Agriculture Reference
In-Depth Information
Currah (2002) gives tables listing the names of cultivars grown in countries
of tropical and subtropical Africa, Asia, the Americas and the Caribbean. The
yields and storage performance of these cultivars are listed by Currah and
Proctor (1990). Onion cultivars developed for early-spring bulbs in southern
Texas and California are widely grown in tropical countries, as these cultivars
can produce large bulbs in the short day-lengths of equatorial regions - for
example, the hybrid cultivars 'Granex 33' and 'Granex 429'. These onions grow
vigorously, produce large, single-centred bulbs, are mild-flavoured, juicy and
low in dry matter, have thin skins and a short storage life (< 2 months) under
ambient tropical conditions. A number of US seed companies market cultivars of
this type throughout the tropical world. More recently, breeders in Israel and
Australia have developed cultivars suitable for tropical production which are
longer storing and have better skin quality, by introducing genes for these
properties from long-day genotypes.
Many indigenous tropical varieties still exist as landraces of farmer-saved
seed. These may show considerable variation in size, shape and colour within
the population. Selection for greater uniformity has stabilized some open-
pollinated named cultivars - e.g. 'Poona Red' (India) and 'Red Creole'
(Louisiana) - and selection continues to produce new or more highly bred,
open-pollinated cultivars. The Creole onions probably originated in the
western Mediterranean but have been grown in Louisiana for more than 150
years. They are fairly slow growing but produce pungent, high dry-matter
bulbs with tough skins typically able to store for 4-5 months in the tropics
(Currah, 2002). They are widely grown throughout the tropics. In the late
1990s a Dutch company (Bejo) introduced cultivars selected from the Indian
cultivar 'Bombay Red', and a US company (Asgrow) introduced cultivars
selected from West African and Brazilian material. These cultivars aimed to
supply tropical consumers with improved medium-sized, pungent red onions
(Currah, 2002). Hybrid shallots for growing from seed in tropical regions have
also been introduced recently by the Dutch company Bejo.
Japanese bunching onion,
Allium fistulosum
L.
The Japanese bunching onion was historically the main allium vegetable of
China and Japan, where it has been cultivated for more than 2000 years, and
it remains very important there. While growing, the Japanese bunching onion
is very similar in appearance to the common onion, but it does not form
dormant bulbs. Further distinguishing features between the two crops are
given in Fig. 1.1 and Table 1.2.
Allium fistulosum
is not known as a wild species, but
A. altaicum
, a wild
relative, is widespread in the mountains of northern and central Mongolia and
southern Siberia, somewhat east of where the wild relatives of the common onion
are centred.
Allium altaicum
forms bulbs with a fibrous, net-like skin that are
