Breeding for improved herbage and seed yield in Setaria sphacelata (Schumach.) Stapf and Hubbard ex Moss

The simultaneous selection for yield of herbage and seed in Setaria sphacelata (Schumach.) Stapf and Hubbard ex Moss was studied, and the amount of variation present for each of these traits in relation to various plant characteristics was assessed in a spaced plant population and its open-pollinated progeny.<p/>When comparing tillers at a similar stage of growth, a high in vitro digestibility was found for those tillers that originated from early-heading plants characterized by short length, light weight and narrow leaves. Comparisons of whole plants at 3 periods of regrowth revealed a negative correlation between in vitro digestibility and dry-matter yield. The variation found for in vitro digestibility was not repeated under sward conditions.<p/>Plants with a high yield of clean seed were early-heading and large-sized. Of the three seed components studied, number of heads had the largest influence on seed yield. A high yield of clean seed did not necessarily mean a high yield of germinating seeds.<p/>Simultaneous selection for herbage and seed yield could be carried out through selection for seed yield only, because of the high genotypic correlation between the two traits and the higher response expected from selection for seed yield. Selection indices should take into account time of head emergence and fresh weight of the plant at seed harvest time when selection was carried out after flowering. For selection before flowering, the index should include number, length and weight of tillers.<p/>The testing of plants in a monoculture at wide spacing and in a sward of another species were compared.<p/>When comparing lax, prostrate and erect growth habits, the erect-growing plant type proved to be the most productive and to have the highest competitive ability under the management applied.<p/>The major research findings are summarized in a proposed breeding scheme.