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Paspalum notatum Flügge is one native forage grasses of southern Brazil. Through intraspecific hybridization, is possible generating progenies with variability for agronomic traits. The objective of this work was to evaluate 24 hybrids and select them for the superior agronomic traits, as well analyze correlations between forage traits that can assist in the selection of genotypes. The hybrids were obtained from crosses among sexual and apomictic clones, and were vegetative propagated in a greenhouse until the transplant to the field. The agronomic traits evaluated were: total green mass (TGM), leaf dry mass (LDM), stem dry mass (SDM), inflorescence dry mass (IDM), dead mass (DeM), total dry mass (TDM), growth habit (GH). Correlations between plant diameter (PD), number of tillers (NT), total dry matter (TDM), plant height (PH), total green matter (TGM), leaf dry matter (LDM), stem dry mass (SDM), number of inflorescences (NINF) and inflorescence dry matter (IDM) were performed using the Pearson correlation coefficient. The hybrids had great variability in all agronomic characteristics measured. Based on the three years of evaluation, hybrids KD9, KF1, KF4, and KD5 produced higher total dry mass than other genotypes. The hybrid KF4 too had greater LDM; KF1 and KF4 were the colder tolerant. These genotypes were selected for evaluations, such as seed production, fertilizer use efficiency, animal performance, and for new crosses. The high correlation of the total dry mass with the other forage components will be useful for indirect select criteria in bahiagrass improving strategies. [ABSTRACT FROM AUTHOR]

ABSTRACT: The objective of the following research was to investigate the physiological responses of two bahiagrass genotypes (Paspalum notatum Flügge) submitted to water restriction, induced by polyethylene glycol (PEG6000), during seed germination. Seeds of cv. Pensacola (diploid) and Bagual ecotype (tetraploid) were placed on paper moistened with osmotic solutions at potentials of 0.0; -0.1; -0.2 and -0.3 MPa. Composed of two subsamples of 100 seeds and four experimental units per treatment, the germination test was conducted in a germination chamber under alternating temperatures of 30 °C (8 hours) and 20 °C (16 hours), with presence of light during the higher temperature. Final germination percentage and germination speed index of the seeds, as well as early growth, activity and expression of antioxidant enzymes of seedlings were evaluated. The water restriction induced by PEG6000 reduced the percentage of germination in Pensacola (from 74% to 59%) and Bagual (34% to 10%). For the latter, the evaluation of seedlings showed higher dry mass in relation to cv. Pensacola (1.7 times higher in root and 1.6 times in shoot). In response to moderate water restriction, the genotypes showed increases in root growth (1.7 times higher in -0.1 compared to 0.0 MPa), both in expression and enzymatic activity (superoxide dismutase and catalase).

The aim of this study was to evaluate CO2 emission, canopy characteristics and herbage accumulation in pastures of pensacola bahiagrass under frequencies of defoliation. The experiment was conducted at the Universidade Estadual Paulista "Julio de Mesquita Filho", Faculty of Agrarian Sciences and Veterinary of UNESP, Jaboticabal, São Paulo, Brasil. The experimental period was from May 3rd to July 26th 2012. The experimental area comprised 28 m2 of pensacola bahiagrass (Paspalum notatum Flügge), divided into 10 plots for allocation of treatment (frequencies of defoliation = 2 or 4 weeks). The following variables were studied: canopy height, light interception, leaf area index, herbage accumulation, tiller density, CO2 emissions, soil temperature and moisture. The frequencies of defoliation in the months of May, June and July slightly affect pensacola bahiagrass characteristics. CO2, soil temperature and moisture are more associated to environmental conditions (months of evaluation) than to the frequencies of defoliation imposed to the canopies.

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Foliage damage as a result of individual freeze events is a major limitation to the expansion of bahiagrass ( Paspalum notatum) pastures and hay production in Southeastern USA. Greater tolerance to such freeze events would allow production deeper into the fall and winter and allow expansion of this species into colder regions. While it has been reported that small cells are more tolerant to freeze damage, this possibility has not been explored in bahiagrass. Specifically, the hypothesis was examined that xylem vessels with smaller diameter in the midrib of leaves are associated with freeze tolerance among bahiagrass genotypes. Vascular bundle diameter was also measured as a possible index of xylem cell size. A total of eight bahiagrass genotypes were eventually studied representing four freeze-sensitive and four freeze-tolerant lines. There was a clear distinction in xylem cell size between the freeze-sensitive and the freeze-tolerant lines. The freeze-tolerant genotypes had xylem element cells that were significantly smaller than the freeze-sensitive genotypes. Averaged across three leaf positions and all genotypes, the xylem element diameter for the freeze-sensitive lines was 222 μm and for the freeze-tolerant lines was only 164 μm. A similar difference was observed in overall vascular bundle diameter with freeze-sensitive lines having a mean of 1168 μm and the freeze-tolerant lines a mean of 917 μm. These results indicated that the diameter of the xylem cells in the vascular midrib of bahiagrass may be an important variable influencing the sensitivity among genotypes to freeze damage. [ABSTRACT FROM AUTHOR]

Um piquete de capim-colonião (Panicum maximum Jacq) submetido a pastoreio contínuo e a roçadas periódicas revelou, seis anos após o plantio, elevado grau de infestação por outras plantas, destacando-se entre elas a grama-batatais (Paspalum notatum Flügge) que apresentou 85% de frequência e 20,9% de biomassa epígea seca relativa. As dicotiledóneas, em conjunto, apresentaram frequência de 95% e biomassa relativa de 38,7% mas a sua contribuição específica foi muito reduzida. O capim-colonião, por sua vez, apesar da frequência de 95%, apresentou apenas 32,2% de biomassa relativa (diminuição de 67,8%). Estas profundas alterações da flora e da vegetação podem ser atribuidas, em grande parte, a dois fatores: a) ação seletiva da roçadeira; b) preferências alimentares e disseminação endozoócora da gramabatatais pelos bovinos.A pasture of Guineagrass (Panicum maximum Jacq.) submitted to continuous grazing and periodic clearing revealed, after six years from its planting, a high degree of weed infestation. Bahiagrass (Paspalum notatum Flügge) exhibited a frequency of 85% and a relative dry epigeous biomass of 20,9%. Dicotyledons as a whole exhibited a frequency of 95% and a relative biomass of 38,7%. On the other hand, Guineagrass, although with a frequency of 95%, exhibited a relative biomass of only 32,2% equivalen t to a decrea se of 67,8%. This great floristic and vegetational change may be ascribed to mechanical selective action of the scythe and to grazing selection and zoochorous dissemination of Bahiagrass by cattle.