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 controlled environment is a means to obtain this goal faster than relying on field trials. Progress in selection will depend on the genetic variation and the heritability of the traits. This investigation shows that artificial screening for winter survival traits reveals significant genetic variation in Dactylis glomerata in all three characters tested: resistance to Fusarium nivale, resistance to Typhula ishikariensis and resistance to freezing. The broad sense heritability of resistance 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 traits by selection for resistance. The genotypic correlation calculated from the analysis of covariance of two half-sib families was found to be approximately 1. Although associated with contradictory data, this finding supports the theory that resistance to different winter stress factors is based on the same genetic trait(s).