The climatic adaptation of populations of cocksfoot (Dactylis glomerata L.) from southern France.
Populations of Dactylis glomerata were sampled along 2 transects in S. France both of which began near the Mediterranean coast, one going 80 km N. to the Massif Central, the other 450 km W. to the Atlantic seaboard. These populations and a group of ecotypes and cultivars were grown in the Mediterranean-type climate of Adelaide, Australia. Seasonal yields, summer survival, heading dates and head numbers were assessed over 2 years. The assessments were related to the climatic conditions prevailing at the respective collecting sites. The ombrothermic relation was used to provide an estimate of summer drought. There was variation in seedling vigour, with populations from dry Mediterranean environments, in particular, lacking vigour. At the first harvest there was more than 20-fold variation in yield. Both transects covered the range from summer-dormant to summer-growing populations, a variation that was related to the duration of the drought period and not to annual rainfall. The ability of a population to survive the summer was inversely correlated with its summer growth. Winter dormancy was detected only in high-altitude populations from the Massif Central. Although a wide variation in heading dates was obtained, it could not be related to position in the transect and macro-climatic factors, but must have been due to micro-climatic or biotic factors. Populations from near the Mediterranean produced the greatest number of heads. Seed retention was highest in populations that were summer-dormant, and these produced many naked seeds when threshed, whereas the summer-growing populations readily shed seed when ripe, the seed being enclosed by glumes.