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

2.1 1
selected and selfed to create the ne* generation. with fumer seledion
for superior
lines by testing phenotypic variation and environmental effeds (Powell et al.. 1990).
Commercialkation of an improved variety may be achieved in 5 years. as shown by the
development of the B. napus cultivar Quantum h m a OH-line (StrÏngham et al.. 1995).
wmpared to up to 9 years by traditional means (Monison and Evans. 1988).
DH technology has been shown, in some self-pollinating crops such as barley
(Bansal et al.. 1994) and B. napus (Scarth et al.. 1991). to improve selecüon efficiency
compared to traditional breeding methods by providing a representative sample of
variation available from a cross between parents. DH wheat lines have shown greater
resistance to diseases such as powdery mildew and septoria blotch than those
obtained by traditional breeding methods such as the pedigree system in which
homozygosity is approached through repeated seleclions (Winzeler et al., 1987). This
was due to the more precise disease assessrnent with the homozygous DH lines. DH
populations have also been shown to produce a similar array of fatty acids to that
obtained by single seed descent in B. napus (Chen and Beversdorf, 1990). The
absence of dominance effects in DH plants rnay be especially useful in selection for
quantitative traits. Snape et al. (1984) demonstrated that the number of genes
segregating for a quantitative trait can be estimated more precisely by evaluating a OH
generation rather than a segregating generation. This allows breeders more
confidence in selection of desirable genotypes.
DH production is also useful for genetic studies such as RFLP mapping (Landry
et. a1.J 991 ; Ferreira et al.. 1994) and study of physiological aspects of embryo