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Background and Objective:
Canola oil is recognized as a
"healthy oil"
because of its relatively low saturated fatty acid content compared
to other vegetable oils. The demand for low saturated fatty acid
content is driven by the increased risk of coronary heart disease
associated with high levels of saturated fatty acids. Nutritionists'
recommendations have influenced consumers preference and resulted in
an enhanced market share for canola oil products in the United
States to 10% of the vegetable oil market. Maintenance of this
market share requires a further reduction of saturated fat levels in
canola oil for several important reasons. A new competitor for
canola has emerged in the form of low saturate soybean oil, which
has been developed with saturate levels less than half the level of
commercial soybean oil. At the same time, saturate levels in the
commercial canola crop has been rising, due to the major conversion
to production of Brassica napus cultivars in western Canada
and the near exclusion of B. rapa cultivars from the
commercial crop. The B. napus cultivars in current
production have saturated fat levels 1.0-1.5% higher than the
saturated fat levels in B. rapa. The environment also
influences the level of saturated fat in the oil. Warmer growing
conditions result in elevated saturate levels in the oil. The need
for low saturate B. napus has been recognized by the canola
industry in Canada as a major priority.
The development of
low saturate canola (Brassica napus) consisted of two
individual projects.
Project 1 was
designed to understand the impact of canola variety and environment on
canola oil yield and quality, identify the management factors that
affect canola oil yield and quality within specific agronomic areas of
Manitoba, and develop a predictive model for canola oil yield and
quality.
Project 2 aimed to
characterize low saturate mutations produced in the B. rapa
lines by microspore mutagenesis, determine the stability of the low
saturate mutations, and develop new low saturate B. rapa lines
for use in B. napus low saturate germplasm development.
Seed harvested
from Manitoba Variety Evaluation Trials (MCVET) grown in 1999, 2000,
and 2001 were evaluated for protein and oil content, and fatty acid
composition of the oil. Trial sites for quality analysis were
selected from different growing regions in Manitoba to maximize
environmental variation between sites.
Variation in total saturated fatty acid content (palmitic
acid + stearic acid + arachidic acid + behenic acid) in canola oil was
predominantly due to the independent effects of environment and
variety. The relative rankings of varieties based on saturates varied
between growing environments (an environment is a specific location in
a specific growing season), however, this type of variation was small
relative to the sole effects of environment and canola variety on
saturates. A similar trend was noted when the four saturated fatty
acids were analyzed separately. Varietal variation in palmitic and
stearic acid contributed equally to variation in total saturates, even
though approximately twice as much palmitic acid is found in the oil.
Attempts to identify environmental parameters
associated with saturate variation were unsuccessful. The observed
environmental variation in saturate content may result from the
cumulative effect of interacting factors, such as temperature,
available soil moisture, relative humidity, biotic stresses, and
available nutrients. Finally, this section of the study revealed that
environment changes resulting in an increase of stearic acid tended to
result in a similar increase in arachidic and behenic acid, but not
palmitic acid.
Variation in saturated fatty acids was also
studied between canola varieties. Palmitic acid and stearic acid, the
two predominant saturated fatty acids in canola oil, were not
associated between varieties, suggesting that the palmitic acid and
stearic acid content in the oil are controlled by different genes.
Stearic acid and arachidic acid content were positively correlated,
suggesting these may be controlled by the same genes. Genetic studies
will be required to confirm this association.
Researchers at the Plant Biotechnology
Institute in Saskatoon utilized microspore mutagenesis followed by
the development of doubled haploid lines to create novel B.
rapa germplasm with altered fatty acid profiles. The doubled
haploid lines of B. rapa were screened for low saturate
variation and selected lines were crossed to B. napus,
using interspecific crosses followed by doubled haploid
development, at the University of Manitoba. The reduced saturate
B. napus lines were grown under controlled environment
conditions and in the field for two years and evaluated to
determine the environmental stability of the low saturate trait.
The low saturate B. napus germplasm generated in this
project has the potential to contribute to the reduction of
saturate levels in canola and specialty oil canola cultivars.
This reduction will maintain and enhance the competitive position
of the western Canadian canola crop.
Acknowledgements:
This project was made possible due to funding
from the Governments of Manitoba and Canada through the
Canada-Manitoba Agri-Food Research and Development Initiative
(ARDI).
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