X International Congress of Genetics (1959)
Gene Systems Regulating Characters of Ecological Races and Subspecies
Jens C. Clausen

Latent Variability in Ryegrass

Wimmera ryegrass is a highly purified strain of Lolium rigidum, a 7-chromosome species native to the Mediterranean region. It is a spring annual that attains flowering without cold treatment. One would therefore not expect vernalization to have any effect on such a species.

J. P. Cooper (1954) found that when Wimmera ryegrass is sown outdoors in spring it will initiate flowering at the seventh to eighth node (mean 7.2). When it is sown in a heated greenhouse and given continuous light, considerable previously hidden variability is disclosed, and the seedlings initiate flowering at various nodes, ranging from the fourth to the twenty-first, as shown in Table V (mean node, 12.5). The variability will again be hidden if, before the continuous light treatment, the seeds are vernalized for six weeks at 3°C. When the cold treatment is followed by continuous light, the plants will initiate flowering at the fourth to the sixth node (mean 5.1).

TABLE V
Wimmera Ryegrass, Lolium rigidum, Latent Variability Revealed at Continuous Illumination (After Cooper, 1954)

 Node of floral initiation
4-5 6-7 8-9 10-11 12-13 14-15 16-17 18-19 20-21 Total
Vernalization at 3°C11 9               20
Heated greenhouse only2   4 7 7 5 1 2 2 30

The cold treatment apparently starts and equalizes certain gene-controlled processes related to development. No previous selection has taken place for the combination of heated greenhouse and continuous light, and the plants accordingly reveal a considerable degree of residual variability under this artificial condition.


CybeRose note: This experiment sheds some light on Avakian's success in converting winter wheat to spring wheat, as well as the report on patrogenesis by Collins & Kempton.