SUGAR-BEET SEED STEEP TREATMENTS TO IMPROVE GERMINATION UNDER COLD, WET CONDITIONS

Modifying the present commercial sugar-beet steep treatment (12 h in 0.2% thiram suspension, 25-degrees-C) to include an initial 2 h steep in 0.3 M hydrochloric acid, decreased fruit weight and cortex density and improved the performance of the inherently slower part of the population under cold, wet conditions. Adding gibberellins (GA4/7) or an N-substituted phthalimide (AC 94377) to the thiram steep was also beneficial whereas kinetin of N6-benzyladenine gave no improvement. Germination was even more rapid and better synchronised following a 4-day seed advancement sequence, particularly when this started with the acid steep. Overall, it was possible to increase the proportion of seeds which gave a root or produced hypocotyls at least 2 cm tall by 9% and 14% respectively; the thermal time needed for the 90th seed to germinate was reduced from 73 to 30 day degrees and synchrony could be improved at least two-fold.