Agriculture Reference
In-Depth Information
7
The edible alliums range from some of the most highly perishable vegetables to
the most long-storing. Some shallot strains probably represent the extreme of
storability, while the delicate green shoots of Chinese chives - which can be
stored for just 2-3 days, even at 0-2°C (Saito, 1990) - represent the extreme of
perishability. The bulb-forming crops - onion, shallot, garlic and rakkyo, which
develop dormant bulbs in response to long photoperiods and high temperatures
- are, by nature, suited to storage. Allium crops harvested as fresh shoots, i.e.
leeks, salad onions, Japanese bunching onions, chives and Chinese chives, are
not harvested in a dormant state, and so their storage life is shorter and the
conditions they require are similar to those for other leafy vegetables. Winter
dormancy, typical of many temperate vegetative plants, is found in many of
these leafy crop species, e.g. in chives (see Chapter 4) and in cultivars of Japanese
bunching onion and of Chinese chive adapted to regions with cold winters.
However, winter dormancy involves the die-back of leafy shoots, and these
crops are not harvested while dormant. Most of this chapter is concerned with the
dormancy and storage of onion bulbs, this being both interesting physiologically
and the most economically important aspect of allium storage. Garlic dormancy
and storage, which has close parallels with onion, is then considered. Finally, and
as a contrast, the storage of leeks and salad onions is described.
The bulbs of edible alliums are naturally dormant organs adapted to main-
taining the plant's viability during a period unfavourable for growth. In the
native habitat of the wild ancestors of onions and garlic, the bulbs may have
enabled the plants to survive periods of summer drought and winter cold.
Rational bulb storage rests on knowledge of the physiology of bulb dormancy
and the pathology of diseases of stored bulbs (see Chapter 5). Numerous studies
have investigated physiological aspects of dormancy in onion bulbs, and rather
fewer have studied this topic in garlic. There have also been many agronomic
studies investigating the influence of various cultural practices and storage
