Vol. 80 No: 4

Title:
Effect of temperature on growth and flowering ability of three Jersey shallot (Allium cepa L. group (Aggregatum() cultivars

Authors:
F. ESNAULT, C. TROMEUR, M.P. KERMARREC and R. POULIQUEN

pp: 413-420

Abstract:
The effect of high temperatures during storage, and the effect of low temperatures and daylength on growing plants were studied in one half-long-shaped bulb variety (cv. ´Mikor`) and in two long-shaped bulb varieties (cvs. ´Jermor` and ´Longor`) in France.The critical physiological age of application of the cold treatment was also investigated. Although high temperatures during storage were confirmed to have a beneficial effect on sprouting and growth, these experiments also revealed that they promoted flowering only in the case of varieties with deep dormancy like cv. ´Mikor`, and when the bulbs were planted in the field in October. Low temperatures applied to buds that had developed two leaves (i.e., after a growth period of 1 month in a greenhouse) led to the production of inflorescences. The best flowering rates of cvs. ´Mikor` and ´Longor` (94% and 34% of buds which were growing at the beginning of the cold treatment, respectively) were obtained by growing plants for 3 months in a phytotron under a 12 h photoperiod with day and night temperatures of 10°C and 6°C, respectively, then transplanting them into the field in March. However, under our conditions, planting cv. ´Longor` bulbs in the field in October produced similar results. For cv. ´Mikor`, the results were more dependent on Winter temperatures. For cv. ´Jermor`, none of the conditions tested led to the development of a consistent number of inflorescences.These experiments show that the chilling requirement varies with cultivar, and that the optimum temperature and duration of the cold treatment and/or photoperiod must be determined for each variety.

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