Apparent vernalization requirement of high yielding spring wheat
Controlled environment studies have demonstrated that the high yield potential of certain spring wheat (Triticum aestivum L.) cultivars may result from a moderate vernalization requirement. The objective of this study was to determine whether apparent vernalization responses of cultivars could be detected when comparing the development of early and late-seeded crops. The effect of delayed seeding on 9 or 10 spring wheat cultivars was studied at Saskatoon over a period of four years. Within years, the earliest and latest dates of seeding differed by a minimum of 22 days. Vernalization effects were apparent in 1983 and 1986 but not in 1985 and 1987. In 1983 and 1986 Growing Degree Day accumulation 14 days after seeding (GDD14) averaged 44 for the earliest date of seeding compared to 120 GDD or more for the later seeding dates. However, the GDD14 for the earliest date of seeding was 121 in 1985 and 134 in 1987. Apparent vernalization effects were manifested by higher main stem leaf number, increased spikelet production and delayed spike emergence. Cultivars were ranked in the following order for apparent vernalization sensitivity: Fielder = Pitic 62 > HY402 > HY320 > Genesis > HY912 > Leader > Glenlea > Neepawa > Katepwa > Siete Cerros > Potam. Fielder had the greatest vernalization requirement and Potam the least. On average, delayed seeding resulted in increased grain yields, but this observation was not consistent over years.
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