AbstractThree of the main problems associated with breeding guineagrass (Panicum maximum Jacq.), an important tropical forage, are seed shattering; low germination rate; and reproduction, which is by apomixis. Three hybrids were developed at the Tropical Agriculture Research Station (TARS) of the USDA-ARS, from sexual female plants and apomictic selections of guineagrass. In addition, an interspecific hybrid, BPIH104, was made from a cross between Brachiaria purpurascens Raddl and Panicum coloratum L. The four hybrids, common guineagrass, and Tobiata, an introduction from Brazil, were evaluated at 4-, 6-, and 8-wk cutting intervals (Cl) during one year in a randomized splft-plot design with four replications. Mean dry matter content (DMC), dry matter yield (DMY), crude protein yield (CPY), and plant height (PHt) increased (P < 0.01) from the 4- to the 8-wk Cl, but mean crude protein concentration (CPC) decreased (P < 0.01). In vitro dry mater digestibility (IVDMD) decreased (P < 0.01) only from the 4- to 8-wk Cl. DMC, CPY, and PHt were positively correlated, and CPC and IVDMD negatively correlated, with DMY. At the 8-wk Cl, Tobiata and BPIH104 were the top yielders with annual yields equivalent to 43 and 41 t/ha, respectively. These and the other hybrids deserve further evaluation under grazing management in Puerto Rico.
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