The Rise of Apomixis in Natural Plant Populations

Apomixis, the asexual reproduction via seed, has many potential applications for plant breeding by maintaining desirable genotypes over generations. Since most major crops do not express natural apomixis, it is useful to understand the origin and maintenance of apomixis in natural plant systems. Here, we review the state of knowledge on origin, establishment and maintenance of natural apomixis. Many studies suggest that hybridization, either on diploid or polyploid cytotypes, is a major trigger for the formation of unreduced female gametophytes, which represents the first step toward apomixis, and must be combined to parthenogenesis, the development of an unfertilized egg cell. Nevertheless, fertilization of endosperm is still needed for most apomictic plants. Coupling of these three steps appears to be a major constraint for shifts to natural apomixis. Adventitious embryony is another developmental pathway toward apomixis. Establishment of a newly arisen apomictic lineage is often fostered by side-effects of polyploidy. Polyploidy creates an immediate reproductive barrier against the diploid parental and progenitor populations; it can cause a breakdown of genetic self-incompatibility (SI) systems which is needed to establish self-fertility of pseudogamous apomictic lineages; and finally, polyploidy could indirectly help to establish an apomictic cytotype in a novel ecological niche by increasing adaptive potentials of the plants. This step may be followed by a phase of diversification and range expansion, mostly described as geographical parthenogenesis. The utilization of apomixis in crops must consider the potential risks of pollen transfer and introgression into sexual crop fields, which might be overcome by using pollen-sterile or cleistogamous variants. Another risk is the escape into natural vegetation and potential invasiveness of apomictic plants which needs careful management and consideration of ecological conditions

Genomic, karyological and morphological changes of South American garlics (Ipheion) provide insights into mechanisms of speciation in the Pampean region

Speciation proceeds through mechanisms that promote reproductive isolation and shape the extent of genetic variation in natural populations, and thus its study is essential to understand the evolutionary processes leading to increased biodiversity. Chromosomal rearrangements are known to facilitate reproductive isolation by hybrid sterility and favour speciation events. The genus Ipheion (Amaryllidaceae, Allioideae) is unique as its species exhibit a remarkable karyological variability but lack population-level genetic data. To unveil the diversification processes acting upon the formation of new lineages within Ipheion in the Pampas of South America, we combined morphology and karyology approaches with genotyping-by-sequencing. Our phylogenomic and population genomics results supported the taxonomic division of Ipheion into three morphological and genetically well-differentiated groups. The origin of Ipheion uniflorum was traced back to its current southern distribution area in the southern Pampean region (in Argentina), from where it had expanded to the north reaching Uruguay. Our results further suggested that chromosome rearrangements and ploidy shifts had triggered speciation events, first during the origin of I. uniflorum and later during its subsequent diversification into I. recurvifolium and I. tweedieanum, in both cases reinforced by extrinsic factors and biogeographical settings. The current study illustrates the analytical power of multidisciplinary approaches integrating phylo- and population genomics with classic analyses to reveal evolutionary processes in plants.Fil: Sassone, Agostina Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentina. Leibniz Institute of Plant Genetics and Crop Plant Research; AlemaniaFil: Hojsgaard, Diego H.. Leibniz Institute of Plant Genetics and Crop Plant Research; AlemaniaFil: Giussani, Liliana Mónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; ArgentinaFil: Brassac, Jonathan. Leibniz Institute of Plant Genetics and Crop Plant Research; AlemaniaFil: Blattner, Frank R.. Leibniz Institute of Plant Genetics and Crop Plant Research; Alemani

New records and range expansion for Paspalum procurrens and P. volcanense in northwestern Argentina and southeastern Bolivia

Paspalum procurrens Quarin and P. volcanense Zuloaga, Morrone & Denham are two rare species of South Americangrasses inhabiting geographically restricted areas which are exposed to ecological degradation due to landscapetransformation and biodiversity losses. We present new records for these species, from the provinces of Jujuy, Salta,Tucumán and Catamarca (Argentina) and departments of Tarija, Chuquisaca, and Santa Cruz (Bolivia). New geographicdistribution maps and the biological relevance of these findings are discussed pinpointing the need for imperativeand assiduous botanical explorations in biodiversity hotspots sensible to the impact of human activities. Ploidylevels in these two species are studied.Fil: Glücksberg, Adriana. Universidad Nacional del Nordeste; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Martínez, Eric Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Universidad Nacional del Nordeste; ArgentinaFil: Honfi, Ana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentina. Universidad Nacional de Misiones; ArgentinaFil: Maldonado, Carla Carolina. Universidad Mayor de San Andrés; BoliviaFil: Hojsgaard, Diego Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Universität Göttingen; Alemani

Sexual modulation in a polyploid grass: a reproductive contest between environmentally inducible sexual and genetically dominant apomictic pathways

In systems alternating between sexual and asexual reproduction, sex increases under unfavorable environmental conditions. In plants producing sexual and asexual (apomictic) seeds, studies on the influence of environmental factors on sex are equivocal. We used Paspalum intermedium to study environmental effects on the expression of sexual and apomictic developments, and on resulting reproductive fitness variables. Flow cytometric and embryological analyses were performed to characterize ploidy and reproductive modes, and effects of local climatic conditions on sexual and apomictic ovule and seed frequencies were determined. Seed set and germination data were collected and used to estimate reproductive fitness. Frequencies of sexual and apomictic ovules and seeds were highly variable within and among populations. Apomictic development exhibited higher competitive ability but lower overall fitness. Frequencies of sexual reproduction in facultative apomictic plants increased at lower temperatures and wider mean diurnal temperature ranges. We identified a twofold higher fitness advantage of sexuality and a Tug of War between factors intrinsic to apomixis and environmental stressors promoting sexuality which influence the distribution of sex in apomictic populations. This points toward a crucial role of local ecological conditions in promoting a reshuffling of genetic variability that may be shaping the adaptative landscape in apomictic P. intermedium plants.Fil: Karunarathne, Piyal. Universität Göttingen; AlemaniaFil: Reutemann, Anna Verena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Schedler, Mara. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Martínez, Eric Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Honfi, Ana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Hojsgaard, Diego Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Universität Göttingen; Alemani

Colección de germoplasma de Paspalum indecorum, P. cromyorhizon, P. maculosum y P. pumilum

Se realizaron viajes de colección de poblaciones de Paspalum indecorum, P. cromyorhizon, P. maculosum y P. pumilum por la Mesopotamia Argentina (Corrientes, Misiones y Entre Ríos). Para la localización de las poblaciones se tuvieron en cuenta los sitios geográficos de colecta de los materiales previamente estudiados de cada una de las especies citados en la bibliografía disponible hasta la fecha y los registros pertenecientes a los Herbarios del Instituto de Botánica del Nordeste (CTES) y de la Universidad Nacional de Misiones (MNES). Las colecciones fueron realizadas durante el periodo de floración de las especies, entre los años 2015 y 2016. Como criterio de colección se estableció una distancia mínima de 50 km entre las poblaciones muestreadas para cada especie. Las poblaciones se seleccionaron basándose en que tuvieran un tamaño mínimo de 200 m lineales de extensión, y se colectaron 20 a 30 plantas individuales, distanciadas entre sí por 10 m aproximadamente, para evitar el muestreo de ramets (i.e. grupo de individuos genéticamente idénticos debido a su reproducción clonal). En cada sitio de colección se tomaron datos de coordenadas geográficas, las cuales fueron utilizadas para realizar un mapa geo-referenciado mediante el programa DIVA-GIS (Hijmans et al., 2004). Además, se tomaron datos del ambiente natural donde se encontraba cada población, principalmente edáficos y de comunidad; e individuos para ejemplares de herbario, que fueron depositados en el Herbario del Instituto de Botánica del Nordeste (CTES) y/o de la Universidad Nacional de Misiones (MNES).Fil: Reutemann, Anna Verena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Martínez, Eric Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; ArgentinaFil: Honfi, Ana Isabel. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Hojsgaard, Diego Hernan. Universität Göttingen; AlemaniaFil: Daviña, Julio Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentina. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales; Argentin

The karyotype of diploid and tetraploid Paspalum cromyorrhizon (Poaceae, Panicoideae, Paspaleae)

Paspalum cromyorrhizon Trin. ex Döll es una especie adaptada a los campos bajos y húmedos, márgenes de ríos y arroyos, en el S de Brasil, Uruguay y NE de Argentina. Se utilizaron individuos diploides (2n = 2x = 20) y tetraploides (2n = 4x = 40) provenientes de poblaciones naturales de P. cromyorrhizon de Corrientes (Argentina) para confeccionar un idiograma del cariotipo de ambos citotipos. El recuento cromosómico se realizó mediante tinción clásica de Feulgen. El citotipo diploide de P. cromyorrhizon presenta un cariotipo compuesto por 20 cromosomas metacéntricos, mientras que el citotipo tetraploide tiene un cariotipo compuesto por 40 cromosomas metacéntricos. La longitud total del complemento cromosómico en diploides es de 32,5 μm y en tetraploides de 63,5 μm, la longitud cromosómica total monoploide es de 15,48 μm en diploides y de 15,21 μm en tetraploides y ambos cariotipos resultaron simétricos. El análisis de los cariotipos confirma el origen autopoliploide propuesto para los tetraploides.Paspalum cromyorrhizon Trin. ex Döll is a species adapted to low and humid fields, river and stream banks, throughout S Brazil, Uruguay and NE Argentine. Diploids (2n = 2x = 20) and tetraploids (2n = 4x = 40) from natural populations of P. cromyorrhizon from Corrientes (Argentina) were used to analyse the karyotype morphometry of both cytotypes. The chromosome count was performed using classical Feulgen staining. The karyotype of diploid P. cromyorrhizon has 20 metacentric chromosomes, while the tetraploid has a karyotype of 40 metacentric chromosomes. The total length of the chromosomal complement in diploids is 32.5 μm and in tetraploids 63.5 μm, the total monoploid chromosome length is 15.48 μm in diploids and 15.21 μm in tetraploids and both karyotypes are symmetrical. Karyotype analysis confirms the autopolyploid origin proposed for tetraploids.Fil: Reutemann, Anna Verena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Martínez, Eric Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Daviña, Julio Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Hojsgaard, Diego Hernan. University of Goettingen; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Honfi, Ana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Universidad Nacional de Misiones. Instituto de Biología Subtropical; Argentin

Chromosome studies in Orchidaceae from Argentina

Abstract The center of diversity of Argentinean orchids is in the northeast region of the country. Chromosome numbers and karyotype features of 43 species belonging to 28 genera are presented here

Chromosome studies in Orchidaceae from Argentina

The center of diversity of Argentinean orchids is in the northeast region of the country. Chromosome numbers and karyotype features of 43 species belonging to 28 genera are presented here. Five chromosome records are the first ones at the genus level; these taxa are Aspidogyne kuckzinskii (2n = 42), Eurystyles actinosophila (2n = 56), Skeptrostachys paraguayensis (2n = 46), Stigmatosema polyaden (2n = 40) and Zygostates alleniana (2n = 54). In addition, a chromosome number is presented for the first time for 15 species: Corymborkis flava (2n = 56), Cyclopogon callophyllus (2n = 28), C. oliganthus (2n = 64), Cyrtopodium hatschbachii (2n = 46), C. palmifrons (2n = 46), Galeandra beyrichii (2n = 54), Habenaria bractescens (2n = 44), Oncidium edwallii (2n = 42), O. fimbriatum (2n = 56), O. pubes (2n = 84), O. riograndense (2n = 56), Pelexia ekmanii (2n = 46), P. lindmanii (2n = 46) and Warrea warreana (2n = 48). For Oncidium longicornu (2n = 42), O. divaricatum (2n = 56) and Sarcoglottis fasciculata (2n = 46+1B?, 46+3B?), a new cytotype was found. Chromosome data support phylogenetic relationships proposed by previous cytological, morphologic and molecular analyses, and in all the cases cover some gaps in the South American literature on orchid chromosomes

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe