Complex sentence: Despite the low rate of growth in production during the Soviet period, some particularly impressive advancements were made in seed development, of which the most useful was the development of a frost-resistant sugar beet, further expanding the growing range of the sugar beet.
Split into simpler sentences: Despite the low rate of growth in production during the Soviet period there were some particularly impressive advancements were made in seed development. Of which the most useful was the development of a frost resistant sugar beet, further expanding the growing range of the sugar beet.