Breeding for earliness and tolerance to lower temperatures during vegetation period was a starting-point in expansion of soybean cultivation to the northern part of the world, characterized by long day conditions, l ower temperatures and a short vegetation period (Holmberg, 1973) .Recently, the interest in soybean has increased and intensive breeding programs started in different countries of northern Europe , among them Poland. Under Polish climatic conditions, most of soybean cultivars and forms from Maturity Group 00 are characterized by too long vegetation period and are very often killed by frost before maturation (Szyrmer, 1968).