COLOR SORTING OF COATED BRASSICA SEEDS BY FLUORESCENT SINAPINE LEAKAGE TO IMPROVE GERMINATION

Color sorting was performed to upgrade seed quality by removal of fluo rescent coated seeds. The fluorescent coating was attributed to sinapi ne leakage from nonviable seeds. Nine seedlots, three seedlots each of cabbage (Brassica oleracea L. Capitata group), broccoli, and cauliflo wer (B. oleracea L. Botrytis group) were custom coated. Seed samples w ere pretreated before coating with or without 1.0% NaOCl for 10 minute s to enhance leakage. All samples revealed a percentage of seeds with fluorescence. The light emission from selected fluorescent and nonfluo rescent coated seeds was quantified by fiber-optic spectrophotometry. Fluorescence was expressed from 400 to 560 nm, with peak emission bein g from 430 to 450 nm. These data confirmed our visual interpretation o f blue-green fluorescence. The ratio of light emission from fluorescen t compared to nonfluorescent coated seeds ranged from 4.5 to 7.0 for a ll samples and averaged 5.7. An ultraviolet (UV) color sorter was empl oyed to separate fluorescent (reject) from nonfluorescent (accept) coa ted seeds. The percentage of nonfluorescent coated seeds (averaged ove r seedlot and NaOCl pretreatment) before and after sorting was 89.5% a nd 95.9%, respectively. Therefore, color sorting was able to remove a high percentage of fluorescent coated seeds with an average loss (reje ction of nonfluorescent coated seeds) of 6%. An increase in the percen t germination was recorded in eight of the nine seedlots following col or sorting, and the greatest improvement was obtained with seedlots of medium quality. Germination of three medium quality lots was increase d by 10 to 15 percentage points. The average increase in germination w ith or without NaOCl pretreatment was 8.2 and 5.5 percentage points, r espectively. In conclusion, the germination of Brassica seedlots could be improved by separating (removing) fluorescent from nonfluorescent coated seeds. UV color sorting technology was employed to demonstrate that seed conditioning could be conducted on a commercial basis to upg rade seed quality.