SEEDBANK CHARACTERISTICS OF HERBICIDE-RESISTANT AND SUSCEPTIBLE SISYMBRIUM-ORIENTALE

Germinability and emergence of Sisymbrium orientale Torn. seed suscept ible and resistant to acetolactate synthase (ALS)-inhibiting herbicide s was investigated. Freshly harvested seed from a field containing con firmed ALS-inhibiting herbicide-resistant (ALS resistant) plants and s usceptible seed from a nearby field was found to exhibit strong innate dormancy initially. However, germinability of seed from both resistan t and susceptible biotypes increased to 50% after 1 month, indicating that innate dormancy had been partly relieved. No significant differen ces in behaviour of resistant vs. susceptible biotypes were recorded o ver 3 years. Field experiments conducted over a 4-year experimental pe riod, to determine seedbank longevity in the absence of fresh seed inp ut to the seedbank, revealed S. orientale to have a short seedbank lif e. Cultivation stimulated seedling emergence compared with no-tillage seedling emergence. These findings establish that persistence of S. or ientale in the seedbank is short if fresh seed production is prevented . This knowledge can be used to manage populations of S. orientale, es pecially in cases such as this where the population is herbicide-resis tant.