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

INTRODUCTION
Production of doubled haploid (DH) plants improves selection efficiency in
BrassiCa napus by providing completely homorygous individuals (Scarth et al., 1991 )
and speeds up commercialization of impmved varieties as demonstrated with the
development of the cultivar Quantum (Stringam et al, 1995). DH Iines are dificult to
maintain in B. rapa which limits their application to population improvement. Selfed
seed is difficult to obtain when inbreeding naturally crosspollinating crops, such as
sporophyticall y self-incompatible B. rapa.
The traditional approach to producing selfed seed from B. rapa is through bud
pollination (Sun, 1938). Bud pollination involves emasculating an immature bud to
expose the stigrna, 2-3 days before flower opening. An anther from the same plant is
used to pollinate the stigma. Bud pollination allows pollination before the stigma is
biologically able to respond to self-pollen which is 1 day prior to flower opening.
However, bud pollination is time consuming and labour intensive. Ferrie and Keller
(1995) found that exposing B. rapa plants to elevated CG levels produced more seed
than bud pollination or NaCl spray treatment, but the CQ treatment is expensive. NaCl
spray treatment is a potentially useful, inexpensive method of producing seffed seed
that can be applied under field conditions.
Incompatible pollination in B. rapa results from callose accumulation on
stigmatal surfaces preventing penetration of the pollen tube through the papillar cell
(Kanno and Hinata, 1969). NaCl solutions overwme this barrier in self-incompatible