Abstract
The obiective of the present study was to determine the time of day when pollens were dispersed and the distance travelled by pollen in grain sorghum. Time of the active pollen dispersal was estimated from seed set on panicle of an A-line (Experiment 1). The distance for pollen dispersal was measured from seed set on panicles of A-lines which were grown at various distances and directions around pollen dispersal field fcr three years. The isolation drstance necessary to produce certified hybrid seeds of *'rain sorghum was estimated (Experiment 2). When paper envelopes were removed from panicles of the A-1ine before 0400 and/or after 1200, seed set on the panicle was not observed. However, seed set was observed between 0600 and 1000. Time of active pollen dispersal is, therefcre, from 0600 to 1000. The isolated plots in which seed set was observed were located less than 400m from the pollen dispersal field. Seed set was not observed in some isolated plots less than 400m, as wind direction and obstacles near the isolated plot prevented pollination. Pollen was dispersed into the isolated plot within 250m from the pollen dispersal field, even though the isolated plot was surrounded by houses and was located on the wind-ward side of main wind direction. Adequate isolation distance for certified hybrid seed production was approximately 400 to 500m, with modifications down to 250 to 300m permitted under certain conditions.
