INFLUENCE OF POLLINATION PATTERN ON INTRAPANICLE CARYOPSIS WEIGHT IN SORGHUM

Recent studies have shown that changes in grain-fill rates within the sorghum [Sorghum bicolor (L.) Moench] panicle cause caryopsis weights to decrease from the apex to the base. Pollination pattern in the sorg hum panicle is also basipetal. The objectives of this study were to de termine if pollination pattern influences intrapanicle caryopsis weigh ts and to determine which components of grain fill are affected by pol lination pattern. Field studies were done in 1990 at Manhattan, KS, on a Reading silt loam [fine-silty, mixed, mesic Typic Argiudoll (0-1% s lope)] and Hays, KS, on a Harney silt loam [fine, montmorillonitic, me sic Typic Argiustoll (0-1% slope)]. At Manhattan, eight pollination-pa ttern treatments were applied to DeKalb DK 46 and its male-sterile par ent, 97A. At Hays, a male-sterile hybrid, KS56A x KS47B, received four of the eight treatments. Panicles were divided into four equal sectio ns; apex, upper middle, lower middle, and base. Different pollination patterns were applied to the sterilized panicles by exposing the appro priate sections to pollen. Differences in caryopsis weights and weight components were determined using analysis of variance and linear regr ession analyses. In all cases, intrapanicle caryopsis weights followed the pollination pattern applied. The panicle sections pollinated firs t had caryopses that were from 1.0 to 2.5 mg heavier than those found in the sections pollinated later. Pollination pattern influenced caryo psis weight by influencing grain-fill rates within the panicle; the le ngth of the grain-fill period did not change. Apparently, caryopses th at were pollinated first were better competitors for assimilates than those pollinated later.