Natural Outcrossing of Sorghum and Sudangrass in the Central Great Plains

cross-fertilization in ‘White Milo’ in Texas, and noted differing percentages of cross-fertilization among heads. Amount of natural outcrossing in a species is one of the primary Sieglinger (1921) reported an average of 5% cross-fertildetermining factors in selection of breeding methods. Existing literaization between white and yellow milo in Oklahoma. ture on natural outcrossing of sorghum is dated and limited in geographical reference. Experiments were designed to investigate natural Fewer experiment results are published on natural outcrossing in contemporary sorghum, Sorghum bicolor (L.) Moench, outcrossing of sudangrass. Hogg and Ahlgren (1943) B- and R-lines, and in sudangrass, Sorghum bicolor (L.) Moench. showed an average of 7% natural cross-fertilization of Four R-lines and four B-lines were seeded in rows in isolation at ‘Piper’ sudangrass with ‘Leoti’ sorghum in Wisconsin. Mead, NE, and allowed to intercross in each of 2 yr. Bulked seed Garber and Atwood (1945) reported 18 to 77% outfrom each row was planted and proportion of offtypes recorded. crossing in an experimental line of sudangrass using seed Outcrossing ranged from 0.1 to 13% in R-lines, and from 0.5 to 9% produced in Pennsylvania, with an increase in crossin B-lines. Outcrossing among sudangrass plants with white or green fertilization between 6 and 26 August. midribs transplanted in isolation in each of 2 yr was estimated by Maunder and Sharp (1963) showed outcrossing perutilizing the dominant gene for white midrib as a marker. Panicles centages of sorghum in Texas to be affected by genotype from green midrib plants were tagged to indicate approximate date of pollination. At maturity, the panicles were divided into top, middle, and floret position on the panicle. ‘Combine Kafir and bottom thirds and threshed. Seed from each panicle section was 60-B’ averaged 3% outcrossing on the upper one-fourth planted and proportion of white midrib plants recorded. Outcrossing and 1% outcrossing on the lower three-fourths of the ranged from 0 to near 100% on individual sudangrass plants and was panicle. ‘Double Dwarf White Feterita’ averaged 10% highly variable. Harvest of panicles pollinated during the middle of outcrossing on the upper one-fourth and 4% outcrossing the pollination period should maximize outcrossing in sudangrass, on the lower three-fourths of the panicle. The authors but the use of nuclear male-sterility genes is still recommended for concluded that “for increased purity (selfing), it would improvement of sudangrass through recurrent selection. For sorghum seem justifiable to discard the upper portion of openbreeding procedures requiring a high degree of self-pollination, selfing pollinated panicles at the time of threshing.” One might under pollination bags is recommended. also conclude that percentage of natural outcrossing could be maximized by saving only the upper portion of the panicle. A