A winter barley variety, from the USSR, 13031, lacking vernalization requirement but sensitive to short days and more frost resistant than varieties now commercially grown in Britain, was hybridized with Shimabara, a Japanese variety which requires vernalization but is less sensitive to short days and more susceptible to frost than 13031. The resulting segregating population was then selected under short days and non-vernalizing conditions and in artificial freezing tests, in order to isolate recombinant lines.

Five lines derived in this way, together with the parents and the standard winter barley variety, Maris Otter, were included in a detailed developmental study made in a glasshouse under cool, short days.

Four of the lines had very similar developmental characters, namely few leaves and a high rate but short duration of spikelet initiation. Developmentally these selections resembled the parent Shimabara more closely than 13031 but the rate of spikelet initiation was faster than that of either parent and the duration of spikelet initiation was shorter. The fifth selection also resembled Shimabara more closely than 13031 but had more leaves and a lower rate and longer duration of spikelet initiation than the other selections. This selection was found to have a strong vernalization requirement.

One selection closely resembled 13031 in its frost resistance but had low short-day sensitivity and no detectable vernalization requirement. The complementary characters of the two parents were therefore recombined in this line.

Vernalization had little effect on the development of any of the genotypes under cool, short days in a glasshouse.