Debra L. McLaren

Possible Escape of a Recombinant Isolate of Potato virus Y by Serological Indexing and Methods of its Detection

Surveys of commercial and seed potato fields for virus diseases (1998 to 2002) in Manitoba established that Potato virus Y (PVY) is of concern in seed potato production. To determine the prevalence of PVY strains, PVY-infected tubers identified by reverse transcription-polymerase chain reaction (RT-PCR) from surveys (2000 to 2001) were grown for symptom expression and strain characterization by strain-specific RT-PCR, bioassays, and serological assays. Of the samples collected (2000 to 2001) and tested by RT-PCR, 4.0% contained PVY. Further analysis of the PVY-positive samples by a duplex RT-PCR facilitating the simultaneous detection of common (PVYO) and tobacco veinal necrosis strains (PVYN/NTN) indicated that 37.5% contained PVYO and 63.5% contained PVYN-type isolates. Analysis of the PVYN-type samples using three monoclonal antibodies (MAbs) showed that all reacted with only the PVYO MAbs and not with the PVYN-specific MAb. Partial nucleotide sequences of both ends of PVY-RNA showed that the PVYN-type isolates resembled those reported in 1996 from Manitoba. These isolates are designated as PVYN:O. In view of the increased incidence of PVYN:O in one production area, seed tubers imported from other provinces of Canada and the neighboring United States were analyzed for PVYN:O. The PVYN:O was detected in imported seeds from Minnesota, Montana, and North Dakota.

Reaction of seedling roots of 14 crop species to Fusarium graminearum from wheat heads

To increase our understanding of the epidemiology of fusarium head blight of wheat and barley, a study was conducted under controlled conditions to determine whether Fusarium graminearum Schwabe from wheat can cause seedling blight or root rot in various crop species. Inoculum of F. graminearum, consisting of a wheat floret infected with the pathogen, was placed adjacent to surface-sterilized seed of each crop in a sterile potting mix. Wheat, barley, oat, rye, triticale, canaryseed, flax, canola (Brassica napus L. and Brassica rapa L.), mustard, bean, field pea, lentil, and chickpea were included in the study. Seedling emergence and root rot severity were scored at 3–4 weeks after seeding. The effect of temperature on seedling blight severity was also tested in barley cv. Brier. Inoculation reduced emergence in all crops, except canola, mustard, and field pea, and increased root rot severity in most crops. Emergence of seedlings was not affected at the lowest temperature (10:5°C day:night) and no root infection occurred. However, as the temperature increased from 10 to 30°C, seedling emergence and establishment were reduced and root rot severity increased. Infection of roots, crowns, and seedlings of the crops grown in rotation with wheat indicates that these crops may act as alternative hosts to F. graminearum.

Recent Advances on Potato virus Y Research in Canada

Significant progress has been made in recent years in understanding pathological, serological and molecular properties of various strains of PVY and the aphid-mediated transmission. PVYO and PVYN appear to be the basic strain groups. Through genome recombination between these two groups, progeny groups whose genome possess one (e.g., PVYN:O or PVYN-Wi) to three (e.g., recombinant PVYNTN or European-PVYNTN) recombinant joints of PVYO and PVYN emerged. PVYN:O causes PVYN-like veinal necrosis in tobacco, but reacts to PVYO-specific antibody. PVYNTN causes potato tuber necrotic ringspot diseases in sensitive potato cultivars, and PVYN-like necrosis in tobacco plants, and reacts to PVYN-specific antibody. Through single nucleotide mutation(s), non-recombinant PVYNTN (or North American PVYNTN) also emerged from PVYN. It is also noteworthy that PVYN isolates originated from North America and Europe may have evolved separately; and to date most recombinant strains appear to be progenies of Eu-PVYN and PVYO. Several RT-PCR-based methodologies have been developed to characterize and detect various strains of PVY. A field survey revealed that PVYN:O has become a predominant strain in Manitoba and neighbouring states in USA. Moreover, three distinct variant groups inciting severe, intermediate and mild veinal/petiole/stem necrosis, respectively, on tobacco plants were observed within the PVYN:O isolates collected in Manitoba. Pathological and molecular diversity within PVYO strain group were revealed in New Brunswick, represented by PVYO-FL as a severe variant and by PVYO-RB as a mild variant. Studies on the transmission of PVY by various species of aphids revealed that aphid behavior plays an important role in the vector-mediated transmission. Application of mineral oil on the growing crop, especially in combination with use of crop borders, reduces aphid-mediated PVY transmission. Based on recent PVY research studies, Bartlett Superior 70 Oil was approved in 2011 for application to potato crops in Canada.ResumenSe ha hecho progreso significativo en años recientes en el entendimiento de las propiedades patológicas, serológicas y moleculares de variantes del PVY y de su transmisión por áfidos. Parece que PVYO y PVYN son los grupos básicos de las variantes. Mediante la combinación del genomio entre estos dos grupos, han emergido otros grupos de progenie cuyos genomios poseen una (e.g., PVYN:O o PVYN-Wi), a tres (e.g., recombinantes PVYNTN o Europeos-PVYNTN) uniones recombinantes de PVYO y PVYN . El PVYN:O causa necrosis venal en Tabaco como PVYN, pero reacciona al anticuerpo específico de PVYO. El PVYNTN causa enfermedad de las manchas anulares necróticas en el tubérculo de variedades susceptibles de papa, y necrosis como PVYN en plantas de tabaco, y reacciona al anticuerpo específico de PVYN. Por vía de mutación(es) de un solo nucleótido, el PVYNTN no-recombinante (o PVYNTN de Norte América) también emergió del PVYN. También es digno de mención que los aislamientos de PVYN originarios de Norte América y Europa pudieron haber evolucionado por separado; y a la fecha parece que la mayoría de las variantes recombinantes son progenies de Eu-PVYN y PVYO. Se han desarrollado varias metodologías basadas en RT-PCR para caracterizar y detectar varias variantes de PVY. Una auscultación en el campo reveló que PVYN:O se ha vuelto una variante predominante en Manitoba y Estados vecinos en EUA. Más aún, se observaron tres grupos distintos de variantes que incitan necrosis de las venas/pecíolo/tallo severas, intermedias y ligeras, respectivamente, en plantas de tabaco dentro de los aislamientos del PVYN:O colectados en Manitoba. Se reveló diversidad patológica y molecular dentro del grupo de variantes del PVYO en New Brunswick, representada por PVYO-FL como una variante severa y PVYO-RB como ligera. Estudios en la transmisión de PVY por varias especies de áfidos revelaron que el comportamiento del áfido juega un papel importante en la transmisión mediada por el vector. La aplicación de aceite mineral en el cultivo en crecimiento, especialmente en combinación con el uso de cultivos de bordo, reduce la transmisión del PVY mediada por el áfido. Con base en estudios recientes, se aprobó el aceite Bartlett Superior 70 en 2011 para su aplicación en cultivos de papa en Canadá.

Crop response to current and previous season applications of phosphorus as affected by crop sequence and tillage

Field studies were conducted over a 4-yr period at two locations in western Manitoba, Canada, to evaluate the effect of phosphorus (P) fertilizer management on crop growth as affected by tillage system through a 2-yr cropping sequence. In the first phase of the cropping sequence, canola (Brassica napus L.), a non-mycorrhizal crop, and spring wheat (Triticum aestivum L.), a mycorrhizal crop, were grown under conventional (CT) and reduced (RT) systems, with 0, 11 and 22 kg P ha-1 applied as monoammonium phosphate (MAP). In the second phase of the sequence, flax (Linum usitatissimum L.) was seeded following the spring wheat or canola, with application of 0 or 11 kg P ha-1 as MAP. Phosphorus application increased the early-season biomass, P concentration, and P accumulation of canola and wheat and the seed yield of canola. Tillage system had no consistent effects on growth, P concentration or uptake, or seed yields of canola or wheat, nor were P by tillage system interactions observed. Early-season biomass pr...

Effect of Rotation on Crop Yield and Quality in an Irrigated Potato System

The productivity of potato (Solanum tuberosum L.) systems may be strongly influenced by rotation. A field study consisting of six rotations (potato with canola (PC), wheat (PW), canola-wheat (PCW), oat-wheat (POW), wheat-canola-wheat (PWCW), and canola underseeded to alfalfa-alfalfa-alfalfa (PCAA)) arranged as an RCBD was established on a clay loam in Manitoba, Canada in 1998 and monitored for twelve years to determine effects on potato yield and quality. Higher yields for canola-containing rotations were evident in three years (P < 0.10), but not beyond 2005. From 2007 onward, 2-year rotations produced a markedly lower yield than other rotations. Yields of 3- and 4-year rotations were similar, although PCW and PCAA were most frequently among the higher-yielding rotations. Overall, PC had a lower specific gravity than other rotations. Results suggest 3- and 4-year rotations, particularly PCW and PCAA, helped maintain productivity. Two-year rotations of PC and PW were not sustainable due to declining yields.ResumenLa productividad de los sistemas de papa (Solanum tuberosum L.) pueden estar fuertemente influenciados por la rotación. Se estableció un estudio de campo consistente en seis rotaciones; papa con canola (PC), con trigo (PW), con canola-trigo (PCW), con avena trigo (POW), con trigo, canola, trigo (PWCW), y con canola mezclada con alfalfa-alfalfa-alfalfa (PCAA), arreglado en un diseño experimental de bloques completos al azar, en un suelo franco-arcilloso en Manitoba, Canadá, en 1998, y monitoreado por doce años, para determinar los efectos en rendimiento y calidad de la papa. Se hicieron evidentes más altos rendimientos en las rotaciones que incluían a la canola en tres años (P < 0.10), pero no más allá de 2005. A partir de 2007, las rotaciones de dos años produjeron un rendimiento más bajo bien marcado que en otras rotaciones. Los rendimientos de rotaciones de 3 y 4 años fueron similares, aunque PCW y PCAA estuvieron entre las más frecuentes de las rotaciones de mayores rendimientos. En general, PC tuvieron gravedad específica más baja que otras rotaciones. Los resultados sugieren que rotaciones de 3 a 4 años, particularmente PCW y PCAA, ayudaron a mantener la productividad. Rotaciones de dos años de PC y PW no fueron sostenibles debido a la disminución en rendimientos.

Identifying and Managing Root Rot of Pulses on the Northern Great Plains

Pulse crops (annual grain legumes such as field pea, lentil, dry bean, and chickpea) have become an important component of the cropping system in the northern Great Plains of North America over the last three decades. In many areas, the intensity of damping-off, seedling blight, root rot, and premature ripening of pulse crops is increasing, resulting in reduction in stand establishment and yield. This review provides a brief description of the important pathogens that make up the root rot complex and summarizes root rot management on pulses in the region. Initially, several specific Fusarium spp., a range of Pythium spp., and Rhizoctonia solani were identified as important components of the root rot disease complex. Molecular approaches have recently been used to identify the importance of Aphanomyces euteiches on pulses, and to demonstrate that year-to-year changes in precipitation and temperature have an important effect on pathogen prevalence. Progress has been made on management of root rot, but more IPM tools are required to provide effective disease management. Seed-treatment fungicides can reduce damping-off and seedling blight for many of the pathogens in this disease complex, but complex cocktails of active ingredients are required to protect seedlings from the pathogen complex present in most commercial fields. Partial resistance against many of the pathogens in the complex has been identified, but is not yet available in commercial cultivars. Cultural practices, especially diversified cropping rotations and early, shallow seeding, have been shown to have an important role in root rot management. Biocontrol agents may also have potential over the long term. Improved methods being developed to identify and quantify the pathogen inoculum in individual fields may help producers avoid high-risk fields and select IPM packages that enhance yield stability.

Seedborne infection affects anthracnose development in two dry bean cultivars

Anthracnose, caused by the seedborne pathogen Colletotrichum lindemuthianum, is a serious disease of dry bean (Phaseolus vulgaris) that can severely reduce seed yield and quality. A 2 year field study examined how seedborne infection (0%, 1%, 2%, 5%, 10%, and 20%) affected seedling emergence, seedling infection, the buildup of anthracnose in the crop canopy, yield, seed mass, and seed discolouration in ‘Navigator’ navy bean and ‘AC Ole’ pinto bean. The incidence of seedling infection was significantly higher in ‘AC Ole’ than it was in ‘Navigator’ resulting in an early establishment of the disease on the pinto bean cultivar. There was a linear increase (P < 0.01) in anthracnose severity within the crop canopy and on the pods with higher rates of seedborne infection in both cultivars. Increases in seedborne infection rates also resulted in a significant decline (P < 0.01) in yield and seed mass. Comparisons of the 0% and the 20% seedborne treatments indicated that severe anthracnose development resulted in yield losses of 27% in ‘Navigator’ and 20% in ‘AC Ole’. These losses are comparable with the extent of yield reductions reported in a previous fungicidal study on anthracnose control in Manitoba. Key words: anthracnose, Colletotrichum lindemuthianum, dry beans, Phaseolus vulgaris, seed transmission. L’anthracnose, causée l’agent pathogène séminicole Colletotrichum lindemuthianum, est une maladie importante des haricots secs qui peut sérieusement en réduire les rendements et la qualité. Une étude sur le terrain, qui s’est échelonnée sur deux ans, a permis d’examiner comment l’infection séminicole (0 %, 1 %, 2 %, 5 %, 10 % et 20 %) influençait l’émergence et l’infection des semis, la prolifération de l’anthracnose sur le feuillage des plants ainsi que le rendement, le poids et la décoloration des semences chez le cultivar de petit haricot blanc ‘Navigator’ et chez celui de haricot pinto ‘AC Ole’. L’incidence de l’infection des semis chez le cultivar ‘AC Ole’ était significativement plus élevée que chez ‘Navigator’, ce qui provoquait la survenue hâtive de la maladie chez le haricot pinto. Il y avait une augmentation linéaire (P < 0,01) quant à la gravité de l’anthracnose sur le feuillage ainsi que sur les cosses affichant des taux plus élevés d’infection séminicole, et ce, chez les deux cultivars. Des augmentations des taux d’infection séminicole entraînent également une baisse significative (P < 0,01) des rendements et du poids des semences. Des comparaisons des traitements séminicoles (0 % et 20 %) ont indiqué que la prolifération massive de l’anthracnose provoquait des baisses de rendement de 27 % chez ‘Navigator’ et de 20 % chez ‘AC Ole’. Ces baisses sont comparables à celles rapportées dans une étude précédente effectuée sur les fongicides et ayant pour but la lutte contre l’anthracnose au Manitoba. Mots-clés : anthracnose, Colletotrichum lindemuthianum, haricots secs, Phaseolus vulgaris, transmission par semence.

Effect of nitrogen fertilizer rate, herbicide rate, and soil disturbance at seeding on the productivity of a wheat-pea rotation

Rotational productivity is a function of the rotational crops and their interactions, as well as the management employed. Understanding the functioning of the overall production system, as well as its component parts, may contribute to improved management. Effects of nitrogen fertilizer rate (25, 50, 75, 100 kg N ha-1 as urea) and herbicide rate (66 or 100% of recommended) applied to wheat, and of the level of soil disturbance at seeding, on the productivity and N status of a 2-yr rotation of spring wheat (Triticum aestivum L.) and field pea (Pisum sativum L.) were assessed over two rotation cycles at two locations in southwestern Manitoba. Management factors typically acted independently to influence the cropping system. In both wheat and pea, high soil disturbance at seeding reduced or tended to reduce plant density in most site-years, resulting in reduced yields in about half of site-years. In 2 site-years where weed pressure was high, wheat yields for high disturbance treatments were less than 60% of ...

Identification of bacterial pathogens and races of Pseudomonas syringae pv. phaseolicola from dry bean fields in Western Canada

Abstract Several bacterial diseases can significantly impact dry bean production in western Canada. The objectives of this study were to assess the incidence of multiple bacterial diseases on dry bean in southern Alberta and to determine the prevalent races causing halo blight (HB) in western Canadian dry bean fields. Field surveys combined with a pathogen isolation component were conducted in 2012–2014 to determine relative frequency of bacterial pathogens. Bacterial pathogens causing HB and brown spot were most commonly isolated from symptomatic tissues, whereas the pathogens causing common blight (CBB) and bacterial wilt were infrequently detected. In order to screen bean breeding lines for resistance to HB, the races of Pseudomonas syringae pv. phaseolicola (Pph) present in western Canada needed to be determined. A total of 114 Pph isolates were recovered from dry bean samples from Alberta, Saskatchewan and Manitoba in 2010–2013. Virulence testing of these isolates on the halo blight dry bean differential set indicated that only races 2 and 6 were present. These races were equally predominant in Manitoba, race 2 comprised 81% of Alberta isolates, and only race 2 occurred in Saskatchewan. Screening of select CBB-resistant breeding lines indicated that all were susceptible to a race 2 isolate of Pph. However, several commercial cultivars either currently grown, or recently registered for commercial production in Alberta, showed reduced susceptibility to HB. These results should be applicable to dry bean breeding programmes attempting to incorporate halo blight resistance into Canadian-adapted dry bean lines.

Influence of alternative management methods on the economics of flax production in the Black Soil Zone

Studies were conducted at two locations on two Orthic Black Chernozemic soils over 4 yr to evaluate the economic effects of tillage system, preceding crop, phosphorus (P) fertilization of the preceding crop, and P fertilizer application on flax (Linum usitatissimum L.) production. Canola (Brassica napus L.), a non-mycorrhizal crop, and spring wheat (Triticum aestivum L.), a mycorrhizal crop, were grown as the preceding crops under conventional (CT) and reduced tillage (RT) systems, with 0, 11 and 22 kg P ha-1 applied as monoammonium phosphate (MAP). The following year, flax was planted with application of 0 or 11 kg P ha-1 as MAP side-banded at seeding. Tillage method had no impact on the net revenue of wheat or canola at either location when averaged over the 2 yr of study. Net revenue of flax was higher (