|
|
|
|
|
|
|
||
|
|
||
|
|||
2000 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. INTERIM REPORT: Year 1 report of project started in 1999 PROJECT OBJECTIVES:
KEY WORDS: canola, mustard, genotype x tillage interac STATEMENT OF PROBLEM 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: Genotype x tillage interactions was examined in four spring Brassicaceae species (B. napus, B. rapa, B. juncea and S. alba). Significant reductions in yield were observed in all four species when direct seeded compared to conventional seeding. Greatest reductions were found where land had previously been in conventional tillage systems. Greatest genotype x tillage interactions was found in yellow mustard (S. alba) and least in canola (B. napus). In mustard species, the most adapted lines sited to direct seeding were not the most adapted to conventional tillage. The results suggest that advances will be made in direct seeded cultivars if they are selected specifically for such tillage 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 three locations, 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 thirty eight canola cultivars (B. napus), sixteen oriental mustard genotypes (B. juncea) and 10 yellow mustard cultivars (S. alba) were grown at 5 locations under direct seed and conventional seed conditions. Four species experiment Averaged over all species, seed yield from direct seeding was significantly reduced (approximately 10%) compared to conventional seeding (Table 1). There was significant species x seeding treatment interaction whereby B. napus and B. rapa yield in the two seed situations were not significantly different, however, the two mustard species (B. juncea and S. alba) showed significant yield loss when direct seeded. This result was unexpected, as past experience had shown that the mustard species (especially S. alba) had show good adaptation to direct seeding. Averaged over both treatments, highest yield was obtained from B. juncea and lowest yield from S. alba, while the two canola species (B. napus and S. alba) were not significantly different. It should be noted that the three sites were chosen to represent one site (Nezperce) which had been under a direct seed system for many years (16 years), one which has been under a direct seed system for four years (Davenport) and the other (Genesee) which had been conventionally seeded until this experiment. A highly significant interaction was observed between sites and seeding treatment (Table 2). At Nezperce (long-term direct seeding), all four species produced significantly higher seed yield from direct seeding compared to conventional tillage and seeding. Conversely, at the other two sites the conventional seeding was more productive. Direct seed resulted in an average 19% and 32% yield loss in direct seeded plots at davenport and Genesee, respectively. Therefore, as might be expected, the benefits for direct seeding Brassica crops increases with years into a direct-seeding system. Greater work will be necessary to allow farmers to overcome any potential yield loss that occurs in the transition period in getting the full benefits of direct seeding systems. Despite the overall yield reduction under direct seeding, the relative performance of the four species, cultivars within species, was constant (Figure 1). However, even with very few cultivars within species, there were changes in relative rank. The B. rapa, cultivars ranked identically under both seeding treatments. In B. napus the highest yielding line ('Hyola.401') under direct seeding was the highest yielding under conventional seeding. However, the second highest yielding canola cultivar ('Sunrise') was ranked last under direct seeding. Similarly, there were changes in relative performance in both mustard species. Regional cultivar testing A similar trend was noted when entries in the Pacific Northwest Canola Variety Trial, and the Pacific Northwest Mustard Variety Trial under conventional and direct-seed situations (Table 3). With the exception of Nezperce (same farm as noted above), all locations showed yield reductions under direct seeding compared to conventional seeding. The greatest limitation in cultivar development is genotype x environment interaction. If cultivar relative performance can be predicted in one environment and that performance is highly related to another, then greatest progress will be made. For example, if performance under conventional tillage is highly related to direct-seeding, then plant breeders need only test breeding lines in one of the systems and the "better" lines can be identified for both. The performance of cultivars under the different treatments can be examined using correlation, higher correlation coefficients between yield from different environments will indicate low genotype x environment interaction, while low correlation coefficient values indicate high interactions and would question selection under one environment to identify cultivars suitable for the other. Correlation coefficients were obtained between all 10 environments in this study (5 locations, each with direct seeded and conventionally seeded plots). Correlation coefficients were averaged for each species according to: (1) between direct seeding and conventional seeding at the same site; (2) between conventional seeding at different sites; (3) between direct-seeding at different sites; and (4) between direct seeding at one site and conventional seeding at another. The average correlation coefficients are shown in Table 4 for each of the three species examined. In general, correlation coefficients for yield between different environments were high for canola, intermediate to high in oriental mustard, and low for yellow mustard. Correlation coefficients for yield between seeding treatments at the same sites were significant for canola and oriental mustard (accounting for 20% and 25% of the total variation in yield in canola and oriental mustard, respectively). Greater genotype x environment interactions was detected in oriental mustard between conventional seeding at different sites that direct seeding at different sites. High correlation between treatments would reduce relative changes in cultivar ranking. Amongst the 38 canola lines tested the top 5 yielding lines under conventional seeding were ranked amongst the top 5 under direct seeding (Table 5). Similarly, in oriental mustard, a reasonable relation existed between performances of the "better" lines under conventional and direct seeding. However, the relationship was not absolute, and the 3rd and 4th ranked cultivars under direct seeding, were ranked 7th and 8th when conventially seeded. As might have been expected for the low correlation between environments in yellow mustard, there was little relationship between performances of cultivars under direct seeding compared to conventional seeding. 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 and direct seeding.
Figure 1. Yield of four cultivars within each of four Brassica species when grown after conventional seeding and direct seeding.
|
||||
 Contact
us: Hans Kok, (208)885-5971
|
Accessibility | Copyright
| Policies | WebStats | STEEP Acknowledgement |
||||
