Perennial Helianthus Research Articles

Secretory Tissues and Volatile Components of Disc Florets in Several Wild Helianthus L. Species

Although flower pollinator interactions are known to be mediated by floral traits, not enough attention has been paid to the research of secretory tissues and volatile components of sunflower disc florets as potentially important parameters in breeding programs. (1) To our knowledge, this is the first integrated study aimed at better understanding the attractiveness of sunflower capitula to insects. In the study, we have made a very detailed comparative analysis of secretory tissues and the characterization of the volatile components (VOCs) of disc florets in 10 wild perennial Helianthus species. (2) For anatomical analyses, cross-sections were obtained from the nectary zone of disc florets using a cryotechnique procedure. Micromorphological observation and morphological and anatomical analysis of disc florets were performed using light and scanning electron microscopy. For VOCs, we applied headspace, GC-FID, and GC/MS analyses. (3) The obtained results indicate that there is a difference between the analyzed traits among studied species. H. eggertii, H. hirsutus, H. mollis, H. resinosus, and H. tuberosus had high disc diameter values, a high cross-section area and disc floret corolla length, as well as the largest cross-section area and thickness of the disc florets nectary. In the analyzed VOCs, 30 different compounds were detected. The highest yield and quantity of α-Pinene was observed in H. mollis. (4) Inflorescence features, such as receptacle diameter, corolla and secretory tissue properties, and floret VOCs production and characterization, provided valuable information that can be used as guidelines in sunflower breeding programs to maximize pollinator attractiveness and increase seed yield.

NGS Reads Dataset of Sunflower Interspecific Hybrids

The sunflower (Helianthus annuus), which belongs to the family of Asteraceae, is a crop grown worldwide for consumption by humans and livestock. Interspecific hybridization is widespread for sunflowers both in wild populations and commercial breeding. The current dataset comprises 250 bp and 76 paired-end NGS reads for six interspecific sunflower hybrids (F1). The dataset aimed to expand Helianthus species genomic information and benefit genetic research, and is useful in alloploids’ features investigations and nuclear–organelle interactions studies. Mitochondrial genomes of perennial sunflower hybrids H. annuus × H. strumosus and H. annuus × H. occidentalis were assembled and compared with parental forms.

First report of leaf anthracnose on the Whorled Sunflower, Helianthus verticillatus, caused by Colletotrichum fioriniae in the United States.

Whorled sunflower, Helianthus verticillatus Small, is an endangered (U.S. Fish and Wildlife Service 2014) perennial sunflower species indigenous to the southern United States (Matthews et al. 2002; Ellis et al. 2008). Helianthus verticillatus has a showy yellow floral display in the Fall that attracts a diversity of insect visitors (Strange et al. 2020). Its hardiness in the landscape and late-season blooming makes it a potential ornamental (Trigiano et al. 2021). In June 2021, anthracnose-like lesions were observed on mature leaves collected from potted H. verticillatus plants grown in the nursery compound at the University of Tennessee, Knoxville, TN, USA. Irregularly shaped leaf spots with 1‒2 mm tan centers were observed on mature leaves, which later expanded to 3‒5 mm, and became dark brown- to- black surrounded by chlorotic halos (Fig.1). Lesions from three infected leaves were excised from a single potted plant, trimmed to 1.5-cm squares with green borders, and surface-sterilized (Trigiano et al. 2018). Tissues were placed onto potato dextrose agar (PDA), amended with 100 mg/ml of each streptomycin sulfate and chlorotetracycline, and incubated at 21 °C in the dark until axenic cultures were obtained. Initially, appressed white- to- pale gray mycelia were formed that turned light pinkish-orange with age (Fig. 2A). Conidia (Fig. 2B-C) were single-celled, hyaline, and cylindrical- to- fusiform with acute ends, and were similar to Colletotrichum fioriniae (Damm et al. 2012). Conidia measured 8.9 ± 1.3 μm long and 3.3 ± 0.6 μm wide (N=40). Genomic DNA was isolated with a Phire Direct Plant PCR kit (Thermo FisherScientific, Waltham, MA). The partial beta-tubulin (TUB2) gene, chitin synthase 1 (CHS-1) gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene, and the internal transcribed spacer (ITS) region of ribosomal DNA were amplified with primers T1/BT2B, CHS-354R/CHS-79F, GDF1/GDR1, and ITS1/ITS4, respectively and sequenced (Damm et al. 2012). The resulting sequences were submitted to GenBank (TUB2, ON036471; CHS-1, ON036472; GAPDH, ON036470; and ITS, ON008206). Consensus sequences had 100% identity with C. fioriniae type culture CBS 128517 accessions JQ949943 (TUB2), JQ948953 (CHS-1), JQ948622 (GAPDH), and MH865005 (ITS rDNA). Because H. verticillatus is endangered, and the scarcity of available plant material, Koch's postulates were performed using a detached leaf assay (Boggess et al. 2022). Six healthy leaves were surface-sterilized using the previously described protocol, longitudinally bisected, and placed on 1.5% water agar in three 15 × 100 mm petri dishes. Three half leaves were inoculated with sterile, 5 mm-diameter PDA plugs (controls). The remaining three leaves were inoculated with 5 mm-diameter PDA plugs of C. fioriniae and incubated as described previously. After ten days, necrotic lesions developed on leaves inoculated with C. fioriniae and were similar to the initially observed lesions on plants. Lesions did not develop on control leaves. Colletotrichum fioriniae was re-isolated from lesions using the previously described protocol. The disease does not appear to cause mortality of H. verticillatus and does not require control measures but does reduce the aesthetic value of the plant. To the best of our knowledge, this is the first report of C. fioriniae infecting H. verticillatus in the United States.

A Quantitative Genetic Study of Sclerotinia Head Rot Resistance Introgressed from the Wild Perennial Helianthus maximiliani into Cultivated Sunflower (Helianthus annuus L.).

Sclerotinia head rot (HR), caused by Sclerotinia sclerotiorum, is an economically important disease of sunflower with known detrimental effects on yield and quality in humid climates worldwide. The objective of this study was to gain insight into the genetic architecture of HR resistance from a sunflower line HR21 harboring HR resistance introgressed from the wild perennial Helianthus maximiliani. An F2 population derived from the cross of HA 234 (susceptible-line)/HR21 (resistant-line) was evaluated for HR resistance at two locations during 2019–2020. Highly significant genetic variations (p < 0.001) were observed for HR disease incidence (DI) and disease severity (DS) in both individual and combined analyses. Broad sense heritability (H2) estimates across environments for DI and DS were 0.51 and 0.62, respectively. A high-density genetic map of 1420.287 cM was constructed with 6315 SNP/InDel markers developed using genotype-by-sequencing technology. A total of 16 genomic regions on eight sunflower chromosomes, 1, 2, 10, 12, 13, 14, 16 and 17 were associated with HR resistance, each explaining between 3.97 to 16.67% of the phenotypic variance for HR resistance. Eleven of these QTL had resistance alleles from the HR21 parent. Molecular markers flanking the QTL will facilitate marker-assisted selection breeding for HR resistance in sunflower.

The Insights into Mitochondrial Genomes of Sunflowers.

The significant difference in the mtDNA size and structure with simultaneous slow evolving genes makes the mitochondrial genome paradoxical among all three DNA carriers in the plant cell. Such features make mitochondrial genome investigations of particular interest. The genus Helianthus is a diverse taxonomic group, including at least two economically valuable species—common sunflower (H. annuus) and Jerusalem artichoke (H. tuberosus). The successful investigation of the sunflower nuclear genome provided insights into some genomics aspects and significantly intensified sunflower genetic studies. However, the investigations of organelles’ genetic information in Helianthus, especially devoted to mitochondrial genomics, are presented by limited studies. Using NGS sequencing, we assembled the complete mitochondrial genomes for H. occidentalis (281,175 bp) and H. tuberosus (281,287 bp) in the current investigation. Besides the master circle chromosome, in the case of H. tuberosus, the 1361 bp circular plasmid was identified. The mitochondrial gene content was found to be identical for both sunflower species, counting 32 protein-coding genes, 3 rRNA, 23 tRNA genes, and 18 ORFs. The comparative analysis between perennial sunflowers revealed common and polymorphic SSR and SNPs. Comparison of perennial sunflowers with H. annuus allowed us to establish similar rearrangements in mitogenomes, which have possibly been inherited from a common ancestor after the divergence of annual and perennial sunflower species. It is notable that H. occidentalis and H. tuberosus mitogenomes are much more similar to H. strumosus than H. grosseserratus.

Effects of Light and Temperature on Germination of Eggert's Sunflower (Helianthus eggertii)

Helianthus eggertii is a rare perennial sunflower of barrens and open habitats in Kentucky, Tennessee, Alabama, and South Carolina in the United States (U.S.). Despite its delisting in the U.S. Endangered Species Act in 2005, little is known about the germination biology of H. eggertii other than seeds require cold stratification for optimal germination. Knowledge about the germination biology of rare species can aid in the management of natural populations and inform strategies for ex situ seed conservation and propagation. We examined how cold stratification, light, and temperature interact to affect seed germination in H. eggertii, and whether germination proportions varied among populations. At the time of maturity in October, seeds have primary physiological dormancy and require cold stratification or prolonged (> 8 wk) incubation in light at cool (15/6 C) temperatures to germinate. Seeds maintained a light requirement for germination when cold stratified in darkness, but not after cold stratification in light. However, seeds germinated to lower proportions after cold stratification in light relative to darkness, and when incubated at temperatures that mimic summer (35/20 C) compared to late spring (25/15 C). Germination varied widely among populations (23-58%), with plants from more open sites exhibiting lower germination proportions than those from partially shaded sites. Our results indicate seeds most likely germinate in early- to mid-spring, and light promotes germination of H. eggertii. Our results highlight the interactive role of light and temperature in determining seed dormancy break and germination in H. eggertii.

Balancing Forage Production, Seed Yield, and Pest Management in the Perennial Sunflower Silphium integrifolium (Asteraceae)

The perennial sunflower Silphium integrifolium Michx. (Asteraceae), also known as silflower, is a prospective dual-purpose forage plus grain crop. Pre-flowering biomass harvest for animal feed and the subsequent delay in plant growth and anthesis has the potential to benefit seed yield and/or offset yield loss from native pests, such as the native North American Eucosma giganteana (Lepidopera: Tortricidae). The aim of this study was to develop a cropping technology for silflower to (A) balance forage and grain production and (B) minimize seed loss. Silflower produced high-quality forage, but biomass harvest in early spring reduced same-season seed production by 45%. Despite significantly delaying flowering, forage harvest alone did not effectively reduce Eucosma colonization, although treating plants with the insecticide permethrin did reduce colonization. Our results do not support the proposal that S. integrifolium could be profitably harvested for both high quality forage and as an oilseed grain within the same season. Nevertheless, our findings suggest the possibility of developing a strategy of alternating between forage or seed production, depending on their differential economic values. The choice between harvesting biomass vs. seed could be made much later in the season for this perennial crop than the choice of planting an annual forage vs. annual grain crop.

The Investigation of Perennial Sunflower Species (Helianthus L.) Mitochondrial Genomes

The genus Helianthus is a diverse taxonomic group with approximately 50 species. Most sunflower genomic investigations are devoted to economically valuable species, e.g., H. annuus, while other Helianthus species, especially perennial, are predominantly a blind spot. In the current study, we have assembled the complete mitogenomes of two perennial species: H. grosseserratus (273,543 bp) and H. strumosus (281,055 bp). We analyzed their sequences and gene profiles in comparison to the available complete mitogenomes of H. annuus. Except for sdh4 and trnA-UGC, both perennial sunflower species had the same gene content and almost identical protein-coding sequences when compared with each other and with annual sunflowers (H. annuus). Common mitochondrial open reading frames (ORFs) (orf117, orf139, and orf334) in sunflowers and unique ORFs for H. grosseserratus (orf633) and H. strumosus (orf126, orf184, orf207) were identified. The maintenance of plastid-derived coding sequences in the mitogenomes of both annual and perennial sunflowers and the low frequency of nonsynonymous mutations point at an extremely low variability of mitochondrial DNA (mtDNA) coding sequences in the Helianthus genus.

A Unique Cytoplasmic-Nuclear Interaction in Sunflower (Helianthus annuus L.) Causing Reduced-Vigor Plants and the Genetics of Vigor Restoration.

Wild Helianthus species are an important genetic resource for sunflower improvement, but sometimes there are adverse interactions between the wild and cultivated sunflowers. This study reports the inheritance of reduced vigor and its restoration resulting from an interaction of perennial Helianthus cytoplasms with nuclear genes of cultivated sunflower lines. The large number of vigor restoration (V) genes identified in cultivated lines are all located at the same locus, designated V1, suggesting a common origin of these genes. Additional V genes derived from the wild perennial species H. giganteus L. and H. hirsutus Raf. are located at a different locus than V1, designated V2. A major difference between the wild annual Helianthus cytoplasms and perennial cytoplasms is the lack of the vigor-reducing cytoplasms, but surprisingly V genes were observed in wild annual H. annuus L. and H. petiolaris Nutt. which were at the same locus as V1. A common vigor-reducing cytoplasmic effect of the perennial Helianthus species and the existence of a common vigor restoration V gene in most perennial Helianthus species could be explained as a result of vigor selection during Helianthus speciation. V1 was mapped on linkage group (LG) 7 of the sunflower genome, using an F2 population derived from MOL-RV/HA 821. V1 co-segregated with an InDel marker ZVG31, with three single-nucleotide polymorphism (SNP) markers, SFW01024, SFW07230, and SFW00604, located above it on the map at a genetic distance of 0.8 cM, and another SNP marker, SFW08671, below it at a distance of 0.4 cM. The physical distance between the two closest flanking SNP markers corresponds to 0.56 and 1.37 Mb on the HA 412-HO and XRQ assemblies, respectively. The tightly linked markers will help select normal vigor progenies when using perennial Helianthus cytoplasms in a breeding program, which will also provide a basis for studying the mechanism of the cytonuclear interaction, and the speciation of annual and perennial Helianthus species.

SSR Analysis of Nuclear DNA of Annual and Perennial Sunflower Species (Helianthus L.)

Genotyping of 29 species of genus Helianthus L., including 5 annual and 24 perennial species from the collection of the N. I. Vavilov All-Russian Institute of Plant Genetic Resources has occurred, for this purpose were selected 52 SSR markers, with localization on all the 17 linkage groups of the sunflower genome. All the studied sunflower samples had unique SSR loci banding patterns. The mean PIC value varied was 0,72, which indicates the high resolution of this SSR based system for sunflower nuclear genome investigations. The discriminatory power of the marker system allowed us to classify all the sunflower species and provide the molecular barcoding. The UPGMA dendrogram, reflecting the genetic differences between 29 species of the genus Helianthus L., was constructed. Allele distribution data of the studied sunflower samples is a database that can be used to determine the levels of genetic variability, provide molecular barcoding and control the genetic integrity of collection sunflower samples.

Taxonomic Diversity of Micromycete Complexes in the Root Zone of a Perennial Wild Species of Sunflower Helianthus Grosseserratus

The aim of our research was to determine the peculiarities of the formation of the taxonomic structure of micromycete complexes in the root zone of the perennial wild species of sunflower Helianthus grosseserratus when grown in the South of Ukraine. Soil samples taken from the root zone of two samples of perennial wild sunflower Helianthus grosseserratus 1630 and H. grosseserratus 1201, which were grown for more than 20 years in one place in the collection nursery of the Institute of Oilseed Crops of NAAS of Ukraine, were studied. Areas where plants are grown have not been treated with herbicides. Samples of fallow soil served as a control. Soil - chernozem ordinary low-humus leached. Soil samples for analysis were taken at the end of the growing season. To isolate microscopic fungi from the soil, the generally accepted method of serial dilutions was used, followed by sowing of the soil suspension on a dense nutrient medium Chapek-Dox. The method of sowing - deep, dilution of the suspension - 1: 1000. Duration of fungi cultivation - 7-14 days in a thermostat at a temperature of 28оС. The experiment was repeated five times. The complex of fungi-micromycetes in soil samples was determined using determinants and original works. The similarity of the species composition of the soil mycobiota of the fallow and the root zone of wild sunflower was determined by the Sorensen coefficient. Reliable indicators of similarity when comparing the species composition of two different associations were considered those in which the Sorensen coefficient was more than 50%.The analysis of the taxonomic structure of the studied mycocenoses revealed qualitative differences in the genus and species composition of micromycete fungi in the rhizosphere of wild sunflower species and fallow soil. In total, of the 29 species of micromycetes we isolated, 11 were found only in the soil of the fallow. According to our data, only 4 species (A. alliaceus, Paecilomyces lilacinus, F. oxysporum var. orthoceras, M. racemosus) were common species in the soil samples of fallow and root zone Helianthus grosseserratus 1630 and H. grosseserratus 1201. The species diversity of micromycetes of the root zone of H. grosseserratus 1201 was wider, and, accordingly, more similar to the soil of the fallow - 15 common species. Micromycetes that were typical for both fallow soil and sunflower are saprotrophs of A. niveus, P. canescens, P. crustosum, P. nigricans, P. thomii, as well as opportunistic species Verticillium album and V. lateritium. A comparative analysis of the lists of species composition of micromycete complexes revealed significant differences between the mycocenoses of the root zone of wild sunflower and fallow soil, as evidenced by the calculated Sorensen coefficients. The data indicated that the similarity of the species composition of the mycobiota H. grosseserratus 1201 with fallow was 66.7% (Cs = 0.67), and Helianthus grosseserratus 1630 - only 35.8% (Cs = 0, 35). The coefficient of similarity of the species composition of the mycobiota of the root zone of wild sunflower was 0.47, which is apparently due to the peculiarities of the composition of the root exudates of plants and their selection zones, which affect the formation of microbial complexes of the rhizosphere and edaphosphere.

Pericarp features of wild perennial Helianthus L. species as a potential source for improvement of technical and technological properties of cultivated sunflower

Although the anatomy of the sunflower achene has been extensively studied, not enough attention is given to the research of the pericarp characteristics as potentially important parameters in the breeding programme. Therefore, we considered that it was important to make very detail comparative analysis of morpho-anatomical characteristics of achene as well as miromorphological and n-alkane characteristics of epicuticular wax of the 18 wild perennial Helianthus species. For anatomical analyses cross-sections were obtained from the middle part of pericarp using cryotechnique procedure. Micromorphological observation, morphological and anatomical analysis of pericarp were performed using Light and Scanning Electron Microscopy. The composition of the epicuticular n-alkanes was characterized by GC-FID and GC/MS analyses. Results showed differences in the distribution of phytomelanin pigment among the species. Denser phytomelanin network in the species H. salicifolius, H. resinous, H. tuberosus, and H. hirsutus may be connected with better resistance to insects and mechanical damages. Species H. resinosus, H. giganteus, and H. hirsutus are characterized by the highest percentage of cuticle and sclerenchyma thickness in the pericarp which can be a predictor of mechanical resistance to biotic and abiotic factors. Species H. strumosus, H. maximiliani, and H. grosseserratus are characterized with thin pericarp, poorly developed cuticle and epicuticle wax, as well as thin sclerenchyma tissue. In the pericarp waxes, C29 was the dominant alkane but several samples had n-alkanes longer than C33.These long-chain n-alkanes may be related to drought tolerance in some species. Obtained results of pericarp characteristics can be useful for improving technical and technological properties of the achene as well as for preservation of collection of wild sunflower species.

Domestication in Real Time: The Curious Case of a Trigenomic Sunflower Population

This study chronicles the ongoing process to domesticate an interspecific trigenomic tetraploid hybrid sunflower derived from a series of interspecific crosses between Helianthus annuus and Helianthus tuberosus. The goal of this process is to develop a perennial oilseed crop that can produce both high value vegetable oil and continuous ground-cover. Selection has focused on developing an ideotype with the domesticated morphology of H. annuus and the below-ground perennial features of H. tuberosus. The overarching challenge in the process of breeding and domesticating this interspecific perennial sunflower is overcoming obstacles associated with interploid meiosis in order to resolve a chromosomally stable hybrid population. As selection progresses through generations of intermating, there are improvements toward the desired ideotype, but selection efficiency is slowed by apparent antagonisms between annual- and perennial morphological targets and irregular meiosis which is especially problematic in a trigenomic tetraploid. This shows that keys toward perennial crop development through interspecific hybridization will be to capitalize on the abundant phenotypic variation within our population, achieve meiotic stability in order to maximize selection efficiency, and to break genetic correlations between annual and perennial traits.

Influence of crop-caring system on the productivity of safflower varieties at herbicide-free and herbicide backgrounds

Influence of crop-caring system on the productivity of safflower varieties at herbicide-free and herbicide backgrounds

Morphological and biochemical characteristics of underground organs in various perennial species of sunflower

Morphological and biochemical characteristics of underground organs in various perennial species of sunflower

Comparison of seed and seedling functional traits in native Helianthus species and the crop H.annuus (sunflower).

Seed functional traits of native Helianthus species contribute towards ecosystem services but limitations to their use in managed programmes exist. Many perennial Helianthus possess seed dormancy. The ability for germination to occur under different temperature and drought conditions, as well as the capacity of germinated seeds to convert into normal seedlings is rarely considered. Our aim was to identify and quantify these constraints through functional trait analyses. In five seed lots of native Helianthus (four perennial and one annual) and five genotypes of sunflower (H.annuus) for comparison, dormancy, thermal and hydro thresholds and times, morphology, mass, oil content and conversion into normal seedlings were quantified. The influence of the seed collection site environment on these traits was also explored. Seed dormancy of the perennial species was overcome by scarification followed by germination in 5mm GA3 . Thermal and hydro-time analyses revealed slower germination for the native seed lots (>1350°Ch) in comparison to the sunflower genotypes (<829.9°Ch). However, native seed lots had a higher capacity to convert into normal seedlings at high temperatures and low water potentials than sunflower genotypes. For the native seed lots, the average monthly temperature of the collection site was negatively correlated with thermal time. Variability in seed functional traits of native Helianthus and greater capacity for germinated seeds to convert into normal seedlings suggests they are better equipped to cope with high temperature and drought scenarios than sunflower. Effective dormancy alleviation is required to facilitate the use of native Helianthus species.

Evolution of invasiveness by genetic accommodation.

Invasion success of species introduced to novel environments may be facilitated by adaptive evolution and by phenotypic plasticity. Here we investigate the independent and joint contribution of both mechanisms as drivers of invasiveness in the perennial sunflower Helianthus tuberosus. We show that invasive genotypes have multiple origins, and that invasive spread was facilitated by the repeated evolution of extreme values in a single trait, clonality. In line with genetic accommodation theory, we establish that this evolutionary transition occurred by refining a preexisting plastic response of clonality to water availability. Further, we demonstrate that under the non-drought conditions typically experienced by this plant in its introduced range, invasive spread is mediated by hybrid vigour and/or two major additive-effect loci, and that these mechanisms are complementary. Thus, in H. tuberosus, evolution of invasiveness was facilitated by phenotypic plasticity, and involved the use of multiple genetic solutions to achieve the same invasiveness trait.

Low Temperature Tolerance in the Perennial Sunflower Helianthus maximiliani

Abstract Species distributed across diverse climate and thermal conditions represent opportune systems for studying tolerance of low temperature stress. We examined variation in cold acclimation capacity and freezing tolerance among three natural populations (Texas, Kansas, and Manitoba) of the perennial sunflower species Helianthus maximiliani, originally collected across 2134 km in central North America. Tolerance to low temperatures was evaluated through leaf electrolyte leakage assays that quantify loss of cellular electrolytes into an aqueous medium due to plasma membrane damage. Freezing tolerance was highest for plants from the northernmost latitude (Manitoba population) under both non cold- acclimated and cold- acclimated experimental conditions. Individuals from Kansas and Texas populations exhibited lower freezing tolerance compared to Manitoba but did not differ from one another. Plants from all populations retain the ability to increase freezing tolerance through the process of cold acclimatio...

Helianthus Grosseserratus, A New Alien Plant Species in Lithuania

Abstract Helianthus grosseserratus M. Martens was first recorded in Lithuania in 2014. Rather large population of this species was found in Siauliai district (northern Lithuania), in the vicinity of Bridai village, on the territory of recultivated former municipal dump. This species can be easily distinguished from other perennial Helianthus species by glabrous stem, long, serrate, alternate leaves on the upper part of the stem and spindle-shaped roots. Supposedly, H. grosseserratus was brought to the area with garden waste or soil used for dump recultivation about 30 years ago and recently it has established in the locality. In the investigated capitula, no developed seeds were found. H. grosseserratus reproduces vegetatively by rhizomes and under favourable conditions can survive for a long time.

Molecular traits to elucidate the ancestry of Helianthus x multiflorus

The triploid perennial Helianthus x multiflorus L. is a beloved garden ornamental, but its phylogenetic origin has long been a source of discussion. Sequence comparison of genes involved in the biosynthesis of the sesquiterpene lactones was used to identify the common sunflower Helianthus annuus L. and the diploid taxon Helianthus decapetalus L. as the most likely parental combination in the origin of the triploid hybrid species. A pair of deletions (22 and 26bp in length) in an intron part of the germacrene A synthase 1 gene differentiated the diploid from the tetraploid karyotype of H. decapetalus. The same deletion was found in one of the two alleles (299bp in length) in H. x multiflorus, whereas a second allele (350bp in length) showed a very high similarity with the sequence found in H. annuus. Quantification of the two amplification products in H. x multiflorus showed a higher concentration of the larger amplicon thus suggesting that H. annuus has contributed an unreduced genome to the hybrid. Comparison of variable regions of the cpDNA showed highest identity of H. x multiflorus with cpDNA sequences of the diploid H. decapetalus. This suggests that H. decapetalus served as the maternal parent in a cross with H. annuus to produce H. x multiflorus.