The impact of crop rotation and N fertilizer on common root rot of spring wheat in the Brown soil zone of western Canada

Abstract

From 2000 to 2003, spring wheat (Triticum aestivum L.) grown in southwest Saskatchewan 1 or 2 yr after summerfallow, and after lentil (Lens culinaris Medik), flax (Linum usitatissimum L.), or continuously with and without fertilizer N was examined for root rot by measuring discoloration of subcrown internodes. Discolored tissue was also plated on nutrient agar for fungal identification. In general, common root rot was present at consistently highest levels in wheat grown after lentil, and at lowest levels in wheat grown continuously with low N fertility. The most common fungal species isolated from affected subcrown internodes were Cochliobolus sativus (Ito and Kurib.) Drechs. ex Dast. and Fusarium spp. Among the latter, F. avenaceum (Fr.) Sacc., F. equiseti (Corda) Sacc. and F. pseudograminearum O’Donnell & T. Aoki were most frequent. Fusarium avenaceum is one of the most common fusarium head blight pathogens in Saskatchewan. Wheat after lentil had one of the highest levels of this fungus. Continuous wheat grown with recommended N rates and wheat grown after summerfallow had in most cases similar root rot levels, but the frequency of fungi differed. Among the crop rotations examined, it appears that the most favourable for development of root rot in wheat was a wheat-lentil rotation. This cereal-pulse system may also contribute to a build-up of F. avenaceum inoculum for the development of fusarium head blight, an important emerging disease of cereals in Saskatchewan. Key words: Crop rotation, common root rot, wheat, Cochliobolus sativus, Fusarium, nitrogen

Root rot severity and fungal populations in spring common, durum and spelt wheat, and Kamut grown under organic management in western Canada

“…However, in those studies, Fusarium cereal pathogens, such as F. culmorum, were among the most commonly isolated fungi and were present at higher levels than in the present study. In contrast to our results, Fernandez and Zentner (2005) reported an overall equal prevalence of C. sativus and Fusarium spp. across all rotation treatments in a long-term crop rotation study that ran under conventional tillage for the previous 34 yr in the same area in southwest Saskatchewan in which the present study was conducted.…”

“…and Stemphylium spp. were isolated at higher frequencies by Fernandez et al (2007a) compared with our study, while Fernandez and Zentner (2005) reported that M. bolleyi occurred at an overall lower relative isolation rate than any of the three most frequent Fusarium species. Many of the genera identified in this study were also isolated by L ukanowski (2009) from the stem bases of winter wheat grown in Poland.…”

“…Many of these species were also previously isolated from discoloured subcrown internodes of common and durum wheat in Saskatchewan (Fernandez and Jefferson 2004;Fernandez and Zentner 2005;Fernandez et al 2007a), although often at different relative frequencies. Among them, Rhizoctonia spp.…”

“…Previous studies conducted under conventional systems showed that rotations with pulse crops can affect both disease severity and the relative incidence of wheat root pathogens. Fernandez and Zentner (2005) reported that the severity of root rot in spring wheat grown in a longterm rotation in southwest Saskatchewan was highest when preceded by a lentil (Lens culinaris L.) crop, which was attributed to the greater percentage isolation of F. avenaceum (Fr.:Fr.) Sacc.…”

Impact of increasing temperature on the fitness of Fusarium pseudograminearum causing crown rot in wheat

“…In addition, salmon coloured sporodochia of the fungus may form on nodes, particularly under leaf sheaths in humid conditions . Crown rot is a globally widespread disease as it occurs in most cereal-producing regions of the world including Australia , Wildermuth et al, 1997, Europe (Pettitt & Parry, 2001, Rossi et al, 1995, North America (Fernandez & Zentner, 2005, Smiley et al, 2005, South Africa (Lamprecht et al, 2006), west Asia and north Africa (Mitter et al, 2006a). Negative impacts are associated with crown rot as the disease significantly reduces grain yield and quality.…”