Perpetual Flowering Research Articles

Genetic gains underpinning a little-known strawberry Green Revolution

The annual production of strawberry has increased by one million tonnes in the US and 8.4 million tonnes worldwide since 1960. Here we show that the US expansion was driven by genetic gains from Green Revolution breeding and production advances that increased yields by 2,755%. Using a California population with a century-long breeding history and phenotypes of hybrids observed in coastal California environments, we estimate that breeding has increased fruit yields by 2,974-6,636%, counts by 1,454-3,940%, weights by 228-504%, and firmness by 239-769%. Using genomic prediction approaches, we pinpoint the origin of the Green Revolution to the early 1950s and uncover significant increases in additive genetic variation caused by transgressive segregation and phenotypic diversification. Lastly, we show that the most consequential Green Revolution breeding breakthrough was the introduction of photoperiod-insensitive, PERPETUAL FLOWERING hybrids in the 1970s that doubled yields and drove the dramatic expansion of strawberry production in California.

The Integrated mRNA and miRNA Approach Reveals Potential Regulators of Flowering Time in Arundina graminifolia.

Orchids are among the most precious flowers in the world. Regulation of flowering time is one of the most important targets to enhance their ornamental value. The beauty of Arundina graminifolia is its year-round flowering, although the molecular mechanism of this flowering ability remains masked. Therefore, we performed a comprehensive assessment to integrate transcriptome and miRNA sequencing to disentangle the genetic regulation of flowering in this valuable species. Clustering analyses provided a set of molecular regulators of floral transition and floral morphogenesis. We mined candidate floral homeotic genes, including FCA, FPA, GI, FT, FLC, AP2, SOC1, SVP, GI, TCP, and CO, which were targeted by a variety of miRNAs. MiR11091 targeted the highest number of genes, including candidate regulators of phase transition and hormonal control. The conserved miR156-miR172 pathway of floral time regulation was evident in our data, and we found important targets of these miRNAs in the transcriptome. Moreover, endogenous hormone levels were determined to decipher the hormonal control of floral buds in A. graminifolia. The qRT-PCR analysis of floral and hormonal integrators validated the transcriptome expression. Therefore, miRNA-mediated mining of candidate genes with hormonal regulation forms the basis for comprehending the complex regulatory network of perpetual flowering in precious orchids. The findings of this study can do a great deal to broaden the breeding programs for flowering time manipulation of orchids.

Role of FaSOC1 and FaCO in the seasonal control of reproductive and vegetative development in the perennial crop Fragaria × ananassa.

The diploid woodland strawberry (F. vesca) represents an important model for the genus Fragaria. Significant advances in the understanding of the molecular mechanisms regulating seasonal alternance of flower induction and vegetative reproduction has been made in this species. However, this research area has received little attention on the cultivated octoploid strawberry (F. × ananassa) despite its enormous agronomical and economic importance. To advance in the characterization of this intricated molecular network, expression analysis of key flowering time genes was performed both in short and long days and in cultivars with seasonal and perpetual flowering. Analysis of overexpression of FaCO and FaSOC1 in the seasonal flowering ‘Camarosa’ allowed functional validation of a number of responses already observed in F. vesca while uncovered differences related to the regulation of FaFTs expression and gibberellins (GAs) biosynthesis. While FvCO has been shown to promote flowering and inhibit runner development in the perpetual flowering H4 accession of F. vesca, our study showed that FaCO responds to LD photoperiods as in F. vesca but delayed flowering to some extent, possibly by induction of the strong FaTFL1 repressor in crowns. A contrasting effect on runnering was observed in FaCO transgenic plants, some lines showing reduced runner number whereas in others runnering was slightly accelerated. We demonstrate that the role of the MADS-box transcription factor FaSOC1 as a strong repressor of flowering and promoter of vegetative growth is conserved in woodland and cultivated strawberry. Our study further indicates an important role of FaSOC1 in the photoperiodic repression of FLOWERING LOCUS T (FT) genes FaFT2 and FaFT3 while FaTFL1 upregulation was less prominent than that observed in F. vesca. In our experimental conditions, FaSOC1 promotion of vegetative growth do not require induction of GA biosynthesis, despite GA biosynthesis genes showed a marked photoperiodic upregulation in response to long days, supporting GA requirement for the promotion of vegetative growth. Our results also provided insights into additional factors, such as FaTEM, associated with the vegetative developmental phase that deserve further characterization in the future.

FLOWERING REPRESSOR AAA+ ATPase 1 is a novel regulator of perennial flowering in Arabis alpina.

Arabis alpina is a polycarpic perennial, in which PERPETUAL FLOWERING1 (PEP1) regulates flowering and perennial traits in a vernalization-dependent manner. Mutagenesis screens of the pep1 mutant established the role of other flowering time regulators in PEP1-parallel pathways. Here we characterized three allelic enhancers of pep1 (eop002, 085 and 091) which flower early. We mapped the causal mutations and complemented mutants with the identified gene. Using quantitative reverse transcriptase PCR and reporter lines, we determined the protein spatiotemporal expression patterns and localization within the cell. We also characterized its role in Arabidopsis thaliana using CRISPR and in A. alpina by introgressing mutant alleles into a wild-type background. These mutants carried lesions in an AAA+ ATPase of unknown function, FLOWERING REPRESSOR AAA+ ATPase 1 (AaFRAT1). AaFRAT1 was detected in the vasculature of young leaf primordia and the rib zone of flowering shoot apical meristems. At the subcellular level, AaFRAT1 was localized at the interphase between the endoplasmic reticulum and peroxisomes. Introgression lines carrying Aafrat1 alleles required less vernalization to flower and reduced number of vegetative axillary branches. By contrast, A. thaliana CRISPR lines showed weak flowering phenotypes. AaFRAT1 contributes to flowering time regulation and the perennial growth habit of A. alpina.

Impact of Nitrate and Ammonium Ratios on Flowering and Asexual Reproduction in the Everbearing Strawberry Cultivar Fragaria × ananassa Albion

Ever-bearing (EB) strawberries are long-day cultivars that show perpetual flowering behavior. Compared to June-bearing short-day cultivars, EB cultivars can initiate flowers with less dependency on light and temperature levels. This leads to a more consistent flowering and fruiting pattern, making EB cultivars favorable for areas with long growing seasons. However, this flowering pattern also brings significant challenges to open-field strawberry nurseries. Consistent flower development in EB cultivars frequently leads to increased labor cost for manual flower removal on nursery ground. The alteration of flowering behavior via fertilizer regimes could be a cost-effective tool for strawberry nurseries. However, while it is known that the source of nitrogen (N) impacts strawberry flowering, its effect on strawberry propagation rates needs further investigation. The objective of this study was to investigate the impact of nitrate (NO3−) to ammonium (NH4+) ratio on flower and daughter plant production in the EB strawberry cultivar ‘Albion’ (Fragaria × ananassa c.v. ‘Albion’). Strawberry plants were grown in a completely randomized design under greenhouse conditions (26.6 °C, 16 h photoperiod). Four treatments of NO3−:NH4+ were implemented: (1) 100%:0%; (2) 80%:20%; (3) 60%:40%; (4) 50%:50%. Strawberry plants fertilized with a 60%:40% NO3−:NH4+ ratio produced 17–31% fewer inflorescences than those fertilized with 100%:0% (8.8 ± 1.19) and 80%:20% (10.3 ± 1.85) ratios. The production of daughter plants remained similar in all four treatments. Our results show that increased ratios of ammonium in combination with decreased ratios of nitrate reduce flowering of EB strawberry cultivars, while propagation rates remain consistent. These results could potentially lead to the development of fertilizer regimes for strawberry nurseries to reduce flower production in EB cultivars.

Effects of Temperature and Photoperiod on the Flower Potential in Everbearing Strawberry as Evaluated by Meristem Dissection

The growing interest in using everbearing (EB) strawberry cultivars to extend the cultivation period has faced some challenges. These include poor runner production due to its perpetual flowering nature; irregular flowering behavior and extended periods of high temperature have caused floral inhibition and reduced yield. As flowering is an interplay between temperature and photoperiod, it is important to investigate the effects of this interaction on the cultivation. Therefore, this study used meristem dissection as a tool to study the effect of temperature and photoperiod on meristem development. Tray plants of two EB strawberry cultivars ‘Florentina’ and ‘Favori’ were grown at 20 °C, 25 °C, and 30 °C under short day (SD) conditions, and subsequently at 20 °C under long day (LD) conditions. The meristem development was analysed every 6 weeks for a 15-week period in SD and for 14 weeks in LD conditions using meristem dissection. The plants showed similar flowering patterns to previously studied everbearing cultivars, which was qualitative LD plants at high temperatures and quantitative LD plants at lower temperatures. Our results show that meristem dissection can be used to determine the temperature and photoperiodic effect on meristem development, and for the occurrence of cropping peaks, and can therefore be used to decide the environmental input and to evaluate yield potential.

Winter manipulation of photoperiod and chill to enhance the perpetual flowering nature of ‘Soprano’

Winter manipulation of photoperiod and chill to enhance the perpetual flowering nature of ‘Soprano’

Beyond flowering time: diverse roles of an APETALA2-like transcription factor in shoot architecture and perennial traits.

Polycarpic perennials maintain vegetative growth after flowering. PERPETUAL FLOWERING 1 (PEP1), the orthologue of FLOWERING LOCUS C (FLC) in Arabis alpina regulates flowering and contributes to polycarpy in a vernalisation-dependent pathway. pep1 mutants do not require vernalisation to flower and have reduced return to vegetative growth as all of their axillary branches become reproductive. To identify additional genes that regulate flowering and contribute to perennial traits we performed an enhancer screen of pep1. Using mapping-by-sequencing, we cloned a mutant (enhancer of pep1-055, eop055), performed transcriptome analysis and physiologically characterised the role it plays on perennial traits in an introgression line carrying the eop055 mutation and a functional PEP1 wild-type allele. eop055 flowers earlier than pep1 and carries a lesion in the A.alpina orthologue of the APETALA2 (AP2)-like gene, TARGET OF EAT2 (AaTOE2). AaTOE2 is a floral repressor and acts upstream of SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 5 (AaSPL5). In the wild-type background, which requires cold treatment to flower, AaTOE2 regulates the age-dependent response to vernalisation. In addition, AaTOE2 ensures the maintenance of vegetative growth by delaying axillary meristem initiation and repressing flowering of axillary buds before and during cold exposure. We conclude that AaTOE2 is instrumental in fine tuning different developmental traits in the perennial life cycle of A.alpina.

Gibberellins Act Downstream of Arabis PERPETUAL FLOWERING1 to Accelerate Floral Induction during Vernalization.

Regulation of flowering by endogenous and environmental signals ensures that reproduction occurs under optimal conditions to maximize reproductive success. Involvement of the growth regulator gibberellin (GA) in the control of flowering by environmental cues varies among species. Arabis alpina Pajares, a model perennial member of the Brassicaceae, only undergoes floral induction during vernalization, allowing definition of the role of GA specifically in this process. The transcription factor PERPETUAL FLOWERING1 (PEP1) represses flowering until its mRNA levels are reduced during vernalization. Genome-wide analyses of PEP1 targets identified genes involved in GA metabolism and signaling, and many of the binding sites in these genes were specific to the A. alpina lineage. Here, we show that the pep1 mutant exhibits an elongated-stem phenotype, similar to that caused by treatment with exogenous GA, consistent with PEP1 repressing GA responses. Moreover, in comparison with the wild type, the pep1 mutant contains higher GA4 levels and is more sensitive to GA prior to vernalization. Upon exposure to cold temperatures, GA levels fall to low levels in the pep1 mutant and in wild-type plants, but GA still promotes floral induction and the transcription of floral meristem identity genes during vernalization. Reducing GA levels strongly impairs flowering and inflorescence development in response to short vernalization treatments, but longer treatments overcome the requirement for GA. Thus, GA accelerates the floral transition during vernalization in A. alpina, the down-regulation of PEP1 likely increases GA sensitivity, and GA responses contribute to determining the length of vernalization required for flowering and reproduction.

Seed traits are pleiotropically regulated by the flowering time gene PERPETUAL FLOWERING 1 (PEP1) in the perennial Arabis alpina.

The life cycles of plants are characterized by two major life history transitions—germination and the initiation of flowering—the timing of which are important determinants of fitness. Unlike annuals, which make the transition from the vegetative to reproductive phase only once, perennials iterate reproduction in successive years. The floral repressor PERPETUAL FLOWERING 1 (PEP1), an ortholog of FLOWERING LOCUS C, in the alpine perennial Arabis alpina ensures the continuation of vegetative growth after flowering and thereby restricts the duration of the flowering episode. We performed greenhouse and garden experiments to compare flowering phenology, fecundity and seed traits between A. alpina accessions that have a functional PEP1 allele and flower seasonally and pep1 mutants and accessions that carry lesions in PEP1 and flower perpetually. In the garden, perpetual genotypes flower asynchronously and show higher winter mortality than seasonal ones. PEP1 also pleiotropically regulates seed dormancy and longevity in a way that is functionally divergent from FLC. Seeds from perpetual genotypes have shallow dormancy and reduced longevity regardless of whether they after‐ripened in plants grown in the greenhouse or in the experimental garden. These results suggest that perpetual genotypes have higher mortality during winter but compensate by showing higher seedling establishment. Differences in seed traits between seasonal and perpetual genotypes are also coupled with differences in hormone sensitivity and expression of genes involved in hormonal pathways. Our study highlights the existence of pleiotropic regulation of seed traits by hub developmental regulators such as PEP1, suggesting that seed and flowering traits in perennial plants might be optimized in a coordinated fashion.

High density linkage map construction and QTL mapping for runner production in allo-octoploid strawberry Fragaria\u2009\xd7\u2009ananassa based on ddRAD-seq derived SNPs

Recent advances in high-throughput genome sequencing technologies are now making the genetic dissection of the complex genome of cultivated strawberry easier. We sequenced Maehyang (short-day cultivar) × Albion (day-neutral cultivar) crossing populations using double digest restriction-associated DNA (ddRAD) sequencing technique that yielded 978,968 reads, 80.2% of which were aligned to strawberry genome allowing the identification of 13,181 high quality single nucleotide polymorphisms (SNPs). Total 3051 SNPs showed Mendelian segregation in F1, of which 1268 were successfully mapped to 46 linkage groups (LG) spanning a total of 2581.57 cM with an average interval genetic distance of 2.22 cM. The LGs were assigned to the 28 chromosomes of Fragaria × ananassa as determined by positioning the sequence tags on F. vesca genome. In addition, seven QTLs namely, qRU-5D, qRU-3D1, qRU-1D2, qRU-4D, qRU-4C, qRU-5C and qRU-2D2 were identified for runner production with LOD value ranging from 3.5–7.24 that explained 22–38% of phenotypic variation. The key candidate genes having putative roles in meristem differentiation for runnering and flowering within these QTL regions were identified. These will enhance our understanding of the vegetative vs sexual reproductive behavior in strawberry and will aid in setting breeding targets for developing perpetual flowering and profuse runnering cultivar.

Comprehensive analysis of the longan transcriptome reveals distinct regulatory programs during the floral transition

BackgroundLongan (Dimocarpus longan Lour.) is an important fruit tree in the subtropical regions of Southeast Asia and Australia. Among the factors affecting D. longan fruit yield, the difficulty and instability of blossoming is one of the most challenging issues. Perpetual flowering (PF) is a crucial trait for fruit trees and is directly linked to production potential. Therefore, studying the molecular regulatory mechanism of longan PF traits is crucial for understanding and solving problems related to flowering. In this study, comparative transcriptome analysis was performed using two longan cultivars that display opposite flowering phenotypes during floral induction.ResultsWe obtained 853.72 M clean reads comprising 125.08 Gb. After comparing these data with the longan genome, 27,266 known genes and 1913 new genes were detected. Significant differences in gene expression were observed between the two genotypes, with 6150 and 6202 differentially expressed genes (DEGs) for ‘SJ’ and ‘SX’, respectively. The transcriptional landscape of floral transition at the early stage was very different in these two longan genotypes with respect to key hormones, circadian rhythm, sugar metabolism, and transcription factors. Almost all flowering-related DEGs identified are involved in photoperiod and circadian clock pathways, such as CONSTANS-like (COL), two-component response regulator-like (APRRs), gigantea (GI), and early flowering (EFL). In addition, the leafy (LFY) gene, which is the central floral meristem identity gene, may inhibit PF formation in ‘SJ’.ConclusionThis study provides a platform for understanding the molecular mechanisms responsible for changes between PF and seasonal flowering (SF) longan genotypes and may benefit studies on PF trait mechanisms of evergreen fruit trees.

PERPETUAL FLOWERING2 coordinates the vernalization response and perennial flowering in Arabis alpina.

The floral repressor APETALA2 (AP2) in Arabidopsis regulates flowering through the age pathway. The AP2 ortholog in the alpine perennial Arabis alpina, PERPETUAL FLOWERING 2 (PEP2), was previously reported to control flowering through the vernalization pathway via enhancing the expression of another floral repressor PERPETUAL FLOWERING 1 (PEP1), the ortholog of Arabidopsis FLOWERING LOCUS C (FLC). However, PEP2 also regulates flowering independently of PEP1. To characterize the function of PEP2, we analyzed the transcriptomes of pep2 and pep1 mutants. The majority of differentially expressed genes were detected between pep2 and the wild type or between pep2 and pep1, highlighting the importance of the PEP2 role that is independent of PEP1. Here, we demonstrate that PEP2 activity prevents the up-regulation of the A. alpina floral meristem identity genes FRUITFUL (AaFUL), LEAFY (AaLFY), and APETALA1 (AaAP1), ensuring floral commitment during vernalization. Young pep2 seedlings respond to vernalization, suggesting that PEP2 regulates the age-dependent response to vernalization independently of PEP1. The major role of PEP2 through the PEP1-dependent pathway takes place after vernalization, when it facilitates PEP1 activation both in the main shoot apex and in axillary branches. These multiple roles of PEP2 in the vernalization response contribute to the A. alpina life cycle.

Genetic characterization of Rosa species using morphological markers

Genetic diversity in roses is unparalleled to any other flower crops. A large number of rose species is grown all around the world. There is a rich wealth of indigenous rose species such as Rosa brunonii, R. macrophylla, R. moschata, R. spinossisima, R. rubiginosa, R. wichuraiana etc. are grown wild in India. They are the important source of genes responsible for various traits, viz. both biotic and abiotic stress tolerance, fragrance, perpetual flowering, hardiness which need to be protected for further use in breeding programs. Morphological markers or traits basedspecies identification are best for visualization, reproducibility and easy to use, besides serving as a reality check for molecular studies. In this study, 31 rose species were characterized for 18 vegetative characters as per PPV FRA guidelines for DUS testing of rose. Genetic diversity of rose species was done based on dissimilarity calculation, hierarchical cluster analysis, linear discriminant analysis and principal component analysis using R software. R. banksiae - R. chinensis‘Viridiflora’ and R. banksiae - R. rubiginosa showed the highest diversity while R. brunoniiand R. dumalis shows least diversity. Species were divided into five major clusters using hierarchical cluster analysis which was validated by linear discriminant analysis. Here, both Indian originating species R. brunonii and R. moschata fell into the same cluster while significant diversity noticed in R. damascena and R. wichuraiana. Results of principal component analysis follow a similar pattern as of dendrogram. R. banksiae was most distinctly placed which is well supported as only thornless species used in the study. Although no single morphological traits can be used to differentiate species, it is necessary to create a passport data for further studies.

Identification of WRKY Gene Family from Dimocarpus longan and Its Expression Analysis during Flower Induction and Abiotic Stress Responses

Longan is an important fruit tree in the subtropical region of Southeast Asia and Australia. However, its blooming and its yield are susceptible to stresses such as droughts, high salinity, and high and low temperature. To date, the molecular mechanisms of abiotic stress tolerance and flower induction in longan have not been elucidated. WRKY transcription factors (TFs), which have been studied in various plant species, play important regulatory roles in plant growth, development, and responses to stresses. However, there is no report about WRKYs in longan. In this study, we identified 55 WRKY genes with the conserved WRKY domain and zinc finger motif in the longan genome. Based on the structural features of WRKY proteins and topology of the phylogenetic tree, the longan WRKY (DlWRKY) family was classified into three major groups (I–III) and five subgroups (IIa–IIe) in group II. Tissue expression analysis showed that 25 DlWRKYs were highly expressed in almost all organs, suggesting that these genes may be important for plant growth and organ development in longan. Comparative RNA-seq and qRT-PCR-based gene expression analysis revealed that 18 DlWRKY genes showed a specific expression during three stages of flower induction in “Sijimi” (“SJ”), which exhibited the “perpetual flowering” (PF) habit, indicating that these 18 DlWRKY genes may be involved in the flower induction and the genetic control of the perpetual flowering trait in longan. Furthermore, the RT-qPCR analysis illustrated the significant variation of 27, 18, 15, 17, 27, and 23 DlWRKY genes under SA (Salicylic acid), MeJA (Methyl Jasmonate), heat, cold, drought, or high salinity treatment, respectively, implicating that they might be stress- or hormone-responsive genes. In summary, we systematically and comprehensively analyzed the structure, evolution, and expression pattern of the DlWRKY genes. The results presented here increase our understanding of the WRKY family in fruit trees and provide a basis for the further elucidation of the biological function of DlWRKY genes in longan.

Extended Vernalization Regulates Inflorescence Fate in Arabis alpina by Stably Silencing PERPETUAL FLOWERING1.

The alpine perennial Arabis alpina initiates flower buds during prolonged exposure to cold. In the accession Pajares, we demonstrate that the length of vernalization influences flowering time and inflorescence fate but does not affect the axillary branches that maintain vegetative growth. The expression of floral organ identity genes gradually increases in the main shoot apex during vernalization, correlating with an increase in floral commitment. In northern Arabidopsis (Arabidopsis thaliana) accessions, the length of vernalization modulates the stable silencing of the floral repressor FLOWERING LOCUS C (FLC). We demonstrate that expression of PERPETUAL FLOWERING1 (PEP1), the ortholog of FLC in A. alpina, is similarly influenced by the duration of the exposure to cold. Extended vernalization results in stable silencing of PEP1 in the inflorescence. In contrast, insufficient vernalization leads to PEP1 reactivation after cold treatment, which correlates with delayed flowering and the appearance of floral reversion phenotypes such as bracts and vegetative inflorescence branches. Floral reversion phenotypes are reduced in the pep1-1 mutant, suggesting that PEP1 regulates the fate of the inflorescence after vernalization. The effect of vernalization duration on stable silencing of PEP1 is specific to meristems that initiate flowering during cold treatment. Extended vernalization fails to silence PEP1 in young seedlings and axillary branches that arise from buds initiated during cold treatment, which remain vegetative. We conclude that the duration of vernalization in A. alpina differentially regulates PEP1 in the inflorescence and axillary branches. PEP1 has a dual role regulating meristem fate; it prevents meristems from flowering and antagonizes inflorescence development after vernalization.

Divergence of regulatory networks governed by the orthologous transcription factors FLC and PEP1 in Brassicaceae species

Genome-wide landscapes of transcription factor (TF) binding sites (BSs) diverge during evolution, conferring species-specific transcriptional patterns. The rate of divergence varies in different metazoan lineages but has not been widely studied in plants. We identified the BSs and assessed the effects on transcription of FLOWERING LOCUS C (FLC) and PERPETUAL FLOWERING 1 (PEP1), two orthologous MADS-box TFs that repress flowering and confer vernalization requirement in the Brassicaceae species Arabidopsis thaliana and Arabis alpina, respectively. We found that only 14% of their BSs were conserved in both species and that these contained a CArG-box that is recognized by MADS-box TFs. The CArG-box consensus at conserved BSs was extended compared with the core motif. By contrast, species-specific BSs usually lacked the CArG-box in the other species. Flowering-time genes were highly overrepresented among conserved targets, and their CArG-boxes were widely conserved among Brassicaceae species. Cold-regulated (COR) genes were also overrepresented among targets, but the cognate BSs and the identity of the regulated genes were usually different in each species. In cold, COR gene transcript levels were increased in flc and pep1-1 mutants compared with WT, and this correlated with reduced growth in pep1-1 Therefore, FLC orthologs regulate a set of conserved target genes mainly involved in reproductive development and were later independently recruited to modulate stress responses in different Brassicaceae lineages. Analysis of TF BSs in these lineages thus distinguishes widely conserved targets representing the core function of the TF from those that were recruited later in evolution.

Perpetual Flowering in Strawberry Species

The genetic control of flowering habit in many species of Fragaria has not been well studied. Identification of flowering traits and patterns for these taxa could be used in the quest for perpetual flowering (PF) genes and for the octoploids, broaden the genepool of available PF parents for breeding programs. As such, clones from the Fragaria germplasm collection housed at the USDA-ARS National Clonal Germplasm Repository in Corvallis, OR, were evaluated to describe flowering habits in various taxa and identify PF clones. Flower presence was recorded monthly for 962 clones of 36 taxa from the first of May through October in 2015 and 2016 to determine flowering habit and pairwise comparisons between taxa were examined using Pearson’s Chi-squared test. Taxa with the largest percent of PF accessions were F. vesca subsp. vesca f. semperflorens, F. vesca subsp. vesca f. alba, F. vesca subsp. americana, and F. virginiana subsp. glauca. These taxa had similar flowering habits to each other but were significantly different (α = 0.05) from most other taxa in which the seasonal flowering (SF) trait was predominant. Fifteen clones that demonstrated the PF phenotype in both 2015 and 2016 were identified. Differing genetic controls have been observed for flowering habit in F. ×ananassa and F. vesca. Additional studies are needed to determine genetic control of flowering in other Fragaria taxa.

Validation of molecular markers associated with perpetual flowering in Octoploid Fragaria germplasm

Perpetual-flowering (PF) is a highly desirable trait within cultivated strawberries (Fragaria ×ananassa) for the commercial and home garden markets. The most widely used source of the PF trait was originally introgressed from a wild F. virginiana subsp. glauca accession collected in the Wasatch Mountains near Salt Lake City, UT in 1955. This source is conferred by a single dominant QTL, FaPFRU, and was recently identified in multiple bi-parental populations. Multiple markers have been proposed as diagnostic tests for marker-assisted selection (MAS). These markers were proposed after looking at a relatively small sample of germplasm. To identify the best diagnostic testing procedure for MAS, the markers were evaluated individually and in combination on a training set of cultivars with known genotypes and the best test was used to determine the distribution of the FaPFRU source of PF within a large sample of octoploid Fragaria germplasm. Of the tests evaluated, the microsatellite marker Bx215 alone was found to have the best diagnostic ability for MAS with an accuracy of 93.1% in controlled conditions. When utilizing the test on 390 F. ×ananassa accessions, 164 accessions were identified to likely have the FaPFRU locus. Nine octoploid Fragaria accessions were PF and did not have this marker, indicating possible recombination events or potentially novel sources of the PF trait. Future work will be needed to dissect the PF trait in these nine individuals.

Identification of successive flowering phases highlights a new genetic control of the flowering pattern in strawberry.

The genetic control of the switch between seasonal and perpetual flowering has been deciphered in various perennial species. However, little is known about the genetic control of the dynamics of perpetual flowering, which changes abruptly at well-defined time instants during the growing season. Here, we characterize the perpetual flowering pattern and identify new genetic controls of this pattern in the cultivated strawberry. Twenty-one perpetual flowering strawberry genotypes were phenotyped at the macroscopic scale for their course of emergence of inflorescences and stolons during the growing season. A longitudinal analysis based on the segmentation of flowering rate profiles using multiple change-point models was conducted. The flowering pattern of perpetual flowering genotypes takes the form of three or four successive phases: an autumn-initiated flowering phase, a flowering pause, and a single stationary perpetual flowering phase or two perpetual flowering phases, the second one being more intense. The genetic control of flowering was analysed by quantitative trait locus mapping of flowering traits based on these flowering phases. We showed that the occurrence of a fourth phase of intense flowering is controlled by a newly identified locus, different from the locus FaPFRU, controlling the switch between seasonal and perpetual flowering behaviour. The role of this locus was validated by the analysis of data obtained previously during six consecutive years.