Denis Pageau

The Frequency and Persistence of Volunteer Canola (Brassica napus) in Quebec Cropping Systems

The presence of volunteer canola is becoming a significant agro-ecological concern, given the large-scale use of herbicide-tolerant varieties in some areas. Our goal was to estimate the frequency and persistence of volunteer canola in Québec cropping systems by surveying fields that included a single canola crop since 1995. A survey was conducted in 131 fields in the main canola-growing areas of Québec: in the Saguenay-Lac Saint-Jean region and the Québec City–La Pocatière area. Volunteer canola plants were counted in 0.25-m2 quadrats every 10 m along a W pattern, and every 15 m along the margins of 88 fields. Volunteer canola plants were found in 90% of the fields surveyed and in a wide range of crops, including cereal, corn, and soybean. Average densities of 4.9 and 3.9 plants/m2 were found 1 yr after canola production in fields and field margins, respectively. Volunteer canola densities decreased significantly over time. However, volunteer plants were still present at low densities 4 and 5 yr after production. Dense stands of volunteer canola were found before postemergence herbicide application in no-till fields (9.8 ± 4.1 plants/m2), suggesting that, contrary to what was suggested in the literature, seeds could become dormant in no-till as well as in tilled systems. A small proportion of the volunteer canola plants observed in no-till fields near Québec City and Ottawa included plants that had overwintered, either originating from fall-germinated seedlings, harvested adult plants that had grown new leaves before the onset of winter, or spring regrowth from the base of unharvested adult plants from experimental plots. The presence and persistence of low densities of volunteer canola may not have been a cause of concern until now. However, producers should be made more aware of the potential short-and long-term problems associated with potential gene flow between different herbicide-tolerant canola (HT canola) varieties and also between HT canola and related weed species. Nomenclature: Canola, Brassica napus L.; corn, Zea mays L.; soybean, Glycine max (L.) Merr. Additional index words: Herbicide-tolerant canola, oilseed rape, weed survey. Abbreviations: HT, herbicide-tolerant (canola).

Impact de l’hernie des crucifères [Plasmodiophora brassicae] sur la productivité et la qualité du canola

Clubroot, a disease caused by Plasmodiophora brassicae, first appeared in canola fields in Quebec in 1997. The objective of this project was to assess the impact of a soil infested with P. brassicae on the productivity and grain quality of canola. In 1998 and 1999, 31 cultivars in total (23 of Brassica napus in 1998 or 25 of B. napus in 1999 and 6 of Brassica rapa) were evaluated. In 2000, 25 cultivars and two lines (70584 et 70585) of B. napus and 6 cultivars of B. rapa were tested. These cultivars or lines were sown on a soil where P. brassicae had been prevalent for a few years and on another soil which had never been sown with a cruciferous crop before. The soil infested with P. brassicae reduced canola productivity. Grain yield losses were 80%, 91%, and 85% in 1998, 1999, and 2000, respectively, for the Argentine cultivars (B. napus). In the Polish cultivars (B. rapa), yield losses were 69%, 96%, and 89%, respectively, for the same years. Clubroot also reduced straw yield, oil content of the grain, and the grain mass. As opposed to overall B. napus cultivars, the two lines of B. napus appeared to be resistant to clubroot in 2000. Grain yields of these two lines were not affected by the disease. Since there is no registered canola cultivar tolerant or resistant to clubroot in Quebec, agronomic practices used to prevent or reduce the incidence of the disease should be encouraged.

Crop rotation, cultivar resistance, and fungicides/biofungicides for managing clubroot (Plasmodiophora brassicae) on canola

Abstract Select biofungicides and fungicides, used alone or with cultivar resistance or crop rotation, were assessed for their potential in integrated management of clubroot disease. The synthetic fungicides pentachloronitrobenzene, fluazinam and cyazofamid showed activities against Plasmodiophora brassicae. The biofungicides Serenade® and Prestop® also suppressed the disease on canola via antibiosis and induced host resistance under controlled-environment conditions. Granular and seed-treatment formulations were developed to facilitate the delivery of biofungicide in field trials. Where P. brassicae resting spore populations were large in the soil, neither biofungicides nor synthetic fungicides were sufficiently effective when applied in the seed furrow. They occasionally reduced clubroot severity on Chinese cabbage. More than 5000 soil microbial isolates indigenous to the Canadian prairies were screened for potential clubroot control, but none showed consistent efficacy. Resistant cultivars reduced clubroot severity and canola yield losses significantly. A 2-year break from canola reduced P. brassicae resting spore concentrations by 90% relative to growing continuous canola or only a 1-year break in heavily infested field plots. This 2-year break alleviated disease impact on plant growth and development in a susceptible canola cultivar. Despite the substantial inoculum reduction after 2 years, the levels were still too high to obtain commercially acceptable yields in a susceptible cultivar. In a resistant cultivar, >2-year breaks increased yields by up to 25% relative to continuous growing of canola. A 2-year interval with non-hosts between canola crops, together with use of resistant cultivars, is recommended to reduce the inoculum load of P. brassicae in soil and achieve maximum yields of canola.

Soybean Tocopherol Concentrations Are Affected by Crop Management

Soybeans are an important source of tocopherols, which have health-beneficial properties. Previous studies have demonstrated that environmental factors may affect soybean tocopherol concentrations; the impact of specific crop management strategies, however, remains poorly understood. Experiments were conducted for 2 years at three sites in Quebec to determine the impact on soybean tocopherol concentrations of seeding rate, row spacing, seeding date, cultivar, and P and K fertilization. Total and alpha-, gamma-, and delta-tocopherol concentrations were determined by high-performance liquid chromatography. Overall, alpha-tocopherol was the most responsive to the factors evaluated; the response of other tocopherols was often lower or inconsistent across environments. The seeding rate affected alpha-tocopherol concentrations in three out of five environments; seeding at a rate of 40 seeds m(-2) resulted in 4% higher concentrations than seeding at a higher rate. Wide row spacing (more than 36 cm) resulted in two out of five environments in 6% higher alpha-tocopherol concentrations as compared to narrower row spacing. The seeding date had a greater impact; mid- to late-May seeding across four environments resulted in 45% greater alpha-tocopherol concentrations than seeding at later dates. Phosphorus and K fertilization had a negligible impact on tocopherol concentrations. Across experiments, large differences were observed between environments; plants grown in northern environments consistently had lower concentrations of alpha- and gamma-tocopherols but higher concentrations of delta-tocopherol. Differences between cultivars were also consistent, ranging between 10 and 30%, depending on the tocopherol. Results demonstrate that soybean tocopherol concentrations are affected by crop management and thus suggest that specific recommended agronomic practices may need to be established for the production of soybeans for the functional food market.

Diverse Rotations and Optimal Cultural Practices Control Wild Oat (Avena fatua)

Abstract In western Canada, more money is spent on wild oat herbicides than on any other weed species, and wild oat resistance to herbicides is the most widespread resistance issue. A direct-seeded field experiment was conducted from 2010 to 2014 at eight Canadian sites to determine crop life cycle, crop species, crop seeding rate, crop usage, and herbicide rate combination effects on wild oat management and canola yield. Combining 2× seeding rates of early-cut barley silage with 2× seeding rates of winter cereals and excluding wild oat herbicides for 3 of 5 yr (2011 to 2013) often led to similar wild oat density, aboveground wild oat biomass, wild oat seed density in the soil, and canola yield as a repeated canola–wheat rotation under a full wild oat herbicide rate regime. Wild oat was similarly well managed after 3 yr of perennial alfalfa without wild oat herbicides. Forgoing wild oat herbicides in only 2 of 5 yr from exclusively summer annual crop rotations resulted in higher wild oat density, biomass, and seed banks. Management systems that effectively combine diverse and optimal cultural practices against weeds, and limit herbicide use, reduce selection pressure for weed resistance to herbicides and prolong the utility of threatened herbicide tools. Nomenclature: Wild oat, Avena fatua L.; alfalfa, Medicago sativa L.; barley, Hordeum vulgare L.; canola, Brassica napus L.; wheat, Triticum aestivum L.

How many test locations and replications are needed in crop variety trials for a target region

How many test locations and replications are needed in crop variety trials is a question every plant breeder has to ask. Simple formulas were developed to estimate the optimum number of replicates and test locations. The optimum number of replicates in a trial was estimated by the formula

Oat mega-environments and test-locations in Quebec

{\text{N}}_{{\text{r}}} {\text{ = 3}}\left( {\sigma _{\epsilon }^{{\text{2}}} /\sigma _{{\text{g}}}^{{\text{2}}} } \right)

Sustainable cereal and forage production in dairy-based cropping systems

Nr= 3σϵ2/σg2, where