EVALUATION OF TRIPLOID AND HEXAPLOID DERIVATIVES FROM Pennisetum glaucum x P. purpureum CROSSES AT THE BEEF RESEARCH UNIT, UNIVERSITY OF FLORIDA

Cv. 4Mott' dwarf napiergrass has unusually high forage quality for a tropical grass (Sollenberger et al., 1988). Mott has been hybridized with pearl millet, and four of the best triploid F, progeny were selected for comparison with Mott and other non-dwarf Pennisetums. This five year study compared the dry matter yield of seven lines of Pennisetum. and also measured in vitro organic matter digestibility (IVOMD), crude protein (CP) and neutral detergent fiber (NDF). The chromosome number of a triploid Fj^ hybrid was doubled and three of the hexaploid progeny were evaluated at the Beef Research Unit in 1988 and 1989. In general, the hybrids showed similar IVOMD to Mott, but had increased leafiness and lower fiber than the tall napiergrass varieties

FORAGE YIELD, QUALITY AND PERSISTENCE OF INTERSPECIFIC PENNISETUM HYBRIDS IN THE CARIBBEAN

The species Pennisetum purpureum includes perennial, high yielding and good quality forage types. However, the need for vegetative propagation has limited its commercial use. In two 2-year experiments, forage yield and quality, and stand persistence of 'Mott' dwarf elephantgrass (P. purpureum) were compared with either those of other pure lines of elephantgrass (N43, N114, N127 and N128) or their interspecific hybrids with pearlmillet (P. glaucum) grown in mixture with glycine (Neonotonia wightii). Grasses were harvested every 60 to 100 days, based on rainfall. In neither year was there a genotype x harvest date interaction for dry matter yield. Annual forage yield of tall pure lines or their triploid hybrid with pearl millet was 21-29 t/ha compared with 9-23 t/ha from Mott and its seeded hexaploid derivatives. Forage in vitro organic matter digestion (IVOMD) for Mott (65%) at 60-day regrowth was similar to the hexaploids, but superior to the tall lines (60%). Minimum crude protein (CP) content and IVOMD of Pennisetum forage stockpiled for 90 days were 7% and 54% for dwarf types and 6% and 54%,for tall types, respectively. Mott cultivar maintained higher plant and tiller numbers than the hybrids. Legume content of dry forage at the final harvest was 40-48% for the hybrids and 28% for Mott. Seed propagated Pennisetum hybrids have a potential for stockpiled forage in the Caribbean if their persistence is improved

Seed controlled deterioration of three interspecific elephant grass × pearl millet hybrids Deterioração controlada de sementes de três híbridos interespecíficos de capim-elefante × milheto

In order to allow using seeds from three interspecific elephant grass &#215;pearl millet hybrids (Original, Cutting and Grazing-types) to set pasture fields, it became necessary to analyze their performances in relation to storage conditions and controlled deterioration. Five moisture content levels and three storage temperatures (40, 50 and 65°C) have been tested for each hybrid. Seed sub samples for each moisture content and storage temperature combination were sealed in laminated aluminum foil packages and stored at those temperatures until complete survival curves have been obtained. The recurrent selection increased seed initial quality (Ki) for grazing-type population (lower and more tillered plants); however inverse results were observed for cutting-type population (higher and less tillered plants). Viability equation constants estimated for Cutting-type, Original and Grazing-type hybrids are: K E = 8.417, 7.735 and 8.285; Cw = 5.037, 4.658 and 4.522; C H = 0.02309, 0.01969 and 0.03655; C Q = 0.000436; 0.000403 and 0.000300, respectively. The viability equation constants for the hybrids are K E = 8.033; Cw = 4.662; C H = 0.02544; C Q = 0.000386. Through the equations, it is feasible to estimate the germination percentage of a seed lot after different storage conditions.<br>Para facilitar o uso de sementes de três híbridos interespecíficos de capim-elefante &#215; milheto (Original, Corte e Pastoreio) para a formação de pastagens, tornou-se necessário analisar o seu comportamento em diversas condições de armazenamento e deterioração controlada. Foram testados para cada híbrido cinco graus de umidade e três temperaturas (40, 50 e 65°C). Em cada combinação de umidade e temperatura, as sementes foram embaladas em papel-alumínio multifoliado e semeadas periodicamente, permanecendo nas estufas até a obtenção de curvas completas de deterioração. A seleção recorrente aumentou a qualidade inicial (Ki) na população de pastoreio (plantas mais baixas e mais perfilhadas) e o inverso ocorreu na população de corte (plantas mais altas e menos perfilhadas). As constantes obtidas para os híbridos Corte, Paraíso e Pastoreio são: K E = 8,417; 7,735 e 8,285; Cw = 5,037; 4,658 e 4,522; C H = 0,02309; 0,01969 e 0,03655; C Q = 0,000436; 0,000403 e 0,000300, respectivamente. Foi possível obter uma equação única de viabilidade para os híbridos, com constantes iguais a: K E = 8,033; Cw = 4,662; C H = 0,02544; C Q = 0,000386. Essa equação possibilita estimar a porcentagem de germinação de um lote de sementes após o armazenamento em diversas condições de temperatura e umidade