Styrian Oil Pumpkin Research Articles

Negative and sex-specific effects of drought on flower production, resources and pollinator visitation, but not on floral scent in monoecious Cucurbita pepo.

The globally changing climatic condition is increasing the incidences of drought in several parts of the world. This is predicted and already shown to not only impact plant growth and flower development, but also plant-pollinator interactions and the pollination success of entomophilous plants. However, there is a large gap in our understanding of how drought affects the different flowers and pollen transfer among flowers in sexually polymorphic species. Here, we evaluated in monoecious Styrian oil pumpkin, and separately for female and male flowers, the responses of drought stress on flower production, petal size, nectar, floral scent and visitation by bumblebee pollinators. Drought stress adversely affected all floral traits studied, except floral scent. Although both flower sexes were adversely affected by drought stress, the effects were more severe on female flowers, with most of the female flowers even aborted before opening. The drought had negative effects on floral visitation by the pollinators, which generally preferred female flowers. Overall, our study highlights that the two flower sexes of a monoecious plant species are differently affected by drought stress and calls for further investigations to better understand the cues used by the pollinators to discriminate against male flowers and against flowers of drought-stressed plants.

A novel O-methyltransferase Cp4MP-OMT catalyses the final step in the biosynthesis of the volatile 1,4-dimethoxybenzene in pumpkin (Cucurbita pepo) flowers

BackgroundFloral scents play a crucial role in attracting insect pollinators. Among the compounds attractive to pollinators is 1,4-dimethoxybenzene (1,4-DMB). It is a significant contributor to the scent profile of plants from various genera, including economically important Cucurbita species. Despite its importance, the biosynthetic pathway for the formation of 1,4-DMB was not elucidated so far.ResultsIn this study we showed the catalysis of 1,4-DMB in the presence of 4-methoxyphenol (4-MP) by protein extract from Styrian oil pumpkin (Cucurbita pepo) flowers. Based on this finding, we identified a novel O-methyltransferase gene, Cp4MP-OMT, whose expression is highly upregulated in the volatile-producing tissue of pumpkin flowers when compared to vegetative tissues. OMT activity was verified by purified recombinant Cp4MP-OMT, illustrating its ability to catalyse the methylation of 4-MP to 1,4-DMB in the presence of cofactor SAM (S-(5′-adenosyl)-L-methionine).ConclusionsCp4MP-OMT is a novel O-methyltransferase from C. pepo, responsible for the final step in the biosynthesis of the floral scent compound 1,4-DMB. Considering the significance of 1,4-DMB in attracting insects for pollination and in the further course fruit formation, enhanced understanding of its biosynthetic pathways holds great promise for both ecological insights and advancements in plant breeding initiatives.

Morphological Characteristics of Selected Fruit Parts and Naked Seeds of Cucurbita pepo var. styriaca

The study aimed to determine the variability of some morphological characters on fruits of selected plants within the population of ESO variety of Styrian oil pumpkin (Cucurbita pepo var. styriaca). For experimental evaluation, we used two years (2020–2021) measurements of 165 selected fruits from individual plants grown in the field conditions in Kolíňany (Slovak Republic). We determined for all samples the range for the weight of fruits (521.50–12744.70 g), length of fruits (85.00–285.00 mm), width of fruits (114.00–320.00 mm), exocarp thickness on the left side (0.10–4.86 mm), exocarp thickness on the right side (0.33–4.56 mm), pericarp thickness on the left side (9.13–57.02 mm), pericarp thickness on the right side (9.77–46.05 mm), placenta weight (89.00 –870.00 g), fresh seed weight (17.30–638.50 g), seed weight after drying (4.53–187.36 g), seed length (12.91–24.00 mm), seed diameter (6.56–14.41 mm), seed thickness (0.41–3.62 mm), the weight of one thousand seeds (15.41–475.66 g). The results document that in our collections there are plants suitable for the next cultivation, and further selective improvement. In practice, only seeds of the ESO variety are used for oil production. The percentage of the weight of the seeds from the total weight of the fruits is only 3–4%. Other parts of the fruit remain in the field after harvesting. After their decomposition and ploughing into the soil, they improve the physico-chemical properties of the soil. However, the results of the experiments confirm that many parts of the fruit, such as the pulp and the placenta, are important raw material sources for use in the food industry, pharmaceuticals, cosmetics, and other areas. When growing butter pumpkin in large areas, it is also possible to collect and use flowers and young – unripe fruits from the plants during the growing season in the food industry and other areas.

Microbiome-Assisted Breeding to Understand Cultivar-Dependent Assembly in Cucurbita pepo.

Recently, it was shown that long-term plant breeding does not only shape plant characteristics but also impacts plant-associated microbiota substantially. This requires a microbiome-integrative breeding approach, which was not yet shown. Here we investigate this for the Styrian oil pumpkin (Cucurbita pepo L. subsp. pepo var. styriaca Greb.) by analyzing the microbiome of six genotypes (the complete pedigree of a three-way cross-hybrid, consisting of three inbred lines and one open pollinating cultivar) in the seed and rhizosphere as well as the progeny seeds. Using high-throughput amplicon sequencing targeting the 16S rRNA and the ITS1 genes, the bacterial and fungal microbiomes were accessed. Seeds were found to generally carry a significantly lower microbial diversity compared to the rhizosphere and soil as well as a different microbial composition, with an especially high fraction of Enterobacteriaceae (40–83%). Additionally, potential plant-beneficial bacterial taxa, including Bacillaceae, Burkholderiaceae, and Pseudomonadaceae, were found to be enriched in progeny seeds. Between genotypes, more substantial changes can be observed for seed microbiomes compared to the rhizosphere. Moreover, rhizosphere communities were assembled for the most part from soil. Interestingly, bacterial signatures are mainly linked from seed to seed, while fungal communities are shaped by the soil and rhizosphere. Our findings provide a deep look into the rhizosphere and seed microbiome assembly of pumpkin-associated communities and represent the first steps into microbiome-driven breeding for plant-beneficial microbes.

Seed Lipid Composition of New Hybrids of Styrian Oil Pumpkin Grown in Poland

Styrian hull-less pumpkins are valued for their use in health-promoting foods such as oils and snacks. Although deriving from Styria, they are now cultivated globally. Seeds of Styrian oil pumpkins are rich in lipids and represent a high-value product. Thus, seed yield and quality are traits of economic importance. These seed characteristics depend mostly on the cultivated variety and plant growing conditions. This study aimed to assess the variation in hull-less seed lipids of new hybrids of Styrian oil pumpkin developed recently for cultivation in moderate/colder climate zones of the north-eastern part of Poland. The study showed that the newly-developed hybrids have a relatively high content of total lipids in seeds, with a substantially higher share of linoleic acid (up to 63%). However, sterols, tocopherols, and squalene content and composition were similar to pumpkin seed oils produced from plants cultivated in other, warmer regions. This study provides insights into the chemical composition of Styrian pumpkin oil produced from hybrids grown under the relatively severe climatic conditions of north-eastern Poland.

Comparison of the physiological responses of an oil-pumpkin cultivar and hybrid under different nitrogen supply conditions

Cucurbita pepo var. styriaca is known as a medicinal crop among other cucurbits. The benefits of cucurbits fruits are very important in terms of human health, purification of blood, removal of constipation, digestion and supplying energy. The mutant styrian oil-pumpkin (Cucurbita pepo L. convar. Pepo var. styriaca Greb.) exposes a complete lack of lignification of the seed testa. For this reason, this kind of naked pumpkin seed is more consumable as snack than other seeds. The vegetative growth of plants is crucial for fruit production. Nitrogen is the most imperative element for the proper vegetative growth and development of plants which significantly increases and enhances yield and its quality by playing a vital role in the biochemical and physiological functions of plants.
 Field studies were conducted to study the effect of nitrogen nutrition on certain physiological parameters and their differences between the styrian oil pumpkin hybrid and cultivar (Gleisdorfi Classic cultivar and GL Rustical hybrid). The small block experiment was carried out based on a factorial experiment with a completely randomised block design and four replications in the Research Institute of Nyíregyháza during the summer period of 2017 and 2018. Three different concentrations of nitrogen fertiliser was applied at sowing. Photosynthetic pigments (chlorophyll-a, -b and carotenoids) were analysed as one of the basic factor of efficient photosynthesis. The yields of two genotypes were also measured in all treatments as seed-weight. The contents of photosynthetic pigments were higher in the oil-pumpkin hybrid, mainly the carotenoids in 2018. The vegetation period of 2018 was drier than in 2017, the hybrid oil-pupmkin was more efficient in stress tolerance than the cultivar with higher carotenoids pool. The obtained yield was more pronounced in the oil-pumpkin hybrid than the cultivar in all examined years. The hybrid GL Rustical was more sensitive to nitrogen treatment than the cultivar Gleisdorfi Classic.

The impact of fruit temperature dynamics on heat stress tolerance of selected oil pumpkin genotypes.

Fruit temperature is a key parameter for fruit growth and quality which is affected by climate, plant vigorousity, solar exposure and fruit thermal properties. In the present study, the variability in temperature dynamics of Styrian oil pumpkin fruits and selected interspecific hybrids involving Cucurbita argyrosperma, C. moschata, C. pepo was analysed in two different periods of hot weather. The temperatures were measured with thermistors on (a) attached fruits, (b) detached fruits exposed to the sun and (c) artificially black coloured fruits. The highest average temperatures were determined in the Styrian oil pumpkin, whereas the lowest temperatures were determined in genotypes with lighter fruit exteriors suggesting that those are less sensitive to heat stress conditions and may represent a good option for the improvements of adaptability to climatic changes. In order to combine lighter and harder pericarp, the most promising genotypes were crossed with wild Cucurbita okeechobeensis. The histological analysis showed that C. okeechobeensis was a good source of genes for obtaining a thicker sclerenchymatic layer within pericarp

The Cucurbita pepo seed microbiome: genotype-specific composition and implications for breeding

Background and aimsPlant breeding activities shape the rhizosphere microbiome but less is known about the relationship of both with the seed microbiome. We analyzed the composition of bacterial communities of seeds and rhizospheres of Styrian oil pumpkin genotypes in comparison to bulk soil to elucidate specific microbial signatures to support a concept involving plant-microbe interactions in breeding strategies.MethodsThe seed and rhizosphere microbiomes of 14 genotypes of oilseed pumpkin and relatives were analyzed using a 16S rRNA gene amplicon sequencing approach, which was assessed by bioinformatics and statistical methods.ResultsAll analyzed microhabitats were characterized by diverse bacterial communities, but the relative proportions of phyla and the overall diversity was different. Seed microbiomes were characterized by the lowest diversity and dominant members of Enterobacteriaceae including potential pathogens (Erwinia, Pectobacterium). Potential plant-beneficial bacteria like Lysobacter, Paenibacillus and Lactococcus contributed to the microbial communities in significant abundances. Interestingly, strong genotype-specific microbiomes were detected for seeds but not for the rhizospheres.ConclusionsOur study indicates a strong impact of the Cucurbita pepo genotype on the composition of the seed microbiome. This should be considered in breeding of new cultivars that are more capable of exploiting beneficial indigenous microbial communities.

Regional heterogeneity and spatial interdependence as determinants of the cultivation of an emerging alternative crop: The case of the Styrian Oil Pumpkin

In the course of the liberalisation and globalisation of agricultural markets the Common Agricultural Policy (CAP) of the European Union (EU) has shifted from quantity-based to quality-based policies, encouraging a diversification of agricultural production. For policy makers it is therefore relevant to understand better the drivers which influence the adoption and spatial distribution of emerging alternative products and production systems in agriculture. Taking the Styrian Oil Pumpkin as an example, the aim of this study is to quantify the determinants of spatial variations in the cultivation of an emerging alternative crop. We estimate Tobit and SLX Tobit models for two regions, drawing on cross-sectional data from the year 2010 of 549 municipalities in the Styrian Oil Pumpkin Protected Geographical Indication (PGI) area. Our findings indicate that, apart from (i) crop-specific factors, there are also (ii) region-specific factors such as marketing possibilities and there is (iii) spatial interdependence influencing spatial variations in oil-pumpkin-cultivated area and we conclude that these factors also need to be considered for the support of other emerging alternative products and production systems in agriculture.

Pectobacterium carotovorum subsp. brasiliensis causing a soft rot on Styrian oil pumpkin in Austria

Styrian oil pumpkin ( Cucurbita pepo subsp. pepo var. styriaca ) is an important crop in the eastern part of Austria, with a cultivated area in 2010 of about 26,000 ha yielding 4 million litres of edible oil worth €60 million per annum.…

Adventitious regeneration in styrian oil pumpkin in relation to the endoreduplication pattern and induced tetraploidy on fusaric acid-supplemented media

We attempted to improve the adventitious regeneration protocol in styrian oil pumpkin for subsequent use in somaclonal variation studies. The endoreduplication status of tissues might play an important role, so endopolyploidy was analyzed by flow cytometry in different organs and major differences were revealed. Endoreduplication was minimal in leaves but in other organs—particularly in the hypocotyl and epicotyl—levels up to 64C were found. The basal part of cotyledons has been reported to be the most responsive for adventitious regeneration and, using image cytometry, we identified it as the least endoreduplicated section, with a cycle value of 1.29 compared to 1.78 and 1.80 in the central and distal parts. Basal cotyledonary explants were subjected to various media combinations, revealing Murashige and Skoog (Physiol Plant 15:473–497, 1962, doi:10.1111/j.1399-3054.1962.tb08052.x) medium supplemented with 1 mg L−1N6-benzylaminopurine (BA), 0.25 mg L−1p-aminobenzoic acid (PABA) and 5 mg L−1 fusaric acid (FA) to be optimal (73.3 % regenerated explants with 1.8 shoots per regenerating explants). FA was added to media as a possible selective agent for somaclonal variation inducing increased tolerance to Fusarium but was surprisingly found to stimulate regeneration at a low concentration (5 mg L−1) and to induce genome doubling at medium concentrations (10 and 20 mg L−1).

Halting the western corn rootworm by crop rotation – yes, but! Effects of oil pumpkin in Styria

The western corn rootworm Diabrotica virgifera virgifera has invaded large parts of the maize growing areas of Central Europe since it was first detected in 1992 near Belgrade, Serbia (eDWarDS et al., 2011). In 2002 the beetle arrived in the eastern parts of Austria and extended in 2012 into the southern and western parts. Only a few cases with observed economic damages have been recorded since in those areas. Official control measures according to EU Decision 2003/766/EG are in place to prevent the further spread of the western corn rootworm. Crop rotation as the most efficient strategy to suppress the western corn rootworm should be applied either alone or in combination with insecticide treatments. In our study we aimed to test the effects of Styrian oil pumpkin rotated with maize on the reproduction of Diabrotica in isolation cages in the field.

Styrian oil pumpkin pollen germinability at higher irradiation doses: optimization of the in vitro germination protocol and irradiation procedure

Protocols for haploid induction in cucurbits are based on pollination with irradiated pollen, but the induction frequency is low and the majority of obtained embryos are zygotic. The longevity of Cucurbita pepo L. pollen is short even under natural conditions; following irradiation, germinability is decreased even further. This study was initiated to develop an optimal in vitro germination medium for styrian oil pumpkin (Cucurbita pepo L. subsp. pepo var. styriaca Greb.) pollen, which would enable accurate germination testing. Different pH values and the addition of sucrose, mannitol, and polyethylene glycol to the Brewbaker and Kwack germination medium were tested. The optimum medium condition was pH 9 and 12.5% (w/v) sucrose, while other tested components were not efficient. Using the optimized medium, X-ray-irradiated (100-700 Gy) pollen germinability was assessed under 2 air humidity conditions. Germinability of pollen irradiated at room humidity (RH) was generally lower than that of pollen irradiated at high humidity (HH). A major variability in pollen size (diameters ranged from 79.2 to 196.5 µm) and 2 subgroups were found in the pollen population. Following irradiation, HH conditions allowed germination of larger pollen grains than those of the nonirradiated control and RH.

Genome Sequence of Serratia plymuthica Strain S13, an Endophyte with Germination- and Plant-Growth-Promoting Activity from the Flower of Styrian Oil Pumpkin

The bacterium Serratia plymuthica strain S13 was demonstrated to colonize various plant-associated microhabitats and to suppress damping-off diseases. The completed genome sequence has a size of 5.5 Mb, containing 4,957 putative protein-encoding regions, and will be used to identify genetic determinants enabling the bacterium to escort a plant’s entire life cycle.

Haploid Induction in Hull-less Seed Pumpkin through Parthenogenesis Induced by X-ray-irradiated Pollen

Production of hull-less seeds of styrian oil pumpkin (Cucurbita pepo ssp. pepo var. styriaca) is increasing as a result of demand for aromatic seed oil and for other uses. Hybrid cultivars have recently been released but a method for haploid induction has not been established. We focused on the development of a parthenogenetic haploid induction protocol based on pollination with pollen irradiated with X-ray radiation at 0, 50, 100, 150, 200, 300, and 350 Gy. Fruit set largely decreased at 200 Gy, whereas a decline in embryo formation was observed at 100 Gy. Various accessions were tested as the female parent or as the pollen donor and large differences were found. The best parthenogenetic response was found in ‘Turkey #2’ (10.0%), ‘Gleisdorfer Ölkürbis’ (4.4%), and ‘Naked Seed’ (3.9%), whereas ‘GL Opal’ and ‘White Acorn’ were efficient as pollen donors. The ploidy level of 3830 putative parthenogenetic embryos was determined using flow cytometry. Four ploidy levels (n, 2n, 3n, and 4n) were found with the majority being diploid. Interestingly, a significant proportion was determined to be tetraploid and this was clearly correlated with increased radiation delivered to pollen grains. Using selected simple sequence repeat markers on diploid embryos, no spontaneous chromosome doubling could be confirmed. In this study, haploid induction in styrian oil pumpkin was elaborated for the first time. We also showed that X-ray pollen irradiation provides an alternative to gamma radiation treatment, yielding a sufficient percentage of haploid plantlets.

Promotion of growth, health and stress tolerance of Styrian oil pumpkins by bacterial endophytes

Substantial yield losses of Styrian oil pumpkin caused by the fungus Didymella bryoniae and bacterial pathogens were recently reported. Here we applied bacterial endophytes with a broad antagonistic activity to pumpkin plants by seed priming. Effects of the bacterial inoculants with and without chemical seed treatments on plant growth and health were evaluated during three different field trials in two consecutive years (2010 and 2011). Biological seed treatments strongly supported the germination of pumpkin seeds. In 2010, the germination of the biologically treated seeds was comparable to the rate following a chemical treatment; whilst in 2011 effects of biological seed treatments were more obvious, including an increased emergence rate up to 109 % by Serratia plymuthica S13. Furthermore, tolerance against desiccation stress was observed for Serratia as well as for Lysobacter gummosus L101 treatment. The biological treatment showed different effects against fungal diseases: no effect on fruit rot was observed, whereas powdery mildew could be significantly suppressed by Paenibacillus polymyxa PB71 and L. gummosus L101 in 2010. In addition, both strains led to reproducible increases in harvest yields. In this study, we found bacterial endophytes suitable as inoculants for plant growth promotion, biocontrol, as well as for enhancing stress tolerance in Styrian oil pumpkins.

Structural diversity of pectins isolated from the Styrian oil-pumpkin (Cucurbita pepo var. styriaca) fruit

To evaluate the seeded fruit biomass of the Styrian oil-pumpkin in view of its pectin component, a series of acidic polysaccharides were isolated by a six-step sequential extraction using hot water, EDTA, dilute HCl (twice) and dilute and stronger NaOH solutions. Chemical, physicochemical and spectroscopy analyses revealed that the first four fractions comprised partially methyl-esterified and acetylated pectins with varying proportions of rhamnogalacturonan regions ramified with galactose- and arabinose-containing side chains and showed considerable polymolecularity. The alkali-extracted polysaccharides contained lower amounts of pectins with homogalacturonan and arabinose-rich rhamnogalacturonan regions next to hemicelluloses prevailing in the last polysaccharide. Using 1H–13C HSQC and HMBC spectroscopy, the resonances of free and methylesterified galacturonic acid residues in the purified acid-extracted pectin were unambiguously established and various diads formed by both residues identified. The results might serve as a basis for searching technological conditions to produce pectin from the oil-pumpkin fruit biomass.

Polysaccharides from the Styrian oil-pumpkin with antioxidant and complement-fixing activity

Pectic polysaccharides have attracted great attention due to their health-promoting potential. From the Styrian oil-pumpkin biomass representing an alternative pectin source, two series of acidic polysaccharide fractions were isolated using in succession hot water, EDTA and dilute HCl. Chemical and spectroscopic (FTIR, NMR) analyses of the fractions revealed the predominance of partially methylesterified and acetylated pectins containing homogalacturonan and ramified rhamnogalacturonan elements, and a minority of phenolic compounds, protein and hemicelluloses. The pectins exhibited moderate antioxidant activities tested by colorimetric DPPH and FRAP assays and EPR method. The activities correlated with the total phenolic content. In the complement-fixing test, most of the pectin fractions exhibited potent effects comparable to the positive control – a pectin from Plantago major. The oil-pumpkin pectins represent potential antioxidant and immunoenhancing additives applicable in food and nutraceuticals.

Microbial Diversity Inside Pumpkins: Microhabitat-Specific Communities Display a High Antagonistic Potential Against Phytopathogens

Recent and substantial yield losses of Styrian oil pumpkin (Cucurbita pepo L. subsp. pepo var. styriaca Greb.) are primarily caused by the ascomycetous fungus Didymella bryoniae but bacterial pathogens are frequently involved as well. The diversity of endophytic microbial communities from seeds (spermosphere), roots (endorhiza), flowers (anthosphere), and fruits (carposphere) of three different pumpkin cultivars was studied to develop a biocontrol strategy. A multiphasic approach combining molecular, microscopic, and cultivation techniques was applied to select a consortium of endophytes for biocontrol. Specific community structures for Pseudomonas and Bacillus, two important plant-associated genera, were found for each microenvironment by fingerprinting of 16S ribosomal RNA genes. All microenvironments were dominated by bacteria; fungi were less abundant. Of the 2,320 microbial isolates analyzed in dual culture assays, 165 (7%) were tested positively for in vitro antagonism against D. bryoniae. Out of these, 43 isolates inhibited the growth of bacterial pumpkin pathogens (Pectobacterium carotovorum, Pseudomonas viridiflava, Xanthomonas cucurbitae); here only bacteria were selected. Microenvironment-specific antagonists were found, and the spermosphere and anthosphere were revealed as underexplored reservoirs for antagonists. In the latter, a potential role of pollen grains as bacterial vectors between flowers was recognized. Six broad spectrum antagonists selected according to their activity, genotypic diversity, and occurrence were evaluated under greenhouse conditions. Disease severity on pumpkins of D. bryoniae was significantly reduced by Pseudomonas chlororaphis treatment and by a combined treatment of strains (Lysobacter gummosus, P. chlororaphis, Paenibacillus polymyxa, and Serratia plymuthica). This result provides a promising prospect to biologically control pumpkin diseases.

Emerging multi-pathogen disease caused by Didymella bryoniae and pathogenic bacteria on Styrian oil pumpkin

The Styrian oil pumpkin, Cucurbita pepo L. subsp. pepo var. styriaca Greb. is a crop of cultural, commercial, and medical importance. In the last decade, yield losses of pumpkins increased dramatically. The ascomycetous fungus Didymella bryoniae (Fuckel) Rehm was identified as main causal agent provoking gummy stem blight as well as black rot of pumpkins. We observed a remarkable phenotypic diversity of the fungal pathogen, which contrasted with a high genotypic similarity. Evidence of pathogenictiy of D. bryoniae on Styrian oil pumpkin was demonstrated in a newly developed greenhouse assay. Isolates representing the five observed phenotypic groups fulfilled the Koch’s postulates. In the field, the fungal disease was often associated with bacterial colonization by Pectobacterium carotovorum, Pseudomonas viridiflava, Pseudomonas syringae and Xanthomonas cucurbitae. The pathogenic behaviour of bacterial isolates on pumpkin was confirmed in the greenhouse assay. The high co-incidence of fungal and bacterial disease suggests mutualistic effects in pathogenesis. With a new assay, we found that bacteria can use the mycelium of D. bryoniae for translocation. We argue that the rapid rise of the multi-pathogen disease of pumpkins results from combined action of versatile pathogenic bacteria and the rapid translocation on a structurally versatile mycelium of the fungal pathogen.