Film Coating Impairs Leaching of Germination Inhibitors in Sugar Beet Seed

Abstract

Polymer film coating has been applied to commercial sugar beet (Beta vulgaris L.) seeds in the USA as an effective delivery system for agrochemicals. This research was conducted to study the impact of polymer film coating on sugar beet seed germination. Twelve seed lots, representing nine monogerm cultivars, had standard germination of 89 to 95%. After film coating (20 g of polyvinyl polymer per kilogram seed), the germination percentage varied from 68 to 94%. Six seed lots, including three lots of cultivar HH55, exhibited significant germination reductions after coating. Besides significant cultivar differences, seed lots within the same cultivar (HH55) also showed different responses to coating. After removal of the pericarp, the true seed of sensitive cultivar HH55 did not show germination reductions after coating. This indicates that the interaction between film coating and pericarp factors accounted for the germination reduction in film‐coated seeds. Sensitivity to film coating was alleviated by presoaking or peroxide treatments. A high negative correlation was found between absorbance at 265 am (A265 nm) of seed steep solution and coated seed germination percentage (r = −0.96***). The A265 nm of steeping solution could reduced to near zero by filtering the solution through the phenolic absorbent polyvinylpyrrolidone. Polymer film coating induced germination reductions in sensitive cnitivars were likely related to restricted oxygen supply to the enclosed embryo and to the retention of water soluble germination inhibitors, which would normally be leached into the germination medium and/or oxidized and deactivated.