Agriculture Reference
In-Depth Information
3
T HE G ENETICS AND P LANT B REEDING
OF A LLIUM C ROPS
INTRODUCTION
The edible allium crops traditionally fall into two groups as regards the breeding
and selection of new cultivars. The main group, which includes onion, leek,
Japanese bunching onion and chives, consists of fertile species that produce
seeds normally. The second group, which includes garlic, rakkyo, great-headed
garlic and the various crops derived from crosses between Allium cepa and A.
fistulosum , rarely produce fertile seeds and are reproduced vegetatively. Chinese
chives produces seeds, but frequently normal meiosis does not occur and seeds
are genetically identical to the mother plant; however, fertile types also exist and
have been used to develop new cultivars.
The techniques of conventional plant breeding, which involve repeated cycles
of hybridization between pollen donor (male) and female parent lines followed by
selection and intercrossing of the offspring of such crosses, are applicable only to
fertile species. The discovery and exploitation of fertile garlic has begun to change
the situation for this crop, and cross-breeding and seed production are under way
(Etoh and Simon, 2002; Zewdie et al. , 2005). Moreover, the techniques of genetic
transformation and somatic cell hybridization now make it possible to transfer
novel genes into the vegetatively propagated species.
Research on genetics and genomics of alliums is reviewed in several
chapters of Rabinowitch and Currah (2002). The breeding and genetics of
onions was reviewed by Pike (1986) and Dowker (1990). Leek breeding has
been reviewed by Currah (1986), Pink (1992) and de Clercq and van
Bockstaele (2002). Aspects of Japanese bunching onion breeding are
summarized by Inden and Asahira (1990) and chive breeding by Poulsen
(1990). Pollination biology has been reviewed by Currah (1990). These
reviews give fuller references to original research reports than does the present
chapter.
 
 
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