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2001 STEEP III Progress ReportRESEARCH PROJECT TITLE: Identifying superior Brassica species and cultivars within species that are suitable for direct seeding throughout the Pacific Northwest region. INVESTIGATORS:
Jack Brown and Donald J. Wysocki, PSES, University of Idaho, Moscow, ID
83844-2339, Tel.: (208) 885-7078, e-mail: jbrown@uidaho.edu
and CSS, Oregon State University, Columbia Basin Agricultural Research
Center, Pendleton OR 97801, Tel: (541) 278-4188, e-mail: wysocki@ccmail.orst.edu.
PROJECT OBJECTIVES
KEY WORDS: canola, mustard, genotype x tillage interactions STATEMENT OF PROBLEMS TO BE ADDRESSED Rainfall in the Pacific Northwest can vary from high (> 20 inches annually) to low (<8 inches annually), and the traditional cropping systems have been winter wheat/summer fallow and wheat/barley/legume rotations. Predominance of monoculture cereal production in these regions over the past 100 years has resulted in a buildup of soil-borne diseases. As a result, farmers have shown increased interest in annual cropping systems and advantages of Brassica crops have induced growers to include them in their crop rotation. At present, growers in the Pacific Northwest region have the option of planting one, or more, of four different spring-planted Brassica species: canola, or rapeseed (from either Brassica napus or B. rapa), yellow mustard (Sinapis alba) or oriental mustard (B. juncea). From the four species available, B. napus is least heat and drought tolerant, followed by B. rapa, and B. juncea, with S. alba showing greatest adaptability to driest regions. Genotype by environment interaction is in some way involved in most problems associated with quantitative genetics and all problems in plant breeding. It is difficult to believe that a change from conventional tillage to direct seeding systems will not be associated with some degree of cultivar by seeding system interaction. To identify the most appropriate spring Brassica species from different regions throughout the Pacific Northwest and to select the most productive cultivars from within each species will require a more detailed description of cultivar response to direct seeding. AGRONOMIC ZONE OF INTEREST: Annual cropping, low, intermediate and high rainfall, non-irrigated ABSTRACT OF RESEARCH FINDINGS The yield potential of cultivars and advanced breeding lines from four Brassica species were examined under direct seeding and conventional tillage systems. All species showed a significant yield reduction when direct seeded, most likely due to later planting and greater weed competition. Results showed that canola cultivar yield under conventional tillage was a good indicator as to performance under direct seeding. In contrast, yellow mustard yield under the two tillage systems was relatively different. It is recommended that Brassica genotypes need to be evaluated under direct seeding and conventional tillage systems to ensure that the most adapted cultivars need to be identified to best suit different management systems. RESULTS AND INTERPRETATION Two separate, but related trials were conducted: (1) Four species experiment, where four cultivars from each of four different Brassica species (B. napus, B. rapa, B. juncea, and S. alba) were grown in an split-plot design at four locations (Moscow ID, Genesee ID, Nez Perce ID, and Davenport WA), where main-plots were seeding treatment (direct v conventional) and species, and cultivars within species were sub-plots and sub-sub-plots respectively; (2) Regional cultivar testing, where twenty eight canola cultivars (B. napus), 9 oriental mustard genotypes (B. juncea) and 11 yellow mustard cultivars (S. alba) were grown at the same 4 locations under direct seed and conventional seed conditions. Four species experiment Seed yield from direct seeded plots were significantly lower than yield from conventionally tilled plots (Table 1). Greatest yield reduction was found in the B. napus (canola) cultivars (33%) and least difference noted in the S. alba (yellow mustard) cultivars (19%). The difference between direct seeded and conventional tillage varied markedly at the different sites. Yield from both tillage treatment were very similar at the Moscow location while the direct seed yield was half that from conventional tillage at Nez Perce (Table 2). The relative performance of the cultivars and species under different tillage systems was similar (Figure 1). The oriental mustard (B. juncea) cultivars proved to be most adapted to either tillage system and were always highest yielding. Regional cultivar testing A similar pattern in treatment effects was noted in the Regional Trial results. The B. napus (canola) cultivars appeared most responsive to direct seeding (Table 3). Averaged over all cultivars, direct seed yield was more than 23% reduced compared to conventional tillage. As with the four species experiment, the yellow mustard cultivars were only slightly lower yielding under direct seeding compared to conventional tillage (11% reduction). The oriental mustard cultivars were intermediate in response with a 19% yield reduction in direct seeded plots. The relationship between performance under the two tillage systems was examined by correlation (Table 4). Overall, the performance of the canola cultivars was relatively similar irrespective of location and tillage management, where performance under conventional tillage provided a good indication as to performance in a no tillage system. The correlation between average yield in both systems was very high (r = 0.91). Indeed four of the top yielding canola cultivars under conventional tillage were amongst the top five lines when direct seeded (Table 5). The good relative relationship between canola yield under the two systems can be seed graphically in Figure 2. The correlation between conventional and direct seeding for oriental mustard (B. juncea) was lower than for the canola, but in most cases was highly significant. Similarly, performance under conventional seeding was a reasonable indicator to performance under direct seeding (Figure 3), where average yield in both systems was correlated at r= 0.83. In contrast, performance of yellow mustard cultivars under conventional tillage provided little indication as to the yield potential when direct seeded. Although only 11 lines were evaluated the five highest yielding lines under conventional tillage included only two of the top five yielding lines when direct seeded. Although the advanced breeding line 'UI.3277', was highest in yield in both tillage systems (Figure 4) there were large relative differences in yield potential of yellow mustard lines in the different management systems (r = 0.39). Overall, there is some indication that the 'better' canola lines under direct seeding can be identified by evaluation of genotypes under conventional tillage systems. It should, however, be noted that the primary character of interest when determining canola line adaptability is early flowering (to avoid head damage). Early flowering under direct seeding would be equally important (or more so) as planting in a direct seed system can often be delayed compared to conventional seeding. Oriental mustard is less sensitive to heat damage and yellow mustard is relatively tolerant to heat so the later seeding under direct seeding is not so influenced by cultivar flowering time. It is therefore concluded that cultivars need to be evaluated and selected for adaptation to different tillage systems in order to ensure cultivars with greatest adaptability to differing management practices. Table 1. Average seed yield of four Brassica species grown under direct-seed and conventional seed situations.
Table 2. Average seed yield over four species, and three sites direct seeded and conventional seeded.
Table 3. Average seed yield of three Brassica species at five sites direct seeded and conventionally seeded.
Table 4. Average correlation coefficient for seed yield between: (1) direct seeded and conventional seeding at the same site; (2) direct seeding at different sites; (3) conventional seeding at different sites; and (4) direct seeding and conventional seeding at different sites, of three Brassica species.
Table 5. Relative ranking of yield of top 5 canola, oriental mustard and yellow mustard lines under conventional tillage (Conv.) and direct seeding (Direct).
Figure 1. Yield of four cultivars within each of four Brassica species when grown after conventional seeding and direct seeding.
Figure 2. Yield of 28 spring canola cultivars grown under conventional tillage and direct seeded into cereal straw.
Figure 3. Yield of 9 oriental mustard cultivars grown under conventional tillage and direct seeded into cereal straw.
Figure 4. Yield of 11 yellow mustard cultivars grown under conventional tillage and direct seeded into cereal straw.
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