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The tetraploid germplasm of Paspalum contains a large diversity that can be used to generate better forages. The objective was to evaluate a group of Paspalum notatum and Paspalum simplex apomictic hybrids for a set of agronomic traits and apomixis expressivity. Forage yield, cold tolerance, winter regrowth, and seed yield were evaluated. The expressivity of apomixis was evaluated in P. simplex hybrids by flow cytometry. Progeny testing with molecular markers was used to determine the genotypic variability in the progeny. Differences within P. notatum and P. simplex hybrids were observed for all traits, and some of them were superior in comparison with the controls. The accumulated forage yield during three years was 988 g m−2 in the P. notatum hybrids, whereas, in P. simplex, the average forage yield per harvest (40 days of regrowth) was 180 g m−2. In P. simplex, the apomixis expressivity varied between 0 and 100%, and 65% of the hybrids showed high apomixis expressivity (superior to 70%). The genotypic mean homogeneity in the progeny was 76% and 85% in P. notatum and P. simplex, respectively. The generation of hybrids with high apomixis expressivity that combine good agronomic performance and homogeneity in the offspring is possible in tetraploid P. notatum and P. simplex.

The genetic systems of Paspalum species have not been extensively studied. We analyzed the ploidy, reproductive mode, mating system, and fertility of four Paspalum species—Paspalum durifolium, Paspalum ionanthum, Paspalum regnellii, and Paspalum urvillei. An analysis of 378 individuals from 20 populations of northeastern Argentina was conducted. All populations of the four Paspalum species were pure tetraploid and had a sexual and stable reproductive mode. However, some populations of P. durifolium and P. ionanthum showed low levels of apospory. Populations of P. durifolium and P. ionanthum had low seed sets under self-pollination but were fertile under open pollination, showing that self-incompatibility likely caused self-sterility. In contrast, populations of P. regnellii or P. urvillei showed no evidence of apospory, and seed sets in both self- and open pollination conditions were high, suggesting that they are self-compatible due to the absence of pollen–pistil molecular incompatibility mechanisms. The evolutionary origin of the four Paspalum species could explain these differences. This study supplies valuable insights into the genetic systems of Paspalum species, which could have implications for their conservation and management.

Paspalum notatum Flüggé is an apomictic grass used for forage and turf. The recent generation of a sexual synthetic tetraploid population of the species provides the uniqueadvantagetoexploitheterosisbyaccumulatingfavorableallelesthroughrecurrent selection cycles. The objective was to evaluate recurrent phenotypic selection (RPS) and recurrent selection based on combining ability (RSCA) as breeding methods. The best sexual genotypes in terms of warm-season growth from a sexual synthetic tetraploid population were selected by RPS and RSCA. The selected genotypes were polycrossed and two new sexual populations were created, which were crossed with superior apomictic genotypes. Both methods allowed obtaining families that were evaluated for summer, fall, and spring growth. Breeding values and heterosis were also calculated. Summer growth for RPS families was greater than for RSCA families (33.1 and 29.08 g plant−1, respectively); however, fall, spring, and accumulated growth were similar. The breeding value for RPS sexual parents was greater than for RSCA sexual parents for summer growth, whereas those for fall and spring growth were similar. A greater level of families with heterosis (80%) was observed for RPS than for RSCA (30%) for summer growth, whereas the levels for fallandspringgrowthweresimilar.Theseresultsindicatethatbothbreedingmethods were successful in improving tetraploid P. notatum. They increased the mean value of the progenies and produced families superior for forage yield by accumulating favorable alleles. Fil: Marcón, 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 Fil: 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 Fil: Zilli, Alex Leonel. 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 Fil: Rodríguez, Gustavo Rubén. 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 Fil: Brugnoli, Elsa Andrea. 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 Fil: Acuña, Carlos Alberto. 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

Recurrent selection based on combining ability has been successfully used in tetraploid bahiagrass (Paspalum notatum Flüggé) to accumulate heterotic effects and exploit hybrid vigor. However, its efficiency depends on an accurate selection of the best genotypes to form a new recombinant population. The objective of this work was to assess the general combining ability of female parents of bahiagrass based on the performance of their progeny for agronomic and morphological traits using a mixed model approach, biplot analysis and selection index. There were evaluated 29 half-sib families generated by crossing 29 sexual tetraploid genotypes from a sexual synthetic tetraploid population and a group of apomictic tetraploid genotypes. Agronomic and morphological traits were analyzed using a mixed model approach (BLUP). The multi-trait analysis was based on a biplot analysis and a selection index using the family BLUPs. BLUP analysis showed significant differences among families for most of the evaluated traits. Sexual female parents of families 5, 9, 8, 28, 21 and 16 were identified as those with greater general combining ability. Biplot showed variability among families and allowed identifying six sexual parents with greater general combining ability. The same sexual parents that exhibited greater general combining ability by BLUP were identified with greater general combining ability by biplot. Selection index was variable and allowed identifying the same best sexual parents that BLUP and biplot. The three analysis methods were equally effective to estimate general combining ability of a group of sexual parents of tetraploid bahiagrass based on the performance of their progeny.

The objective of this review is to analyze and describe the impact that mode of reproduction in Paspalum has on germplasm conservation, genetic improvement and commercialization of cultivars. Germplasm collection and conservation can now berethought considering the new available information related to how diversity is allocated in nature and how it can be transferred between the sexual and apomictic germplasm using novel breeding approaches. A quantification of species and accessions conserved around the world is analyzed in relation to the main germplasm banks. Because of the importance of apomixis in Paspalum species different breeding approaches have been used and tested. Knowledge related to the inheritance of apomixis, variable expressivity of the trait and techniques for early identification of apomicts has helped to improve the efficiency of the breeding methods. Novel breeding techniques are also being developed and are described regarding its advantages and limitations. Finally, the impact of reproductive mode on the popularity of the released cultivars is discussed Fil: Acuña, Carlos Alberto. 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 Fil: 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 Fil: Zilli, Alex Leonel. 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 Fil: Brugnoli, Elsa Andrea. 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 Fil: 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 Fil: Marcón, 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 Fil: Urbani, Mario Hugo. 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 Fil: 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

Genetic improvement in apomictic forage species has been restricted because of the absence of genetic variability in sexual germplasm with the same ploidy level. Following a new breeding scheme, a sexual synthetic tetraploid population (SSTP) of Paspalum notatum has been generated. The objectives of this work were: (a) to evaluate the genetic variability in SSTP by means of molecular markers, morphologic and agronomic traits, and seed fertility and quality traits and (b) to assess the transference of genetic variability from the apomictic germplasm to the sexual one. Molecular markers revealed a twofold higher level of variability in the SSTP in comparison with the sexual germplasm utilised for its generation, and similar levels with the apomictic ones; moreover, markers showed that most of the variability was inherited from theapomictic germplasm. Morphologic and agronomic traits and seed fertility and quality traits showed high levels of variation in the three groups of genotypes indicating that the new breeding scheme was effective in transferring variability from the apomictic germplasm to the SSTP. This new population will be useful in breeding of P. notatum, and the breeding scheme used for its generation may be used in other apomictic species. Fil: Zilli, Alex Leonel. 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 Fil: Acuña, Carlos Alberto. 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 Fil: Schulz, Roberto R.. Universidad Nacional del Nordeste; Argentina Fil: Marcón, 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 Fil: Brugnoli, Elsa Andrea. 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 Fil: Novo, Sabina F.. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina Fil: 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 Fil: 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

Bahiagrass (Paspalum notatum Flüggé) is one of the main components of the South American grasslands, and it is cultivated for forage and turf around the world. At present, hybridization is the most common breeding technique for the species, and its goal is to obtain superior apomictic hybrids. The objective of the present study was to determine the relationship between heterosis, reproductive behavior, and genetic distances between parents in tetraploid bahiagrass. Genetic distance between 24 sexual tetraploid genotypes and 24 apomictic tetraploid genotypes of P. notatum was evaluated using Simple Sequence Repeat (SSR) and Inter Simple Sequence Repeat (ISSR) markers. Crosses were made between parents with low, intermediate or high genetic distances. Six families were generated. A marker linked to apospory in bahiagrass was used to determine segregation for mode of reproduction, and embryo sac were characterized to estimate the level of apospory expressivity. The ratio between sexual and aposporous hybrids ranged from 1:1 to 9:1 among families. Discontinuous variation for apospory expressivity was observed among hybrids, with either low or high levels being exhibited. A significant relationship between genetic distance and proportion of aposporous hybrids was observed. Heterosis was observed for all the evaluated traits and its level was dependent on the parental combination. Genetic distances between parents was related to heterosis, mainly for forage yield, which is the most important trait in forage species. Hence, molecular markers may be useful to predict the occurrence of heterosis for this trait. Fil: Marcón, 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 Fil: 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 Fil: Rodríguez, Gustavo Rubén. 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 Fil: Zilli, Alex Leonel. 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 Fil: Brugnoli, Elsa Andrea. 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 Fil: Acuña, Carlos Alberto. 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

Fil: Zilli, Alex Leonel. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina. Fil: Zilli, Alex Leonel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; Argentina. Fil: Brugnoli, Elsa Andrea. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina. Fil: Brugnoli, Elsa Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; Argentina. Fil: Marcón, Florencia. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina. Fil: Marcón, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; Argentina. Fil: M. B. Billa. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina. Fil: Billa, M.B. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; Argentina. Fil: Ríos, Esteban Fernando. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina. Fil: Ríos, Esteban Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; Argentina. Fil: Martínez, Edgardo J. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina. Fil: Martinez, Edgardo J. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; Argentina. Fil: Acuña, Carlos Alberto. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina. Fil: Acuña, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica del Nordeste; Argentina. Breeding procedures developed for apomictic species are based on the idea of fixing superior hybrids by apomixis. However, scarce information is available about the occurrence of heterosis in apomictic hybrids. The objective was to generate a group of apomixis-segregating tetraploid bahiagrass (Paspalum notatum Flüggé) families, evaluate the occurrence of heterosis for a series of agronomic and morphological traits, determine the level of apospory expressivity among hybrids, and estimate the genetic distance among parents and its relationship to heterosis and apospory expressivity. In total, 11 tetraploid families were generated by crossing sexual and apomitic genotypes. The segregation for mode of reproduction was analyzed using a random amplified polymorphic DNA (RAPD) marker linked to apospory in bahiagrass, and the level of apospory expressivity was determined using embryo sac observations. The genetic distances between parents were determined using inter-simple sequence repeat (ISSR) markers. The ratio between sexual and aposporic hybrids varied from 1:1 to 7:1 among families. Discontinuous variation for apospory expressivity was observed in the hybrids, with either low or high levels being exhibited. Midparent, high-parent, and standard heterosis was observed for all evaluated characteristics. The level of heterosis was dependent on the combination of parents involved and also on the specific trait. There was a low correlation between genetic distances among parents and initial growth and the level of apospory expressivity. The occurrence of heterosis and the segregation and expressivity for apospory were highly dependent on the combination of sexual and apomictic parents.

Fil: Zilli, Alex Leonel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico (Nordeste). Instituto de Botánica del Nordeste; Argentina. Fil: Zilli, Alex Leonel. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Fil: Hojsgaard, Diego Hernan. Universität Göttingen. Albrecht-von-Haller Institute for Plant Sciences. Department of Systematics, Biodiversity and Evolution of Plants; Alemania. Fil: Brugnoli, Elsa Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico (Nordeste). Instituto de Botánica del Nordeste; Argentina. Fil: Brugnoli, Elsa Andrea. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Fil: Acuña, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico (Nordeste). Instituto de Botánica del Nordeste; Argentina. Fil: Acuña, Carlos Alberto. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Fil: Honfi, Ana Isabel. Universidad Nacional de Misiones. Facultad de Ciencias Exactas, Químicas y Naturales. Instituto de Biología Subtropical; Argentina. Fil: Honfi, Ana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico (Nordeste). Instituto de Biología Subtropical; Argentina. Fil: Urbani, Mario Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico (Nordeste). Instituto de Botánica del Nordeste; Argentina. Fil: Urbani, Mario Hugo. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Fil: Quarin, Camilo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico (Nordeste). Instituto de Botánica del Nordeste; Argentina. Fil: Quarin, Camilo Luis. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Fil: Martínez, Eric Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico (Nordeste). Instituto de Botánica del Nordeste; Argentina. Fil: Martínez, Eric Javier. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentina. Paspalum is one of the most important genera of the Poaceae family due to its large number of species anddiversity. The subgenus Anachyris comprises six species mainly from South America grouped together bysharing rare spikelet characteristics. A genetic analysis using ISSR markers, compared with the morpho-logical and phenotypic variation observed in each one species, was used to establish genetic relationshipsamong 40 accessions with several ploidy levels, belonging to 5 species of the subgenus Anachyris. Fourteen accessions of Paspalum malacophyllum (2x and 4x), 12 of P. simplex (2x, 3x, 4x and 6x), 4 of P. procurrens(2x and 4x), 4 of P. usterii (4x) and 6 of P. volcanensis (4x) were analysed. A total of 227 ISSR loci (98.7%polymorphic) were detected among all accessions, with variable loci number and percentages of poly-morphism according to species delimitations. Six main groups were identified by cluster analysis basedon Jaccard?s genetic distance and UPGMA, four of which matched all the respective accessions of P. sim-plex, P. procurrens, P. usterii and P. volcanensis, while the other two were consistent with two differentgroups of accessions of P. malacophyllum, one involving most tetraploid accessions, and the other onegrouping together a tetraploid and two diploid accessions. The distinctive morphological characteristicsand the separate clustering of these tetraploid and diploid cytotypes suggest to consider a new multiploidspecies complex inside the subgenus Anachyris. Both cytotypes of P. procurrens, and the four co-specificcytotypes of P. simplex consistently clustered together forming two specific groups for the two multi-ploid taxons. This is in agreement with the existence of high phenotypic similarities between diploid andtetraploid cytotypes of P. procurrens, and among diploid, triploid, tetraploid and hexaploid cytotypes of P. simplex. Since the polyploid cytotypes of these species are reproduced by apomixis, the specific genetic clustering by ISSR markers and morphological and cytological results support the hypothesis that thetwo multiploid species were originated by autopolyploidy. Our results confirm previous studies suggest-ing a monophyletic origin for the subgenus Anachyris and are concordant with previous data regardinggenomic homologies and phylogenetic analyses in the genus.

Acroceras macrum is a warm-season grass used for pas-tures, and it has high nutritive value. The scarcegenetic and reproductive information about this grassis limiting its breeding for forage. The objective of thisresearch was to determine the number of genotypesand cytotypes present in a collection established inArgentina, and to estimate the diversity of this speciesbased on molecular markers, and morphological andagronomic characteristics. The number of genotypesamong forty-seven accessions was determined usingISSR markers. The identified genotypes were furthercharacterized for ploidy levels. In addition, the geneticdistances among them were estimated with ISSRmarkers. They were also propagated and planted intothe field following a randomized complete blockdesign with four replications, and a group of sixteenmorphological and agronomic variables were evalu-ated. A total of twenty-seven genotypes were identi-fied in this collection; twenty-two genotypes weretetraploid (2n = 4x = 36) and five were hexaploid(2n = 6x = 54). These two cytotypes were foundclearly separated by both genetic and phenotypic char-acteristics. Above-ground biomass, internode length,initial growth and number of spikelets per inflores-cence were the most variable traits. The high diversitypresent in this collection will allow for the initiationof a breeding programme for A. macrum. Fil: Ferrari Usandizaga, Silvana C.. Instituto Nacional de Tecnología Agropecuaria; Argentina Fil: Brugnoli, Elsa Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina Fil: Weiss, Alejandra I.. Instituto Nacional de Tecnología Agropecuaria; Argentina Fil: Zilli, Alex Leonel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina Fil: Schedler, M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina Fil: Pagano, E. M.. Instituto Nacional de Tecnología Agropecuaria; Argentina Fil: Martínez, Eric Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina Fil: Acuña, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina

The tetraploid cytotype of Paspalum simplex has a wide geographical distribution and reproduces by apomixis, while the diploid grows in a restricted area in northern Argentina and behaves as cross-pollinated. The objective was to evaluate the genetic diversity among and within natural diploid and tetraploid populations of P. simplex growing in sympatry and allopatry by studying the phenotypic variability and DNA polymorphisms. Twenty three phenotypic traits and ten ISSRs molecular markers were used for evaluating the variability present in 6 populations of P. simplex. Two populations were diploid and four were tetraploid. One of the tetraploid populations was sympatric to a diploid population, while the rest of the populations were allopatric. A rich diversity was observed for specific traits, especially for seasonal biomass yield, presence of a terminal raceme in the inflorescence, and leaf pubescence. The 2x and 4x populations growing in proximity were closely related. Diversity was higher within diploid populations when compared with the evaluated tetraploid populations. Among the tetraploid populations, the one sympatric with a diploid population exhibited the greatest diversity. Gene flow occurs between 2x sexual and 4x apomictic populations of P. simplex. A unidirectional pathway seems to be involved for the creation of new 4x genotypes from highly variable 2x populations. Fil: Brugnoli, Elsa Andrea. Ministerio de Ciencia, Tecnología e Innovación Productiva. Agencia Nacional de Promoción Cientifíca y Tecnológica; Argentina; Universidad Nacional del Nordeste. Secretaria de Ciencia y Tecnologia; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina; Fil: Urbani, Mario Hugo. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina; Fil: Quarin, Camilo Luis. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina; Fil: Martínez, Eric Javier. 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; Fil: Acuña, Carlos Alberto. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste. Instituto de Botánica del Nordeste (i); Argentina