Plasticity, life cycle and interference potential of field violet (Viola arvensis Murr.) in direct-seeded wheat and canola in central Alberta

Abstract

Field violet is an established weed of field crops in Europe and eastern North America. It has recently been identified in field crops of central Alberta. Natural infestations of field violet in direct-seeded wheat and canola in central Alberta were observed in 2002 and 2003. Field violet exhibited summer annual, winter annual and short-lived perennial life cycles. Plants emerged in variable flushes, with peaks in early-June and September. Very few annuals produced seed during the season if they emerged after June, but some (< 45%) of these plants successfully overwintered. Summer annuals began dispersing mature seed 7 wk after emergence, but were also capable of persisting in a quiescent state for extended periods (up to 19 wk). Wheat and canola yield loss attributable to field violet was minimal. We compared domestic and European field violet accessions to determine if the study population represented a unique agroecotype. Plants from both cohorts grown in the greenhouse were near-identical, suggesting that differences resulted from phenotypic plasticity, rather than genetic divergence. Field violet appears to be well adapted to growing conditions and farming practices in Alberta, but is a poor competitor and is unlikely to cause serious crop production losses. Key words: Environmentally regulated plasticity, field violet, Viola arvensis, weed emergence, weed phenology