Seedbank characteristics of herbicide-resistant and susceptible Sisymbrium orientale

Germinability and emergence of Sisymbrium orientale Torn. seed susceptible and resistant to acetolactate synthase (ALS)-inhibiting herbicides was investigated. Freshly harvested seed from a field containing confirmed ALS-inhibiting herbicide-resistant (ALS resistant) plants and susceptible seed from a nearby field was found to exhibit strong innate dormancy initially. However, germinability of seed from both resistant and susceptible biotypes increased to 50% after 1 month, indicating that innate dormancy had been partly relieved. No significant differences in behaviour of resistant vs. susceptible biotypes were recorded over 3 years. Field experiments conducted over a 4-year experimental period, to determine seedbank longevity in the absence of fresh seed input to the seedbank, revealed S. orientale to have a short seedbank life. Cultivation stimulated seedling emergence compared with no-tillage seedling emergence. These findings establish that persistence of S. orientale in the seedbank is short if fresh seed production is prevented. This knowledge can be used to manage populations of S. orientale, especially in cases such as this where the population is herbicide-resistant.