TOST 5 is a variety of flax (Linum usitatissimum L. f. elongata) intended for the production of flax fiber. It is an early-maturing variety with a vegetative period ranging from 75 to 98 days depending on the growing region. The plant is tall with a long stem and a medium-sized flower calyx. Petal color changes from blue-violet in the bud stage to blue at full development. Seeds are brown, with a mass of 1000 seeds being about 4.5–4.8 g. The capsule is small, without a fringed false septum.
The variety is characterized by high resistance to lodging (about 4 points), shattering (from 3.3 to 4.7 points), and drought (3–4 points). In different regions, straw yield varies from 45.7 to 71.1 c/ha, exceeding average standards, while seed yield ranges from 4.4 to 6.6 c/ha. Fiber content in the plant reaches 29.3–35.4%, and the yield of long fiber is from 21.4 to 23.2%. The relative tensile strength of the fiber is within 14.8–15.8 gf/tex. The variety shows moderate resistance to Fusarium wilt and rust, but may be susceptible to bacterial blight and anthracnose.
TOST 5 is recommended for cultivation in the Northwestern, Volga-Vyatka, and Western Siberian regions. Due to its characteristics, it is suitable for industrial flax fiber production, ensuring high-quality raw materials. The variety is characterized by the stability of its indicators and is adapted to various climatic conditions, making it a profitable choice for farmers focused on obtaining high-quality flax fiber.
