T. Kelly Turkington

Integrating Cropping Systems with Cultural Techniques Augments Wild Oat (Avena fatua) Management in Barley

Abstract Wild oat causes more crop yield losses and accounts for more herbicide expenditures than any other weed species on the Canadian Prairies. A study was conducted from 2001 to 2005 at four Canadian Prairie locations to determine the influence of repeated cultural and herbicidal management practices on wild oat population density, biomass, and seed production, and on barley biomass and seed yield. Short or tall cultivars of barley were combined with normal or double barley seeding rates in continuous barley or a barley–canola–barley–field-pea rotation under three herbicide rate regimes. The same herbicide rate regime was applied to the same plots in all crops each year. In barley, cultivar type and seeding rate were also repeated on the same plots year after year. Optimal cultural practices (tall cultivars, double seeding rates, and crop rotation) reduced wild oat emergence, biomass, and seed production, and increased barley biomass and seed yield, especially at low herbicide rates. Wild oat seed production at the quarter herbicide rate was reduced by 91, 95, and 97% in 2001, 2003, and 2005, respectively, when tall barley cultivars at double seeding rates were rotated with canola and field pea (high management) compared to short barley cultivars at normal seeding rates continuously planted to barley (low management). Combinations of favorable cultural practices interacted synergistically to reduce wild oat emergence, biomass and seed production, and to increase barley yield. For example, at the quarter herbicide rate, wild oat biomass was reduced 2- to 3-, 6- to 7-, or 19-fold when optimal single, double, or triple treatments were combined, respectively. Barley yield reductions in the low-management scenario were somewhat compensated for by full herbicide rates. However, high management at low herbicide rates often produced more barley than low management in higher herbicide rate regimes. Nomenclature: Wild oat, Avena fatua L.; barley, Hordeum vulgare L.; canola, Brassica napus L.; field pea, Pisum sativum L.

Progress towards the Sustainable Management of Clubroot (Plasmodiophora brassicae) of Canola on the Canadian Prairies

Progress towards the Sustainable Management of Clubroot [Plasmodiophora brassicae] of Canola on the Canadian Prairies Stephen E. Strelkov, Sheau-Fang Hwang, Ronald J. Howard, Murray Hartman and T. Kelly Turkington University of Alberta, Edmonton, AB; Alberta Agriculture and Rural Development, Edmonton, AB, Alberta Agriculture and Rural Development, Brooks, AB; Alberta Agriculture and Rural Development, Lacombe, AB; Agriculture and Agri-Food Canada, Lacombe, AB Corresponding author E-Mail: stephen.strelkov@ualberta.ca

Diversity of Fusarium head blight populations and trichothecene toxin types reveals regional differences in pathogen composition and temporal dynamics

Analyses of genetic diversity, trichothecene genotype composition, and population structure were conducted using 4086 Fusarium graminearum isolates collected from wheat in eight Canadian provinces over a three year period between 2005 and 2007. The results revealed substantial regional differences in Fusarium head blight pathogen composition and temporal population dynamics. The 3ADON trichothecene type consistently predominated in Maritime provinces (91%) over the sampled years, and increased significantly (P<0.05) between 2005 and 2007 in western Canada, accounting for 66% of the isolates in Manitoba by the end of the sampling period. In contrast, 3ADON frequency was lower (22%, P<0.001) in the eastern Canadian provinces of Ontario and Québec and did not change significantly between 2005 and 2007, resulting in two distinct longitudinal clines in 3ADON frequency across Canada. Overall, genetic structure was correlated with toxin type, as the endemic population (NA1) was dominated by 15ADON isolates (86%), whereas a second population (NA2) consisted largely of 3ADON isolates (88%). However, the percentage of isolates with trichothecene genotypes that were not predictive of their genetic population assignment (recombinant genotypes) increased from 10% in 2005 to 17% in 2007, indicating that trichothecene type became an increasingly unreliable marker of population identity over time. In addition, there were substantial regional differences in the composition of recombinant genotypes. In western and maritime provinces, NA2 isolates with 15ADON genotypes were significantly more common than NA1 isolates with 3ADON genotypes (P<0.001), and the reverse was true in the eastern provinces of Québec and Ontario. Temporal trends in recombinant genotype composition also varied regionally, as the percentage of 15ADON isolates with NA2 genetic backgrounds increased approximately three fold in western and Maritime provinces, while the opposite trends were observed in Québec and Ontario. The results indicate that F. graminearum population dynamics in Canada have been influenced by a complex adaptive landscape comprising different regional selective pressures, and do not reflect a simple model of dispersal and integration following the introduction of a novel pathogen population. In addition, we identified F. graminearum strains that produce the recently discovered A-trichothecene mycotoxin (NX-2) for the first time in Canada, representing a significant expansion of the known range of NX-2 producing strains in North America.

Race structure of Pyrenophora triciti-repentis (tan spot of wheat) in Alberta, Canada

Abstract Tan spot is an important foliar disease of wheat caused by Pyrenophora tritici-repentis. Eight races of this fungus have been identified based on their virulence on a wheat differential set. Previous surveys revealed that most isolates collected from the Canadian Prairies belong to races 1 and 2 of P. tritici-repentis and carry the ToxA gene. However, pathogen populations from Alberta, a major wheat-producing province, have not been characterized. In this study, the virulence of 45 isolates of P. tritici-repentis from Alberta was evaluated on six differential wheat genotypes. Race 1 was found to be most common, representing 62% of the isolates tested, while race 2 was the second most common (36% of isolates). A single isolate of race 3 was also found (2% of total), but no other races were identified. Polymerase chain reaction and Southern blot analyses with ToxA and ToxB-specific primers and probes were conducted to confirm the race designations of the tested isolates. The ToxA gene was identified in each isolate classified as race 1 or race 2, but not in the race 3 isolate. Sequencing of ToxA from 16 isolates collected in different parts of the province revealed that the sequences were identical. The ToxB gene was not found in isolates classified as races 1 or 2, but a ToxB homologue was identified in the race 3 isolate. These results confirm that the P. tritici-repentis populations in Alberta follow the toxin or inverse gene-for-gene model, and serve to validate the race-based classification system for this pathogen.

Movement of Plasmodiophora brassicae resting spores in windblown dust

Abstract Clubroot (Plasmodiophora brassicae Wor.) of canola (Brassica napus L.) was first detected in Alberta, Canada, near Edmonton in 2003. Since that time it has become a severe problem in canola production, spreading throughout central Alberta, with isolated cases of the disease also identified in southern Alberta, Saskatchewan and Manitoba. Clubroot is believed to be spreading mostly via the movement of P. brassicae-infested soil on farm machinery. This study examined the potential for the spread of the pathogen in windblown dust from infested fields. Dust samplers were placed at four locations, three in central Alberta and one in southern Alberta, in 2011 and 2012. Soil particles in suspension and moving through saltation were collected in samplers at heights ranging from 0 to 1 m. Total genomic DNA was extracted from the collected soil samples and subjected to conventional polymerase chain reaction (PCR) and quantitative PCR analysis for the detection and quantification of P. brassicae in the samples. The DNA of P. brassicae was detected in samplers at all locations in both years. There was no clear association between sampling height and the frequency of samples testing positive for the presence of P. brassicae DNA, or between sampling height and the amount of P. brassicae DNA. The results indicate that P. brassicae resting spores can be carried by wind-borne dust and that wind-mediated dispersal likely contributes to spread of this pathogen.

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.

Effects of seeding rate, nitrogen rate and cultivar on barley malt quality

BACKGROUND Crop management tools have been shown to affect barley kernel size and grain protein content, but the direct effect on malt quality is not well understood. The present study investigated the effect of seeding rate, nitrogen fertilisation and cultivar on malt quality. RESULTS Higher seeding rates produced barley with less grain protein and smaller, more uniformly sized kernels. The small, uniformly sized kernels modified more completely, leading to malt with higher extract and lower wort β-glucan than malt from low-seeding-rate barley. Increasing rates of nitrogen fertilisation caused grain protein levels to increase, which limited endosperm modification and reduced malt extract levels. AC Metcalfe showed better modification and higher malt extract than CDC Copeland, but CDC Copeland had better protein modification at higher fertilisation rates, which resulted in less reduction of malt extract as nitrogen rate increased. CONCLUSION Higher seeding rates reduced kernel size and grain protein levels without compromising malt extract owing to better endosperm modification of the more uniformly sized kernels. Negative effects of higher nitrogen rates on malt quality can be reduced through development of cultivars with improved ability to modify protein during malting.

Virulence of Pyrenophora teres populations in western Canada

Abstract Net blotch, caused by Pyrenophora teres, is an economically important disease of barley. The pathogen has two morphologically similar but genetically distinct forms: P. teres f. teres (Ptt) and P. teres f. maculata (Ptm), which cause net form net blotch (NFNB) and spot form net blotch (SFNB), respectively. The virulence of a collection of 39 Ptt and 27 Ptm isolates collected from western Canada was evaluated by inoculating these isolates onto sets of barley differential hosts. One week following inoculation, the second and third leaves of each plant were rated for disease severity on scales of 1–10 (for Ptt) or 1–9 (for Ptm). Plants rated <5 and ≥5 were scored as resistant and susceptible to Ptt, respectively, while plants rated 1–3 and >3 were scored as resistant and susceptible to Ptm. The experiment was repeated. Cluster analysis revealed 16 and 13 distinct pathotype groups, respectively, among the 39 and 27 representative Ptt and Ptm isolates. The barley differentials CI 5791 and CI 9820 were resistant to all isolates of Ptt except one, whilst the differential CI 9214 was resistant to all isolates of Ptm except two. Therefore, the differential lines CI 5791 and CI 9820, for Ptt, and CI 9214, for Ptm, can still be considered as potentially useful sources of resistance for Canadian barley breeding programmes.

Prevalence of mating type idiomorphs in Pyrenophora teres f. teres and P. teres f. maculata populations from the Canadian prairies

Abstract The fungus Pyrenophora teres Drechs. occurs as two morphologically similar but genetically distinct forms, P. teres f. teres (Ptt) and P. teres f. maculata (Ptm), which cause the net form and spot form of net blotch of barley, respectively. A collection of 220 isolates from the Canadian prairie provinces (Alberta, Saskatchewan and Manitoba) was evaluated for mating type (MAT) idiomorph distribution and frequency. Fungal isolates were classified as Ptt or Ptm using form-specific polymerase chain reaction (PCR) primers. PCR analysis with MAT-specific primers indicated that the MAT1 and MAT2 idiomorphs of Ptt and Ptm could be identified within the same field, on the same plant, and on the same leaf. There was no significant departure from the expected 1:1 MAT1/MAT2 ratio for both forms in all three provinces or in the Canadian prairies population as a whole. Polymorphic simple sequence repeat primers were used to detect evidence of possible recombination between the two forms. Cluster analysis revealed that all P. teres isolates, including 30 isolates causing intermediate symptoms, clustered in two distinct groups conforming to either Ptt or Ptm. Therefore, hybridization was not detectable from the 220 isolates collected in western Canada. Pyrenophora teres f. teres is still the dominant form (58%) of the net blotch pathogen, and the data suggest both Ptt and Ptm go through regular cycles of sexual reproduction in the Canadian prairies.

Weed Interference Impacts and Yield Recovery after Four Years of Variable Crop Inputs in No-Till Barley and Canola

Abstract A 2-yr (2009 to 2010), no-till (direct-seeded) “follow-up” study was conducted at five western Canada sites to determine weed interference impacts and barley and canola yield recovery after 4 yr of variable crop inputs (seed, fertilizer, herbicide). During the initial period of the study (2005 to 2008), applying fertilizer in the absence of herbicides was often worse than applying no optimal inputs; in the former case, weed biomass levels were at the highest levels (2,788 to 4,294 kg ha−1), possibly due to better utilization of nutrients by the weeds than by the crops. After optimal inputs were restored (standard treatment), most barley and canola plots recovered to optimal yield levels after 1 yr. However, 4 yr with all optimal inputs but herbicides led to only 77% yield recovery for both crops. At most sites, when all inputs were restored for 2 yr, all plots yielded similarly to the standard treatment combination. Yield “recovery” occurred despite high weed biomass levels (> 4,000 kg ha−1) prior to the first recovery year and despite high wild oat seedbank levels (> 7,000 seeds m−2) at the end of the second recovery year. In relatively competitive narrow-row crops such as barley and canola, the negative effects of high soil weed seedbanks can be mitigated if growers facilitate healthy crop canopies with appropriate seed and fertilizer rates in combination with judicious herbicide applications to adequately manage recruited weeds. Nomenclature: Wild oat, Avena fatua L.; barley, Hordeum vulgare L.; canola, Brassica napus L. Resumen Se realizó un estudio de “seguimiento” de 2 años de duración (2009 a 2010), en cero labranza (siembra directa), en cinco localidades del oeste de Canadá para determinar el impacto de la interferencia de malezas y la recuperación del rendimiento de la cebada y la colza después de 4 años de suministros variables de cultivos (semilla, fertilizante, herbicidas). Durante el período inicial del estudio (2005 a 2008), la aplicación de fertilizante en ausencia de herbicidas fue a menudo peor que la aplicación no óptima de insumos; en este caso, los niveles de biomasa de malezas fueron los más altos (2,788 a 4,292 kg ha−1), posiblemente debido a la mejor utilización de nutrientes por parte de las malezas que por los cultivos. Después de que los insumos óptimos fueron restablecidos (tratamiento estándar), la mayoría de las parcelas de cebada y colza recuperaron los niveles de rendimiento óptimos después de un año. Sin embargo, 4 años con todos los insumos óptimos, excepto herbicidas, llevaron a solamente una recuperación del rendimiento de 77% para ambos cultivos. En la mayoría de los sitios, cuando todos los insumos fueron restablecidos por 2 años, todas las parcelas tuvieron rendimientos similares a la combinación del tratamiento estándar. La “recuperación” del rendimiento ocurrió a pesar de los altos niveles de biomasa de malezas (>4,000 kg ha−1) previo al primer año de recuperación y a pesar de los altos niveles del banco de semillas de Avena fatua (>7,000 semillas m−2) al final del segundo año de recuperación. En cultivos en hileras angostas relativamente competitivos, tales como cebada y colza, los efectos negativos de altos bancos de semillas pueden ser mitigados si los productores facilitan doseles de cultivos saludables con dosis apropiadas de semilla y fertilizante en combinación con aplicaciones juiciosas de herbicidas para manejar adecuadamente las malezas emergidas.