Abstract:

Background and Aims: The diploid cytotype of Paspalum rufum (Poaceae) reproduces sexually and is self-sterile; however, recurrent autopolyploidization through 2n + n fertilization and the ability for reproduction via apomixis have been documented in one genotype of the species. The objectives of this work were to analyse the variation in the functionality of apomixis components in diploid genotypes of P. rufum and to identify individuals with contrasting reproductive behaviours. Methods: Samples of five individuals from each of three natural populations of P. rufum (designated R2, R5 and R6) were used. Seeds were obtained after open pollination, selfing, conspecific interploidy crosses and interspecific interploidy self-pollination induction. The reproductive behaviour of each plant was determined by using the flow cytometric seed screen (FCSS) method. Embryo sacs were cleared using a series of ethanol and methyl salicylate solutions and observed microscopically. Key Results: In open pollination, all genotypes formed seeds by sexual means and no evidence of apomeiotic reproduction was detected. However, in conspecific interploidy crosses and interspecific interploidy self-pollination induction, variations in the reproductive pathways were observed. While all plants from populations R2 and R6 formed seeds exclusively by sexual means, three genotypes from the R5 population developed seeds from both meiotic and aposporous embryo sacs, and one of them (R5#49) through the complete apomictic pathway (apospory + parthenogenesis + pseudogamy). Cytoembryological observations revealed the presence of both meiotic and aposporous embryo sacs in all the genotypes analysed, suggesting that parthenogenesis could be uncoupled from apospory in some genotypes. Conclusions: The results presented demonstrate the existence of variation in the functionality of apomixis components in natural diploid genotypes of P. rufum and have identified individuals with contrasting reproductive behaviours. Genotypes identified here can be crossed to generate segregating populations in order to study apomixis determinants at the diploid level. Moreover, analysis of their expression patterns, quantification of their transcript levels and an understanding of their regulation mechanisms could help to design new strategies for recreating apomixis in a diploid genome environment.

Author affiliation: Delgado Benarroch, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Laboratorio de Biología Molecular; Argentina

Author affiliation: Galdeano, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

Author affiliation: Sartor, Maria Esperanza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

Author affiliation: Quarin, Camilo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

Author affiliation: Espinoza, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

Author affiliation: Ortiz, Juan Pablo Amelio. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Laboratorio de Biología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

Abstract:

Las hojas de la yerba mate se utilizan para la preparación del mate, una infusión de profunda raigambre histórica, social y cultural en Sudamérica. Su cultivo reviste importancia estratégica para varios países de la región, especialmente Argentina, Brasil y Paraguay. Nuestro objetivo fue establecer una población segregante y construir un mapa de ligamiento genético preliminar de esta especie para facilitar la futura identificación de loci asociados con caracteres de interés agronómico. Dos genotipos genéticamente divergentes con comportamiento contrastante respecto a la tolerancia a sequía se seleccionaron como progenitores femenino y masculino. Mediante cruzamientos controlados y rescate de embriones, se estableció una población F tipo 1 “pseudo-test cross” de 700 individuos, con potencial para extenderse hasta 1900. Un subgrupo de 117 plantas fue empleado para construir un mapa genético marco. Se ensayaron 5 combinaciones de cebadores de AFLP y 16 cebadores de RAPDs, para generar 119 marcadores informativos, de los cuales el 68,9% se ajustó a los valores de segregación mendeliana esperados. El análisis de ligamiento se realizó con el programa JoinMap 3.0. Los marcadores originados en cada progenitor se analizaron independientemente para generar un mapa femenino formado por 11 grupos de ligamiento y otro masculino con 16 grupos. Las distancias genéticas cubiertas por los mismos fueron de 223 cM y 678 cM, respectivamente. Este trabajo permitió establecer una progenie de mapeo segregante para yerba mate y construir un mapa genético preliminar que podrá usarse como base para la futura identificación de marcadores ligados a genes de interés agronómico.

Author affiliation: Stein, Juliana. Universidad Nacional de Rosario; Argentina

Author affiliation: Luna, Claudia Verónica. 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

Author affiliation: Espasandin, Fabiana Daniela. 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

Author affiliation: Sartor, Maria Esperanza. 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

Author affiliation: Espinoza, Francisco. 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

Author affiliation: Ortiz, Juan Pablo Amelio. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; 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; Argentina

Author affiliation: Sansberro, Pedro Alfonso. 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

Author affiliation: Pessino, Silvina Claudia. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; Argentina

Abstract:

Las hojas de la yerba mate se utilizan para la preparación del mate, una infusión de profunda raigambre histórica, social y cultural en sudamérica. Su cultivo reviste importancia estratégica para varios países de la región, especialmente Argentina, Brasil y Paraguay. Nuestro objetivo fue establecer una población segregante y construir un mapa de ligamiento genético preliminar de esta especie para facilitar la futura identificación de loci asociados con caracteres de interés agronómico. Dos genotipos genéticamente divergentes con comportamiento contrastante respecto a la tolerancia a sequía se seleccionaron como progenitores femenino y masculino. Mediante cruzamientos controlados y rescate de embriones, se estableció una población F tipo 1 ?pseudo-test cross? de 700 individuos, con potencial para extenderse hasta 1900. Un subgrupo de 117 plantas fue empleado para construir un mapa genético marco. Se ensayaron 5 combinaciones de cebadores de AFLP y 16 cebadores de RAPDs, para generar 119 marcadores informativos, de los cuales el 68,9% se ajustó a los valores de segregación mendeliana esperados. El análisis de ligamiento se realizó con el programa JoinMap 3.0. Los marcadores originados en cada progenitor se analizaron independientemente para generar un mapa femenino formado por 11 grupos de ligamiento y otro masculino con 16 grupos. Las distancias genéticas cubiertas por los mismos fueron de 223 cM y 678 cM, respectivamente. Este trabajo permitió establecer una progenie de mapeo segregante para yerba mate y construir un mapa genético preliminar que podrá usarse como base para la futura identificación de marcadores ligados a genes de interés agronómico.

The “yerba mate” leaves are used to make an infusion named “mate tea”, which is deeply rooted in the historical, social and cultural tradition of South America. Its sustainable use is of strategic significance to several countries of this region, particularly Argentina, Brazil and Paraguay. Our objective was to establish a segregating population and build a framework genetic map, in order to contribute to the future identification of loci associated with desirable traits. Two genetically divergent genotypes with contrasting drought tolerance capacity were selected as female and male parents. A “pseudo-test cross” F1 population of 700 individuals, with potential to be extended to 1900 individuals, was produced after controlled crossing followed by embryo rescue. A subset of 117 plants was used to produce a framework genetic map. Five AFLP primer combinations and 16 RAPD primers generated 119 informative markers, out of which 68.9% showed the expected Mendelian segregation values. Linkage analyses were carried out by using Joinmap 3.0. Markers originated from each progenitor were independently evaluated to generate a female map including 11 linkage groups and a male one with 16 linkage groups. Total genetic distances covered by the female and male maps were 223 cM and 678 cM, respectively. This work allowed the establishment of a yerba mate segregating population and the construction of a preliminary genetic map, which will be used as a framework for the future identification of markers linked to genes of interest.

Author affiliation: Stein, Juliana. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; Argentina

Author affiliation: Luna, Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

Author affiliation: Espasandin, Fabiana Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

Author affiliation: Sartor, Maria Esperanza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

Author affiliation: Espinoza, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

Author affiliation: Ortiz, Juan Pablo Amelio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; Argentina

Author affiliation: Sansberro, Pedro Alfonso. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

Author affiliation: Pessino, Silvina Claudia. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; Argentina

Abstract:

Gametophytic apomixis is an asexual mode of reproduction by seeds. This trait is present in several plant families and is strongly associated with polyploidy. Paspalum rufum is a forage grass with sexual self-incompatible diploids (2n = 2x = 20) and aposporous-apomictic pseudogamous tetraploids (2n = 4x = 40). In previous work embryological observations of the diploid genotype Q3754 showed 8.8-26.8% of the ovaries having one meiotic plus an aposporous-like embryo sac, suggesting some capability for apomictic reproduction. The objective of this work was to characterize progenies derived from Q3754 to determine if aposporous sacs were functional and generated progenies via apomixis at the diploid level. Re-examination of Q3754 ovaries showed that 12.5% of them contained one sexual plus an aposporous sac confirming previous results. Progeny tests were carried out on two experimental families (H 1 and S1) employing heterozygous RAPD marker loci. Family H1 was obtained crossing Q3754 with a natural diploid genotype (Q3861) and S1 derived from the induced self-pollination of Q3754. Genetic analysis of H1 showed that all individuals derived from sexual reproduction. However, 5 out of 95 plants from S1 showed the same heterozygous state as the mother plant for 14 RAPD loci suggesting a clonal origin. Further experiments, designed to test the functionality of aposporous sacs by flow cytometric analyses, were carried out on a third family (M 1) obtained by crossing Q3754 with the tetraploid plant Q3785. Histograms of 20 M1 plants showed 15 diploids (75%), 4 triploids (20%) and 1 tetraploid (5%). Triploids and the tetraploid may have originated from functional aposporous embryo sacs. Likewise, the reconstruction of the developmental route of 40 individual seeds demonstrated that 11 of them (27.5%) derived from fertilized aposporic sacs. The results presented in this work indicate that gametophytic apomixis is effectively expressed at the diploid level in Paspalum rufum and could be the foundation of a recurrent auto-polyploidization process in the species.

Author affiliation: Siena, Lorena Adelina. Universidad Nacional de Rosario; Argentina

Author affiliation: Sartor, Maria Esperanza. 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

Author affiliation: Espinoza, Francisco. 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

Author affiliation: Quarin, Camilo Luis. 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

Author affiliation: Ortiz, Juan Pablo Amelio. Universidad Nacional de Rosario; 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; Argentina

Abstract:

Paspalum plicatulum is a perennial rhizomatous grass with natural diploid and polyploid cytotypes. In this study, we investigated the occurrence of sequence polymorphisms arising immediately after genome autoduplication in this species. Two mixoploid plants (4C and 7D) were previously obtained through colchicine treatment of seeds generated by open pollination of a diploid plant (H14-2x). Diploid and tetraploid sectors from both mixoploids were dissected to generate two ploidy series (4C- 2x/4C-4x and 7D-2x/7D-4x). Molecular fingerprints were generated from the maternal plant H14-2x, both ploidy series (4C-2x/4C-4x and 7D-2x/7D-4x), and a tetraploid plant (C1) produced by selfing 7D-4x. Our results indicate that immediately after polyploidization P. plicatulum suffers genetic rearrangements affecting *28–38 % of the genome. Band gain and loss were equally prevalent at a statistically significant level. At least 5.62 % of the genome experimented recurrent genetic variation in a non-random basis with a confidence of 94.88 %. A significant proportion of novel bands (36 out of 195; 18.4 %) was detected in the C1 tetraploid plant. Half of these bands were not amplified in either H14-2x or 7D-4x, while the remainders were present in H14-2x but absent in 7D-4x. Our results indicate the occurrence of a considerable number of genetic changes in P. plicatulum immediately after polyploidization, some of which were recurrently detected in different independent events. Moreover, we confirmed that after polyploidization, lost ancestral alleles were spontaneously recovered in further generations, a phenomenon previously reported by other research groups.

Author affiliation: Weihmüller, Emilse. Universidad Nacional de Rosario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Beltrán, Celina. Universidad Nacional de Rosario; Argentina

Author affiliation: Sartor, Maria Esperanza. 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

Author affiliation: Espinoza, Francisco. 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

Author affiliation: Spampinato, Claudia Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro de Estudios Fotosinteticos y Bioquimicos. Universidad Nacional de Rosario. Facultad de Cs.bioquímicas y Farmaceuticas. Centro de Estudios Fotosinteticos y Bioquimicos; Argentina

Author affiliation: Pessino, Silvina Claudia. Universidad Nacional de Rosario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Abstract:

Background Apomixis is an alternative route of plant reproduction that produces individuals genetically identical to the mother plant through seeds. Apomixis is desirable in agriculture, because it guarantees the perpetuation of superior genotypes (i.e. heterotic hybrid seeds) by self-seeding without loss of hybrid vigour. The Paspalum genus, an archetypal model system for mining apomixis gene(s), is composed of about 370 species that have extremely diverse reproductive systems, including self-incompatibility, self-fertility, full sexual reproduction, and facultative or obligate apomixis. Barriers to interspecific hybridization are relaxed in this genus, allowing the production of new hybrids from many different parental combinations. Paspalum is also tolerant to various parental genome contributionsto the endosperm, allowing analyses of how sexually reproducing crop species might escape from dosage effects in the endosperm. Scope In this article, the available literature characterizing apomixis in Paspalum spp. and its use in breeding is critically reviewed. In particular, a comparison is made across species of the structure and function of the genomic region controlling apomixis in order to identify a common core region shared by all apomictic Paspalum species and where apomixis genes are likely to be localized. Candidate genes are discussed, either as possible genetic determinants (including homologs to signal transduction and RNA methylation genes) or as downstream factors (such as cell-to-cell signalling and auxin response genes) depending, respectively, on their co-segregation with apomixis or less. Strategies to validate the role of candidate genes in apomictic process are also discussed, with special emphasis on plant transformation in natural apomictic species.

Author affiliation: Ortiz, Juan Pablo Amelio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina; Universidad Nacional de Rosario. Facultad de Cs.agrarias. Laboratorio de Biologia Molecular; Argentina;

Author affiliation: Quarin, Camilo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina;

Author affiliation: Pessino, Silvina Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina; Universidad Nacional de Rosario. Facultad de Cs.agrarias. Laboratorio de Biologia Molecular; Argentina;

Author affiliation: Acuña, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina;

Author affiliation: Martínez, Eric Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina;

Author affiliation: Espinoza, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina;

Author affiliation: Hojsgaard, Diego Hernan. Universitat Of Gottingen; Alemania; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina;

Author affiliation: Sartor, Maria Esperanza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina;

Author affiliation: Cáceres, María Emilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Tandil. Centro de Investigación Veterinaria de Tandil; Argentina; Consiglio Nazionale Delle Ricerche; Italia;

Author affiliation: Pupilli, Fulvio. Consiglio Nazionale Delle Ricerche; Italia;

Abstract:

Paspalum rufum Nees is a perennial grass that forms a multiploid complex. natural populations are composed mainly of diploid (2n = 2x = 20) and tetraploid(2n = 4x = 40) cytotypes. The diploid form is sexual and highly self-sterile, while the tetraploid is pseudogamous aposporous apomict and self-fertile. Diploids can also develop aposporous sacs, and some of them complete apomixis. The objective of this work was to analyse apospory expressivity (a gametophytic apomixis component) in diploid hybrids and colchicine-induced autotetraploids of the species. One F1 family was created by crossing two diploid individuals (R6#45 9 R5#49) carrying aposporous sacs in 5.8 and 13 % of their ovules, respectively. Moreover, two synthetic autotetraploids were obtained by colchicine treatment of mature seeds from R6#45. The hybrid origin of the F1s was confirmed by segregation analyses of a morphological trait and molecular markers, and the ploidy level of experimental plants was determined by flow cytometry. Apospory expressivity was estimated by embryo sacs observation at anthesis. Out of the 39 hybrids analysed, 38 showed aposporous embryo sacs. Expressivity of the trait ranged from 0 to 36 %, and some individuals differed significantly for both progenitors? values. Both doubled-diploid plants showed 25 and 32 % of apospory expressivity, which was significantly higher than that observed in R6#45. Results presented in this work revealed a high variability in apospory expressivity of diploid hybrids and suggested that more than one allele are controlling the trait. Moreover, the new induced doubled-diploid plants showed that apospory expressivity is highly ploidy dependent.

Author affiliation: Delgado, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina

Author affiliation: Sartor, Maria Esperanza. 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

Author affiliation: Espinoza, Francisco. 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

Author affiliation: Soliman, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina

Author affiliation: Galdeano, Florencia. 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

Author affiliation: Ortiz, Juan Pablo Amelio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentina

Abstract:

The Plicatula group of the grass genus Paspalum contains about 30 species. Most are tetraploid and reproduce by apomixis, though some of them contain sexual diploid races. We crossed a sexual colchicine-induced autotetraploid plant of brownseed paspalum (Paspalum plicatulum Michx.) with apomictic tetraploid P. guenoarum Arechav., also from the Plicatula group. Crossability was 35% and the progeny showed morphological characteristics intermediate to those of the parents but resembling more the male parent. The random amplifi ed polymorphic DNA (RAPD) analysis showed that the whole progeny amplifi ed bands that were specifi c of the male parent, confi rming its hybrid origin. Meiotic chromosome behavior of hybrids exhibited primarily bivalent and quadrivalent associations similar to those of the two parents. This suggests that natural tetraploid P. guenoarum shares the same basic chromosome set with that of autotetraploid P. plicatulum, and both species probably originate from the same ancestral species. Fourteen out of 23 hybrids reproduced only sexually, while nine were obligate or highly apomictic. Seed set ranged from 11 to 55% among the hybrids. Our results open the possibility of exchanging genes at the tetraploid level in breeding programs of P. plicatulum and P. guenoarum. This possibility is based on their rate of crossability, the degree of fertility among the hybrids, the segregation observed for the reproductive mode in the F1 progeny, and the very simple procedure fl ow cytometry seed screen (FCSS) used to determine the reproductive mode for each hybrid.

Author affiliation: Aguilera, Patricia Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina

Author affiliation: Sartor, Maria Esperanza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina

Author affiliation: Galdeano, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina

Author affiliation: Espinoza, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina

Author affiliation: Quarin, Camilo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina

Abstract:

Soybean mosaic virus (SMV) is the causal agent of a commonly occurring disease of soybean [Glycine max (L.) Merr.] that can be effectively controlled through the deployment of single, dominant genes known as Rsv genes, which confer resistance to different strains of SMV. The Rsv1-n allele in PI 507389 conditions a lethal necrosis (LN) reaction on inoculation with specific SMV strains, including SMV-G1, -G5, and -G6. The objective of the current study was to examine effects of the Rsv1-n allele introgressed into the susceptible genotype ‘Essex’ background alone or in combination with either Rsv3 or Rsv4 resistance genes by inoculation with six different SMV strains. Presence of Rsv1-n and its LN as well as severe mosaic reactions to the strains tested were masked when the gene was pyramided with Rsv3 and Rsv4 Thus in some cases, the LN-causing gene may go undetected in breeding populations. Pyramided isolines containing Rsv1-n and Rsv4 together were susceptible to SMV-G6, displaying a mosaic reaction, although Rsv4 alone confers resistance against all known strains. This study demonstrates the importance of selecting against the Rsv1-n allele to prevent its introduction into breeding programs

Author affiliation: Sartor, Maria Esperanza. 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

Author affiliation: Quarin, Camilo Luis. 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

Author affiliation: Espinoza, Francisco. 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

Abstract:

Cytogeographical variability among 564 plants from 26 populations of Turnera sidoides subsp. pinnatifida in mountain ranges of central Argentina was analysed with meiotic chromosome counts and flow cytometry and is described at regional and local scales. Populations were primarily tetraploids (2n = 4x = 28), although diploid (2n = 2x = 14), hexaploid (2n = 2x = 42), and mixed populations of diploids and triploids (2n = 3x = 21) were also found. Diploids, triploids, and hexaploids were fewer in number and restricted to narrow areas, while tetraploids were the most common and geographically widespread cytotype. Diploids grew at higher altitudes and in colder and wet locations; tetraploids had the broadest ecological spectrum, while hexaploids occurred at the lowest altitudes and in drier conditions. The cytotypes were also spatially segregated at a microgeographical scale. Diploids grew in the piedmont, tetraploids were in the adjacent valley, and in the contact zone of both cytotypes, patches of diploids and triploids were found. At a regional scale, the distribution of the cytotypes may be governed by a combination of ecological and historical variables, while segregation in the contact zone may be independent of the selective environment because the cytotypes are unable to coexist as a result of reproductive exclusion. The role of triploids is also discussed. © 2010 The Botanical Society of Japan and Springer.

Author affiliation: Elias, Fernanda Gabriela. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina

Author affiliation: Sartor, Maria Esperanza. 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

Author affiliation: Solis Neffa, Viviana Griselda. 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