Winter mushroom, Flammulina velutipes, needs low temperature during its cultivation. To save on farm costs, especially during summer, a strain adaptable to a higher or elevated-temperature must be developed. At the start of breeding program, parental strains which could endure high temperature were obtained. Seuenty four dikaryotic strains were collected and divided into four groups according to the nature of temperature. They also had different fruiting temperature. Finally we selected three brown strains ASI 4048, 4057 and 4072, and collected their spores. These selected strains can germinate even at a high temperature of $32^{circ}C$, which were dramatically higher than the other strains. Based on these results, the new white strain adapted to mid-temperature by backcross mating was developed. Molecular markers were applied to select white fruitbody producing strains without cultivation. They showed a specific band which co-segregated with brown fruitbody forming strains in $BC_1F_1$ progenies. Selected white strains were tested under several elevated temperature conditions.