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  Colocasia hybrids
From: "Alex Burgess" <alexcburgess at hotmail.com> on 2004.07.14 at 14:28:09(11757)
Dear Brian,

Following are two quotes taken from an article on the FAO website
(http://www.fao.org/DOCREP/005/AC450E/ac450e00.htm#Contents) which may be
the best tips for what you are trying to do:

1. "Natural flowering occurs only occasionally in taro, but flowering can
be artificially promoted by application of gibberellic acid (see later). The
inflorescence arises from the leaf axils, or from the centre of the cluster
of unexpanded leaves. Each plant may bear more than one inflorescence. The
inflorescence is made up of a short peduncle, a spadix, and spathe. The
spadix is botanically a spike, with a fleshy central axis to which the small
sessile flowers are attached. The spadix is 6-14cm long, with female flowers
at the base, male flowers towards the tip, and sterile flowers in between,
in the region compressed by the neck of the spathe. The extreme tip of the
spadix has no flowers at all, and is called the sterile appendage. The
sterile appendage is a distinguishing taxonomic characteristic between
dasheen and eddoe types of taro. In eddoe types, the sterile appendage is
longer than the male section of the spadix; in dasheen types, the appendage
is shorter than the male section.

The spathe is a large yellowish bract, about 20 cm long, which sheathes the
spadix. The lower part of the spathe wraps tightly around the spadix and
completely occludes the female flowers from view. The top portion of the
spadix is rolled inward at the apex, but is open on one side to reveal the
male flowers on the spadix. The top and bottom portions of the spadix are
separated by a narrow neck region, corresponding to the region of the
sterile flowers on the spadix.

Pollination in taro is probably accomplished by flies. Fruit set and seed
production occur only occasionally under natural conditions. Fruits, when
produced, occur at the lower part of the spadix. Each fruit is a berry
measuring 3-5mm in diameter and containing numerous seeds. Each seed has a
hard testa, and contains endosperm in addition to the embryo."

2. "Flowering and seed set in taro are relatively rare under natural
conditions. Most plants complete their field life without flowering at all,
and some cultivars have never been known to flower. For many years, this
characteristic was a great hindrance to taro improvement through cross
pollination. However, the problem was solved when it was discovered that
gibberellic acid (GA) could promote flowing in taro (Wilson, 1979).

Essentially, plants are grown from corms or cormels to the 3-5 leaf stage in
the field, and then treated with 15,000 ppm GA, a process known as
?pro-gibbing? (Alvarez & Hahn, 1986). Alternatively, the plants could be
multiplied in a seedbed, and pro-gibbed at the 1-2 leaf stage with 1,000 ppm
GA. A third method involves leaving taro in the field at the end of the
growing season and then pro-gibbing the first leaves that emerge at the
onset of the next rainy season. Whichever method is used, pro-gibbed plants
produce normal flowers 2-4 months after treatment.

Today, researchers are able routinely to induce flowering of both taro and
tannia by the application of GA. Controlled pollination can then be carried
out on the flowers that are produced. The resulting seeds, thousands per
spadix, are first germinated in nutrient media in petri dishes. The
plantlets are later transplanted to humid chambers in the greenhouse. When
the seedlings have reached a height of 15-20cm, they can be transplanted to
the field. The large genotypic and phenotypic variability resulting from
this process affords the plant breeder ample scope for selection."

3. Following are some other sources:

These guys have successfully bred hybrid colocasias for disease resistance
(a good thing to consider in your own program) and you could contact them to
find out how they did it (or perhaps for a specimen or two!):

http://www.spc.org.nc/AC/arttaro.htm

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