1,336 research outputs found

    Analysis of the meiotic segregation in intergeneric hybrids of tilapias

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    Tilapia species exhibit a large ecological diversity and an important propensity to interspecific hybridisation. This has been shown in the wild and used in aquaculture. However, despite its important evolutionary implications, few studies have focused on the analysis of hybrid genomes and their meiotic segregation. Intergeneric hybrids between Oreochromis niloticus and Sarotherodon melanotheron, two species highly differentiated genetically, ecologically, and behaviourally, were produced experimentally. The meiotic segregation of these hybrids was analysed in reciprocal second generation hybrid (F2) and backcross families and compared to the meiosis of both parental species, using a panel of 30 microsatellite markers. Hybrid meioses showed segregation in accordance to Mendelian expectations, independent from sex and the direction of crosses. In addition, we observed a conservation of linkage associations between markers, which suggests a relatively similar genome structure between the two parental species and the apparent lack of postzygotic incompatibility, despite their important divergence. These results provide genomics insights into the relative ease of hybridisation within cichlid species when prezygotic barriers are disrupted. Overall our results support the hypothesis that hybridisation may have played an important role in the evolution and diversification of cichlids

    Preferential homologous chromosome pairing in a tetraploid intergeneric somatic hybrid (Citrus reticulata + Poncirus trifoliata)revealed by molecular marker inheritance

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    The creation of intergeneric somatic hybrids between Citrus and Poncirus is an efficient approach for citrus rootstock breeding, offering the possibility of combining beneficial traits from both genera into novel rootstock lineages. These somatic hybrids are also used as parents for further tetraploid sexual breeding. In order to optimize these latter breeding schemes, it is essential to develop knowledge on the mode of inheritance in the intergeneric tetraploid hybrids. We assessed the meiotic behavior of an intergeneric tetraploid somatic hybrid resulting from symmetric protoplast fusion of diploid Citrus reticulata and diploid Poncirus trifoliata. The analysis was based on the segregation patterns of 16 SSR markers and 9 newly developed centromeric/pericentromeric SNP markers, representing all nine linkage groups of the Citrus genetic map. We found strong but incomplete preferential pairing between homologues of the same ancestral genome. The proportion of gametes that can be explained by random meiotic chromosome associations (τ) varied significantly between chromosomes, from 0.09 ± 0.02 to 0.47 ± 0.09, respectively, in chromosome 2 and 1. This intermediate inheritance between strict disomy and tetrasomy, with global preferential disomic tendency, resulted in a high level of intergeneric heterozygosity of the diploid gametes. Although limited, intergeneric recombinations occurred, whose observed rates, ranging from 0.09 to 0.29, respectively, in chromosome 2 and 1, were significantly correlated with τ. Such inheritance is of particular interest for rootstock breeding because a large part of the multi-trait value selected at the teraploid parent level is transmitted to the progeny, while the potential for some intergeneric recombination offers opportunities for generating plants with novel allelic combinations that can be targeted by selection

    Transfer of recessive skr crossability trait into well-adapted French wheat cultivar Barok through marker-assisted backcrossing method

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    In order to increase genetic diversity in cereals, interspecific or even intergeneric crosses are worthwhile, especially wheat by rye crosses for triticale production. However, these crosses often fail due to inhibiting genes. To overcome this obstacle, crossability trait, present in a few wheat cultivars, can be transferred into other wheat lines of agronomical interest. Nevertheless, this transfer remains tedious through conventional backcrossing methods because it is a recessive trait, which requires selfing generations and complex evaluation by many crosses. Here, we present a marker-assisted backcrossing method to transfer this trait more quickly and easily. We chose to introduce the recessive crossability skr, located on chromosome 5BS and originating from Asian wheat, into Barok, a non-crossable French wheat cultivar, with good agronomic characteristics. Six molecular markers, close to the Skr locus, were used to check the transfer of the gene at each of the three backcrosses, without selfing generation nor crosses with rye. Finally, we crossed the predicted crossable lines with rye to validate their crossability. We obtained sixteen lines, morphologically similar to Barok, exhibiting high crossability rate (30%). The markers were thus efficient to transfer the skr crossability but they remain too far from the Skr locus to be considered as diagnostic markers. Indeed, genotyping and phenotyping on other wheat cultivars showed some discrepancies. Nevertheless, this opens the way to enhance genetic diversity more easily and to improve traits of agronomic interest in triticale or wheat as well as to study further barriers to intergeneric crosses

    Transfer of Dicamba Tolerance from Sinapis arvensis to Brassica napus via Embryo Rescue and Recurrent Backcross Breeding

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    Citation: Jugulam M, Ziauddin A, So KKY, Chen S, Hall JC (2015) Transfer of Dicamba Tolerance from Sinapis arvensis to Brassica napus via Embryo Rescue and Recurrent Backcross Breeding. PLoS ONE 10(11): e0141418. https://doi.org/10.1371/journal.pone.0141418Auxinic herbicides (e.g. dicamba) are extensively used in agriculture to selectively control broadleaf weeds. Although cultivated species of Brassicaceae (e.g. Canola) are susceptible to auxinic herbicides, some biotypes of Sinapis arvensis (wild mustard) were found dicamba resistant in Canada. In this research, dicamba tolerance from wild mustard was introgressed into canola through embryo rescue followed by conventional breeding. Intergeneric hybrids between S. arvensis (2n = 18) and B. napus (2n = 38) were produced through embryo rescue. Embryo formation and hybrid plant regeneration was achieved. Transfer of dicamba tolerance from S. arvensis into the hybrid plants was determined by molecular analysis and at the whole plant level. Dicamba tolerance was introgressed into B. napus by backcrossing for seven generations. Homozygous dicamba-tolerant B. napus lines were identified. The ploidy of the hybrid progeny was assessed by flow cytometry. Finally, introgression of the piece of DNA possibly containing the dicamba tolerance gene into B. napus was confirmed using florescence in situ hybridization (FISH). This research demonstrates for the first time stable introgression of dicamba tolerance from S. arvensis into B. napus via in vitro embryo rescue followed by repeated backcross breeding. Creation of dicamba-tolerant B. napus varieties by this approach may have potential to provide options to growers to choose a desirable herbicide-tolerant technology. Furthermore, adoption of such technology facilitates effective weed control, less tillage, and possibly minimize evolution of herbicide resistant weeds

    Restoring Polyhyrdoxybutyrate (PHB) Depolymerase Expression in a Bald Mutant of Streptomyces sp. SFB5A

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    Polyhydroxybutyrate (PHB) is a biodegradable, plastic-like polymer produced by some bacteria and degraded by others. The filamentous bacterium Streptomyces sp. SFB5A degrades PHB for growth using an extracellular PHB depolymerase, encoded by the phaZ gene. A morphological mutant of this bacterium, bld4, cannot form aerial filaments and cannot produce PHB depolymerase, despite having the phaZ gene. The inability to synthesize PHB depolymerase may be due to a mutation in a gene encoding one of its transcriptional regulators. A gene (lrp) coding for a potential transcriptional regulator is located 2,700 base pairs upstream from phaZ. Our goal was to clone lrp from wild type Streptomyces sp. SFB5A into Escherichia coli and introduce it into bld4 to see if morphology and PHB depolymerase synthesis are restored

    Relationship of Latitude-of-Origin to Winter Survival and to Forage and Seed Yields of Wheatgrass (Agropyron species) in Subarctic Alaska

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    Five field experiments evaluating and comparing numerous grasses were conducted over seven years at the Matanuska Research Farm (61.6°N) near Palmer in southcentral Alaska. Grasses were 34 strains within 14 species of wheatgrass (Agropyron) derived from various geographic areas spanning 32 degrees of latitude; also included were the intergeneric hybrid Agroelymus palmerensis Lepage, Siberian wildrye (Elymus sibiricus L.), two bromegrass (Bromus) cultivars, and one timothy (Phleum pratense L.) cultivar. They were grown in broadcast-seeded plots for forage (two cuts per year), in drilled rows for seed production, and as individual plants in rows for winter-survival determinations

    Morphology and cytology of flower chimeras in hybrids of Brassica carinata × Brassica rapa

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    Hybridization between white flowered Brassica carinata and yellow flowered B. rapa were made, and the flower chimeras were observed in a few hybrids. The simple single sequence molecular markers verified the hybridity of those hybrids. Chimeras were justified and totally classified based on the morphological characteristics of the flower petals that appeared in the hybrids of B. carinata and B. rapa. Two kinds of flower chimeras were observed: one type was different flower petals were with different colour in one branch; another type was that yellow petals were with white variegations, but the variegation size and shape were different in different petals. The meiosis and mitosis analysis showed that the partial or complete separation of parental genomes inferred to occur in pollen mother cells, shoot and early-developed petals in the flower chimeral hybrids, which hinted that the occurrence of complete or partial segregation of parental genomes in the somatic cells might be the reason for theproduction of flower chimera in the hybrids of B. carinata and B. rapa

    Procedures for Transfer of Agronomic Traits from Alien Species to Crop Plants

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    The steps involved in the transfer of alien genetic variation will be outlined and the impact of recent technologies on improving the efficiency of the process will be discussed. The selection of parents is the first step; it is critically important that each selection be carefully screened for maximum expression of the desired trait. The crossing process is becoming increasingly more efficient with improved efficiency of growth regulators and embryo rescue media. Doubled haploid methods are being used to facilitate the production of chromosome addition lines. Molecular methods such as RFLPs, RAPDs, chromosome banding, and in situ hybridization add an increased level of resolution to the identification of chromosome additions and the monitoring of introgressed chromosome segments. Emerging technologies such as monocot transformation, chromosome-specific libraries, and transposon tagging may soon replace some of the traditional methods of gene transfer

    Intergeneric Hybridization of Two Stickleback Species Leads to Introgression of Membrane-Associated Genes and Invasive TE Expansion

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    Interspecific hybridization has occurred relatively frequently during the evolution of vertebrates. This process usually abolishes reproductive isolation between the parental species. Moreover, it results in the exchange of genetic material and can lead to hybridogenic speciation. Hybridization between species has predominately been observed at the interspecific level, whereas intergeneric hybridization is rarer. Here, using whole-genome sequencing analysis, we describe clear and reliable signals of intergeneric introgression between the three-spined stickleback (Gasterosteus aculeatus) and its primarily distant freshwater relative to the nine-spined stickleback (Pungitius pungitius) that inhabit northwestern Russia. Through comparative analysis, we demonstrate that such introgression phenomena occur in the moderate-salinity White Sea basin, although it is not detected in Japanese sea stickleback populations. Bioinformatical analysis of the sites influenced by introgression showed that they are located near transposable elements, whereas those in protein-coding sequences are primarily found in membrane-associated and alternative splicing-related genes.Intergeneric Hybridization of Two Stickleback Species Leads to Introgression of Membrane-Associated Genes and Invasive TE ExpansionpublishedVersio
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