Los objetivos de este trabajo fueron: i) Evaluar los efectos del tamaño del embrión, el genotipo y el ácido 2,4-diclorofenoxiacético (2,4-D) sobre la regeneración de plantas a partir de embriones híbridos de maíz x T. dactyloides; ii) Determinar el nivel de tolerancia a la salinidad y alcalinidad de T. dactyloides en estadio vegetativo temprano y compararlo con el del maíz (línea B73, ampliamente difundida como progenitora de híbridos comerciales) en las mismas condiciones; iii) Evaluar el comportamiento de generaciones avanzadas (MT41 y MT51 ) de un híbrido F1 (2n = 56) de maíz x T. dactyloides altamente estéril que mostró tolerancia a la salinidad por NaCl. Para cumplir el primer objetivo, se polinizaron cuatro genotipos de maíz (2n = 20) con T. dactyloides (2n = 72). Los embriones se aislaron del cariopse a los 13, 14, 15, 16 ó 19 días después de la polinización y se colocaron sobre un medio básico sin reguladores de crecimiento ó con 4,6 mol L-1 de 2,4-D. Para cumplir el segundo objetivo, se cultivaron plantas de maíz y T. dactyloides en soluciones nutritivas que contenían 5 mM del tampón clorhidrato de Tris-ClH[hidroximetil]-aminometano y dos niveles de salinidad y dos pH diferentes: 1 mM NaCl-pH 5,8 (control); 1 mM NaCl-pH 8,5; 101 mM NaCl-pH 5,8; 101 mM NaCl-pH 8,5. Para cumplir el tercer objetivo, se cultivaron plantas de maíz (línea B73) y los híbridos MT41 y MT51 en soluciones nutritivas con pH 5,8 y dos niveles de salinidad: 1 y 101 mM de NaCl. Los tratamientos comenzaron a los 7 días (maíz e híbridos) y 14 días (T. dactyloides) después de la siembra (DDS) y las determinaciones se realizaron a los 22 y 38 DDS, respectivamente. Los embriones de 1,25 mm de longitud o menos originaron el 99,4 % de los callos con capacidad de regeneración. Tres de los híbridos originaron un número similar de plantas hasta los 6 meses después de la siembra de los embriones. El cuarto híbrido, obtenido del cruzamiento con la línea de maíz B73, dio lugar a callos caulogénicos, / García, MD. (2012). Obtención de híbridos de maíz y Tripsacum dactyloides y evaluación de su utilidad potencial en la mejora genética del maíz [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17451

Eastern gamagrass [Tripsacum dactyloides (L.) L.] is a warm-season, perennial grass which is native to large areas across North America. Cultivars, selections and ecotypes suitable for erosion control, wildlife planting, ornamental, forage and biofuel applications are commercially available. Plantings are commonly established from seed; however, seed quality and dormancy are barriers to establishment. The objective here was to investigate parameters that contribute to inconsistent performance of this seed kind to subsequently improve seed lot quality. Forty-two seed lots were used, with seed fill and germination potential ranging from 78- 100% and 11-91%, respectively. Actual germination and dormant seed ranged from 0-40% and 1-85%, respectively. Seed count per pound ranged from 3195 to 8344 and was influenced by genotype. Alternating laboratory temperature regimes were generally more effective in promoting germination than constant temperatures. Optimal germination occurred at 15/25, 20/30 or 20/35 ºC (16/8 hours), but was not consistent across cultivars or seed lots. These data suggest that germination temperature contributes to inconsistent laboratory germination and poor stands observed for untreated and pretreated seeds sown under field conditions. Eleven primary dormancy breaking treatments were tested and most improved germination. Although not commercially feasible, cupule removal plus caryopsis scarification hastened germination and completely eliminated seed dormancy. Soaking in H2O2 (18 hr) improved germination, but the effect was not consistent. Moist chilling (5 or 10 °C) was generally superior to other treatments and remains the most simple, effective and consistent dormancy-breaking treatment, although duration varies by seed lot. Benefits of moist chilling and H2O2 treatment were retained for short periods in seeds dried from approximately 55% to 13% moisture content. Removal of empty and light-weight cupules improved seed lot purity and germination, although removal of as much as 40% of the volume was necessary. The priming treatments tested were less than satisfactory in improving germination or the range of germination temperatures compared to moist chilling treatment alone. Eastern gamagrass seed lot quality is highly variable, but can be improved. Multiple physical and physiological targets of opportunity have been identified to improve seed lot quality in eastern gamagrass.

Master of Science / Department of Agronomy / Clenton E. Owensby / Currently there are no model inputs for eastern gamagrass [Tripsacum dactyloides (L.) L] for use in the National Research Council's (NRC) beef cattle model. This study was conducted to determine model inputs for two eastern gamagrass varieties for use with the forage database of the NRC model. Cattle producers in the Midwestern US will be able to evaluate eastern gamagrass in a forage system and estimate net energy for maintenance (NEm), metabolizable protein (MP), and degradable intake protein (DIP) balance for various production scenarios. Eastern gamagrass varieties 'Iuka' and 'Pete' were arranged in a split-plot randomized complete block experiment with four replications. Varieties were whole plots with harvest maturities as split plots. Plant tissue was harvested from both varieties at four maturities: vegetative/early elongation, anthesis, seed shattering and dormancy. Various compositional attributes were determined on forage samples to enable the determination of model inputs for predicting energy and protein balances. A slight difference between varieties was found for crude protein concentration (p<0.05). Differences (p<0.05) due to maturity were found for all analyses used in the model, corroborating the decline in nutritive value of eastern gamagrass with advancing maturity. Neutral detergent fiber (NDF) ranged from 593 g kg-1 at the vegetative/early elongation stage of maturity to 731 g kg-1 at dormancy. Assumed animal and environmental inputs were used for beef cattle at two stages: nonlactating 160 d prepartum and 60 d peak lactation. Energy and protein balance were estimated using level I of the model. The vegetative/early elongation stage of development supplied the greatest amount of MP. Digestible intake protein declined as plant tissue matured. All but the vegetative/early elongation stage of maturity were limited in DIP for cows in both stages of production. Soybean meal was used as a protein supplement in amounts ranging from 0.8 kg to 1.4 kg to meet nutritional demands of cattle grazing eastern gamagrass at anthesis, seed shattering and dormancy. In the simulations conducted, eastern gamagrass would be an acceptable forage source for beef cattle provided that appropriate protein supplementation was given when the forage was at more advanced stages of maturity.

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is a warm season, perennial grass native to the Great Plains from southern Canada to Mexico (Beetle, 1950). This newly developed, low input, turf-type grass is recommended for use on low maintenance sites (Falkenberg-Borland and Butler, 1982; Pozarnsky, 1983; Wu and Harivandi, 1989; Shearman et al., 2005). Recently, the use of buffalograss as a turfgrass has increased due to its drought tolerance, low nutrient requirements, and low growing height (Harivandi and Wu, 1995; Frank et al., 2004). It is an excellent choice in California where water use is limited. Unsightly winter dormancy of buffalograss can be overcome by growing mixtures of buffalograss and fine fescue (Festuca spp.). Overtime species composition can be overtaken by the fine fescue, unintentionally converting the mixed turfgrass stand to a fine fescue monostand (Severmutlu, et al., 2005). Research on buffalograss establishment in fine leaved fescues from seed or by vegetative methods was completed from 2007 to 2009 at the California Polytechnic State University Horticulture Unit in San Luis Obispo, California. Comparisons were made between mixtures of eight cultivars of buffalograss (Prairie, Prestige, UC Verde, 609, Bowie, Cody, Texoka, and Bison) and three fine leaved fescue species [hard fescue (Festuca trachyphylla Thuill.), sheep fescue (Festuca ovina L), and red fescue (Festuca rubra L.)] to determine which combination and establishment strategy provides the highest quality turf for the California central coast region. Evaluations made on buffalograss establishment and competitive ability when grown in pre-existing fine fescue turfgrasses showed seeded cultivars (Bowie, Cody, Texoka, and Bison) were unsuccessfully established (zero percent coverage in two growing seasons), and vegetative cultivar (Prairie, Prestige, 609 and UC Verde) establishment was greatly dependent on the type of cultivar planted. After two growing seasons, buffalograss cultivar UC Verde had the highest establishment rate (38.6 percent living ground cover) and Prestige had the lowest (11.4 percent living ground cover). Results from this study do not recommend establishing seeded buffalograss cultivars into pre-existing fine leaved fescue turfgrass stands. Vegetative buffalograss cultivars can be established into pre-existing fine leaved fescue turfgrass stands; however, this process is too slow for most turfgrass practitioners and is quite unsightly in winter dormancy during the establishment process.

Four forage grasses from botanic alien species - Tripsacum dactyloides, Axonopus scoparius, Panicum maximum and Melinis minutiflora - were found in a fragment of Forest Dense Ombrófila Submontana in process of recruitment, in an urban environment in Blumenau, Santa Catarina state, in the South of Brazil. The vegetation of this forest area was inventoried. The classification of the natural regeneration of secondary vegetation showed a predominance of medium sucessional stages. In initial sucessional stages, herbaceous plants were found among non-native forage grasses. The species Melinis minutiflora and Panicum maximum were found along the border of the fragment, close to highways, isolated and not forming large clumps. Both are recorded in the invasive alien species database managed by the Horus Institute for Environmental Conservation and Development (www.institutohorus.org.br), part of the I3N invasive alien species thematic network, a component of IABIN (Inter American Biodiversity Information Network). Tripsacum dactyloides and Axonopus scoparius don't appear in such a bank, which includes Brazil. Both species were assessed through the software developed by the I3N invasive alien species thematic network, the Risk Assessment Tool for the Establishment and Invasion by nonnative species. The data assessment on Tripsacum dactyloides shows that it poses a high risk for its potential in becoming an invasive species. There was no conclusive resulted about the species Axonopus scoparius due to the inadequacy of information available on the species. / Quatro gramíneas forrageiras exóticas: Tripsacum dactyloides, Axonopus scoparius, Panicum maximum e Melinis minutiflora foram encontradas num fragmento de Floresta Ombrófila Densa Submontana do bioma Mata Atlântica em processo de regeneração natural, em Blumenau, SC (ambiente urbano). Foi feita a caracterização da vegetação presente na área através de inventário florestal com a classificação dos estágios sucessionais de regeneração natural indicando a predominância de uma fitocenose em estágio sucessional médio, com presença de área em estágio sucessional inicial. Aí foram diagnosticadas plantas de porte herbáceo, entre as quais as gramíneas forrageiras tropicais exóticas. As espécies Melinis minutiflora e Panicum maximum ocorreram na borda do fragmento, próximo a rodovias, na forma de plantas isoladas. Ambas constam no banco de dados de plantas invasoras da rede temática para espécies exóticas invasoras (I3N) da Rede Interamericana de Informação sobre Biodiversidade (IABIN). Tripsacum dactyloides e Axonopus scoparius não constam em tal banco, que inclui o Brasil. Ambas as espécies foram submetidas ao Software desenvolvido pela rede I3N, a Ferramenta de Análise de Risco de Estabelecimento e Invasão, e segundo a análise desta ferramenta alimentada com os dados obtidos neste trabalho o risco associado à Tripsacum dactyloides de se transformar numa espécie invasora é considerado alto. Não houve resultado conclusivo sobre a espécie Axonopus scoparius devido à insuficiência de informações sobre a espécie.