Progeny lines of chromosome-doubled haploids from crosses between one winter and four spring barley varieties were analysed for winter hardiness and vernalization requirement in the field . About one quarter or less of the offspring lines required vernalization under field conditions showing that winter versus spring habit of growth is controlled by at least two pairs of genes . The vernalization requirement could be measured quantitatively by testing a few plants in a greenhouse after artificial cold treatment during germination . The individual winter lines tested required from two to seven weeks of vernalization in order to flower as early as possible . The cold treatment had no effect on the time of flowering in the spring lines .
Winter hardiness varied from zero to 100% plant survival in the field . The majority of the lines requiring vernalization survived better than 90% and the survival of the rest was at least 60% . The winter survival of the spring lines varied from zero per cent (about one third of the lines) to 100% . Hence, it is possible to obtain lines of good winter hardiness without requirements for cold treatment . Conversely, a selection for vernalization requirement has a positive effect on winter hardiness .