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—Origin of tetraploid and hexaploid wheat and tetraploid Aegilops peregrina and Aegilops kotschyi. The possible paths of introgression of WPG118 DNA sequences from polyploid wheat into tetraploid Ae. peregrina and from diploid Aegilops searsii into tetraploid Ae. kotschyi are denoted by dashed arrows.
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Introgressive hybridization has played a crucial role in the evolution of many plant species, especially polyploids. The duplicated genetic material and wide geographical distribution facilitate hybridization and introgression among polyploid species having either homologous or homoeologous genomes. Such introgression may lead to the production of...
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This study evaluates the potential of flow cytometry for chromosome sorting in two wild diploid wheats Aegilops umbellulata and Ae. comosa and their natural allotetraploid hybrids Ae. biuncialis and Ae. geniculata. Flow karyotypes obtained after the analysis of DAPI-stained chromosomes were characterized and content of chromosome peaks was determin...
Ribosomal internal transcribed spacer (ITS) sequences were used to evaluate the phylogenetics of Zea and Tripsacum. Maximum likelihood and polymorphism parsimony were used for phylogenetic reconstructions. Zea ITS nucleotide diversity was high compared to other plant species, but approximately equivalent to other maize loci. Coalescence of ITS alle...
Genetic analyses of reproductive barriers represent one of the few methods by which theories of speciation can be tested. However, genetic study is often restricted to model organisms that have short generation times and are easily propagated in the laboratory. Replicate hybrid zones with a diversity of recombinant genotypes of varying age offer in...
Successful hybridisation and subsequent introgression lead to the transfer of genetic material across species boundaries. In this process, species relative abundance can play a significant role. If one species is less abundant than the other, its females will receive many heterospecific gametes, increasing mate-recognition errors and thus hybridisa...
Effects of polyploidisation on gene flow between natural populations are little known. Central European diploid and tetraploid populations of Arabidopsis arenosa and A. lyrata are here used to study interspecific and interploidal gene flow, using a combination of nuclear and plastid markers.
Ploidal levels were confirmed by flow cytometry. Network...
Citations
... However, interploidy crosses also have significant effects on genetic diversity during plant evolution, enabling gene transfer between species (62,63). The transfer of genes across a ploidy barrier has been documented between polyploids and their diploid progenitors (64)(65)(66)(67)(68)(69). Unidirectional interploidy hybridization (pollen flow) has been reported in several genera (9,26,28), which supports the hypothesis proposed by ref. 70 that gene transfer is more likely to occur from diploid to tetraploid species, although examples of it proceeding in the reverse direction are also known (71). ...
Polyploidy is a major evolutionary force that has shaped plant diversity. However, the various pathways toward polyploid formation and interploidy gene flow remain poorly understood. Here, we demonstrated that the immediate progeny of allotriploid AAC Brassica (obtained by crossing allotetraploid Brassica napus and diploid Brassica rapa) was predominantly aneuploids with ploidal levels ranging from near-triploidy to near-hexaploidy, and their chromosome numbers deviated from the theoretical distribution toward increasing chromosome numbers, suggesting that they underwent selection. Karyotype and phenotype analyses showed that aneuploid individuals containing fewer imbalanced chromosomes had higher viability and fertility. Within three generations of self-fertilization, allotriploids mainly developed into near or complete allotetraploids similar to B. napus via gradually increasing chromosome numbers and fertility, suggesting that allotriploids could act as a bridge in polyploid formation, with aneuploids as intermediates. Self-fertilized interploidy hybrids ultimately generated new allopolyploids carrying different chromosome combinations, which may create a reproductive barrier preventing allotetraploidy back to diploidy and promote gene flow from diploids to allotetraploids. These results suggest that the maintenance of a proper genome balance and dosage drove the recurrent conversion of allotriploids to allotetraploids, which may contribute to the formation and evolution of polyploids.
... 41 Despite the fact that A. geniculata (MMUU) and A. triuncialis (UUCC) not sharing homologous genomes with common wheat (AABBDD), the natural introgression of DNA sequences from wheat into related nonhomologous wild species has been described previously, as was the case of A. peregrina (SSUU). 42 Evidence of these wheat DNA introgressions in natural Aegilops populations surveyed in the Mediterranean area have been reported for these species using molecular markers, questioning the strength of reproductive barriers. Arrigo et al. 4 detected that a mean of 2.8% of the A. geniculata, 24% of the A. triuncialis and 16% of the A. neglecta individuals from naturally occurring populations showed signs of substantial wheat introgression. ...
BACKGROUND
Cultivated bread wheat (Triticum aestivum L.) spontaneously hybridizes with wild/weedy related Aegilops populations, but little is known about the actual rates at which this hybridization occurs under field conditions. It is very important to provide reliable empirical data on this phenomenon in order to assess the potential crop–wild introgression, especially in the context of conducting risk assessments for the commercialization of genetically modified (GM) wheat, as gene flow from wheat to Aegilops species could transfer into the wild species genes coding for traits such as resistance to herbicides, insects, diseases or environmental stresses.
RESULTS
The spontaneous hybridization rates between wheat and A. geniculata and A. triuncialis, which are very abundant in the Mediterranean area, have been estimated for the first time in the northern part of the Meseta Central, the great central plateau which includes the largest area of wheat cultivation in Spain. Hybridization rates averaged 0.12% and 0.008% for A. geniculata and A. triuncialis, respectively. Hybrids were found in 26% of A. geniculata and 5% of A. triuncialis populations, at rates that can be ≤3.6% for A. geniculata and 0.24% for A. triuncialis.
CONCLUSION
The detection of Aegilops spp.–wheat hybrids in Aegilops populations indicates that gene flow can occur, although wheat is considered a crop with a low‐to‐medium risk for transgene escape. These data on field hybridization rates are essential for GM wheat risk assessment purposes. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
... This is due to several reasons. High levels of diversity can be the outcome of secondary contact between crops and their wild relatives which are not their direct progenitors, but still close enough for successful hybridization; this generally happens outside the center of origin (Elstrand et al. 1999;Weissmann et al., 2005). In addition, movement of a crop to new environments via migration or trade, which was common with new and successful domesticates, increase the diversity of the species as it is selected for adaptation to its new environment (e.g., Bedoya et al., 2017;Crites, 1993). ...
In the classical mythologies of all civilizations, agriculture is fundamentally of divine origin. The appearance of agriculture in mythology was almost always associated with other features of civilization: settled life, household arts, formal religion, and government by laws. The mythologies of the Native Americans are enormously varied and complex, this chapter presents themes of the Aztec and Maya to compare with the Incan myth already cited. Many narcotic and hallucinogenic plants have been used in religious ceremony and ritual. The most extensively developed model for agricultural origins is that cultivation was an invention or discovery. Every model proposed so far for agricultural origins or plant domestication has generated evidence against it. A “no‐model model” leaves room for whole arrays of motives, actions, practices, and evolutionary processes. The most conspicuous difference between hunting‐gathering economies and agricultural ones is in the size of the human populations that can be supported.
... Another study by Wang et al. (2013) identified that overexpression of a novel EPSPS transgene for glyphosate resistance increased growth and fecundity in weedy rice in absence of glyphosate treatment. However, these fitness advantage traits due to glyphosate-insensitive EPSPS overexpression can easily spread to weedy rice species that can cross-pollinate with the crop plants (Arrigo et al., 2011;Ellstrand, 2003;Perez-Jones et al., 2006;Wang et al., 2013;Weissmann et al., 2005). Recent evidences show that most of the weedy rice species have arisen from de-domestication of cultivated rice varieties and not from the common wild progenitors (Gross et al., 2010;Lawton-Rauh and Burgos, 2010;Thurber et al., 2013). ...
Glyphosate is a popular, systemic, broad‐spectrum herbicide used in modern agriculture. Being a structural analog of phosphoenolpyruvate (PEP), it inhibits 5‐enolpyruvylshikimate 3‐phosphate synthase (EPSPS) which is responsible for the biosynthesis of aromatic amino acids and various aromatic secondary metabolites. Taking a lead from glyphosate‐resistant weeds, two mutant variants of the rice EPSPS gene were developed by amino acid substitution (T173I + P177S; TIPS‐OsEPSPS and G172A + T173I + P177S; GATIPS‐OsEPSPS). These mutated EPSPS genes were overexpressed in rice under the control of either native EPSPS or constitutive promoters (maize ubiquitin [ZmUbi] promoter). The overexpression of TIPS‐OsEPSPS under the control of the ZmUbi promoter resulted in higher tolerance to glyphosate (up to three‐fold of the recommended dose) without affecting the fitness and related agronomic traits of plants in both controlled and field conditions. Furthermore, such rice lines produced 17‐ 19% more grains compared to the wild type (WT) in the absence of glyphosate application and the phenylalanine and tryptophan contents in the transgenic seeds were found to be significantly higher in comparison to WT seeds. Our results also revealed that the native promoter guided expression of modified EPSPS genes did not significantly improve the glyphosate tolerance. The present study describing the introduction of a crop‐specific TIPS mutation in class I aroA gene of rice and its overexpression have potential to substantially improve the yield and field level glyphosate‐tolerance in rice. This is the first report to observe that the EPSPS has role to play in improving grain yield of rice.
... The risk of crop-to-wild gene flow is particularly severe if crops possessing purposefully bred traits partake in hybridization with wild plants (Newhouse et al., 1992). Such gene flow may cause, for example, the transfer of herbicide resistance to weedy species, which could, among other repercussions, lead to massive economic losses (Seefeldt et al., 1998;Zemetra & Hansen, 1998;Weissmann et al., 2005). ...
... Besides hybridization for experimental and breeding purposes, the hybridization potential of Triticeae crops under natural conditions has been assessed repeatedly. Known cases of successful intergeneric hybridization include crosses between wheat and sea barley (Hordeum marinum Huds.; Guadagnuolo et al., 2001), jointed goatgrass (Aegilops cylindrica Host; Morrison et al., 2002;Gandhi et al., 2006), and other Aegilops L. species (Weissmann et al., 2005;Arrigo et al., 2011). ...
... Such concerns are not, however, limited to the genus Elymus. A series of studies conducted on the genus Aegilops (Seefeldt et al., 1998;Wang et al., 2001;Weissmann et al., 2005) have not only demonstrated that crop-to-wild hybridization poses a serious threat to the genetic integrity of wild Aegilops species, but that artificially introduced genes for herbicide resistance have already escaped into the gene pools of wild plants. ...
Hybridization, polyploidization and crop‐to‐wild gene transfer within the agriculturally important tribe Triticeae are well explored experimentally, but the true consequences of both phenomena under natural conditions remain understudied. The present paper reports on an investigation of three species of couch grasses (Elymus hispidus, E. repens and E. caninus) examining the ploidy levels and absolute genome sizes (1,081 plants from 302 natural populations in Central Europe, verified by chromosome counts) and their morphological delimitation. In the present study, the hexaploid level prevailed in E. hispidus and E. repens whereas E. caninus was exclusively tetraploid. Introgressive hybridization between hexaploid species, unidirectionally shifted towards E. hispidus, was indicated by a continual pattern of genome size values. We did not find any evidence for heteroploid hybridization involving tetraploid E. caninus; however, we detected minority cytotypes among both E. caninus plants (hexaploid) and E. repens–E. hispidus hybrids (heptaploid and nonaploid) suggesting the formation of unreduced gametes. Morphometric results (367 plants, RDA, PCA and correlation analysis) mirrored the continual homoploid pattern of absolute genome size (including the unidirectional shift), and a significant correlation between absolute genome size and morphology was confirmed. Moreover, morphometric analyses detected additional characters for the delimitation of the Elymus taxa under study. Considering the crossability of E. hispidus with Triticum aestivum (bread wheat), the revealed extent of introgressive hybridization has implications for assessing the potential risk of gene flow between crops and troublesome weeds. This article is protected by copyright. All rights reserved.
... Hybridization has been defined as the interbreeding of individuals from two populations, or groups of populations, which are distinguishable on the basis of one or more heritable characters (Dowling and Secor 1997), and it occurs when there are incomplete reproductive barriers between two taxa (Counterman and Noor 2006). The fraction of species that hybridize is variable, but on average around 10% of animal and 25% of plant species are known to hybridize with at least one other species (Mallet 2007), even if they are distantly related (Weissmann et al. 2005). Hybridization can operate in different directions: reducing taxon diversity by eliminating the boundaries between species, particularly if gene flow occurs into one or both parental taxa (which might facilitate adaptive evolution; Fig. 5.2a); generating new taxa by homoploid or allopolyploid hybrid speciation (Fig. 5.2b) as in the case of P. dumosus that derived from the hybridization of P. vulgaris and P. coccineus (Mina-Vargas et al. 2016); and merging the two hybridizing taxa (Pastorini et al. 2009;Schneider et al. 2011). ...
Crop plants that sustain modern civilizations, including common bean (Phaseolus vulgaris), were domesticated and improved by thousands of years of human selection, which transformed wild ancestors into high-yielding domesticated descendants. Understanding how the genome of crop species has been shaped through time, with and without human intervention, is a fascinating field of research. In addition, defining the loci and associated polymorphisms behind the emergence of domestication and improvement traits in P. vulgaris is of major importance. Uncovering intra- and inter-species introgression events that could indicate transferred genes, which together with domestication protein-coding and non-coding genes that have given rise to domestication and adaptive traits are required for future improvement strategies. Such strategies, in our view, will depend to a significant extent on crop re-wilding, given the local adaptations undergone by their wild relatives and climate change. Essential tools for reaching these goals have recently been developed, such as the complete genome sequences (~600 Mb) of a Mesoamerican and an Andean accession, as well as a large gene expression atlas. Further, there are significant re-sequencing efforts for both wild and domesticated genotypes, which will play a major role in the future of this crop. Altogether, this information will allow the genetic dissection of the characters involved in the domestication and adaptation of the crop and their further implementation in breeding strategies faced with an ever-expanding human population and unpredictable environmental challenges.
... Aegilops peregrina (Hack.) Maire and Weiller and wheat, Weissmann et al. 2005; Oryza rufipogon Griff. and cultivated rice in Asia, Song et al. 2006; Coffea arabica L. and coffee cultivars in Ethiopia, Aerts et al. 2013; Medicago falcata L. and cultivated alfalfa in Estonia, Kaljund and Leht 2013). ...
Prunus fruticosa is a rare shrub occurring in Eurasian thermophilous forest-steppe alliances. The species frequently hybridizes with cultivated Prunus species in Europe (allochthonous tetraploid P. cerasus and partly indigenous diploid P. avium). Propidium iodide flow cytometry, distance-based morphometrics, elliptic Fourier analysis and embryology were employed to evaluate the extent of hybridization in six Slovak populations. Flow cytometric analyses revealed three ploidy levels: diploid (P. avium), triploid (P. × mohacsyana) and tetraploid (P. fruticosa, P. × eminens and P. cerasus). In addition, P. fruticosa and P. cerasus, at the tetraploid level, were found to differ in absolute genome size. An embryological evaluation suggested the existence of a triploid block in P. × mohacsyana and significant potential for hybridization among tetraploid taxa (indicated also by a continuous distribution of genome size data and further mirrored by morphometrics). Although hybrids significantly differ in ploidy level and embryological characteristics, they are almost indistinguishable using morphological characters. Hybridization with P. cerasus thus turns out to be a significant threat to wild populations of P. fruticosa compared to the relatively weak influence of P. avium.
... A sequence-based comparison of the two bands revealed that the DNA sequences of the two fragments were almost identical, except that 53 bp had been deleted from the shorter TQ27 band (see Figure 1, right). This DNA sequence was identified in previous studies as a low-copy-number chromosomespecific sequence, mapped to the long arm of chromosome 3B (3BL) of common wheat (Liu et al. 2003;Weissmann et al. 2005). Here, we report on another homeoallele of this locus from the DD genome (Ae. ...
... triuncialis, U t U t C t C t and Ae. neglecta, U n U n X n X n ) shares a parental species genome with wheat (but see also [19] for Near East accessions of Ae. peregrina whose S genome is close to the wheat B genome). Although breeders have been highly successful in introgressing Aegilops choromosomic regions in wheat for agronomic purposes, there is little evidence of successful natural introgression of cultivated wheat genes in Aegilops genomes. ...
Gene flow from crop to wild relatives is a common phenomenon which can lead to reduced adaptation of the wild relatives to natural ecosystems and/or increased adaptation to agrosystems (weediness). With global warming, wild relative distributions will likely change, thus modifying the width and/or location of co-occurrence zones where crop-wild hybridization events could occur (sympatry). This study investigates current and 2050 projected changes in sympatry levels between cultivated wheat and six of the most common Aegilops species in Europe. Projections were generated using MaxEnt on presence-only data, bioclimatic variables, and considering two migration hypotheses and two 2050 climate scenarios (RCP4.5 and RCP8.5). Overall, a general decline in suitable climatic conditions for Aegilops species outside the European zone and a parallel increase in Europe were predicted. If no migration could occur, the decline was predicted to be more acute outside than within the European zone. The potential sympatry level in Europe by 2050 was predicted to increase at a higher rate than species richness, and most expansions were predicted to occur in three countries, which are currently among the top four wheat producers in Europe: Russia, France and Ukraine. The results are also discussed with regard to conservation issues of these crop wild relatives.
... Repeated backcrossing of wide hybrids to their parental species has also contributed to the evolution and speciation of some species by gene introgression, i.e., the infiltration of chromosomes or chromosome fragments from one species into another through repeated backcrossing of wide hybrids to their parental species (Mallet 2007). Besides its role in evolution and speciation of species, gene introgression from crops, especially genetically modified crops, into the wild species, may increase the capability of the wild species to adapt to agricultural environments and compete with the cultivated forms, which is viewed as a possible threat to the environment and to agriculture (Weissmann et al. 2005 ). In application, wide hybridization and resulting wide hybrids have been widely used as an important tool of chromosome manipulation (also referred to as chromosome engineering) for crop improvement. ...
Training addressed the recent advances in oilseed Brassica plant pathology particularly on various aspects of plant disease management through lectures, practical and field visits. Scientific areas covered including diagnostics, IDM, pathogen diversity, epidemiology, resistance breeding, cultural practices, conventional and molecular approaches etc.
We are highly grateful to Prof. Arvind Kumar, Hon’ble Vice Chancellor, Rani Lakshmi Bai
Central Agricultural University, Jhansi for his constant support, guidance and encouragement in making the training a great success. We gratefully acknowledge the help and guidance received from Dr. N.S. Rathore, DDG (Edn) & Dr. M. B. Chetti, ADG (HRD), ICAR. We would be failing in our duty if we do not put on record the help and guidance received from Dr. Dhiraj Singh, Director, DRMR in conducting the proceedings of the training through practical and field visits.
