Etiology of the rhizoctonia root rot complex of canola in the Peace River region of Alberta

Fernandez, M. R. 2007. Fusarium populations in roots of oilseed and pulse crops in eastern Saskatchewan. Can. J. Plant Sci. 87: 945-952. Roots of canola, flax, lentil and pea crops, commonly grown in rotation with wheat and barley on the Canadian Prairies, were sampled for extent of discolouration and associated fungal populations in eastern Saskatchewan, in 2000 and 2001. Fusarium was the genus most commonly isolated from pulse crops, particularly lentil, and one of the most common genera isolated from oilseed crops. The discolouration severity of pulse and flax roots was associated with Fusarium spp., and that of canola with Alternaria spp. Cochliobolus sativus and other commonly isolated species appeared to be present in roots as weak pathogens or saprophytes. Most of the Fusarium spp. have also been isolated from cereal crops affected by crown/root rot or fusarium head blight (FHB) in the province, although at different relative levels. These included F. avenaceum, the most commonly isolated species, and F. culmorum and F. graminearum, which were among the least prevalent species. This is the first report of isolation of F. graminearum from roots of field-grown pulse and oilseed crops in western Canada. For most crops, the number of tillage operations in the previous 3 yr was positively associated with the occurrence of C. sativus and negatively associated with that of F. avenaceum. Our results suggest that the noncereal crops examined would help to maintain or increase Fusarium inoculum in plant tissue, which might contribute to the development of crown/root rot and FHB in subsequently grown cereal crops, especially under conditions more conducive to disease development. This would especially be the case for pulse crops, which had the highest levels of root discolouration, and F. avenaceum. However, noncereal crops would not be significant reservoirs of inoculum of F. culmorum or F. graminearum.

Section: Discussionsupporting

confidence: 80%

“…x 0 represents instances where isolate was not detected. 1987; Sturz and Bernier 1987), although this fungus was shown not to be pathogenic to canola seedlings (Gugel et al 1987). Fusarium equiseti was also reported to be a weak pathogen of lentil by Bhalla et al (1984).…”

Section: Discussionmentioning

confidence: 99%

Fusarium populations in roots of oilseed and pulse crops grown in eastern Saskatchewan

Fernandez¹

2007

“…A number of strains have been identified that tend to attack certain host species. This specialization often coincides with anastomosis grouping (Keijer 1996), but a wide range of virulence/aggressiveness can occur among isolates within an anastomosis group (Gugel et al 1987;Kaminski and Verma 1985). The impact of R. solani on the host plant also depends on the density of inoculum in the soil (van Bruggan et al 1986a,b;Phillips 1989).…”

Section: Mots Clésmentioning

confidence: 99%

Etiology, impact and control of rhizoctonia seedling blight and root rot of chickpea on the Canadian prairies

Hwang¹,

Gossen²,

Chang³

et al. 2003

. 2003. Etiology, impact and control of rhizoctonia seedling blight and root rot of chickpea on the Canadian Prairies. Can. J. Plant Sci. 83: 959-967. Studies were undertaken to assess the impact of seedling blight and root rot caused by Rhizoctonia solani AG-4 on nodulation and seed yield of chickpea. The effects of pathogen inoculum concentration and seed damage on disease severity were also measured. Chickpea seedlings were grown under controlled-environment conditions in sterilized soil amended with pathogenic isolates of R. solani and in field plot experiments where the inoculum was incorporated with the seed at planting. In greenhouse experiments, emergence and dry matter production declined and root rot severity increased with increasing inoculum concentration. Root rot reduced nodulation where lesions covered more than 25% of the root surface. For chickpea cultivar Sanford this level of infection was sufficient to reduce root mass, but for the cultivar Tyson, more than half of the root was covered with lesions before root mass began to decline. In a comparison of seed treatment fungicides, thiram + carbathiin (Vitaflo 280) and carbathiin + thiabendazole (Crown at 6 mL of product kg -1 seed) significantly increased seedling emergence and seed yield compared to the inoculated control. In an assessment of the effects of seed damage, seedling survival and seed yield were similar for both healthy and mechanically damaged seed. Rhizoctonia solani has the potential to be an important constraint to chickpea production in the prairie region of western Canada. 83: 959-967. Les auteurs ont essayé d'évaluer l'incidence de la brûlure et du piétin causés par Rhizoctonia solani AG-4 sur la nodulation et le rendement grainier du pois chiche. Ils ont aussi déterminé dans quelle mesure la gravité de la maladie était influencée par la concentration de l'inoculum pathogène et les graines abîmées. Les plantules de pois chiche ont été cultivées en milieu contrôlé, dans du sol stérilisé auquel on a ajouté un isolat pathogène de R. solani, et sur des parcelles expérimentales, au sol desquelles on a incorporé l'inoculum avec la graine, à la plantation. Lors des expériences en serre, l'usage d'un inoculum de plus en plus concentré entraîne une baisse du taux de levée et de la production de matière sèche ainsi qu'une hausse de la gravité du piétin. Le piétin réduit la nodulation quand les lésions couvrent plus de 25 % de la surface des racines. Avec le cultivar Sanford, ce degré d'infection suffit à réduire la masse des racines, mais avec de Tyson, cette dernière ne diminue que lorsque plus de la moitié des racines sont couvertes de lésions. Lors d'un essai comparatif sur les fongicides destinés aux semences, l'usage de thiram + carbathiin (Vitaflo 280) et de carbathiin + thiabendazole (Crown, à raison de 6 ml par kg de semences) entraîne une hausse sensible du taux de levée et du rendement grainier par rapport au témoin inoculé. En ce qui concerne les graines endommagées, le taux de survie des plantules et le rendement grainier r...

“…At each location, five contiguous plants were selected. Roots were washed, boiled for 10 min and dried at room temperature with forced air flow for at least 48 h. The preserved roots were assessed for disease infection, usually within 3 months, using the BGRR rating scale (0-5) developed by Gugel et al (1987), the incidence of plants with BGRR rating >3, and disease severity based on diseased root area (H. Klein-Gebbinck, unpublished). Although the dried roots showed some shrinkage, disease ratings were similar to those of fresh roots.…”

Section: Methodsmentioning

confidence: 99%

Residue management and crop sequence effects on the yield and brown girdling root rot of canola

Soon¹,

Klein-Gebbinck²,

Arshad³

2005

. 2005. Residue management and crop sequence effects on the yield and brown girdling root rot of canola. Can. J. Plant Sci. 85: 67-72. Brown girdling root rot (BGRR) is a serious and widespread disease of canola (Brassica rapa L.) in the Peace River region of northwestern Canada. There is no chemical control treatment for the pathogen, and farmers have observed that the disease is more severe when canola follows red fescue (Festuca rubra L.) or clover (Trifolium spp.) compared to summer fallow. A field study was conducted to determine how crop sequences following red fescue termination can be combined with residue and tillage management to reduce BGRR infection and increase canola yield. The five treatments consisted of rotations of: continuous canola (CCC) and oat (Avena sativa L.)-oat-canola (OOC), both managed using reduced tillage (RT), and wheat (Triticum aestivum L.)-wheat-canola (WWC), managed using RT, conventional tillage (CT) or no-till (NT). Canola yield followed the trend: OOC(RT) = WWC(RT) > WWC(CT) > CCC(RT) = WWC(NT). BGRR infection increased with tillage intensity: WWC(CT)> CCC(RT) = WWC(RT) = OOC(RT) > WWC(NT), and was reduced when canola followed two cereal break crops. Yield was highest when canola was preceded by a cereal crop and lowest without a break crop. The low yield with NT was attributed to poor crop emergence from a hard seed bed with unbroken turf and to competition from re-emerged fescue in the third year after fescue breaking. This study demonstrated that the cropping sequence and tillage system used influenced canola yield to a greater extent than did BGRR infection. Il n'y a aucun traitement chimique de commande pour le microbe pathogène, et les fermiers ont observé que la maladie est plus grave quand le canola suit la fétuque rouge (rubra L de Festuca.) ou trèfle (espèces de trifolium.) comparé à la jachère en été. Une étude sur le terrain a été conduite pour déterminer comment des ordres de récolte suivant l'arrêt de fétuque rouge peuvent être combinés avec le résidu et la gestion de labourage pour réduire le rendement de canola d'infection et d'augmentation de BGRR. Les cinq traitements se sont composés des rotations de : canola continu (ccc) et avoine (l'avoine commune L.)-oat-canola (OOC), tous les deux a contrôlé en utilisant le labourage réduit (droite), et le blé (triticum aestivum L.)-wheat-canola (WWC), contrôlé en utilisant la droite, labourage conventionnel (CT) ou aucun-jusqu'à (NT). Le rendement de Canola a suivi la tendance : OOC(RT) = WWC(RT) WWC(CT) CCC(RT) = WWC(NT). L'infection de BGRR a augmenté avec l'intensité de labourage : WWC(CT) CCC(RT) = WWC(RT) = OOC(RT) WWC(NT), et a été réduit quand le canola a suivi deux récoltes de coupure de céréale. Le rendement était le plus haut quand le canola a été précédé par une récolte de céréale et le plus bas sans récolte de coupure. Le bas rendement avec le NT a été attribué à l'apparition faible de récolte d'un lit dur de graine avec le gazon ininterrompu et à la concurrence de la fétuque réapparue par la troisième an...