María Ferriol

Genetic diversity of a germplasm collection of Cucurbita pepo using SRAP and AFLP markers

Cucurbita pepo is a highly polymorphic species. The cultivars can be grouped into eight morphotypes in two subspecies, ssp. pepo and ssp. ovifera. A collection of 69 accessions representative of the morphotypes and some unclassified types was used for analysing the morphological and molecular diversity of this species. This collection includes commercial cultivars and Spanish landraces, which represent the great diversification of types that have arisen in Europe after this species arrived from America. For the molecular variability studies, two PCR-based systems were employed, AFLP and SRAP, which preferentially amplify ORFs. Principal coordinates analysis and cluster analysis using the UPGMA method clearly separate the accessions into the two subspecies through the use of both markers. However, the gene diversity and the genetic identity values among morphotypes and subspecies varied between the two marker systems. The information given by SRAP markers was more concordant to the morphological variability and to the evolutionary history of the morphotypes than that of AFLP markers. In ssp. ovifera, the accessions of the different morphotypes were basically grouped according to the fruit colour. This may indicate different times of development and also the extent of breeding in the accessions used. This study has allowed identification of new types that can be employed for the development of new cultivars. The landraces of the spp. ovifera, used as ornamental in Europe, have proved to be of great interest for preserving the diversity of C. pepo.

Genetic diversity of some accessions of Cucurbita maxima from Spain using RAPD and SBAP markers

Increasing the knowledge of the molecular diversity of a crop is essential for extending its genetic base, identifying cultivars and selecting parental varieties for breeding programs. In this sense, Cucurbita maxima Duch. is poorly characterised. Nineteen accessions of this species and 8 related Cucurbita accessions were included in a genetic diversity analysis. For this purpose, Random Amplified Polymorphic DNA markers (RAPDs), which analyse neutral variability, and Sequence-Based Amplified Polymorphism (SBAPs), which preferentially amplify coding regions of the genome, were used. While the UPGMA cluster and the principal coordinates analysis obtained using RAPDs did not group the different accessions according either to fruit morphological criteria or to passport data (origin and agro-climatic conditions), the principal coordinates analysis obtained using SBAPs grouped the different pumpkin accessions fundamentally according to the type of use (human consumption, animal fodder or ornamental). This passport trait is reported to be associated with agronomic breeding characters of interest. The usefulness of both types of markers for discriminating accessions of breeding interest is discussed.

Mechanical transmission of Tomato leaf curl New Delhi virus to cucurbit germplasm: selection of tolerance sources in Cucumis melo

Cucurbits are major crop species, including fruits and vegetables cultivated worldwide that supply essential vitamins and minerals to current diets in developed and developing countries. Viral diseases are main factors affecting cucurbits cultivation. The most widespread and damaging have been aphid-borne viruses belonging to the Potyviridae family. Whitefly-transmitted begomoviruses (Geminiviridae) have been identified more recently in different cucurbit species. A severe outbreak of Tomato leaf curl New Delhi virus (ToLCNDV) occurred in pumpkins and melons in the main production area of Southern Spain in 2012–2014. We developed a mechanical inoculation method to facilitate the screening of germplasm against this virus. Mechanical transmission with this method was confirmed in 4 genera and 13 species of the family, including the main crops, cucumber, melon, watermelon and pumpkins, and also crop-related exotic germplasm (landraces and wild species) used for cucurbits breeding. Diversity in the response was observed within and among species. Tolerance to mechanical transmission of ToLCNDV was identified in melon, within Cucumis melo subsp. agrestis var. momordica and in wild agrestis accessions. All the tolerant accessions came from India, the country in which this virus was firstly reported. Some of these accessions have been previously reported to be tolerant or resistant to other viruses and as they are fully crossable to commercial melons, they are good sources to develop new melon varieties with tolerance to ToLCNDV.

De novo assembly of the zucchini genome reveals a whole-genome duplication associated with the origin of the Cucurbita genus

Summary The Cucurbita genus (squashes, pumpkins and gourds) includes important domesticated species such as C. pepo, C. maxima and C. moschata. In this study, we present a high‐quality draft of the zucchini (C. pepo) genome. The assembly has a size of 263 Mb, a scaffold N50 of 1.8 Mb and 34 240 gene models. It includes 92% of the conserved BUSCO core gene set, and it is estimated to cover 93.0% of the genome. The genome is organized in 20 pseudomolecules that represent 81.4% of the assembly, and it is integrated with a genetic map of 7718 SNPs. Despite the small genome size, three independent lines of evidence support that the C. pepo genome is the result of a whole‐genome duplication: the topology of the gene family phylogenies, the karyotype organization and the distribution of 4DTv distances. Additionally, 40 transcriptomes of 12 species of the genus were assembled and analysed together with all the other published genomes of the Cucurbitaceae family. The duplication was detected in all the Cucurbita species analysed, including C. maxima and C. moschata, but not in the more distant cucurbits belonging to the Cucumis and Citrullus genera, and it is likely to have occurred 30 ± 4 Mya in the ancestral species that gave rise to the genus.

Ecological germination requirements of the aggregate species Teucrium pumilum (Labiatae) endemic to Spain

Teucrium pumilum L., T. lepicephalum Pau, T. libanitis Schreber, T. turredanum Losa & Rivas Goday, and T. carolipaui Vicioso ex Pau (Labiatae) constitute an aggregate included in the Pumilum subsection (Polium section). These species are endemic and geographically restricted to central and south-eastern Spain. They grow under different climatic conditions and have different edaphic requirements, particularly the gypsum and lime affinities. The effects of some ecological factors (i.e. edaphic and climatic factors) on the germination parameters of these Teucrium species were investigated. The species under study differed in their germination behaviour. The majority of the germination parameters appeared more correlated to edaphic than to climatic factors and particularly to the water availability in the soil. The calcicolous T. carolipaui, which grows in the driest habitat, had a more rapid germination than the gypsophilous species. This could be due to the existence of a narrower optimal germination period for T. carolipaui. The different germination requirements of these species of Teucrium are important results to be considered in conservation programs of these endemic and endangered taxa.

Composition of the essential oil of Dictamnus hispanicus from Spain

Abstract The composition of the essential oil of Dictamnus hispanicus Webb ex. Willk. collected in eastern Spain was analyzed by GC and GC/MS. The main constituents identified were methyl chavicol (79%) and limonene (7%). The high oil yield (72.0% fresh plant material) and the proportion of the main compounds support the consideration of D. hispanicus as a separate species of the S. and CS. Europe as D. albus aggregate or as a new chemotype of the polymorphic D. albus.

Allogamy-Autogamy Switch Enhance Assortative Mating in the Allotetraploid Centaurea seridis L. Coexisting with the Diploid Centaurea aspera L. and Triggers the Asymmetrical Formation of Triploid Hybrids

Hybridization between tetraploids and their related diploids is generally unsuccessful in Centaurea, hence natural formation of triploid hybrids is rare. In contrast, the diploid Centaurea aspera and the allotetraploid C. seridis coexist in several contact zones where a high frequency of triploid hybrids is found. We analyzed the floral biology of the three taxa to identify reproductive isolation mechanisms that allow their coexistence. Flowering phenology was recorded, and controlled pollinations within and between the three taxa were performed in the field. Ploidy level and germination of progeny were also assessed. There was a 50% flowering overlap which indicated a phenological shift. Diploids were strictly allogamous and did not display mentor effects, while tetraploids were found to be highly autogamous. This breakdown of self-incompatibility by polyploids is first described in Centaurea. The asymmetrical formation of the hybrid was also found: all the triploid intact cypselae came from the diploid mothers pollinated by the pollen of tetraploids. Pollen and eggs from triploids were totally sterile, acting as a strong triploid block. These prezygotic isolation mechanisms ensured higher assortative mating in tetraploids than in diploids, improving their persistence in the contact zones. However these mechanisms can also be the cause of the low genetic diversity and high genetic structure observed in C. seridis.

First Report of Tomato leaf curl New Delhi virus infecting Zucchini in Morocco

Tomato leaf curl New Delhi virus (ToLCNDV, genus Begomovirus, family Geminiviridae) is a devastating pathogen vectored by the whitefly Bemisia tabaci, causing significant yield losses to several crops. ToLCNDV is a bipartite begomovirus first reported on tomato (Solanum lycopersicum L.) in 1995 in India and soon after found in other Asian countries particularly on vegetables of the Cucurbitaceae and Solanaceae families (revised in Zaidi et al. 2017). Further spread of ToLCNDV occurred after 2012, with recent reports in Mediterranean countries, initially in Spain (Juarez et al. 2014) and more recently in Tunisia (Mnari-Hattab et al. 2015) and Italy (Panno et al. 2016) affecting mainly zucchini (Cucurbita pepo L.), melon (Cucumis melo L.) and cucumber (Cucumis sativus L.). During spring 2017, generalized leaf symptoms including yellowing and curling, as well as stunting of plants were observed in several zucchini fields of one of the commonest commercial Moroccan cultivar, ‘Suha’ F1 (Sakata Vegetables Europ...

Effects of nettle slurry (Urtica dioica L.) used as foliar fertilizer on potato (Solanum tuberosum L.) yield and plant growth

Organic agriculture is becoming increasingly important, and many natural products are now available for organic farmers to manage and improve their crops. Several ethnobotanical studies have indicated that the use of nettle slurry as fertilizer in organic farming for horticultural crops is spreading. Sometimes, however, the consequences of using these natural products have been poorly evaluated, and there is very little scientific evidence for the effects of using these slurries. In this study, we aimed to analyze the possible effect of nettle slurry on potato yields produced by organic farming. To achieve this main objective, we assessed the effect of nettle slurry on potato yields, plant size and growth parameters, chlorophyll content, and the presence of pests and diseases. Different slurry doses were assessed in 36 plots and nine variables were measured during the crop cycle. Under these field experimental conditions, nettle slurry (including one treatment with Urtica in combination with Equisetum) had no significant effects on yield, chlorophyll content, or the presence of pests and diseases in organic potato crops. The highest chlorophyll content was found in the double dose treatment, but the difference was not significant. This result, together with a small improvement in plant height with the double dose treatment, might indicate very slight crop enhancement which, under our experimental conditions, was not enough to improve yield. The Urtica and Equisetum slurry chemical analyses showed very low levels of nitrogen, phosphorus, and potassium.

Distribution and ecological segregation on regional and microgeographic scales of the diploid Centaurea aspera L., the tetraploid C. seridis L., and their triploid hybrids (Compositae)

Although polyploidy is considered a ubiquitous process in plants, the establishment of new polyploid species may be hindered by ecological competition with parental diploid taxa. In such cases, the adaptive processes that result in the ecological divergence of diploids and polyploids can lead to their co-existence. In contrast, non-adaptive processes can lead to the co-existence of diploids and polyploids or to differentiated distributions, particularly when the minority cytotype disadvantage effect comes into play. Although large-scale studies of cytotype distributions have been widely conducted, the segregation of sympatric cytotypes on fine scales has been poorly studied. We analysed the spatial distribution and ecological requirements of the tetraploid Centaurea seridis and the diploid Centaurea aspera in east Spain on a large scale, and also microspatially in contact zones where both species hybridise and give rise to sterile triploid hybrids. On the fine scale, the position of each Centaurea individual was recorded along with soil parameters, accompanying species cover and plant richness. On the east Spanish coast, a slight latitudinal gradient was found. Tetraploid C. seridis individuals were located northerly and diploid C. aspera individuals southerly. Tetraploids were found only in the habitats with strong anthropogenic disturbance. In disturbed locations with well-developed semi-fixed or fixed dunes, diploids and tetraploids could co-exist and hybridise. However, on a fine scale, although taxa were spatially segregated in contact zones, they were not ecologically differentiated. This finding suggests the existence of non-adaptive processes that have led to their co-existence. Triploid hybrids were closer to diploid allogamous mothers (C. aspera) than to tetraploid autogamous fathers (C. seridis). This may result in a better ability to compete for space in the tetraploid minor cytotype, which might facilitate its long-term persistence.