Talk Unintended spillage of viable oilseed rape seeds along transportation routes in Austria: ecological risk assessment and management of feral plants

Oilseed rape (OSR; Brassica napus) is a worldwide cultivated crop of hybrid origin. Although OSR is unknown as a wild plant, it frequently occurs as a feral plant and is able to hybridise with many related species. Because of their small size, OSR seeds are regularly spilled during handling and transportation. Genetically modified (GM), herbicide resistant OSR is now widely grown in North America. Transportation and handling activities have been identified as main cause of the unintended occurrence and subsequent establishment of feral GM OSR populations in countries without GM OSR cultivation, e.g. Japan and Switzerland. Import restrictions in countries banning cultivation of GM OSR are based on concerns that introgression of transgenes may cause problems with weed management and compromise the integrity of genetic resources in wild relatives. We surveyed abundance and genetic diversity of feral OSR at 60 sampling sites in Austria, aiming to assess the risk of establishment of feral populations from non GM seed imports. Sampling sites included predefined hotspots with a high expectation for seed spillage such as switchyards, border railway stations, main ports, and OSR importing oil mills as well as randomly selected road sections (2 kilometres), railway stations and small ports. For comparison, 37 seed samples grown in Austria during the last ten years as well as eight varieties from abroad were obtained from commercial breeders. A total of 2,113 feral OSR individuals were sampled from spring to summer in 2014 and 2015. At 44 sampling sites, feral OSR was found. DNA was extracted from young leaves to assay genotypes at ten microsatellite loci. Genetic diversity among commercial varieties was lower than in earlier studies using similar methods. Feral populations had higher genetic diversity than the commercial varieties, but less than 5% of the genetic variance was distributed among populations. This result indicates that feral populations along transport routes and near processing facilities receive a constant input of diverse seeds. The highest allelic richness was observed at ports and oil mills, rendering these sites of primary concern with respect to possible escape of transgenic OSR. Measures to reduce spillage of imported OSR seeds and their establishment should focus on herbicide application and also on intensification of alternative weed management such as mowing or spraying of organic herbicides. The mode of seed packing during transportation is an important factor: whereas loose transport facilitates seed loss, closed big bags limit spillage. More intense controls should be implemented at railway borders in Austria to prevent spillage due to inappropriate transportation facilities such as defect or sloppily closed unloading hatches of goods wagons. Border railway stations to Italy were identified as spillage hotspots. Because different voltage is used for running the trains (Austria 15 kV, Italy 3 kV), they have to come to a stop at the border. Moreover, sufficient cleaning of goods wagons as well as loading areas of trucks and ships is an essential measure.

oilseed rape (OSR), Brassica napus, feral crop, transport, handling, import, seed spillage, genetically modified, herbicide resistance, ecological risk assessment, population genetics, measures