
Peter Van DijkKeygene · Vegetable Crops and Research
Peter Van Dijk
Doctor of Philosophy
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Introduction
I am a plant geneticist specializing in reproduction traits and processes such as apomixis, hybridization and polyploidization. At the Netherlands Institute of Ecology (KNAW-NIOO), I investigated these topics from an evolutionary/ecological point of view, now at KeyGene, from a more applied perspective concerning their use in plant breeding and hybrid seed production. In early 2022 we cloned the parthenogenesis gene in apomictic dandelions.
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Publications
Publications (85)
Apomictic plants are able to produce clonal seeds. This reproductive system allows the one-step fixation of any valuable trait for subsequent generations and would pave the way for a revolution in the agricultural system. Despite that, the introduction of apomixis in sexually reproducing crops has been hampered due to the difficulty in characterisi...
We describe both the terminology and use of symbols introduced by Mendel in his 1866 paper and discuss some misconceptions concerning their interpretation.
According to the revisionist interpretation of Mendel's pea crosses, his primary aim was not to study the inheritance of traits. Instead, he was interested in the question raised by Linnaeus as to whether new species could arise from the hybridization of existing species. The genetic interpretation is therefore seen as ahistorical by the revisionis...
Apomixis is considered a potentially revolutionary tool to generate high-quality food at a lower cost and shorter developmental time due to clonal seed production through apomeiosis and parthenogenesis. In the diplosporous type of apomixis, meiotic recombination and reduction are circumvented either by avoiding or failing meiosis or by a mitotic-li...
The two lectures Gregor Mendel gave in the spring of 1865 to the Natural Science Society in Brno can be considered the ultimate origin of genetics. Here we reconstruct these lectures and their settings using digitized historical newspapers, and we compare these to Mendel's 1866-paper "Experiments on plant hybrids". The newspapers explained to their...
There are few historical records concerning Gregor Johann Mendel and his work, so theories abound concerning his motivation. These theories range from Fisher’s view that Mendel was testing a fully formed previous theory of inheritance to Olby’s view that Mendel was not interested in inheritance at all, whereas textbooks often state his motivation w...
Apomixis, the clonal formation of seeds, is a rare yet widely distributed trait in flowering plants. We have isolated the PARTHENOGENESIS (PAR) gene from apomictic dandelion that triggers embryo development in unfertilized egg cells. PAR encodes a K2-2 zinc finger, EAR-domain protein. Unlike the recessive sexual alleles, the dominant PAR allele is...
According to Hugo Iltis, Mendel had made a journey to Italy in the 1860s, not knowing when or for what purpose. Mendel might then have also paid a visit to Pope Pius IX, and become acquainted with the “later” Cardinal Teodolfo Mertel. Oswald Richter had already discovered that Mendel had received a 3-months pass for the Italian states in mid-August...
Tracing Mendel's international travels in the 1860's
Apomixis in the common dandelion (Taraxacum officinale) consists of three developmental components: diplospory (apomeiosis), parthenogenesis, and autonomous endosperm development. The genetic basis of diplospory, which is inherited as a single dominant factor, has been previously elucidated. To uncover the genetic basis of the remaining components,...
From a letter Gregor Mendel wrote to his brother-in-law, and a photograph of a large group of people in Paris, it is known that Mendel visited the International Exhibition in London in August 1862. There has been speculation about the status and composition of this travel group; for example, whether it was an official delegation from the city of Br...
A controversy arose over Mendel’s pea crossing experiments after the statistician R.A. Fisher proposed how these may have been performed and criticised Mendel’s interpretation of his data. Here we re-examine Mendel’s experiments and investigate Fisher’s statistical criticisms of bias. We describe pea varieties available in Mendel’s time and show th...
Taraxacum koksaghyz Rodin, a dandelion from the steppes of south-eastern Kazakhstan, has been known for long time as potential rubber producer, as a temperate region alternative to the tropical rubber tree Hevea brasiliensis Müll. Arg.. In this work, we evaluate Taraxacum bicorne Dahlst. (wild populations), a closely related congener of T. koksaghy...
What is rubber and where does it come from? Rubber is a natural product produced by plants and is present in many of the goods used in our daily lives. Rubber has had an important role in human history, throughout the development of human civilizations. It still plays an important role, and that is why we need to search for new rubber sources. Nowa...
Gregor Mendel’s crossing experiments in pea are the foundation of classical genetics, but since the importance of his 1866 paper was not understood until after long after his notebooks were burned, we know little...
Despite the fact that Gregor Mendel is generally respected as the founder of genetics, little is known about the origin of and motivat...
Gregor Mendel’s “Experiments on Plant Hybrids” (1865/1866), published 150 years ago, is without doubt one of the most brilliant works in biology. Curiously, Mendel’s later studies on Hieracium (hawkweed) are usually seen as a frustrating failure, because it is assumed that they were intended to confirm the segregation ratios he found in Pisum. Had...
Key message:
Using fine mapping techniques, the genomic region co-segregating with Restorer - of - fertility ( Rf ) in pepper was delimited to a region of 821 kb in length. A PPR gene in this region, CaPPR6 , was identified as a strong candidate for Rf based on expression pattern and characteristics of encoding sequence. Cytoplasmic-genic male ste...
Taraxacum koksaghyz Rodin (TKS) has been studied in many occasions as a possible alternative
source for natural rubber production of good quality and for inulin production. Some tire companies are
already testing TKS tire prototypes. There are also many investigations on the production of bio-fuels
from inulin and inulin applications for health imp...
Introduction of apomixis, asexual reproduction through seeds, into crop species has the potential to dramatically transform plant breeding. A new study demonstrates that traits can be stably transferred between generations in newly produced apomictic lines, and heralds a breeding revolution needed to increase food production for the growing planet.
Apomixis in dandelions (Taraxacum: Asteraceae) is encoded by two unlinked dominant loci and a third yet undefined genetic factor: diplosporous omission of meiosis (DIPLOSPOROUS, DIP), parthenogenetic embryo development (PARTHENOGENESIS, PAR), and autonomous endosperm formation, respectively. In this study, we determined the chromosomal position of...
Cultivation of the Russian dandelion (Taraxacum koksaghyz) as a rubber producing crop was abandoned more than 50 years ago. Recently the interest in the Russian dandelion has renewed, due to the increasing demand for natural rubber, health problems associated with Hevea rubber and the potential vulnerability of the Hevea production system. Morpholo...
Taraxacum officinale L. (dandelion) is a vigorous weed in Europe with diploid sexual populations in the southern regions and partially overlapping populations of diploid sexuals and triploid or tetraploid apomicts in the central and northern regions. Previous studies have demonstrated unexpectedly high levels of genetic variation in the apomictic p...
Conclusions presented by VOLIS et al., J. Appl. Bot. Food. Qual. 83, 60-63 (2009) are shown to be incorrect. VOLIS et al. consider Taraxacum koksaghyz as a rare species as a result of overcollecting in the past. It is shown in the present paper that VOLIS et al. explored the Kazakhstan localities in a wrong part of the season and not at the habitat...
DIPLOSPOROUS (DIP) is the locus for diplospory in Taraxacum, associated to unreduced female gamete formation in apomicts. Apomicts reproduce clonally through seeds, including apomeiosis, parthenogenesis, and autonomous or pseudogamous endosperm formation. In Taraxacum, diplospory results in first division restitution (FDR) nuclei, and inherits as a...
•DNA methylation can cause heritable phenotypic modifications in the absence of changes in DNA sequence. Environmental stresses can trigger methylation changes and this may have evolutionary consequences, even in the absence of sequence variation. However, it remains largely unknown to what extent environmentally induced methylation changes are tra...
*DNA methylation can cause heritable phenotypic modifications in the absence of changes in DNA sequence. Environmental stresses can trigger methylation changes and this may have evolutionary consequences, even in the absence of sequence variation. However, it remains largely unknown to what extent environmentally induced methylation changes are tra...
DNA methylation is an epigenetic mechanism that has the potential to affect plant phenotypes and that is responsive to environmental and genomic stresses such as hybridization and polyploidization. We explored de novo methylation variation that arises during the formation of triploid asexual dandelions from diploid sexual mother plants using methyl...
In asexual organisms, the clone constitutes a level above the individual. Most dandelions (Taraxacum officinale
s.l.) reproduce asexually through apomixis, asexual reproduction through seeds. A clone can be seen as a superorganism that is born, that growths, degenerates and eventually dies. Apomixis in dandelions is controlled by a few dominant gen...
The evolutionary questions studied in apomictic plants and parthenogenetic animals are often the same. This chapter gives
a basic introduction to apomixis in flowering plants, in order to make the botanical apomixis literature more accessible to
non-specialists. The focus is on the differences and similarities with parthenogenetic animals. The foll...
The process of meiosis involves genetic shuffling that dilutes the desirable traits of sexually reproducing crops. Identification of a mutation in which shuffling does not occur is a step forward for plant breeders.
Aim To determine patterns in diversity of a major Antarctic plant species, including relationships of Antarctic populations with those outside the Antarctic zone.
Location Antarctic Peninsula, Maritime Antarctica, sub-Antarctic islands, Falkland Islands and South America.
Methods Amplified fragment length polymorphisms (AFLPs) and chloroplast seque...
The European distribution of diploid and tetraploid cytotypes of Plantago media has been studied on three different scales: Europe as a whole, the Pyrenees and the upper Rio Gallego valley (Central Pyrenees). On a European scale, the tetraploids are widely and more or less continuously distributed; the diploids are restricted and disjunct. In the P...
1. Fig wasps (Hymenoptera: Agaonidae) represent an important model system for studies of sex ratio evolution, mainly because they may adjust their sex ratios in response to the numbers of ovipositing females (foundresses) that enter a fig and their clutch size.
2. Until recently, it was assumed that all foundresses fail to re‐emerge from the figs t...
Apomixis, asexual reproduction through seeds, has the potential to revolutionize agriculture if its genetic basis can be elucidated. However, the genetic control of natural apomixis has remained obscure until quite recently, owing to all the complications of Mendelian genetics, such as epistatic gene interactions, components that are expressed spor...
This paper reviews studies of genetic linkage mapping of apomixis loci, exemplified by our own model Taraxacum officinale (common dandelion; Asteraceae). Genetic linkage mapping of apomixis loci in natural apomicts is of interest in order to isolate the associated genes and introduce apomixis into crop species. Investigating chromosomal regions lin...
The levels of genetic diversity and gene flow may influence the long-term persistence of populations. Using microsatellite markers, we investigated genetic diversity and genetic differentiation in island (Krakatau archipelago, Indonesia) and mainland (Java and Sumatra, Indonesia) populations of Liporrhopalum tentacularis and Ceratosolen bisulcatus,...
Microsatellite markers for Ficus montana and Ficus septica were developed using genomic libraries enriched for di-, tri- and tetranucleotide repeats. The subsets of five and three best scorable primer pairs were characterized on 24 F. montana and 36 F. septica individuals, respectively. For F. montana, loci showed five to 14 alleles per locus and e...
Apomixis, the ability to produce asexual seeds, constitutes, along with out- crossing and selfing, one of the three major breeding systems in the angiosperms. However, apomixis is by far the least common of these three, despite theoretical advantages of apomixis over outcrossing and selfing. Darlington and Stebbins argued more than 50 years ago tha...
Apomixis, the ability to produce asexual seeds, constitutes, along with out-crossing and selfing, one of the three major breeding systems in the angios-perms. However, apomixis is by far the least common of these three, despite theoretical advantages of apomixis over outcrossing and selfing. Darlington and Stebbins argued more than 50 years ago tha...
Apomictic plants often produce pollen that can function in crosses with related sexuals. Moreover, facultative apomicts can produce some sexual offspring. In dandelions, Taraxacum, a sexual-asexual cycle between diploid sexuals and triploid apomicts, has been described, based on experimental crosses and population genetic studies. Little is known a...
This study aims at developing and characterizing new microsatellite primer pairs in Taraxacum officinale auct. to produce polymorphic markers for genetical and evolutionary studies on apomixis in this sexual-apomictic complex. A total of 24 diploid plants were tested for allelic polymorphism and heterozygosity. Out of nine loci three deviated signi...
In many plant and animal species, sexual and asexual forms have different geographical distributions (‘geographic parthenogenesis’). The common dandelion Taraxacum officinale s.l. provides a particularly clear example of differing distributions: diploid sexuals are restricted to southern and central Europe, while triploid asexuals occur across Euro...
A male-specific amplified fragment length polymorphism (AFLP) marker was identified in the functionally dioecious fig species, Ficus fulva. A total of 89 polymorphic fragments from three primer combinations were produced, of which one (246bp) was present in all males (n=23) and absent in all females (n=24) of two populations. This strong associatio...
In this study, we mapped the diplosporous chromosomal region in Taraxacum officinale, by using amplified fragment length polymorphism technology (AFLP) in 73 plants from a segregating population. Taraxacum serves as a model system to investigate the genetics, ecology, and evolution of apomixis. The genus includes sexual diploid as well as apomictic...
In apomictic dandelions, Taraxacum officinale, unreduced megaspores are formed via a modified meiotic division (diplospory). The genetic basis of diplospory was investigated in a triploid (3x = 24) mapping population of 61 individuals that segregated approximately 1:1 for diplospory and meiotic reduction. This population was created by crossing a s...
This study aims at developing and characterizing new microsatellite primer pairs in Taraxacum officinale auct. to produce polymorphic markers for genetical and evolutionary studies on apomixis in this sexual-apomictic complex. A total of 24 diploid plants were tested for allelic polymorphism and heterozygosity. Out of nine loci three deviated signi...
In order to gain insight into the causes of parapatric diploid and tetraploid distributions in Plantago media chloroplast DNA (cpDNA) restriction site polymorphism was studied in 36 European populations. Parapatric distributions are often explained by adaptive differences between cytotypes to an underlying heterogeneity in environmental factors. Al...
Natural hybrids between Ficus septica and two closely related dioecious species, F. fistulosa and F. hispida, were confirmed using amplified fragment length polymorphisms (AFLP) and chloroplast DNA markers. Ficus species have a highly species-specific pollination mutualism with agaonid wasps. Therefore, the identification of cases in which breakdow...
The ecological and evolutionary opportunities of apomixis in the short and the long term are considered, based on two closely related apomictic genera: Taraxacum (dandelion) and Chondrilla (skeleton weed). In both genera apomicts have a wider geographical distribution than sexuals, illustrating the short–term ecological success of apomixis. Allozym...
Apomictic seed development in dandelion ( Taraxacum officinale) involves (1) restitutional meiosis (diplospory), (2) egg cell parthenogenesis, and (3) autonomous endosperm development. The question is whether these elements of apomixis are controlled by one single gene or by several independent genes. Five triploid non-apomictic hybrids, obtained i...
Microsatellite markers for the pollinator fig wasp Liporrhopalum tentacularis were developed using genomic libraries enriched for di-, tri- and tetranucleotide repeats. A subset of 31 positive clones was sequenced and primers were designed. Eleven primer pairs produced polymorphic amplification products in L. tentacularis. Eight markers gave unambi...
In the autonomous apomictic Taraxacum
officinale (common dandelion), parthenogenetic egg cells develop into embryos and central cells into endosperm without prior fertilisation. Unreduced (2n) megaspores are formed via meiotic diplospory, a nonreductional type of meiosis. In this paper, we describe the normal developmental pathways of sexual and ap...
Some dandelions are diplosporous gametophytic apomicts. In order to study the inheritance and breakdown of apomixis, crosses were made between diploid sexuals and triploid apomicts. To investigate their breeding system, four nonapomictic diploid and 10 nonapomictic triploid hybrids were pollinated with diploids and the progenies were analysed. Seed...
Taraxacum officinale L. (dandelion) is a vigorous weed in Europe with diploid sexual populations in the southern regions and partially overlapping populations of diploid sexuals and triploid or tetraploid apomicts in the central and northern regions. Previous studies have demonstrated unexpectedly high levels of genetic variation in the apomictic p...
Taraxacum officinale L. (dandelion) is a vigorous weed in Europe with diploid sexual populations in the southern regions and partially overlapping populations of diploid sexuals and triploid or tetraploid apomicts in the central and northern regions. Previous studies have demonstrated unexpectedly high levels of genetic variation in the apomictic p...
Most plant species produce genetically variable seeds by the fusion of meiotically reduced egg cells and pollen grains. However, a small proportion of seed plants produces clonal, asexual seeds by the process of apomixis. The fixation of heterosis by apomixis is of great interest for plant breeding. The prospect of changing sexual crop species into...
Some dandelions, Taraxacum, are diplosporous gametophytic apomicts. Crosses between closely related diploid sexuals and triploid apomicts were made to study the inheritance of apomixis. Seed-set was less than one-third of that in diploid x diploid crosses, probably because of the inviability of aneuploid pollen or zygotes. Almost 90% of the viable...
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Microsatellite markers were developed in Taraxacum officinale to study gene flow between sexual and apomictic plants and to identify clones. Twenty five thousand genomic DNA clones were hybridized with a (CT)12D probe. The density of (GA/CT)n
repeats was estimated at one every 61 kb in the T. officinale genome, which translates to 13 500 repeats pe...
Mitochondrial variation in Plantago lanceolata was used to detect new CMS types. Directional reciprocal crosses were made between plants which differed in mtDNA restriction
patterns. Differential segregation of male steriles in reciprocal crosses indicated that the parents differed in CMS type.
MtDNA variation revealed nine RFLP patterns, which co...
The evolution of reproductive isolation by flowering time displacement between two cytotypes that produce inviable hybrids was studied by computer simulations in an isolation-by-distance model. Flowering time distribution was stabilized by mass-action, both by the mating procedure and by pollen-limited seed-production in early or late flowering pla...
Genetic variation is one of the means which enable a species to occupy an extensive geographic distribution and to occur in large numbers in heterogeneous environments. Genetic differentiation within a species can be manifested on different levels. Geographic races may occur in geographically different parts of the species range. In that case only...
The hypothesis of autotetraploidy in Plantago media (2n = 12 and 2n = 24) was tested. The two cytotypes are morphologically very similar. Rare 4X and 3X hybrids were obtained in inter-ploidy crosses. The reproductive isolation between 2X and 4X is post-zygotic and can be broken down and introduced by colchicine treatment. The studied diploid and te...
The hypothesis of autotetraploidy in Plantago media (2n = 12 and 2n = 24) was tested. The two cytotypes are morphologically very similar. Rare 4X and 3X hybrids were obtained in inter-ploidy crosses. The reproductive isolation between 2X and 4X is post-zygotic and can be broken down and introduced by colchicine treatment. The studied diploid and te...
Exposure of spinach plants to 250 ppb H2S for two days resulted in a 70% decrease of the serine concentration of the leaves. The concentration of most amino acids increased on average by 100%, cyst(e)ine at least by 1400%. Also the ammonia concentration increased upon H2S exposure. The concentrations of glutamate, glutamine and aspartate were unalt...