Agriculture Reference
In-Depth Information
Although more than 400 longan cultivars have been developed in
China, less than 10 are economically important (Chian
et al.
, 1996; Liu and
Ma, 2001). More than 200 clonal cultivars are maintained at the National
Longan Germplasm Repository at the Fruit Research Institute, Fujian.
More than 50 cultivars have been identifi ed in Taiwan, though less than 5
cultivars are widely cultivated (Yen and Chang, 1991). In Thailand, 'E-Daw'
accounts for more than 90% of longan production (Subhadrabandhu and
Yapwattanaphun, 2001). There are about 20 cultivars of longan in Australia,
mostly introduced from China, Thailand and the USA. A longan clone
'Kohala' has been released in Hawaii and displays prolifi c vegetative growth
and produces heavy crops in Hawaii as well at Homestead, Florida. There are
numerous longans, with a wide range of characteristics (Table 9.3). Molecular
markers are being developed to identify longan cultivars.
CULTURAL PRACTICES
Propagation
Sexual
Seed propagation is used to produce litchi seedlings from selected cultivars for
breeding and selection studies and for production of rootstocks for grafting.
Litchi seeds remain viable in the fruit for about a month after harvest with a
moisture content of 45%; viability is soon lost within 4-5 days once removed
from the fruit and the moisture content falls below 27%. Seeds packed in moist
sphagnum moss may be shipped, though seeds frequently germinate in the
packing within a week. Germination and seedling development is improved
by the use of the large seeds and mycorrhizal soil for germination. Seeds
germinate within 4-10 days in soil, sand, vermiculite, perlite, peat, wood
shavings or mixtures of these materials, with adequate moisture and aeration.
Seedlings are not used for new planting as they have a long juvenile phase of
up to 10 years.
Longan seeds are also recalcitrant and quickly lose their viability after
removal from the fruit. Similar to litchi, longan seedlings have a long juvenile
period of greater than 8 years.
Asexual
Litchi and longan are usually propagated by air-layering, the method used by
Chinese propagators for centuries. Moist peat or sphagnum moss is wrapped
around the girdled area of a branch and held in place with plastic sheets
cut to about 25-30 cm
2
, with the ends fastened with string or some taping
material, such as plastic electrician's tape. Sui cient roots are formed in 8-10
weeks, and the success rate is nearly 100%. There is no need to apply growth
