the root. And the endosperm before the treatment was essential for the ver203 expression during vernalization in wheat. In Arabidopsis thaliana, the pattern of expression showed that the gene corresponding to ver203 was expressed at low temperature for 14 days. Gibberellin (GA3) may accelerate the expression of ver203 gene in Arabidopsis exposed to low temperature. However, it could not replace vernalization treatment to initiate the gene expression.

The effect of day length, vernalization and DNA demethylation on the flowering time in Arabidopsis thaliana

We studied the effect of three factors on the induction of flowering in Arabidopsis thaliana, i.e. vernalization, day length and DNA demethylation. Seven natural late flowering genotypes and 13 late flowering mutants were used in the experiments. The effect of the vernalization and the short day (SD) was uniform in all genotypes used, resulting in shortening (vernalization) or extension of the period before the appearance of the first flower primordia. On the other hand, the effect of the demethylating agent (5‐azacytidine [5‐azaC]) was not uniform in the genotypes used. In all natural late genotypes (except Lu‐1), the shortening of the flowering time (FT) after 5‐azaC treatment was observed. On the contrary, only five mutants –dl, pm, M63, M73 and fca‐1– showed a shortening of the FT, while in the majority of the late flowering mutants, no significant response (earlier flowering) was found. The different response to the vernalization and demethylation treatment in late flowering mutants shows the possibility of two different pathways leading to the flowering, both of which are regulated by DNA demethylation. The different response of natural and induced late flowering genotypes after 5‐azaC treatment shows that genes that play a role in flower development are of a different nature.

Growth and Development of Oenothera fruticosa Is Influenced by Vernalization Duration, Photoperiod, Forcing Temperature, and Plant Growth Regulators

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 (Tb) 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); (2R,3R+2S,3S)-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).

Early Heading Mutants of T. monococcum and Ae. squarrosa, A- and D-Genome Ancestral Species of Hexaploid Wheat.

Two induced mutants for early heading in diploid species of Triticum monococcum and Aegilops squarrosa, A- and D-genome ancestral species common to common wheat, were analyzed for the genetic behavior of the heading trait. The T. monococcum mutant headed earlier than its wild type under the long-day condition with vernalization treatment, whereas the Ae. squarrosa mutant headed under the short-day condition without any difference from the long-day one. These results indicate that the former is a mutant for narrow-sense earliness, and the latter, for photoperiod sensitivity. Earliness of both mutants was found to be controlled by a recessive gene. These early-heading mutants could be useful sources for the breeding of heading earliness of common wheat, as well as for genetic analysis for the determination of heading time.