THE CLASSIFICATION, ORIGINS, DISTRIBUTION AND ECONOMIC IMPORTANCE OF THE MAJOR VEGETABLE CROPS - Onions and other Vegetable Alliums - page 5

North America.
Typically, alliums are plants of open, sunny, dry sites in fairly arid climates.
Many species are found in steppes, dry mountain slopes, rocky or stony open
sites or summer-dry, open, scrubby vegetation (Hanelt, 1990). They are weakly
competitive and therefore are not normally found in dense vegetation.
However, some woodland species exist - for example, A. ursinum and also some
pasture species and important weeds, including A. vineale and A. carinatum .
The annual pattern of growth (phenology) varies widely. Depending on
species, flowering can occur in spring, summer or autumn and the growth and
development period can vary from 2-3 months in spring to early summer to
several cycles per year of leaves or even continuous leaf formation. They can be
short- or long-lived perennials. Species of summer-dry regions may show
summer dormancy, whereas there are also winter-dormant types adapted to cold
regions. Some species from arid regions have only a short growing season in
spring and early summer. The crop species have a high nuclear DNA content (see
Chapter 3) and fructans as their reserve carbohydrates (see Chapter 8), both
features of plants that grow by rapid cell expansion in the cool temperatures of
late winter and early spring (Hendry, 1993).

THE TYPES, HISTORY AND EVOLUTION OF THE
EDIBLE CROPS

The names and taxonomic grouping of the edible alliums important in
commerce are shown in Table 1.1 The seven main food crop species are easily
distinguishable, and Table 1.2 and Fig. 1 show features that can be used in
identification of these crops.

Table 1.1. Groupings within the genus Allium that contain the major crops (from
Table 1, Friesen et al ., 2006).

Subgenus Section Species English crop name

Butomissa Butomissa A. tuberosum Chinese chives

Allium Allium A. sativum Garlic

A. ampeloprasum Leek, kurrat, great-headed

garlic, pearl onion

Cepa Schoenoprasum A. schoenoprasum Chives

Cepa Cepa A. cepa Onion, shallot, multiplier

or potato onion

A. fistulosum Japanese bunching onion

A. oschaninii French grey shallot

Cepa Sacculiferum A. chinense Rakkyo