Evidence for the role of abscisic acid in the genetic and environmental control of dormancy in wheat (Triticum aestivumL.)

Abstract

AbstractGrain production of two wheat cultivars (Triticum aestivum L. cv Recital and Scipion), known for their different germination behaviour, was studied at two different temperatures. The study of dormancy onset during grain development showed that in both cultivars, dormancy developed on the mother plant. In Recital grain, after a period of high germinability, dormancy developed for a transient period. However, full germination was obtained on medium supplemented with fluridone, showing that dormancy was associated with abscisic acid (ABA) biosynthesis inside the grain. Dormancy progressively disappeared during natural drying, at a slower rate for grains developing at 15°C than for grains developing at 25°C. However, at both temperatures, the release from dormancy was complete at maturity. In Scipion grain, dormancy was almost total throughout grain development irrespective of the temperature. However, grains could germinate in the presence of fluridone: changes in sensitivity to fluridone were observed during grain development, showing an increase in dormancy during the first half of development, followed by a progressive decrease during the second half. This decrease occurred later for grains developing at 15°C than for those developing at 25°C. In Scipion grain, unlike the cultivar Recital, release from dormancy was not completed before the end of development on the mother plant. An additional dry storage period was necessary which was shorter for grains developed at 25°C than for grains produced at 15°C. A comparison of embryo ABA levels after a 24-h culture in the presence or absence of fluridone, allowed the ABA synthesis to be estimated. It appears that the depth of dormancy was related to the estimated ABA synthesis capacity of the embryos.