RESISTANCE TO WINTER STRESS FACTORS IN HALF-SIB FAMILIES OF DACTYLIS-GLOMERATA, TESTED IN A CONTROLLED ENVIRONMENT

Improved winter hardiness is an important objective in Norwegian grass breeding. Selection for winter hardiness based on performance in a co ntrolled environment is a means to obtain this goal faster than relyin g on field trials. Progress in selection will depend on the genetic va riation and the heritability of the traits. This investigation shows t hat artificial screening for winter survival traits reveals significan t genetic variation in Dactylis glomerata in all three characters test ed: resistance to Fusarium nivale, resistance to Typhula ishikariensis and resistance to freezing. The broad sense heritability of resistanc e to snow mould fungi between 0.4 and 0.5, and for freezing resistance between 0.5 and 0.7, indicates good possibilities for improving the t raits by selection for resistance. The genotypic correlation calculate d from the analysis of covariance of two half-sib families was found t o be approximately 1. Although associated with contradictory data, thi s finding supports the theory that resistance to different winter stre ss factors is based on the same genetic trait(s).