Expression of Vernalization Genes in Near-lsogenic Wheat Lines: Duration of Vernalization Period

Vernalization periods ranging from 0 to 11 weeks at 4 °C were used to study the reproductive development of four near-isogenic lines of wheat (Triticum aestivum L. em. Thell). From the results for days to anthesis two types of gene action were identified, a threshold (all-or-nothing) response (vrn3 and/or vrn4) and a cumulative (graded) response (vrn1). The action of another gene (vrn2) intensified these two responses. Based on the action of genes, a model relating days to anthesis to genotype was derived. Final leaf number and days to anthesis were shown to be closely related after adjusting for differences due to the duration of vernalization treatment. No relationship between days to anthesis and spikelet number was observed. This study emphasises the need to understand vernalization at the level of the gene in terms of responses and interactions. Such knowledge should enable the plant breeder to predict and more precisely control reproductive development.