Summary
This greenhouse study demonstrated that glyphosate application significantly increased root rot disease severity in glyphosate-resistant sugar beet when challenged with specific isolates of Rhizoctonia solani (AG-2-2) and moderately virulent Fusarium oxysporum (FOB13), but not with highly virulent pathogen strains. The disease increase was plant-mediated rather than fungal-mediated, as glyphosate showed no direct impact on fungal growth or germination in vitro; instead, glyphosate triggered tissue-specific shikimic acid accumulation in sugar beet, which was greater in susceptible cultivars. The findings suggest that post-emergence glyphosate use in sugar beet weed management requires precautions when certain soil-borne pathogens are present.
Regional applicability
Sugar beet cultivation and glyphosate-resistant variety deployment are practised in the United Kingdom, though the study was likely conducted in North America (based on author affiliation patterns typical of this era). The findings are transferable to UK sugar beet production systems where glyphosate-resistant varieties and post-emergence glyphosate are used, particularly in regions with endemic Rhizoctonia or Fusarium pressure.
Key measures
Disease severity scores following glyphosate application and pathogen inoculation; fungal growth rates and overwintering structure germination in vitro; shikimic acid accumulation in plant tissues by cultivar susceptibility
Outcomes reported
The study measured disease severity of Rhizoctonia solani and Fusarium oxysporum on glyphosate-resistant sugar beet following glyphosate application in greenhouse conditions. It also examined fungal growth responses and shikimic acid accumulation in plant tissues to determine the mechanism of disease increase.
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