Flowering physiology and some vegetative traits of short-day shallot: A comparison with bulb onion

Abstract

SummaryThe critical physiological age of shallot (Allium cepa var. aggregatum) grown from seed and sets, and the effect of temperature on stored bulbs and the flowering habit were studied in Israel. Three short-day genotypes were grown from seeds or sets. Prior to storage, bulbs were sorted according to size and incubated in low (5-10°C), intermediate(13-20°C) or high (30°C) temperatures for various periods. Plants were grown in the open fieldand inthe phytotron, and their vegetative and blooming development was investigated. Our findings show significant genotypic differences in flowering; cold treatment is essential for floral initiation; and the length of the juvenile phase is tightly dependent on the environment. In the field, early-sown shallots had a faster growth rate, accumulated more mass, and produced earlier and more auxillary buds and side shoots than those from the late sowing. Shallots can be induced to flower by cold treatment in storage, the optimum temperature being 5-10°C, whereas high and intermediate storage temperaturesdelay the development of the inflorescence. During growth, high temperatures may suppress already initiated nflorescences.Plants from larger sets flowered more readily than those from small ones, and genotypes varied significantly in their response to cold induction. The impact of genotype and environment on bulb and seed production as well as the similarities anddifferences in flowering habits between shallot and bulb onion are discussed.