The Application of Ooubled Haploid Plants to Population ... - MSpace

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1988). This is accomplished by providing an in Mm culture environment for the haploid
em bryos similar to that provided by the ernbryo sac for zygotic embryos in vivo. for
example, by inducing desiccation toleranœ and dehydration of the embryos. In v h
embryos do not naturally develop desiccation tolerance or undergo dehydration or
domancy. To induce these conditions, abscisic acid (ABA). cold and heat treatments
along with desiccation have been implemented to increase the frequency of conversion
from embryos to plants (Kott and Beversdorf. 1990; Senaratna et al.. 1991 ; Brown et
al., 1993).
Self-pollination or inbreeding to produce homozygosity in obligate outcrossing
crops leads to inbreeding depre&on. seen as a loss in population performance, due to
the expression of deleteflous homozygous recessive alleles. lnbreeding depression
has been reported in DH lines of B. rapa expressed as poor germination rates, spindly
branching, reduced height, late floweting. lack of pollen, low seed set and poor seed
quality (Dewan et al., 1995). OH production does not avoid inbreeding by minimizing
the repeated cycles of inbreeding. In order to exploit the benefits of DH development in
cross pollinating crops, there must be a recovery of performance to at least the level of
the original heterozygous population.
Genotype Analysis
Traditional plant breeding techniques are based on the selection of a genotype
using phenotypic analysis. Phenotype is not an accurate indicator of genotype when