Effectiveness of fungicide seed treatments for preventing seed-to-seedling transmission of Fusarium graminearum under controlled-environment conditions

Abstract

Fusarium head blight (FHB) is well established in the eastern prairies, but for the most part it has been absent from western regions, especially under dryland conditions. This has been largely attributed to dry and hot conditions during some years, and the limited occurrence of F. graminearum in the western prairies. It is of importance to prevent the movement of F. graminearum, the most important FHB pathogen in North America, to areas where this pathogen is not commonly found. Three controlled-environment studies, using different Fusarium-infected common and durum wheat seed lots, were conducted to determine the effectiveness of currently registered fungicide seed treatments in improving seedling emergence and plant development, and preventing the growth of F. graminearum from infected seed to plant tissue. Fungicide treatments improved seedling emergence from the most infected seed over the untreated infected control, but most treatments did not improve emergence in the other experiments. Plant growth in the fungicide treatments was either similar to or slower than in the untreated controls. Fusarium graminearum was isolated from discoloured tissue in all treatments and was generally more common in crowns than in subcrown internodes. No fungicide treatment reduced discolouration of plant tissue or percentage isolation of F. graminearum or other Fusarium spp. consistently. We conclude that while currently registered seed treatments might be effective in improving seedling emergence in some infected wheat seed lots, they do not prevent the growth of F. graminearum from seeds to plant tissue. For the western prairies, the use of fungicide seed treatments as a strategy in the prevention of spread of FHB would require that they be effective primarily against F. graminearum. Performance of fungicide seed treatments against Fusarium-infected wheat seed should also be determined under typical growing conditions across the western prairies.Key words: Seed treatments, fungicides, wheat, root rot, crown rot, Fusarium graminearum, Fusarium avenaceum

Effect of fungicide seed treatments on root pathogens of cereal crops under field conditions

“…The absence or very low levels of F. graminearum in the uninfected control in all 3 yr of the study confirmed that the presence of this pathogen in the SIs of the infected treatments resulted primarily from seed-borne infections. However, in some cases, the low levels of this pathogen in the infected treatments, and the variability in isolations among replicates, resulted in differences in F. graminearum levels among treatments not being always statistically significant, as suggested from a growth chamber study by Fernandez et al (2009). For some of the years, the low levels of F. graminearum could also be attributed to less than suitable environmental conditions for growth of this pathogen, such as low precipitation and high temperatures in 2003, and low temperatures in 2004(May et al 2010.…”

“…We therefore conclude that none of the fungicide seed treatments consistently reduced SI discoloration across all siteyears. In a controlled-environment study using a soilless mix, evaluation of common and durum wheat at a later growth stage (GS 46) showed no effect of seed treatment on discoloration severity (Fernandez et al 2009). …”

“…Percentage of SIs with severe (SI-S), and moderate or severe (SI-MS), discoloration was calculated for each plot. A piece (1Á2 cm) of each discolored SI was surface-disinfested for 1 min in 0.6% NaOCl, rinsed twice in sterile distilled water, and plated on modified potato dextrose agar for fungal identification (Fernandez et al 2009). Fungi growing out of each piece of SI tissue were identified after incubation for 7Á10 d at 22/188C with a photoperiod of 16 h light and 8 h dark.…”

“…In field trials, Jones (1999) reported that some of the seed treatments tested controlled seedling blight in wheat caused by seed-borne Fusarium infections, while Klein and Burgess (1987) showed that seed treatments did not affect the incidence of infection and whitehead formation in wheat plants derived from seeds infected by F. pseudograminearum O'Donnell & T. Aoki. Fernandez et al (2009) reported that none of the fungicide seed treatments tested under controlled-environment conditions resulted in a consistent reduction in disease severity or the recovery of F. graminearum from subcrown internodes or crowns of wheat.…”

“…Fusarium graminearum and other Fusarium spp. in infected common and durum wheat seed were recovered from subcrown internodes and crowns of plants derived from those seeds under controlled-environment conditions using a soil-less medium (Fernandez et al 2009). …”