Spring Canola Cultivars Research Articles

Evaluation of the Relationships among Yield and Related Traits in Spring Canola Cultivars using Path Analysis

Evaluation of the Relationships among Yield and Related Traits in Spring Canola Cultivars using Path Analysis

Canola integration into semi-arid wheat cropping systems of the inland Pacific Northwestern USA

The inland Pacific Northwestern USA (iPNW) wheat-producing region has a diversity of environments and soils, yet it lacks crop diversity and is one of the few semi-arid wheat-growing regions without significant integration of oilseeds. Four major agroecological zones, primarily characterised by water availability, feature distinctly different fallowed and annually cropped systems, each presenting different challenges and opportunities to integrate winter and spring canola. Although major interests in regional energy crops and rotational diversification spurred feasibility research on iPNW canola food, feed and fuel production in the 1970s, commercial canola adaptation has lagged behind other semi-arid wheat regions for various socioeconomic, ecophysiological and agronomic reasons. New federal crop insurance policies will reduce economic risks in new crop adaptation, and oilseed processing facilities are creating new local markets. Although canola management largely relies on wheat farm equipment, agronomic approaches require strategic adjustments to account for physiological differences between canola and cereals including seed size, seedling morphology and responses to temperature extremes. Climate change predictions for the region threaten to exacerbate current hot and dry summers and research aims to develop and adapt flexible winter and spring canola-based systems to regional water and temperature stressors in each zone. Adaptation will require novel planting, fertilisation and weed control strategies to successfully establish improved winter canola cultivars in hot dry summers that survive cold winters, and spring canola cultivars direct-seeded in cool wet springs. The adaptation of winter and spring canola will somewhat mirror the rotational placement of winter and spring cereals within each zone. Economic analysis of oilseed break crop benefits such as weed and disease control will help to demonstrate the medium-term economic benefits of crop diversification to support the growth of a regional canola industry in the iPNW.

Evaluation of drought tolerance some of spring canola cultivars (Brassica napus L)

Evaluation of drought tolerance some of spring canola cultivars (Brassica napus L)

Growth, recovery, and yield of dual-purpose canola (Brassica napus) in the medium-rainfall zone of south-eastern Australia

The effect of grazing of vegetative canola (Brassica napus) with sheep on crop growth and yield was investigated in two field experiments (Expts 1 and 2) in 2008 at Wagga Wagga, New South Wales, Australia. The experiments included a range of cultivars, sowing rates, and grazing periods to investigate the influence of these factors on grazing biomass, crop recovery, and grain yield. Three spring canola cultivars (representing triazine-tolerant, conventional, and hybrid types) were used in both experiments and were sown at three sowing rates and grazed by sheep for 7 days in midwinter in Expt 1, while two different grazing periods were compared in Expt 2. Supplementary irrigation was applied to Expt 1 to approximate average growing season conditions, while Expt 2 received no irrigation. Increased sowing rate produced greater early shoot biomass for grazing, but the-triazine tolerant cultivar produced less biomass than the conventional or hybrid cultivars in both experiments. Grazing reduced dry matter and leaf area by >50%, delayed flowering by 4 days on average, and reduced biomass at flowering by 22–52%. However, there was no impact of cultivar or sowing rate on the recovery of biomass and leaf area after grazing. Grazing had no effect on final grain yield under supplementary irrigation in Expt 1, but reduced grain yield under the drier regrowth conditions in Expt 2. The results demonstrate that grazing canola is feasible under average seasonal conditions in a medium-rainfall environment (400–600 mm) without yield penalty, provided the timing and intensity of grazing are matched to available biomass and anticipated seasonal water supply to support grain production. More broadly, we suggest that grain yield reductions from grazing could be avoided if suitable conditions for regrowth (residual dry matter, length of regrowth period, and adequate moisture) can generate biomass levels in excess of a target value of ~5000 kg ha–1 at flowering. This target value represents a biomass level where >90% of photosynthetically active radiation was intercepted in our study, and in other studies represents a biomass level above which there is little further increase in potential yield. Such a target provides a basis for more objective grazing management but awaits further confirmation with experimentation and modelling.

Refining crop and livestock management for dual-purpose spring canola (Brassica napus)

Dual-purpose canola (Brassica napus) describes the use of a canola crop for grazed winter forage before seed production, a practice that has only recently been developed in southern Australia. Long-season winter canola has been grazed without yield penalty in higher rainfall zones of Australia (>650 mm) and the USA, but the potential areas are small. The feasibility to graze spring canola varieties across wider areas of the medium-rainfall (450–650 mm), mixed-farming zone in Australia is therefore of interest. We conducted a series of six field experiments involving a range of canola cultivars and grazing management and agronomy systems from 2007 to 2009 at Young in southern New South Wales, Australia, to determine the feasibility of and refine the principles for grazing dual-purpose spring canola without significant yield penalty. Mid-season, Australian spring canola cultivars including conventional and hybrid varieties representing a range of herbicide tolerance (triazine-tolerant, Clearfield®, and Roundup Ready®) were sown from 16 April to 12 May and grazed with sheep at a range of growth stages from early vegetative (June) to mid-flowering (September). In general, early-sown crops (sown mid-April) provided significant grazing (~800 dry sheep equivalent grazing days/ha) in winter before bud elongation, and recovered with no impact on grain yield or oil content. As previously reported, yield was significantly reduced (by up to 1 t/ha) when grazing occurred after buds had elongated (late July), due to the delayed flowering associated with bud removal by sheep and insufficient time for biomass and yield recovery. However, yield was also reduced in crops grazed before bud elongation if insufficient residual biomass remained (<1.0 t/ha for late July lock-up) to facilitate crop recovery even when there was little delay in crop development. We suggest that refinements to the existing ‘phenology-based’ grazing recommendations would assist to avoid yield loss in grazed spring varieties, and propose three grazing stages (safe, sensitive, and unsafe) that integrate the impacts of time, crop growth stage, residual biomass, and seasonal conditions to avoid yield loss under different circumstances. Such refinements to reduce the likelihood of grazing-induced yield loss would provide more confidence for mixed farmers to maximise the benefits from dual-purpose canola in different environments. Based on the outcomes of these experiments, dual-purpose spring canola is likely to have significant potential for wider application in other mixed farming zones, with similar region-specific refinements based on the principles reported here.

STUDIES ON DIFFERENTIAL RESPONSE OF SPRING CANOLA CULTIVARS TO BORON TOXICITY

Although many states recommend boron (B) fertilizer for many field crops, information about B toxicity of canola is lacking. This experiment was carried out at Central Anatolia, Turkey from 2002 to 2003, to determine genotypic range in B efficiency of eight spring canola cultivars, to identify the B-inefficient cultivars and to identify specific responses. The cultivars were grown under B moderate deficiency (extractable B 0.56 mg kg−1) and toxic B applied (15 kg B ha−1) conditions. According to the results, seed yield varied significantly among the cultivars and B application decreased the seed yield by 31% on average. Also, toxic B application reduced protein and oil contents similar to seed yield, and increased leaf B concentration in all varieties. This study has shown that leaf B concentration has increased considerably when B is applied to Pactol and Star cultivars, but seed yield of +B and −B has not shown significantly a change. It is possible to say that Star and Pactol—which have not been affected by the toxic B application—are genotypes that are tolerant to B toxicity and may be cultivated at B toxic lands.

Reproductive phenology of transgenicBrassica napuscultivars: Effect on intraspecific gene flow

Pollen-mediated gene flow in space is well documented and isolation distances are recommended to ensure genetic purity of Brassica napus seed crops. Isolation in time could also contribute to gene flow management but has been little investigated. We assessed the effects of asynchronous and synchronous flowering on intraspecific B. napus gene flow by seeding adjacent plots of transgenic spring canola cultivars, either resistant to glyphosate or glufosinate, over a 0-4 week interval and measuring outcrossing rates and seed-set. Outcrossing rates, evaluated in the center of the first adjacent row, were reduced to the lowest level in plots flowering first when the seeding interval > 2 weeks. Increasing the time gap increased outcrossing rates in plots flowering second up to a seeding interval of two weeks. Flowers that opened during the last week of the flowering period produced fewer seed (< 10% of total seed production) and a smaller fraction of outcrossed seed (-25%). Observed time gap effects were likely caused by extraneous pollen load during the receptivity of productive seed-setting early flowers. Clearly, manipulation of B. napus flowering development through staggered planting dates can contribute to gene flow management. The approach will need to be validated by additional site-years and increased isolation distances.

EFFECTS OF ROW SPACING AND SEEDING RATES ON SOME AGRONOMICAL TRAITS OF SPRING CANOLA (BRASSICA NAPUS L.) CULTIVARS

The objective of the study was to evaluate the effects of row spacing and seeding rates on agronomical traits of three spring canola (Brassica napus L.) cultivars in Iran during 2003-2004. Traits evaluated were plant height, number of seeds pod-1, number of pods main stem-1, number of pods plant-1, 1000-seed weight, seed yield, and seed oil content. The experimental lay-out was split-split plot based on randomized complete block design with 4 replications. 3 row spacing of 12, 18 and 24 cm constituted the main plot, 2 seeding rates of 4 and 6 kg ha-1 as split plot and 3 spring canola cultivars of Hyola 401, Hyola 60 and RGS-003 (lately-used hybrid, new hybrid and new cultivar, respectively) comprised the split-split plot. Results showed that the highest seed yield was obtained at 12 cm row spacing, followed by 7.4% reduction in seed yield as row spacing increased to 24 cm. An increase in seeding rates from 4 to 6 kg ha-1 resulted in a decrease in number of pods plant-1 but other traits were not influenced. The highest number of pods plant-1 was obtained by applying 4 kg ha-1 seeding rates. The hybrid Hyola 401 had better performance than two other cultivars in plant height, number of grains pod-1, number of pods main stem-1, seed yield and seed oil content. The interaction of row spacing × seed rates and also row spacing × cultivars were significant only for the number of pods main stem-1. The lowest one was obtained at 12 cm row spacing with 6 kg ha -1 seed rates. RGS-003 at 12 cm row spacing showed the highest number of pods main stem-1, statistically equal to Hyola 401 grown at 24 cm row spacing.

Nitrogen Utilization Efficiency in Canola Cultivars at Grain Harvest

Canola (Brassica napus L.) cultivars with improved nitrogen utilization efficiency (NUE) at grain harvest are of interest to growers to reduce fertilizer inputs. Our objective was to determine whether cultivar-specific responses in NUE (seed yield per N accumulated in the whole plant) could be related to the differences in dry matter and N partitioning among various plant parts. Four spring canola cultivars were grown in a glasshouse under the conditions of low and high N supply. When compared to high-N treatment, deficient N conditions resulted in a similar decrease in dry weight for all cultivars, averaging 46% for shoot, 47% for root, and 45% for dropped leaves. The reductions in N concentrations at low-N compared to high-N treatment were much smaller and averaged 15% for shoot, 16% for root and 10% for dropped leaves. Although significant variations occurred for dry weight, N concentration and N uptake in various plant sections, all cultivars accumulated a similar amount of N in total plant biomass at harvest. However, significant differences in plant biomass, seed yield and consequently, NUE existed because more N-efficient cultivars Eyre and Charlton produced larger seed yields than less N-efficient cultivars Pinnacle and Rainbow. No consistent variations in N concentration in various plant parts could be established among tested cultivars. Thus, cultivar-specific responses in NUE were mainly attributed to the differences in the root-to-shoot ratio and harvest index. N-efficient Eyre produced seed yield similar to the highest yielding Charlton, though it had the smallest plant dry weight of all cultivars. In contrast, N-inefficient Rainbow had the largest plant biomass, but produced the smallest seed yield because of its lowest harvest index and the highest root-to-shoot ratio. The absence of cultivar×N treatment interactions indicated that cultivars performed similarly for plant biomass, N uptake and seed yield across two contrasting N supplies. Canola cultivars significantly differed in NUE despite a similar amount of absorbed N in plant biomass; more N-efficient cultivars outyielded less N-efficient ones primarily because of cultivar-specific variations in the root-to-shoot ratio and harvest index.

Canola cultivars differ in nitrogen utilization efficiency at vegetative stage

Previous research indicated genotype-specific responses in nitrogen utilization efficiency (NUE) for oilseed rape ( Brassica napus L.), but mechanisms behind those differences are unknown. Our objective was to determine whether cultivar variations in NUE (dry matter production per unit of N absorbed) could be related to the differences in N and nitrate uptake and partitioning. Four Australian spring canola cultivars (Eyre, Charlton, Pinnacle and Rainbow) were grown in glasshouse under conditions of low- and high-N supply. All cultivars were at the same growth stage when harvested 60 days after sowing (rosette stage with five leaves at low-N supply and nine leaves at high-N supply). Cultivars significantly differed in total N uptake in roots and shoots, but not when the whole plants were considered. Although all cultivars had similar total N uptake per plant, significant differences in NUE existed because of differences in plant biomass. N-efficient cultivars Charlton and Rainbow produced larger plant biomass and had lower N concentration in various aboveground plant parts (including dead leaves) than N-inefficient cultivars Pinnacle and Eyre. Nitrogen concentration in roots did not differ significantly among cultivars. Regardless of N supply, N concentrations in various plant parts were in the order: young blades > old blades > roots > young petioles > stems > old petioles > dead leaves. No significant variation in nitrate-N concentration in roots or various aboveground plant parts was found among tested cultivars. The absence of cultivar × N treatment interaction for plant dry weight, N concentration, N uptake, and consequently NUE, clearly indicated that cultivars that performed best at high-N supply also showed similar responses under N-deficient conditions. Despite similar total N uptake per plant, significant differences in NUE existed because more N-efficient cultivars produced larger plant biomass and tended to have lower N concentrations in all plant parts (except roots) compared with less N-efficient cultivars.

Physiological and Harvest Maturity of Canola in Relation to Seed Quality

The ability to identify physiological (PM) and harvest maturity (HM) of canola (Brassica napus L.) by phenological characteristics would permit timely harvest to avoid problems of both under‐ and overripe pods. This study was conducted to identify PM and HM of six winter and spring canola cultivars using morphological and physiological markers including seed and pod color, seed dry weight (DWT), seed moisture content (SMC), and to measure seed quality (germination and vigor) at PM and HM. Pods and seeds from each cultivar were sampled at weekly intervals from pod formation until HM. Standard germination, accelerated aging, and cold tests were conducted to assess seed quality. Canola attained PM when pods turned from green to greenish‐yellow or light brown, and contained seeds ranging from brownish green to greenish brown and light brown. The seeds were firm. Seed DWT did not change significantly from PM to HM. Seed MC at maximum DWT ranged from 203 to 360 g kg−1. Pods at HM were yellow to brown and the seeds were brown or dark brown to black, depending on the cultivar. The SMC was near 100 g kg−1 and the seeds were hard and rattled inside the pod. Seeds of all cultivars had greater germination and vigor at HM than at PM. Canola can be harvested 2 wk before reaching HM without affecting yield; however, SMC at this stage is not suitable for direct harvest and seed quality is not at the highest level.

Effects of Swathing on Yield and Quality of Spring Canola in Northern Idaho

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.

Inhibition of polygalacturonase activity produced by Leptosphaeria maculans by leaf extracts of canola and its relationship to calcium

Leptosphaeria maculans, the causal agent of blackleg of canola, produces several cell-wall-degrading enzymes, including polygalacturonases, during infection. Extracts of leaves from spring canola cultivars inhibited the polygalacturonase activity produced by a highly virulent isolate of L. maculans. Polygalacturonase inhibitory activity was present in cotyledons and leaf tissue from spring canola cultivars. The level of polygalacturonase inhibitory activity in leaf extracts was significantly correlated to the resistance of the canola cultivars to L. maculans as measured by a cotyledon disease assay. The polygalacturonase inhibitory activity was not affected by autoclaving or protease digestion, but it was decreased by dialysis and the addition of ethylenediaminetetra-acetic acid, suggesting that the polygalacturonase inhibitor was not a protein, but was a low molecular weight, heat stable compound(s) that was affected by the chelation of divalent cations by ethylenediaminetetra-acetic acid. Calcium levels in leaf extracts from different cultivars were significantly positively correlated to the level of polygalacturonase inhibitory activity and the resistance of the cultivars to L. maculans. The possible roles of calcium in the resistance of canola to cell wall degradation is discussed. This is the first report of a polygalacturonase inhibitory material in canola tissue.