Canola oil increases in polyunsaturated fatty acids and decreases in oleic acid in drought-stressed Mediterranean-type environments

Seed fatty acid (FA) composition, oil and protein (meal) was assessed on five canola (Brassica napus) varieties in 14 cropping environments in southern Australia, including several low rainfall drought-stressed environments. We modelled the relationship between seed quality attributes and growing season rainfall and temperature using a linear mixed model. Variance components for variety and years within locations were relatively large, but variance components for variety x environment interaction were small or insignificant for most seed quality traits. Mean oleic acid content varied from 57% in 'Surpass 300TT' to 62% in 'ATR-Beacon'. As growing season rainfall decreased from 300 mm (moderate) to 150 mm (severe drought stress), mean oleic acid decreased by 3.8%, linoleic acid increased by 2.0%, linolenic acid increased by 1.7%, and saturated FA decreased by 0.4%. Seed oil (% dry weight) decreased by 3.2% and protein in meal (% dry weight) increased by 3.9% across the same rainfall range. High oleic acid composition was associated with higher rainfall and cooler average minimum and maximum temperatures during the growing season.