Development of cultivars of both tetraploid (Brassica napus L.) and diploid (B. rapa L.) rapeseed with reduced levels of polyunsaturated fatty acids and increased levels of oleic acid could increase both the utility and value of the oil. The objective of this experiment was to use chemcical mutagenesis to induce mutations for these traits in rapeseed. Imbibed seed of ‘R‐500’ (B. rapa) and ‘Cascade’ (B. napus) were treated with 5% v/v of ethyl methanesulfonate. The M2 generations of these populations were screened to identify mutants with low levels of polyunsaturated fatty acids (PUFA) using a modified thiobarbituric acid procedure. Putative mutants and their derived progeny were increased in the greenhouse and the seed analyzed for fatty acid composition using gas chromatography. The most promising mutant identified from 4 734 M2 seeds of B. rapa, was M‐30, which had 2.1% linoleic acid and 3.0% linolenic acid, vs. 11.9% linoleic and 8.6% linolenic acid in the original cultivar. This mutant was crossed with ‘Tobin’ to derive F4 lines having <6% total PUFA and oleic acid concentrations >87%. The most promising mutant identified from 39 504 M2 seeds of B. napus was X‐82, which had 6.6% PUFA, vs. 27.4% PUFA in Cascade. Several M3 and M4 lines derived from X‐82 had <6% total PUFA and >88% oleic acid. The development of commercial cultivars with reduced levels of polunsaturated fatty acid in both B. rapa and B. napus could develop new markets for both industrial rapeseed and edible canola oil.

The effect of late season insect infestation on seed yield, yield components, oil content and oil quality of two canola species (Brassica napus L. and B. rapa L.) and two mustard species (B. juncea L. and Sinapis alba L.) was examined over 2 years. In each year, ten genotypes from each species were evaluated with late season insects controlled with either methyl parathion or endosulfan insecticides, and without insecticides. Major late season insect damage in 1992 was caused by cabbage seedpod weevil (Ceutorhynchus assimilis Paykull), while diamondback moth (Plutella xylostella L.) and aphids (primarily cabbage aphids, Brevicoryne brassicae L.) were major insect pests in 1993. Insecticide application was very effective in controlling diamondback moth larvae and adult cabbage seedpod weevils, but only partially effective in controlling aphids. Higher numbers of diamondback moth larvae were observed on mustard species compared to canola species. S. alba was completely resistant to cabbage seedpod weevil and there was no damage due to this pest observed. Aphid colonization was observed on plants from all species, but infestation on S. alba and B. rapa occurred too late to have a major effect on seed yield. Seed oil content of canola species was significantly reduced by insect damage although oil quality (indicated by fatty acid profile) was not affected by insect attack. Uncontrolled insect infestation reduced seed yield of canola species by 37 and 32% in B. napus and B. rapa, respectively. Least yield reduction occurred in S. alba, where average yield reduction from plants in untreated control plots was <10% of insecticide treated plants. S. alba, therefore, has good potential as an alternative crop suitable for northern Idaho because it can be grown with reduced late season insecticide application.

Spring canola (Brassica napus L.) is a new crop in the Pacific Northwest and growers have adopted cultural practices used in western Canada where spring canola (or rapeseed) must be swathed to hasten maturity and avoid frost damage. The aim of this study was to evaluate the effect of preharvest swathing on the seed yield and seed quality, and determine the best time to swath in northern Idaho, if swathing is needed. Five spring canola cultivars were planted in 1992 and 1993 to compare seed yield and quality of swathed and direct harvest crops. In 1994, commercial agricultural machinery was used in larger plots, to compare seed yield and quality from three different swathing dates with direct harvest. In 1992, directly harvested canola had higher yields than swathed canola. The following year, yield of directly harvested and swathed canola were not different. In commercial scale trials, yield loss was linearly related to time of swathing with the least reduction occurring when swathed at 60 to 80% brown seed, and most yield loss occurring when swathed at 10 to 20% brown seed. Therefore, optimal swathing time would be when most seeds were brown. Swathing canola resulted in smaller seed and greater chlorophyll content. However, swathed crops had lower seed moisture content, which may ease harvest operations. We recommend that canola should only be swathed in northern Idaho in cool and wet growing seasons, where harvest is delayed. Research Question Spring canola is a new crop to Pacific Northwest growers and farmers have adopted cultural practices used in western Canada where spring canola is grown extensively. A high proportion of Canadian canola is swathed prior to harvest. The aim of this study was to: (i) evaluate the effect of preharvest swathing on the seed yield and seed quality; and (ii) determine the best time to swath in northern Idaho, if swathing is advantageous with conventional harvest methods. Literature Summary The short growing season in western Canada requires that canola be swathed prior to harvest to hasten maturity and avoid frost damage. Because of the longer growing season in northern Idaho, swathing of spring canola may not be required. No swathing studies have been conducted under dryland conditions that prevail in the Palouse region of eastern Washington and northern Idaho. Study Description Five spring canola cultivars were planted in 1992 and 1993 to compare seed yield and quality of swathed and direct harvest crops. When approximately 35 to 40% of seeds on the main raceme had changed from green to brown, plants from half of each plot were swathed. After drying in windrows, the swathed plots were harvested. The other half of the plot was direct harvested when mature. In 1994, larger plots, using commercial agricultural machinery, were used to: (i) compare seed yield and quality from three different swathing dates (10–20%, 35–40%, and 60–80% seed color change) plus direct harvest; and (ii) compare seed yield and quality between swathed and nonswathed canola when harvest is delayed. Applied...

Residual levels of sulfonylurea (SU) herbicides in the soil have limited rapeseed (Brassica napus L. var. napus) production in the Pacific Northwest. In a greenhouse screening procedure, the test herbicide suppressed the growth of susceptible rapeseed plants but allowed normal growth of resistant plants. Mutant (M2) populations of ‘Cascade’, ‘Bridger’, and ‘Cathy’ winter rapeseed, ‘R‐500’ spring rapeseed (B. rapa L. subsp. rapa), and ‘Tilney’ spring mustard (Sinapis alba L.; syn F. hirta Moench.) were screened with DPX‐G8311, a 5:1 mixture of the SU herbicides chlorsulfuron (2‐chloro‐N‐[[(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl)amino]carbonyl]benzenesulfonamide) and metsulfuron {(methyl l‐[[[[(4‐methoxy‐6‐methyl‐l,3,5‐triazin‐2‐yl)‐amino]carbonyl]amino]sulfonyl]benzoate)}, applied preemergence at 7.5 g a.i. ha−1. Approximately 243 000 M2 seedlings were screened and 178 were selected for additional tests. In progeny tests, several M3 and M4 families were identified that survived 6.5 g a.i. ha−1 DPX‐G8311 applied preemergence but failed to survive the same rate of DPX‐G8311 applied postemergence. DPX‐G8311 was applied preemergence at 0 to 64 g a.i. ha−1, to one M3 and six M4 families to determine a dose × family response relationship. Calculated 50% growth reduction (GR50) values for both number of nodes produced and dry weight accumulation were up to 25 times greater for the selected M3 and M4 families than for the susceptible cultivar Cascade. Rapeseed lines resistant to soil residual levels of SU herbicides but susceptible to SU herbicide foliar applied would allow rapeseed to be planted after a small‐grain cereal to which a SU herbicide had been applied.

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