Cocksfoot Grass (Dactylis Glomerta L.): Ecotypes in Relation to the Biotic Factor

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Abstract
Seed samples (143) of this species were collected from 6 countries in different parts of the world, and 315 individual plants were dug up in toto from representative habitats in England, Scotland, and Wales and were transplanted to the Welsh Plant Breeding Station. The seed was sown in the greenhouse during Dec. and Jan., and the seedlings were planted out with wide spacing in May, June, or July. Critical studies of the plants were commenced the season after the planting out and were continued 8 yrs. The 458 collections produced 11,328 individual plants for study. In addition, 14,925 progeny plants obtained from selfing representative plants were also set out widely spaced and studied in the majority of cases to the 2nd generation, many to the 3rd, and some to the 4th. The vegetative characters, inflorescence, and growth-form characteristics were studied. For the different growth-form groups data were obtained on yield, height, height/diameter and length of leaves, seasonal growth, and tiller development. The vegetative groups were classified into lax hay, dense hay, tussocks, cups, spreading pasture type, and dense pasture type, and these are defined and illustrated. The groups were studied in relation to genetical stability and vigor of cross-fertilized and selfed progeny and the distribution of the F2, F3, and F4 progeny plants in the 6 vegetative groups; also in relation to habitat and ecotypical selection. It is concluded that D. glomerata, ecotypically considered, shows very marked habitat relationships; that conditions not sufficiently exacting to reduce the representatives of a species to a single well-marked ecotype do operate to reduce the potential variability of the species as a whole within an inner circle of variability; that it is impossible to form a correct picture of the attributes of any particular species unless and until truly representative individuals are collected from every characteristic habitat upon which the species occurs, and are brought together and grown under one set of uniform conditions.

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