SEED WEIGHT INFLUENCE ON SEEDLING HYDROCYANIC ACID POTENTIAL IN SORGHUM

Grain sorghum [Sorghum bicolor (L.) Moench] typically produces larger seeds than sudangrass [S. bicolor, formerly S. sudanense (Piper) Stapf]; and grain sorghum seedlings are higher in hydrocyanic acid potential (HCN-p) than sudangrass seedlings. Previous studies have shown a seed-parent effect on seed weight and HCN-p in reciprocal F1 hybrids of sorghum X sudangrass. This study was conducted to determine whether the seed-parent effect on HCN-p could be attributed primarily to the difference in seed size between reciprocal sorghum X sudangrass hybrids. Large and small seeds of low-HCN-p sudangrass, high-HCN-p sorghum, and their reciprocal hybrids, were visually selected, individually weighed, and planted in growth chambers. Height, fresh weight, and HCN-p of the resulting 7-d-old shoots were measured. On average, the selected large seeds weighed almost-equal-to 1.6 times as much as the small seeds. Shoots from the large seeds were almost-equal-to 1.2 times as tall and 1.4 times as heavy as those from small seeds, and they contained almost-equal-to 1.3 times as much HCN per shoot as did shoots from small seeds. However, the HCN-p (mg kg-1 fresh wt.) of the shoots from large seeds was only slightly greater than that of shoots from small seeds (709 and 701 for first leaves of shoots, and 278 and 267 for shoot remainders from large and small seeds, respectively). Shoots from 5-d-old light-grown and etiolated seedlings also failed to show appreciable differences in HCN-p due to seed size. It was concluded that the seed-parent effect on shoot HCN-p in crosses of sorghum and sudangrass was not caused primarily by the seed-parent effect on seed weight.