THE INFLUENCE OF GENES FOR VERNALIZATION RESPONSE ON DEVELOPMENT AND GROWTH IN WHEAT

Studies were made of the influence of genes for vernalization response on the growth and development of four near-isogenic lines of bread wheat (Triticum aestivum L.). The duration from sowing of flower initiation, terminal spikelet formation and ear emergence all increased with increasing vernalization response. There was a close positive relationship between the days from sowing to flower initiation and from sowing to ear emergence, indicating that the duration of either phase of development is a useful measure of relative vernalization when daylength does not limit the rate of development. Total spikelet number per ear and the duration of spikelet initiation increased with increasing vernalization response and there was a correspondingly higher rate of spikelet initiation in the two lines with stronger vernalization response. Most of the differences in growth between the lines were associated with differences in development cused by the vrn genes. Maximum total above-ground dry matter and total leaf area per plant increased with increasing vernalization response but relative growth rate and leaf area per plant were not significantly different between the lines. There were no differences in net assimilation rate between the four lines until 40 d from sowing; thereafter it decreased, with the greatest decrease in the line with the strongest vernalization response.