Vernalization Time Research Articles

A premature stop codon in BrFLC2 transcript results in early flowering in oilseed-type Brassica rapa plants

Nonsense-mediated mRNA decay (NMD)-mediated degradation of BrFLC2 transcripts is the main cause of rapid flowering of oilseed-type B. rapa 'LP08' plants. Many Brassica species require vernalization (long-term winter-like cooling) for transition to the reproductive stage. In the past several decades, scientific efforts have been made to discern the molecular mechanisms underlying vernalization in many species. Thus, to identify the key regulators required for vernalization in Brassica rapa L., we constructed a linkage map composed of 7833 single nucleotide polymorphism markers using the late-flowering Chinese cabbage (B. rapa L. ssp. pekinensis) inbred line 'Chiifu' and the early-flowering yellow sarson (B. rapa L. ssp. trilocularis) line 'LP08' and identified a single major QTL on the upper-arm of the chromosome A02. In addition, we compared the transcriptomes of the lines 'Chiifu' and 'LP08' at five vernalization time points, including both non-vernalized and post-vernalization conditions. We observed that BrFLC2 was significantly downregulated in the early flowering 'LP08' and had two deletion sites (one at 4th exon and the other at 3' downstream region) around the BrFLC2 genomic region compared with the BrFLC2 genomic region in 'Chiifu'. Large deletion at 3' downstream region did not significantly affect transcription of both sense BrFLC2 transcript and antisense transcript, BrFLC2as along vernalization time course. However, the other deletion at 4th exon of BrFLC2 resulted in the generation of premature stop codon in BrFLC2 transcript in LP08 line. Cycloheximide treatment of LP08 line showed the de-repressed level of BrFLC2 in LP08, suggesting that low transcript level of BrFLC2 in LP08 might be caused by nonsense-mediated mRNA decay removing the nonsense transcript of BrFLC2. Collectively, this study provides a better understanding of the molecular mechanisms underlying floral transition in B. rapa.

Comprehensive speed breeding: a high-throughput and rapid generation system for long-day crops.

Breeding cycle time largely determines the efficiency of crop genetic improvement. To accelerate the generation progress, Watson et al. (2018) proposed a concept of 'speed breeding (SB)' by extending the photoperiod and increasing the light intensity during plant growth. However, there have been few reports on the successful application of SB in semi-winter and winter long-day crops. Here, we propose a comprehensive speed breeding (CSB) system for the rapid generation and high-throughput culture of long-day crops, which can accomplish 4.5 generations for both semi-winter canola and winter wheat per year. With the aid of extra far-red light, three and 5.5 generations can be accomplished for the typical winter and semi-winter type canola. CSB also exhibits high efficiency in spring type canola, and can achieve up to 6.5 and 5.5 generations with or without extra far-red light, respectively. This strategy is expected to greatly accelerate gene pyramiding of superior alleles, screening of recombinants for QTL mapping and functional genomics research by rapid purification of multiple mutated alleles.

Variation in seasonal timing traits and life history along a latitudinal transect in Mimulus ringens.

Seasonal timing traits are commonly under recurrent, spatially variable selection, and are therefore predicted to exhibit clinal variation. Temperate perennial plants often require vernalization to prompt growth and reproduction; however, little is known about whether vernalization requirements change across the range of a broadly distributed species. We performed a critical vernalization duration study in Mimulus ringens, coupled with population genomic analysis. Plants from eight populations spanning the latitudinal range were exposed to varying durations of 4°C vernalization between 0 and 56days, and flowering response was assessed. RADSeq was also performed to generate 1179 polymorphic SNPs, which were used to examine population structure. We found unexpected life history variation, with some populations lacking vernalization requirement. Population genomic analyses show that these life history variants are highly divergent from perennials, potentially revealing a cryptic species. For perennial populations, minimum vernalization time was surprisingly consistent. However, once vernalized, northern populations flowered almost 3weeks faster than southern. Furthermore, southern populations exhibited sensitivity to vernalization times beyond flowering competency, suggesting an ability to respond adaptively to different lengths of winter. Mimulus ringens, therefore, reveals evidence of clinal variation, and provides opportunities for future studies addressing mechanistic and ecological hypotheses both within and between incipient species.

Temporal Expression Pattern of Bolting-Related Genes During Vernalization in Sugar Beet

To screen candidate marker genes implicated in vernalization, bolting-related agronomic traits and the expression of genes homologous to the bolting and flowering-related genes in Arabidopsis thaliana were investigated in KWS9147 during 16-week (w) chilling. Bolting-related agronomic traits showed that less than 10-w chilling was not sufficient for bolting. A transitional period was determined between 10 and 14 weeks when vernalization time was enough for bolting in some seedlings. After 14-w chilling, nearly all seedlings were well vernalized. At the transcriptional level, the expression of 19 candidate genes was significantly changed in response to chilling (change fold > 2 and P value < 0.05). In particular, three genes (BvGI, BvBTC1 and BvFVE1) were notable, as their expression continuously increased or decreased during 8–16-w chilling, when BI and BD were significantly changed. On the basis of correlation analysis, a co-expression network containing two modules was constructed. BvGI, BvBTC1 and BvFVE1 were located at the centre of the first module, which co-expressed with the other 3 photoperiodic genes. In the second module, BvFT1 and BvFT2 were associated with BvLHY, BvGATA22 and BvFVE2. Our study on the temporal expression pattern of bolting and flowering-related genes during vernalization provides valuable information for preliminary screening of key regulators and may facilitate the future molecular breeding of vernalization-insensitive varieties.

Molecular cloning and functional analysis of a cold-regulated gene Wcor18 in wheat

To explore the function of COR gene in wheat, Wcor18 was cloned from wheat cultivar Jing 841. Expression level of Wcor18 increased with vernalization time prolongation. The full length of Wcor18 gene is 498 bp and encodes 165 amino acids. The predicted Wcor18 protein is a type of unstable hydrophilic protein and is prone to be hydrolyzed and to be oxidized. Gene structure analysis and phylogenetic tree analysis showed Wcor18 gene contains two exons and coding proteins are quite conservative among the donor ancestors of common wheat. Wcor18 can quickly respond to low temperature, high salt, drought, and ABA stresses at wheat seedling stage. The highly expression of Wcor18 gene under the − 15 °C and the rapid response of Wcor18 gene under several stress conditions indicated that the gene may play many roles in stress response of wheat.

Temporal Aspects of Vernalization and Flowering in Long-day Storage Onion

Vernalization is an important step for floral initiation in onion (Allium cepa), but our understanding of the minimum vernalization time for long-day storage onions to gain floral competence is limited. A series of time course experiments were conducted over 4 years to determine the effects of vernalization time on sprouting, scape emergence, and flowering in ‘Cortland’, ‘Sherman’, and CUDH2107. We found an endodormancy period is present in the bulbs of these cultivars that lasts for 8 to 10 weeks. In addition, these three accessions achieve optimum uniform scape emergence after chilling for 14 weeks at 10 °C. On average, when bulbs were chilled for 14 weeks, it took 96.8 ± 15.6 days from planting to flowering in all accessions evaluated. As storage duration under vernalizing temperatures increases, the time to sprouting, scape emergence, and flowering decrease. Furthermore, the variance in time from sprouting to scape emergence was greatly reduced between 10 and 12 weeks of storage for ‘Cortland’ and CUDH2107, and between 12 and 14 weeks for ‘Sherman’. After 10 weeks of chilling, each additional week of storage resulted in an average decrease in time to flowering of 4.1%. We also observed large percentages of bulbs flowering without receiving any vernalization. This observation supports our finding that the relationship between vernalization and flowering in long-day storage onion is facultative rather than obligate. These findings help define the relationship between dormancy, vernalization, and flowering in long-day storage onion.

Produção de alho submetido a períodos de vernalização e épocas de plantio em região de clima semiárido

RESUMO Com o objetivo de avaliar a produção de alho nobre submetido a períodos de vernalização e épocas de plantio, realizou-se um experimento em Baraúna-RN, de maio a outubro de 2012. Os tratamentos foram dispostos no esquema de parcelas subdivididas, delineamento experimental de blocos casualizados completos, com três repetições. Nas parcelas foram alocadas as épocas de plantio (22 de maio, 5 de junho e 23 de junho), e nas subparcelas os períodos de vernalização pré-plantio do alho-semente (4±1°C durante 50, 55, 60, 65 e 70 dias). Foram avaliados comprimento de plantas, número de folhas, ciclo, estande final, massa média de bulbos, percentagem de plantas com bulbos, produtividade total de bulbos, classificação dos bulbos, número de bulbilhos por bulbo e classificação dos bulbilhos. O plantio em 22 de maio proporcionou maiores comprimento de plantas, número de folhas, estande final e massa média de bulbos; o ciclo decresceu com o tempo de vernalização; houve formação de bulbos com diferenciação de bulbilhos em todos os tratamentos sem, entretanto, haver ocorrência de plantas com superbrotamento; a produtividade total de bulbos aumentou com o tempo de vernalização de até 63 dias nos plantios em 22 de maio e 23 de junho, com médias de 5,20 e 3,85 t/ha; a combinação entre o plantio em 22 de maio e 65 dias de vernalização, foi a que proporcionou maior número de bulbilhos por bulbo e maior percentual de bulbos comerciais, distribuídos nas classes 3, 4 e 5. Esses resultados evidenciam ser possível o cultivo de alho nobre na região de Mossoró-RN utilizando o processo de frigorificação do alho-planta.

Physiological and molecular characterization of two inbred radish lines with different bolting times

The radish (Raphanus sativus L.) is an important Brassicaceae root vegetable crop worldwide. Several studies have been conducted concerning radish breeding. There are major challenges to prevent premature bolting in spring plantings. Here, we performed the characterization of two inbred radish lines which vary in bolting time. “Late bolting radish” (NH-JS1) and “early bolting radish” (NH-JS2) were generated by a conventional breeding approach. The two inbred lines showed different bolting phenotypes depending on vernalization time at 4°C. NH-JS1, the late bolting radish, was less sensitive to cold treatment and the less sensitivity was inversely proportional to the duration of the vernalization. We also measured gene expression levels of the major bolting time related genes in the NH-JS1 and NH-JS2 lines. RsFLC1 plays a central role in the timing of flowering initiation. It is a strong repressor and it’s transcript is highly expressed in NH-JS1 compared to NH-JS2 under no treatment and vernalization conditions. RsFRI, a positive regulator of RsFLC, is also highly expressed in NH-JS1 compared to NH-JS2 regardless of vernalization. In contrast, RsSOC1, suppressed by FLC as a floral integrator gene, showed the most difference, a 5-fold increase, between NH-JS1 and NH-JS2 under vernalization conditions. From these results, we conclude that NH-JS1 showed a late flowering phenotype after cold treatment due to the expression differences of flowering time regulator genes rather than difference sensitivity to cold. These results may be useful to understand the control mechanisms of flowering time and may help identify molecular markers for selecting late bolting trait in radish.

ANALYSIS OF GENOMIC DNA METHYLATION AND GENE EXPRESSION IN CHINESE CABBAGE (Brassica rapa L. ssp. pekinensis) AFTER CONTINUOUS SEEDLING BREEDING.

Vernalization plays a key role in the bolting and flowering of Chinese cabbage (Brassica rapa L. ssp. pekinensis). Plants can switch from vegetative to reproductive growth and then bolt and flower under low temperature induction. The economic benefits of Chinese cabbage will decline significantly when the bolting happens before the vegetative body fully grows due to a lack of the edible value. It was found that continuous seedling breeding reduced the heading of Chinese cabbage and led to bolt and flower more easily. In the present study, two inbred lines, termed A161 and A105, were used as experiment materials. These two lines were subjected to vernalization and formed four types: seeds-seedling breeding once, seedling breeding twice, seedling breeding thrice and normal type. Differences in plant phenotype were compared. DNA methylation analysis was performed based on MSAP method. The differential fragments were cloned and analyzed by qPCR. Results showed that plants after seedling breeding thrice had a loosen heading leaves, elongated center axis and were easier to bolt and flower. It is suggested that continuous seedling breeding had a weaker winterness. It was observed that genome methylation level decreased with increasing generation. Four differential genes were identified, short for BraAPC1, BraEMP3, BraUBC26, and BraAL5. Fluorescent qPCR analysis showed that expression of four genes varied at different reproduction modes and different vernalization time. It is indicated that these genes might be involve in the development and regulation of bolting and flowering of plants. Herein, the molecular mechanism that continuous seedling breeding caused weaker winterness was analyzed preliminarily. It plays an important guiding significance for Chinese cabbage breeding.

The influence of vernalization time and day length on flower induction of radish (Raphanus sativus L.) under controlled and field conditions

This research was carried out to identify an alternative model plant for the study of vernalization among the cultivars that are commonly grown in Turkey and the influence of vernalization and day length on the flowering of radishes (Raphanus sativus L.) under controlled and field conditions throughout 2003, 2004, and 2005. In this study, 6 radish cultivars (Raphanus sativus L. cvs. 'Siyah,' 'Beyaz,' 'Antep,' 'İri Kırmızı,' 'Red Cherry F_1,' and 'Cherry Belle') were used in the laboratory and field experiments as plant material. Under the controlled conditions, 2 day length periods (8 and 16 h light) and 5 vernalization times (0, 5, 10, 15, and 20 days at 5 °C) were studied as the main factors. Under the field conditions, the day length and the changes in vernalization times were provided by different sowing dates. It was determined that flowering did not occur when the vernalization time was less than 15 days during both the long days (LD) and short days (SD) for Siyah. All the same, it was determined that except for Siyah, other cultivars could not flower without being vernalized during SD. Besides this, it was determined that under the field conditions, different sowing dates had an impact on flowering rates. Contrastingly, in early sowings of Siyah, all cultivars showed flowering of up to 88.72%. The study reveals that Antep, Beyaz, İri Kırmızı, Red Cherry F_1, and Cherry Belle have a facultative vernalization response; cold exposure is not required for flowering, but flowering can occur more rapidly after cold treatment. Siyah, in contrast, has an obligate requirement for cold treatment and thus cannot flower without prior cold exposure.

Shasta Daisy Cultivars Respond Differently to Photoperiod and Vernalization

Abstract Inconsistencies have been reported in the role of vernalization and photoperiod on growth and flowering of Leucanthemum x superbum Bergmans ex J. Ingram cultivars. Five cultivars were used to determine the effects of vernalization and photoperiod on days to flower, shoot height, growth index, flower shoot number, and quality rating. Plants received 0, 3, 6, 9, or 12 weeks of vernalization time (VER) at 4.4C (40F) and afterward were placed under either natural short days (SD) or night-interrupted lighting (NIL) in a greenhouse. ‘Becky’ showed an obligate requirement for NIL to flower with 100% of plants flowering under NIL and 0% of plants flowering under SD regardless of VER. Vernalization for 6 weeks before NIL increased shoot height, growth index, flower shoot number, and quality rating but the fewest days to flower occurred after 12 weeks of VER. ‘Silver Princess’, ‘Snow Cap’, ‘Snow Lady’, and ‘Summer Snowball’ showed a facultative requirement for NIL to flower. Plants under NIL flowered earlier, were larger, had more flower shoots, and had a higher overall quality rating than plants under SD. Shoot height and growth index were highest under NIL after 3 and 6 weeks of VER, flower shoot number was highest after 3 to 9 weeks of VER, but days to flower was least after 12 weeks of VER. Therefore, NIL after 3 or 6 weeks of VER would maximize plant size and quality for practical application in the cultivars studied but result in more DTF when compared to 12 weeks of VER.

Vernalização do alho para cultivo in vitro

Com o objetivo de avaliar o período de vernalização sobre a incidência do índice de pseudoperfilhamento em plantas de alho (Allium sativum L.) cultivadas in vitro, visando maior multiplicação, foi conduzido este experimento em laboratório da UFLA (MG). Utilizou-se o delineamento inteiramente casualizado com seis períodos de vernalização (40; 50; 60; 70; 80 e 90 dias) em câmara frigorífica a 5±2°C, com quatro repetições, utilizando-se a cultivar Roxo Pérola de Caçador. O tratamento com 90 dias de vernalização foi o que apresentou os melhores resultados para as variáveis bulbo/meristema/tubo, massa fresca total das plantas e dos bulbos com 1,81 bulbo/meristema/tubo, 235,32 mg plantas-1 e 110,51 mg bulbo-1, respectivamente. A massa fresca media por bulbo obtida não evidenciou diferenças significativas entre os tratamentos, no entanto, o tratamento com 90 dias de vernalização (58,68 mg bulbo-1) apresentou-se com uma produção de bulbos 79,29% superior ao tratamento com 60 dias de vernalização, que demonstrou o pior resultado.

A model plant for vernalization studies

Vernalization requirements of Raphanus sativus L. ‘Early 40 Days’, ‘Chinese Radish Jumbo Scarlet’, ‘Everest’, and ‘Minowase Early Long White’ were studied to determine their potential as model plants for vernalization studies. Leaf number below the inflorescence and days to anthesis decreased as vernalization time increased from 0 to 15 days at 6.5°C for all cultivars. ‘Early 40 Days’, ‘Everest’, and ‘Minowase Early Long White’ flowered but ‘Chinese Radish Jumbo Scarlet’ did not flower under long-day-conditions (inductive) at 18°C without vernalization, i.e. ‘Chinese Radish Jumbo Scarlet’ has an obligate vernalization requirement. ‘Chinese Radish Jumbo Scarlet’ was completely vernalized in 5–10 days. Use of ‘Chinese Radish Jumbo Scarlet’ as a model plant for vernalization studies is discussed.

The Effect of Post-veneralization Temperature on Seedstalk Elongation and Flowering in Carrots1

Abstract Seedstalk height of carrot (Daucus carota L.) was reduced as the post-vernalization temperature increased from 15/21° to 27/32°C (night/day) with no significant effect on flowering and seed formation. Seedstalks of ‘Royal Chantenay ’ carrot were most affected by the high temperatures and ‘Scarlet Nantes’ were the least affected while ‘Danvers 126’ was intermediate. Few plants had macroscopic seedstalk development 6 weeks after vernalization although the temperature during this period had a permanent influence on ultimate seedstalk height. Carrots grown at 27/32° during the initial 6 weeks following vernalization and then transferred to the optimum 15/21° grew no taller than plants held at 27/32°. Vernalization temperatures of 0°, 5°, and 10° for 10 weeks did not affect the percentage of plants flowered, time of bolting, or rate of seedstalk elongation. Ultimate seedstalk height was reduced only in ‘Royal Chantenay’ vernalized at 10°. Flowering was decreased by post-vernalization temperatures of 27/32° and 2l/27°C when carrots were stored only 5 weeks at 5° but not, after storage for 10 weeks or more. Increasing the vernalization time to 10 weeks hastened the rate of bolting in all three cultivars and increased ultimate seedstalk height in only ‘Royal Chantenay’ and ‘Danvers 126.’ Temperature during the first year of root growth, foliage removal from mature roots prior to storage, and photoperiod following vernalization did not affect seedstalk elongation or flowering.

Factors Influencing Flowering of Rhubarb1,2

Abstract Flowering of rhubarb (Rheum spp.) was affected by plant age and vernalization temperature and by vernalization time in young crowns. Year-old crowns flowered after storage at 0°C or 5°C for 3 months or more. All 19 week-old crowns flowered after storage at 0°C for 3 months or more and some flowered after storage at 5°C. The 16 week-old crowns flowered only after 4½ and 6 months storage at 0°C. None of the 13 week-old crowns flowered. There was no flowering of crowns stored at 10°C regardless of age or length of storage. Growing temperature and photoperiod following vernalization did not influence flowering.