Dormancy of June-bearing strawberry (Fragaria x ananassa Duch. cv 'Elsanta') as influenced by photoperiod

The induction of dormancy was studied in Fragaria x ananassa Duch. (cv 'Elsanta') along the plant development, in two different culture conditions imposed in climate chambers. First, the plants were submitted to the regular decrease of photoperiod and temperature regimes recorded in Belgium during summer and fall (average data over a 10 year period, published by the Institut Royal de Meteorologie, Bruxelles, Belgium). These conditions are referred to as "fall conditions". In a second experiment, the plants were submitted to the regular decrease of photoperiod regimes recorded in Belgium during summer and fall, while the temperature was maintained at 15degreesC constant (D/N). This experimental situation is referred to as "photoperiod conditions". Plant growth, especially petiole length, was followed during "fall" and "photoperiod" experimental conditions as well as after transfer of the plants at different dates from the two described conditions to long day conditions (16h, 21/18degreesC D/N) for assessing the alteration of the plant growth potential. Results pointed to a clear difference in the evolution of leaf emergence between the two experiments. As previously shown (Bodson and Verhoeven, in press), in "fall conditions" the leaf emergence stopped at the end of October. But in "photoperiod conditions", the leaf emergence continued regularly till the end of the culture. However, in both experimental conditions, the growth of the leaves emerging from September to October was strongly reduced. The plant growth potential, expressed by the size, at full growth, of the leaf or inflorescence axis emerging from the terminal bud, decreased progressively from early September till November for the "fall conditions", but remained unchanged for plants grown in "photoperiod conditions". These results show that the stunted habit of the strawberry plant in fall is not a relevant indicator of the plant physiological status, especially for estimating its growth capacity.