During 1988 and 1989, seven species of Brassica and a single species of Eruca (E. sativa L.) were evaluated to determine if they were adapted to the Mediterranean climate of the Pacific Northwest. These species have been grown as oilseed crops in Europe, Asia, or Africa (Downey 1966; Downey and Robbelen 1989). The agronomic potential and genetic diversity of current germplasm accessions of three of the most promising species were evaluated in a series of trials during the 1989 and 1990 growing seasons.
The 1988 study was sown on Apr. 27 at Moscow, Idaho, in a field in which spring peas (Pisum sativum L.) had been green manured the previous year. No additional fertilizer was applied. Flea beetle control required applications of 1.7 kg/ha of carbaryl (1-naphthyl N-methyl-carbamate) on May 14 and 1.7 kg/ha of permethrin [3-(phenoxphenyl) methyl (1RS)-cis, trans-3-(2,2-dichloroethenyl)-2,2-dimethyl cyclopropane carboxylate] on May 24 and June 13. Aphids were controlled by a single application of 1.4 kg/ha malathion (diethyl mercaptosuccinate, S-ester with 0,0-dimethyl phosphorodithioate) on July 12.
The 1989 study was sown on Apr. 26 in a field in Moscow, Idaho, which had produced a barley (Hordeum vulgare L.) crop the previous year. Nitrogen (76 kg/ha) was applied as ammonium nitrate (34-0-0) prior to planting. In 1989, flea beetles were controlled by applications of 2.5 kg/ha of carbaryl on May 19, May 22, June 1, and June 5. Aphids were controlled by applying 1.4 kg/ha of malathion on July 5 and July 13.
Oil yield (%) was determined using a Newport MKIIIA Nuclear Magnetic Resonance (NMR) instrument on 12 g of oven-dried, open-pollinated seed obtained from each plot. The NMR was calibrated using the cultivar 'Bridger' as a standard and all samples were analyzed with a 32 sec integration period.
Fatty acid composition was determined by the on 0.5 g of open pollinated seed. Oil was extracted from the ground seed using 4 ml of anhydrous ethyl ether. The oil solution was taken up in a syringe using a synthetic cotton ball as a filter and mixed with 200 µl of 20% tetramethylammonium hydroxide in methanol. The sample was shaken and allowed to settle for 1 min before 2 ml of distilled water was added. The sample was again shaken and allowed to settle to form an immersion layer. A 1 µl sample of the upper immersion layer was injected by a Varian model 8000 Autosampler into a Varian Model 3700 Gas Chromatograph (GC) equipped with a flame ionization detector with a Supelco 3.05 m glass column containing 3% SP-2310 and 2% SP-2300 on a 100/120 mesh chromasorb WAW support. Helium was used as the carrier gas, and the column was maintained at 220°C. Injector and detector temperatures were maintained at 250° and 300°C, respectively. A Varian Model 4290 integrator was used to determine relative concentrations of the major fatty acids by integration of total area under each curve. A rapeseed standard prepared by Supelco (Cat. No. 4-7019) was used as the control to identify the retention time of each of the seven major fatty acid found in rapeseed and run as every 20th sample.
The 1990 trial contained four commercial cultivars of B. juncea and four commercial cultivars of B. hirta and was planted on 20 Apr. in a field which had been fallowed the previous year. This study was fertilized with 90 kg/ha of nitrogen applied as urea (45-0-0) prior to planting. The six row plots were 4.7 m in length. Rows were spaced 15 cm apart and plots were planted on 1.5 m centers using a randomized complete block design with four replications. The seed was treated with carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) at the rate of 2.8 kg/ha to provide flea beetle control but plots also required applications of 1.7 kg/ha of phosmet N-(mercapto-methyl)-phthalimide S-(0-0-dimethylphosphorod-ithioate) on May 17 and on June 15. Aphids were controlled by applying 1.4 kg/ha of malathion on July 17.
In 1990 the B. hirta accessions were evaluated in two trials. The two row plots contained 31 accessions and the six row plots had 28 accessions of B. hirta and three commercial cultivars of rapeseed. Both trials were planted on Apr. 19, 1990 using the same procedures described for the 1990 mustard cultivar trial.
The 1990, germplasm evaluation of B. juncea which contained trial of 383 accessions and nine commercial cultivars of B. juncea was planted on Apr.18 in Moscow, Idaho. The field had produced oats (Avena sativa L.) the previous year. Individual plots consisted of two rows and the trial had two replications. The field was fertilized with 112 kg/ha of nitrogen and weed control was achieved with applications of 1.8 liters/ha of trifluralin (alpha, alpha, alpha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) and 2.9 liters/hg of triallate [S-(2,3,-Trichloroallyl) diisopropylthiocarbamate].
The 1990 evaluation of B. carinata germplasm was unreplicated and contained 160 accessions, that were planted on Apr. 19. This study was planted and maintained using the same procedures described for the other 1990 trials.
The 35 individual accessions had average seed yields which ranged from 0.5 to more than 3.5 Mg/ha. In both years, the B. hirta accessions UCD 79 and UCD 1272 produced the highest average seed yields. These accessions also had low levels of oil and relatively large seed size. Commercial seed yields of rapeseed or canola must exceed 2.2 Mg/ha to be economically competitive with other spring planted crops currently grown in the Pacific Northwest. Both the species and individual accessions within a species showed significant variation for both oil content and seed size in this trial.
Seed yield of the eight cultivars included in the 1990 trial ranged from 0.3 to 2.0 Mg/ha (Table 2). The cultivar `Blaze' had the lowest yield and very poor stand establishment, indicative of poor quality seed. Oil contents of the cultivars ranged from 22.4 to 31.7%. In the very dry conditions of 1990, B. hirta produced the highest seed yield, but the average oil content of the B. juncea was 7.7% higher.
Many of the cultivars of the two species of mustard currently grown in Canada produced excellent crops in the Mediterranean climate of the Pacific Northwest. This indicates that crops of condiment mustard could be grown commercially in this area if sufficient market could be identified. Finite markets for condiment mustard have historically limited Canadian production (Downey et al. 1975). Because of the relatively small markets for condiment mustard, larger markets could be tapped if mustard cultivars were developed that could be utilized as oilseed crops. Incorporation of high oil content, low levels of glucosinolates, and specific fatty acid composition into these two species could allow widespread commercial production of spring mustard in the Pacific Northwest.
The two 1990 trials of B. hirta differed in relative seed yield, reflecting the inflated yield potential often observed in the smaller two row plots (Fig. 1). The two row plots had average seed yields of 3.5 Mg/ha while the six row plots grown nearby had average seed yields of only 1.0 Mg/ha. Seven accessions from the replicated six row plots produced in excess of 1.4 Mg/ha despite the extremely dry weather observed during the summer of 1990. Cultivars which produce high seed yields under the dry conditions experienced in July and August in the Pacific Northwest will need to be developed if commercial production of spring mustard is to be successful. Oil content of all the B. hirta accessions evaluated in 1990 were less than 33%.
As measured by the Tes-Tape procedure (Downey et al. 1975), glucosinolate levels showed a wide range of variation (Fig. 3). The two lines with the lowest Tes-Tape scores, BHLG-3553 and GHLG-3568, were obtained from Keith Downey of Agriculture Canada at Saskatoon, Saskatchewan. These lines had levels of glucosinolates that slightly exceeded the maximum level allowed in canola cultivars. Fatty acid composition of 35 select lines B. hirta showed a wide range of variation. Four of the lines obtained from Agriculture Canada had less than 8% erucic acid, but canola oils marketed in the United States must have less than 2% erucic acid as required by the Food and Drug Administration. This indicates that additional selection will be necessary to improve both the meal and the oil if B. hirta is to be developed as an economically competitive oilseed crop.
The 383 accessions and nine commercial cultivars of B. juncea evaluated in 1990 produced seed yields which ranged from 0.3 to 10.3 Mg/ha (Fig. 4). Four accessions, 72-525, 'Common Brown' ('ComBrown'), 77-18, and 'Juzanka', produced excellent seed yields and appeared to be well adapted to the Pacific Northwest. Oil contents of the B. juncea accessions and cultivars ranged from 28.6 to 41.1% (Fig. 5 ). Only two accessions, 'Jubileja' and 77-978, had greater than 40% oil content indicating that commercial cultivars of B. juncea would need to be selected for this important trait if this crop were to be grown as an oilseed crop.
Canadian researchers have recently developed B. juncea germplasm with low levels of glucosinolates and low levels of erucic acid (Love et al. 1990). These traits are being incorporated into commercial cultivars to allow expanded canola oil production in the drier regions of western Canada. Incorporation of these traits into the higher yielding accessions identified in this study could allow rapid development of oilseed cultivars adapted to the Pacific Northwest.
Even in small plots, only eleven accessions of B. carinata produced seed yields which exceeded 2.0 Mg/ha (data not presented). Oil content of these accessions ranged from 22.1 to 34.6%, indicating that additional improvement would be needed in the oil content of this species to allow commercial production. Additional evaluation of B. carinata for the Pacific Northwest is not planned at this time since other species show more potential for this area.
In our studies, B. hirta had excellent agronomic potential but currently available cultivars and accessions had low oil contents, high levels of glucosinolates, and intermediate levels of erucic acid in the oil. Selection of canola and industrial quality cultivars of B. hirta would allow expanded production of this drought and pest tolerant species. Brassica hirta (Sinapis alba L.) is grown as white mustard on about 57,000 ha annually in Canada for use as condiment mustard (Downey and Robbelen 1989). This species has shown tolerance to both flea beetles and selected species of aphids (Lamb 1980; Putman 1977). White mustard can tolerate drought and high temperatures during flowering and seed fill (Downey 1966; Downy et al. 1975). Selected accessions of B. hirta have been reported to have oil contents which exceed 42% (Persson 1986). Erucic acid levels have ranged from about 5 to 55%. All existing accessions have had relatively high levels of glucosinolates which reduces the quality of the meal residue remaining after oil extraction. Since most commercial cultivars of this species were developed for production of condiment mustard, only limited selection has been practiced on characteristics need as an oilseed crop.
Brassica juncea has been grown as brown or Oriental mustard on about 85,000 ha annually in Canada (Downey 1966; Downy and Robbelen 1989). This highly drought tolerant species originated in the Middle East but has been widely grown across Europe, Asia, and Africa (Downey 1966; Downey et al. 1975). In our studies, this species has produced good seed yields and oil contents which can approach 40%. Researchers in Canada recently reported the development of experimental lines of B. juncea which produce canola quality seed. Commercial cultivars of oilseed B. juncea should be available within three to five years (Love et al. 1990). Incorporation of these quality characteristics into adapted accessions could allow rapid development of oilseed cultivars adapted to the northern United States.
The rapeseed program at the University of Idaho will continue to evaluate accessions of both B. hirta and B. juncea for both agronomic potential and oilseed quality over the next few years. Lines with promising characteristics will be hybridized and segregating lines selected for both agronomic potential and oilseed quality. The development of improved cultivars which combine high seed yield potential with specific fatty acid composition and low levels of glucosinolates would allow expanded production of spring planted Brassica species as oilseed crops across the Pacific Northwest.
|Seed yield (Mg/ha)||Oil content (%)||Seed weight (g/100)|
|B. hirta Moench. |
(white or yellow mustard)
|B. carnita A. Braun |
|B. nigra (L,) Koch |
|B. juncea (L.) Cross |
(brown, Oriental, or Indian mustard)
|Eruca sativa L. |
|B. tournefortii (Gouan) |
|B. campestris L. |
(birdsrape mustard or Polish rape)
|LSD (P = 0.05)||1.1||1.2||2.3||4.3||0.18||0.06|
|Flowering date Julian||Seed yield (Mg/ha)||Oil content (%)|
|CJ 86/Z||B. juncea||172||---||4.3||---||35.2||---|
|Common Brown||B. juncea||172||180||4.1||1.5||34.0||30.8|
|CW 89 TY||B. hirta||170||180||3.9||1.7||30.9||23.1|
|Lethbridge 22-A||B. juncea||170||177||3.7||1.4||35.5||31.1|
|LSD (P = 0.05)||1.8||1.8||0.4||0.4||2.4||0.8|