Natural variation in physical responses to waterlogging across climate-diverse pennycress accessions
Fluctuations in flooding and differences in hydrological gradients affect the geographic distribution of plant species across ecosystems, resulting in the presence of adaptive traits in populations that confer enhanced fitness in flooded environments. Many winter annual crops, such as pennycress (Thlaspi arvense L.), are subjected to heavy precipitation events during their growing season, which are increasing in frequency due to climate change. Therefore, it is essential to identify pennycress accessions with natural variation in flooding resilience. In this study, we used climate modeling data to assess spring soil moisture levels in the geographic origins of 471 natural pennycress accessions. We selected 34 accessions with variations in predicted soil moisture to test survivability under prolonged waterlogging at the rosette stage. This identified variation in waterlogging tolerance, where six accessions had 0% survivability and nine accessions had 100% survivability. It took at least seven weeks for the first accessions to die under waterlogging, indicating that pennycress is hardy to prolonged waterlogging at the vegetative stage. Furthermore, we chose three "susceptible" and five "tolerant" accessions to waterlog for one week at the reproductive stage, the growth stage aligned with heavy spring rainfall. Six accessions had significantly reduced seed weight at maturity after recovery from waterlogging, and two accessions had minimal impacts on growth and seed yield after waterlogging. These two accessions can be used in future studies to explore adaptive traits, such as changes in root characteristics, as well as the genetic variation that contributes to pennycress waterlogging tolerance.