AgResearch Ltd., Hamilton, New Zealand.
Bio-Protection Research Centre, Lincoln University, Lincoln, New Zealand.
PLoS One. 2021 Nov 30;16(11):e0259912. doi: 10.1371/journal.pone.0259912. eCollection 2021.
When successful, the operation of local and international networks of crop seed distribution or "seed systems" ensures farmer access to seed and impacts rural livelihoods and food security. Farmers are both consumers and producers in seed systems and benefit from access to global markets. However, phytosanitary measures and seed purity tests are also needed to maintain seed quality and prevent the spread of costly weeds, pests and diseases, in some countries regulatory controls have been in place since the 1800s. Nevertheless, seed contaminants are internationally implicated in between 7% and 37% of the invasive plant species and many of the agricultural pests and diseases. We assess biosecurity risk across international seed trade networks of forage crops using models of contaminant spread that integrate network connectivity and trade volume. To stochastically model hypothetical contaminants through global seed trade networks, realistic dispersal probabilities were estimated from quarantine weed seed detections and incursions from border security interception data in New Zealand. For our test case we use contaminants linked to the global trade of ryegrass and clover seed. Between 2014 and 2018 only four quarantine weed species (222 species and several genera are on the quarantine schedule) warranting risk mitigation were detected at the border. Quarantine weeds were rare considering that average import volumes were over 190 tonnes for ryegrass and clover, but 105 unregulated contaminant species were allowed in. Ryegrass and clover seed imports each led to one post-border weed incursion response over 20 years. Trade reports revealed complex global seed trade networks spanning >134 (ryegrass) and >110 (clover) countries. Simulations showed contaminants could disperse to as many as 50 (clover) or 80 (ryegrass) countries within 10 time-steps. Risk assessed via network models differed 18% (ryegrass) or 48% (clover) of the time compared to risk assessed on trade volumes. We conclude that biosecurity risk is driven by network position, the number of trading connections and trade volume. Risk mitigation measures could involve the use of more comprehensive lists of regulated species, comprehensive inspection protocols, or the addition of field surveillance at farms where seed is planted.
当成功运作本地和国际作物种子分销网络或“种子系统”时，可确保农民获得种子，并影响农村生计和粮食安全。农民既是种子系统的消费者也是生产者，他们从进入全球市场中受益。然而，为了保持种子质量和防止昂贵的杂草、害虫和疾病的传播，还需要植物检疫措施和种子纯度测试。在一些国家，自 19 世纪以来就已经实施了监管控制。尽管如此，种子污染物在国际上被认为是 7%至 37%的入侵植物物种以及许多农业害虫和疾病的成因。我们使用整合了网络连通性和贸易量的污染物传播模型，评估了草料作物国际种子贸易网络的生物安全风险。为了通过全球种子贸易网络随机模拟假设的污染物，我们从新西兰的检疫杂草种子检测和边境安全截获数据中估计了现实的扩散概率。对于我们的测试案例，我们使用与黑麦草和三叶草种子的全球贸易相关的污染物。在 2014 年至 2018 年期间，在边境仅发现了四种需要减轻风险的检疫杂草物种（检疫清单上有 222 种和几个属）。考虑到黑麦草和三叶草的平均进口量超过 190 吨，但有 105 种不受监管的污染物被允许进入，检疫杂草是罕见的。20 年来，黑麦草和三叶草种子进口各导致一次边境后杂草入侵反应。贸易报告显示，跨越 134 多个（黑麦草）和 110 多个（三叶草）国家的复杂全球种子贸易网络。模拟表明，污染物可在 10 个时间步内扩散到多达 50 个（三叶草）或 80 个（黑麦草）国家。通过网络模型评估的风险与通过贸易量评估的风险相比，有 18%（黑麦草）或 48%（三叶草）的时间存在差异。我们的结论是，生物安全风险由网络位置、贸易联系数量和贸易量驱动。缓解措施可以包括使用更全面的受监管物种清单、全面的检查协议，或在种植种子的农场增加田间监测。
