Characterization of dandelion (Taraxacum officinale Weber in F.H. Wigg.) biotype morphology, chemical composition and response to glyphosate

Abstract

Dandelion plants at the Lethbridge Research Centre, Alberta, have several different leaf shapes and possibly include individuals that are tolerant to glyphosate. The objectives of this study were to determine whether different leaf shapes are due to genotypic differences, whether chemical composition varies with leaf shape, and whether plants vary in their response to glyphosate. Plants with possible glyphosate tolerance were collected in 1998 from a pasture field where forage grasses were terminated with glyphosate, and from an alfalfa (Medicago sativa L.) field where no herbicides had been applied. Image analysis of plants that were progeny of the original collection indicated that they have significantly different leaf shapes. DNA analysis confirmed that genotypic differences associated with leaf shape exist among dandelion plants collected at the Lethbridge Research Centre. The biotypes had different metal concentrations, which may be a concern if plants are sampled to monitor metal contamination. All biotypes had acceptable metal concentrations for use as cattle feed. In greenhouse tests, all biotypes required similar doses of glyphosate to reduce growth by 50%. All biotypes have considerable tolerance to glyphosate at rates to at least 1.8 kg a.e. ha-1, root fragments remained that were capable of supporting new leaf growth. Key words: Dandelion, DNA, glyphosate, leaf shape, mineral content, protein