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Apetalous canola (Brassica napus) hybrid seed production


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Hogarth, Corey Robert 1998 , 'Apetalous canola (Brassica napus) hybrid seed production', PhD thesis, University of Tasmania.

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Canola has become an important crop in Australia as demand for its oil continues to
increase and the benefits of including it in cropping rotations are recognised. During
flowering canola produces an inefficient crop canopy of bright yellow flowers,
which reduces radiation penetration. This results in increased leaf senescence and
slower crop growth during this stage of development.
In an attempt to alleviate this effect the apetalous characteristic (absence of flower
petals) was introduced into breeding lines, and incorporated into a cytoplasmic male
sterility (CMS) system. The ogura CMS used was a newly developed system which
had been introduced from radish (Raphanus sativus) .
This study investigated the yields obtained from apetalous male sterile canola lines,
in order to determine if apetalous hybrid seed can be produced commercially. Over
three years of field trials the yields obtained from apetalous male sterile lines were
significantly lower than those of a male sterile petalled line also containing the
ogura CMS. The low yields were attributed to the apetalous male sterile lines
setting a low percentage of pods from potential pod sites, and very few seeds/pod.
Apetalous male sterile plants showed a strong response to hand pollination, by
setting more pods and seeds/pod than plants which were not artificially pollinated,
while there was no effect seen in the petalled control. This implied that the
apetalous male sterile plants were not being adequately pollinated in the field by
insect vectors, which in this study was primarily honey bees. Observations made in
the field of bee numbers and behaviour showed that the apetalous lines attracted a
similar number of bees as the petalled line, however a high percentage of apetalous
flowers were 'side-worked' and therefore unlikely to be pollinated. Pollen transfer experiments conducted in the glasshouse investigated the effect of
bees side-working flowers and showed that the amount of pollen deposited on
apetalous male sterile flowers was 60% lower than on flowers with petals, this
appeared to be the major reason that apetalous flowers produced fewer seeds/pod.
Both the apetalous and petalled male sterile lines were found to produce fewer
seeds/m2 from each row the further it was situated from the pollen source.
Logarithmic regression equations were calculated which were able to explain a large
proportion of the variation in the number of seeds/m2 between rows. It was
proposed that these regression models could be useful in determining A:R line ratios
for hybrid seed production blocks.

Item Type: Thesis - PhD
Authors/Creators:Hogarth, Corey Robert
Keywords: Canola
Copyright Holders: The Author
Copyright Information:

Copyright [1998 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1999. Includes bibliographical references

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