Vernalization Requirement Research Articles

Trait characterization of genetic resources reveals useful variation for the improvement of cultivated Nordic red clover

AbstractRed clover (Trifolium pratense L.) is the most important forage legume in the Nordic region, but its utilization is limited by poor persistency. The improvement of cultivated red clover can potentially take advantage of the numerous wild populations and landraces conserved in gene banks; however, there is often limited information available on the phenotypic and genetic characteristics of this material. We characterized 48 populations conserved at NordGen for a number of traits and compared them to commercial cultivars. The material was evaluated in field trials at four locations over two years and in an experiment under controlled conditions. Considerable variation was identified, with stem length, growth type and flowering date having the highest broad sense heritabilities. Traits related to plant size were strongly associated with late flowering and upright growth and differed between landraces/cultivars on the one hand and wild populations on the other. There was a large genotype by environment interaction on winter survival, which only partially correlated with freezing tolerance under controlled conditions. A majority of gene bank accessions exceeded the commercial cultivars in winter survival and freezing tolerance and can therefore be a genetic resource for future improvement of these traits. The phenotypic variation among accessions was associated with two main axes of climatic variation at the collection site. Petiole length of young plants under controlled conditions as well as plant size in the field increased with increasing summer temperature and decreasing summer precipitation, while number of leaves and an apparent vernalization requirement, recorded under controlled conditions, increased with decreasing annual and winter temperature. We discuss the implications these results have for collection, conservation and utilization of red clover genetic resources in the Nordic region.

Features of modern winter wheat varieties in terms of winter hardiness components under conditions of Ukrainian Forest-Steppe

In recent years, there has been a significant change in climatic conditions affecting the cultivation and yield of winter wheat. Therefore, the creation of wheat varieties with high adaptive potential is one of the main tasks of modern breeding. A significant component of the overall adaptive potential of winter wheat is winter hardiness, which is determined by a set of characters enabling plants to overwinter. To a large extent, winter hardiness is determined by gene systems that control vernalization requirement duration, photoperiod reaction, and frost resistance. The research is aimed at determining the features of modern winter wheat varieties developed at the V. M. Remeslo Myronivka Institute of Wheat of the National Academy of Agrarian Sciences of Ukraine in terms of winter hardiness components and adaptive potential in the environment of the Central part of the Ukrainian Forest-Steppe. Winter bread wheat varieties Estafeta myronivska, Hratsiia myronivska, MIP Assol, and Balada myronivska were studied. They also were crossed on incomplete diallele scheme with three near-isogenic lines derived from Erythrospermum 604 with different alleles of Vrd genes 1) Vrd1Vrd1vrd2vrd2, 2) vrd1vrd1Vrd2Vrd2, and 3) vrd1vrd1vrd2vrd2. It was established that vernalization requirement duration in the varieties Estafeta myronivska and Balada myronivska was short whereas in the varieties Hratsiia myronivska and MIP Assol it was medium. All the varieties studied have medium photoperiod sensitivity. The results of the hybridological analysis indicate the absence of the Vrd1 and Vrd2 genes in the varieties. Frost tolerance of these varieties is at the same level and higher than in the highly tolerant to the low temperatures variety Myronivska 808. Thus, the results indicate the possibility of recombining different levels of expression of these traits in genotypes by breeding efforts. This has great practical importance in farming, because in recent years the areas of crops harvested late (corn, sunflower, etc.) in the production conditions has significantly increased. It causes a shift in sowing dates of winter wheat to a later period. In this case, varieties Estafeta myronivska, Hratsiia myronivska, MIP Assol, and Balada myronivska are able to undergo sufficient hardening, to satisfy the vernalization requirement, and to form a high level of winter hardiness. Their relatively medium photoperiod sensitivity allows vegetation to be restored a little earlier in the spring and winter reserves of moisture to be used more effectively.

Diversity and association analysis of important agricultural trait based on miniature inverted-repeat transposable element specific marker in Brassica napus L.

Abatract Miniature inverted-repeat transposable elements (MITEs) are a group of DNA transposable element (TE) which preferentially distributed with gene associated regions. Tens of MITEs families have been revealed in Brassica napus genome, they scatter across the genome with tens of thousands copies and produce polymorphisms both intra- and inter-species. Our previous studies revealed a Tourist-like MITE, Monkey King, associated with vernalization requirement of B. napus, however there are still few studies reveal MITE association with agricultural traits in B. napus. In the present study, 80 polymorphic markers were developed from 55 MITEs, and used to evaluate genetic diversity in a panel of B. napus accessions consisting of 101 natural and 25 synthetic genotypes. Five agricultural traits, oil content, glucosinolate content, erucic acid content, weight of thousand seeds (WTS) and plant height, were investigated across 3-years field experiments, in addition, two traits, hypocotyl length and root length, were evaluated at the 4-leaf stage in the laboratory. Correlations between the MITE-based markers and seven traits were analyzed, finally, 10 polymorphic markers produced by 6 pairs of MITE specific primers were revealed relatively high correlation with 5 traits. Two polymorphic markers were anchored with two candidate genes, BnaA02g13530D and BnaA08g20010D, respectively, which may contribute to glucosinolate content and WTS. This research may contribute to genetic improvement through utilization of MITE-induced polymorphisms in Brassica species.

Genome Triplication Leads to Transcriptional Divergence of FLOWERING LOCUS C Genes During Vernalization in the Genus Brassica.

The genus Brassica includes oil crops, vegetables, condiments, fodder crops, and ornamental plants. Brassica species underwent a whole genome triplication event after speciation between ancestral species of Brassica and closely related genera including Arabidopsis thaliana. Diploid species such as Brassica rapa and Brassica oleracea have three copies of genes orthologous to each A. thaliana gene, although deletion in one or two of the three homologs has occurred in some genes. The floral transition is one of the crucial events in a plant’s life history, and time of flowering is an important agricultural trait. There is a variation in flowering time within species of the genus Brassica, and this variation is largely dependent on a difference in vernalization requirements. In Brassica, like in A. thaliana, the key gene of vernalization is FLOWERING LOCUS C (FLC). In Brassica species, the vernalization response including the repression of FLC expression by cold treatment and the enrichment of the repressive histone modification tri-methylated histone H3 lysine 27 (H3K27me3) at the FLC locus is similar to A. thaliana. B. rapa and B. oleracea each have four paralogs of FLC, and the allotetraploid species, Brassica napus, has nine paralogs. The increased number of paralogs makes the role of FLC in vernalization more complicated; in a single plant, paralogs vary in the expression level of FLC before and after vernalization. There is also variation in FLC expression levels between accessions. In this review, we focus on the regulatory circuits of the vernalization response of FLC expression in the genus Brassica.

Process-based analysis of Thinopyrum intermedium phenological development highlights the importance of dual induction for reproductive growth and agronomic performance

Intermediate wheatgrass (Thinopyrum intermedium (Host) Barkworth & D.R. Dewey) is being developed for use as a new perennial grain crop through breeding and agronomic research. However, progress has been hampered by lack of understanding of environmental requirements for flowering and grain production. Therefore, we developed a phenology model for IWG adapted from the STICS soil-crop model. The model was compliant with experimental results (relative root mean square error = 0.03). The optimal vernalizing temperature was between 4 and 5°C, optimal daylength between 13 and 14h, while daylength below 11h slowed reproductive development. Vernalization requirement was found to be a constraining inductive process. Including a photoperiod limitation to the model with temperature improved its ability to predict induction at various latitudes. Therefore, timing and duration of vegetative vs. reproductive growth may differ between environments and change reproductive tiller elongation earliness, weed competitiveness, management timing, and stress conditions during phases critical to grain yield. Accurate phenology models will enable optimal field management and inform future breeding strategies. However, plasticity may lead to divergent ideotypes under various agroecosystems.

Kernza intermediate wheatgrass (Thinopyrum intermedium) response to a range of vernalization conditions

Expansion of perennial grain and forage Kernza intermediate wheatgrass to temperate regions may be limited by its vernalization requirements. We compared vegetative and reproductive traits of Kernza plants grown in the greenhouse under four environmental treatments of temperature and day length for a 7 week induction period. The percent of plants that flowered and spikes per plant decreased from 83% and 8.2 at 4 °C and 10 h to 15% and 0.4 at 26 °C and 15 h, respectively. The variability observed suggests that there is potential for selection for reduced vernalization requirements in Kernza populations.

Transient reprogramming of crop plants for agronomic performance.

The development of a new crop variety is a time-consuming and costly process due to the reliance of plant breeding on gene shuffling to introduce desired genes into elite germplasm, followed by backcrossing. Here, we propose alternative technology that transiently targets various regulatory circuits within a plant, leading to operator-specified alterations of agronomic traits, such as time of flowering, vernalization requirement, plant height or drought tolerance. We redesigned techniques of gene delivery, amplification and expression around RNA viral transfection methods that can be implemented on an industrial scale and with many crop plants. The process does not involve genetic modification of the plant genome and is thus limited to a single plant generation, is broadly applicable, fast, tunable and versatile, and can be used throughout much of the crop cultivation cycle. The RNA-based reprogramming may be especially useful in plant pathogen pandemics but also for commercial seed production and for rapid adaptation of orphan crops.

Assessment of interspecific hybridization between wild beet Beta vulgaris L. subsp. maritima and cultivated sugar beet under Moroccan conditions

Obtaining a viable and fertile beet hybrid resulting from wild and cultivated sugar beet crosses under Moroccan conditions is challenging. To deal with hybridization, barriers in sugar beet, such as concordance of flowering period between biannual and annual subspecies, flowering aptitude according to vernalization requirement, genotype incompatibility and hybrid sterility, should be overcome. In our study, interspecific hybrids were obtained from crosses between 17 cultivated sugar beet Beta vulgaris subsp. vulgaris and 17 Beta vulgaris subsp. maritima, collected in different regions of Morocco. Twenty-two agro-morphological traits were used for the evaluation of 208 hybrid plants, under greenhouse conditions. CH and WH hybrids were collected on cultivated and wild parents separately. Most of the hybrids behaved as annual plants, of which 83.17% were able to flower and produce seeds without any vernalization requirements. All WH hybrids and 57.06% of CH hybrids were morphologically similar to their wild parent. However, 24% of CH hybrids were phenotypically similar to their cultivated parent. The remaining CH hybrid plants were behaving as intermediate genotypes between both wild and cultivated parents. Our results showed the success of interspecific beet crosses and emphasized the high variability among hybrid genotypes. This is of great importance for sugar beet improvement and breeding programs and interspecific crosses patterns understanding.

Total FLC transcript dynamics from divergent paralogue expression explains flowering diversity in Brassica napus.

Summary Flowering time is a key adaptive and agronomic trait. In Arabidopsis, natural variation in expression levels of the floral repressor FLOWERING LOCUS C (FLC) leads to differences in vernalization. In Brassica napus there are nine copies of FLC. Here, we study how these multiple FLC paralogues determine vernalization requirement as a system.We collected transcriptome time series for Brassica napus spring, winter, semi‐winter, and Siberian kale crop types. Modelling was used to link FLC expression dynamics to floral response following vernalization.We show that relaxed selection pressure has allowed expression of FLC paralogues to diverge, resulting in variation of FLC expression during cold treatment between paralogues and accessions. We find that total FLC expression dynamics best explains differences in cold requirement between cultivars, rather than expression of specific FLC paralogues.The combination of multiple FLC paralogues with different expression dynamics leads to rich behaviour in response to cold and a wide range of vernalization requirements in B. napus. We find evidence for different strategies to determine the response to cold in existing winter rapeseed accessions.

Effect of Gibberellic Acid on Growing-Point Development of Non-Vernalized Wheat Plants under Long-Day Conditions.

The goal of this study was to determine whether the application of gibberellic acid (GA3) to seeds of common wheat varieties with different vernalization and photoperiod requirements affects the transition from vegetative to generative stage. Three varieties of wheat with different photoperiod sensitivities and vernalization were selected for the experiment—the winter varieties, Mironovskaya and Bezostaya, and the spring variety, Sirael. Seeds were treated with different concentrations of GA3 and plants were grown under long-day conditions with monitoring of their photosynthetic activity (Fv/Fm, Pn, E, gs). We monitored the activity of the photosynthetic apparatus by checking the plants to see if they were growing properly. The phenological stages of the wheat species were checked for indications of a transition from the vegetative to the generative stage. Selected concentrations of GA3 had no effect on the compensation of the vernalization process (transition to the generative phase). Chlorophyll fluorescence was one of the factors for monitoring stress. The variety, Bezostaya, is similar to the spring variety, Sirael, in its trends and values. The growth conditions of Bezostaya and Sirael were not affected by the activity of the photosynthetic apparatus. The development of growing points in winter varieties occurred at the prolonged single ridge stage. The spring variety reached the stage of head emergence after sixty days of growth (changes to the flowering phase did not appear in winter wheat). Application of GA3 to the seeds had no effect on the transition of the growing point to the double-ridge generative stage. The present study highlights the priming effect of GA3 on seeds of common wheat varieties with different vernalization and photoperiod requirements as it affected the transition from vegetative to generative stage.

GENETIC BASIS OF ADAPTATION: FLOWERING TIME AND DEGREE OF DORMANCY OF SEEDS IN NORTHERN NATURAL ARABIDOPSIS THALIANA POPULATIONS

The study is devoted to the problem of the genetic basis of plant adaptation. The important adaptive traits of the model species of Arabidopsis thaliana were studied: vernalization requirement, flowering time and the time of seed germination in plants of northern natural populations (Karelia). Specific expression patterns of the gene FLC and VIN3 , which control these traits, have been revealed. A low level of FLC mRNA transcripts in non-vernalized plants at the rosette stage was established, with followed by increased expression on the 10-30th day of vernalization, which differs from the data of other researchers. The initially low level of VIN3 mRNA transcripts in non-vernalized plants unexpectedly increases in some populations during vernalization on the 20th day, in contrast to literature data. It has been shown that a longer vernalization (9 week) is required for a mass transition to flowering of plants from populations of the northern periphery of the species range in the Onega Lake basin compared to vernalization (6 weeks) of plants from the milder climate of Lake Ladoga islands. A study of the degree of dormancy of seeds, which affects the time of germination, showed that in cold climates A. thaliana seeds have a stronger dormancy at a high summer temperature (22 ºС) compared to a cool autumn temperature (10 ºС). This ensures their germination in the autumn and flowering in the spring, after the end of vernalization. It is suggested that in Karelian Arabidopsis thaliana populations located on the northern periphery of the species range, one of the mechanisms of plant adaptation to a cold climate is adaptive pleiotropy, exhibited in the peculiarities of the expression of the FLC and VIN3 genes, which control the timing of seed germination in autumn and flowering plants in spring, after vernalization, which ensures both seedling survival and maximum reproductive success.

The transition to flowering in winter rapeseed during vernalization.

Flowering time is a major determinant of adaptation, fitness and yield in the allopolyploid species rapeseed (Brassica napus). Despite being a close relative to Arabidopsis thaliana, little is known about the timing of floral transition and the genes that govern this process. Winter, semi-winter and spring type plants have important life history characteristics that differ in vernalization requirements for flowering and are important for growing rapeseed in different regions of the world. In this study, we investigated the timing of vernalization-driven floral transition in winter rapeseed and the effect of photoperiod and developmental age on flowering time and vernalization responsiveness. Microscopy and whole transcriptome analyses at the shoot apical meristems of plants grown under controlled conditions showed that floral transition is initiated within few weeks of vernalization. Certain Bna.SOC1 and Bna.SPL5 homeologs were among the induced genes, suggesting that they are regulating the timing of cold-induced floral transition. Moreover, the flowering response of plants with shorter pre-vernalization period correlated with a delayed expression of Bna.SOC1 and Bna.SPL5 genes. In essence, this study presents a detailed analysis of vernalization-driven floral transition and the aspects of juvenility and dormancy and their effect on flowering time in rapeseed.

Cropping effect and variety adaptability of winter-seeded spring wheat in Inner Mongolia Plain irrigation area

<p indent=0mm>Growing spring wheat in Inner Mongolia is challenging because of the short growing period, dry-hot winds, and heat-forced maturity. There are also problems with growing winter wheat varieties, such as frost damage, spring droughts, or “late spring cold”. These factors have restricted efforts to increase yields. In order to cope with these challenges, this study adopted a “winter-seeded spring wheat” planting model for growing wheat in Inner Mongolia and investigated wheat varieties with different vernalization requirements through two consecutive field trials. The effects of different varieties on seed germination and seedling emergence, growth, leaf physiological, root traits, and yield formation were analyzed. The results indicated that the spring varieties and some winter varieties of the tested wheat varieties were overwintered as seed and passed the vernalization stage, and matured normally in the following year. Under winter sowing conditions, the spring field germination rate of the tested wheat varieties was lower than that of spring sowing wheat, but the root system developed, and the adaptability to low temperature and drought was stronger. Three wheat varieties suitable for winter-sowing in the Inner Mongolia plain irrigation area were screened out by systematic clustering, including the spring variety Yongliang 4, winter cultivar Ningdong 11 and semi-winter cultivar Henong 7106. Their common characteristics were higher overwintering emergence rate, stronger stress resistance, relatively well-developed root system and higher yield performance, among which, Yongliang 4 could reach the same level as spring-seeded.

FLC and SVP Are Key Regulators of Flowering Time in the Biennial/Perennial Species Noccaea caerulescens.

The appropriate timing of flowering is crucial for plant reproductive success. Studies of the molecular mechanism of flower induction in the model plant Arabidopsis thaliana showed long days and vernalization as major environmental promotive factors. Noccaea caerulescens has an obligate vernalization requirement that has not been studied at the molecular genetics level. Here, we characterize the vernalization requirement and response of four geographically diverse biennial/perennial N. caerulescens accessions: Ganges (GA), Lellingen (LE), La Calamine (LC), and St. Felix de Pallières (SF). Differences in vernalization responsiveness among accessions suggest that natural variation for this trait exists within N. caerulescens. Mutants which fully abolish the vernalization requirement were identified and were shown to contain mutations in the FLOWERING LOCUS C (NcFLC) and SHORT VEGETATIVE PHASE (NcSVP) genes, two key floral repressors in this species. At high temperatures, the non-vernalization requiring flc-1 mutant reverts from flowering to vegetative growth, which is accompanied with a reduced expression of LFY and AP1. This suggested there is “crosstalk” between vernalization and ambient temperature, which might be a strategy to cope with fluctuations in temperature or adopt a more perennial flowering attitude and thus facilitate a flexible evolutionary response to the changing environment across the species range.

Developmental regulation and metabolic changes of RILs of crosses between spring and winter wheat during low temperature acclimation

Winter survival in wheat requires programmed potential modulations to develop low temperature (LT) acclimation for its growth and yield. The purpose of the present study was to understand the relationships between developmental regulations and metabolic changes during LT acclimation and vernalization under field conditions. Six wheat recombinant inbred lines (RILs) of F8 generation resulted from cross Mironovskaya 808 (winter-habit parent) and Pishtaz (spring-habit parent) with different vernalization requirements and reproductive development, whose growth habits were determined by Vrn-1 loci, were cultivated under greenhouse and field conditions. Plants were sampled on three dates (Dec. 12, Jan. 11, and Feb. 10) as different phenological development stages. Early and rapid transition from vegetative to reproductive phase measured by double ridge (DR) formation and final leaf number (FLN) occurred in spring genotypes, including Pishtaz parent and RILs 4006 and 4014. They also had the lowest enzymatic antioxidants activity and contents of anthocyanins, total phenols, flavonoids, lignin, proline and carotenoids and the highest damage indices (H2O2 and MDA) among genotypes. RILs 4012 and 4016 had higher FLN than Pishtaz and remained in vegetative phase longer and showed higher tolerance (LT50 and metabolites) as compared to spring genotypes. In contrast, Mironovskaya 808 parent and RILs 4005 and 4003 spent the longest time in the vegetative phase and showed the highest level of LT tolerance (confirmed by LT50, damage indices and pigment contents). The highest level of LT tolerance in all genotypes, obtained at the vegetative/reproductive transition, significantly decreased with the onset of the reproductive phase. Our results suggested that LT tolerance was established from developmental regulations and potential metabolic networks following longer vegetative phase in wheat.

MiR396 is involved in plant response to vernalization and flower development in Agrostis stolonifera

MicroRNA396 (miR396) has been demonstrated to regulate flower development by targeting growth-regulating factors (GRFs) in annual species. However, its role in perennial grasses and its potential involvement in flowering time control remain unexplored. Here we report that overexpression of miR396 in a perennial species, creeping bentgrass (Agrostis stolonifera L.), alters flower development. Most significantly, transgenic (TG) plants bypass the vernalization requirement for flowering. Gene expression analysis reveals that miR396 is induced by long-day (LD) photoperiod and vernalization. Further study identifies VRN1, VRN2, and VRN3 homologs whose expression patterns in wild-type (WT) plants are similar to those observed in wheat and barley during transition from short-day (SD) to LD, and SD to cold conditions. However, compared to WT controls, TG plants overexpressing miR396 exhibit significantly enhanced VRN1 and VRN3 expression, but repressed VRN2 expression under SD to LD conditions without vernalization, which might be associated with modified expression of methyltransferase genes. Collectively, our results unveil a potentially novel mechanism by which miR396 suppresses the vernalization requirement for flowering which might be related to the epigenetic regulation of VRN genes and provide important new insight into critical roles of a miRNA in regulating vernalization-mediated transition from vegetative to reproductive growth in monocots.

Evaluation of currently registered herbicides for fall bearing year red sorrel (Rumex acetosella L.) management in lowbush blueberry (Vaccinium angustifolium Aiton)

Red sorrel is a common creeping herbaceous, perennial weed species in lowbush blueberry fields and reproduces asexually via ramets from creeping roots. Ramets emerge throughout the season but remain vegetative due to a vernalisation requirement for flowering. This weed may therefore be managed with fall herbicide applications, but few currently registered herbicides have been evaluated for fall red sorrel management in lowbush blueberry. The objectives of this research were to (i) determine the effect of various herbicide treatments on red sorrel shoot and root biomass in the greenhouse, (ii) determine the effect of fall bearing year herbicide applications on overwintered red sorrel ramet density in the field, (iii) determine if reduced overwintered ramet density reduces flowering ramet density in the field, and (iv) estimate the potential for red sorrel to recover from fall bearing year herbicide applications. Dicamba, tribenuron-methyl, and glufosinate reduced red sorrel shoot and root biomass in the greenhouse and reduced overwintered ramet density in the field. Clopyralid, sulfentrazone, and flumioxazin reduced shoot and root biomass in the greenhouse but exhibited limited efficacy in the field. Nicosulfuron + rimsulfuron and glyphosate were ineffective in both the greenhouse and field. Dichlobenil and pronamide reduced overwintered ramet density in the field. Reduction of overwintered ramet density did not consistently reduce flowering ramet density. Dichlobenil reduced seedling density at two sites, but no herbicide consistently reduced summer non-bearing year ramet density. Fall herbicide applications alone, therefore, do not appear to maintain red sorrel suppression in lowbush blueberry fields.

The relationship between root system development and vernalization under contrasting irrigation in bread wheat lines with the introgressions from a synthetic hexaploid

The properties of the root system are especially important under drought, which is currently the most significant climate threat worldwide. The aim of this work was to investigate the relationship between the root system development and vernalization requirements under contrasting irrigation conditions in bread wheat using lines with alien introgressions. A set of single chromosome substitution lines Chinese Spring (Synthetic 6x, AABBDD) and D-genome derived introgression lines were used to study the relationships. It was found that 1A substitution resulted in a substantial reduction of root length and weight while 5D substitution, on the contrary, led to a significant increase compared to the recipient and the donor under both irrigation regimes. The greatest root weight, root length, and number of days to flowering were detected in the lines carrying a common introgression fragment of the 5D chromosome connected with the molecular marker Xgwm292 and the Vrn-D1 gene. The lines with the introgression in this region had a significantly larger root length and weight compared with the recipient and donor under all conditions of irrigation. The combination of prolonged vernalization and drought negatively affected the development of roots in all lines with the most pronounced effect on root weight. With the use of monosomic analysis, it was shown that the Vrn-A1 gene has a substantial reducing effect on the root length and weight. The revealed relationship between the flowering time and root system development can be used for breeding of wheat cultivars more adapted for growing in arid conditions.

Floral induction and dormancy behaviour in ‘Chilean white strawberry’ (Fragaria chiloensis (L.) Mill. subsp. chiloensis f. chiloensis)

The flowering process in Fragaria x ananassa has been widely studied, while the favourable environmental conditions for Fragaria chiloensis subsp. chiloensis f. chiloensis, the ‘'Chilean white strawberry', are not well understood. With the objective to study the floral induction and dormancy process in this species, several experiments were conducted from 2016 to 2019 using the ecotype ‘Contulmo’ for ‘Chilean white strawberry’ and the cv. ‘Camarosa’ for F. x ananassa, the latter as a reference genotype. Growth parameters and the differentiation state of apex were evaluated at two locations in Chile (33°38’ S and 38°45’ S) as well as in climate-controlled growth chamber (9 °C and 8 -h photoperiod). Additionally, the chilling requirement for dormancy release after different cold storage periods (2 °C in darkness) was determined in this species. This requirement was field-verified (38°45’ S) over two seasons. The ‘Chilean white strawberry’ showed continuous and reduced growth, without changes under different temperature and photoperiod conditions, with values significantly different from those of cv. ‘Camarosa’. In both locations, the floral and dormancy induction started late (June), occurred only in a part of the plants (20-30%) and them yielded a single inflorescence. In addition, it was determined that the ‘Chilean white strawberry’ require approximately 900-1,000 chilling units for dormancy release. Our results indicated that flowering is favoured only with low temperatures, lower than those necessary for many short-day genotypes. This characteristic, together with the late flowering, suggests that there is a vernalization requirement for this species. Temperature increase is probably the main factor involved in the current floral behaviour of ‘Chilean white strawberry’, however this can decreasing even more in a climate change context.

The molecular mechanism of vernalization in Arabidopsis and cereals: role of Flowering Locus C and its homologs

Winter varieties of plants can flower only after exposure to prolonged cold. This phenomenon is known as vernalization and has been widely studied in the model plant Arabidopsis thaliana as well as in monocots. Through the repression of floral activator genes, vernalization prevents flowering in winter. In Arabidopsis, FLOWERING LOCUS C or FLC is the key repressor during vernalization, while in monocots vernalization is regulated through VRN1, VRN2 and VRN3 (or FLOWERING LOCUS T). Interestingly, VRN genes are not homologous to FLC but FLC homologs are found to have a significant role in vernalization response in cereals. The presence of FLC homologs in monocots opens new dimensions to understand, compare and retrace the evolution of vernalization pathways between monocots and dicots. In this review, we discuss the molecular mechanism of vernalization-induced flowering along with epigenetic regulations in Arabidopsis and temperate cereals. A better understanding of cold-induced flowering will be helpful in crop breeding strategies to modify the vernalization requirement of economically important temperate cereals.