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

6-3
B. rapa OH Iines. Seleded DH Iines can then be randornly interpollinated into
composite populations to improve the agronornic performance of the population. It may
be useful to identify and select optimum OH Iines for development of the composite
populations by deterrnining cornbining abilities expressed in controlled crosses.
However, this would be time consurning and labour intensive. lt may be necessary to
determine the optimum number of DH lines required for interpollination in the
development of composite populations for difFerent populations.
RAPD analysis may provide a rapid, easy method of charaderizing genotypes
for optimization of composite population development by identifying groups of DH Iines
that are heterogeneous. Incorporation of these Iines may maximize the heterotic effed
or minimize the level of inbreeding that could be obtained through interpollination of the
Iines. RAPD analysis deterrnined that the populations produced from 22 OH Iines
should have led to the greatest level of heterogeneity and potentially the most
improvement in agronomic peHomance above the DH lines. This interpretation
differed from the results of the field study of composite development which detemined
that interpollination of only 8 Reward DH lines was required to improve the population
performance above that of the DH lines. Contradiction between these results may be
the result of the limitations in the field study which encompassed only one year and two
locations.
RAPD analysis may also be useful in future studies for predicting the level of
heterosis that rnay be expressed when OH lines are chosen and intercrossed based on
their RAPD profile. To further optimize interpollination between individual DH lines