Abstract
Seeds present a naturally occurring package of germplasm with ideal attributes for collection, distribution and, in the case of orthodox seed, long term storage. From a phytosanitary perspective seeds are often considered a relatively low-risk option for movement of germplasm across borders. Most published data are concerned with diseases of commercial crops and little is known about the risks associated with wild collected, non-commercial seeds. However, there is demonstrable risk associated with the movement of any plant germplasm which can pose a risk to both crops and the wider environment. Presented here are a discussion on seed standards and the difference between seed borne and seed transmitted pathogens, with case studies presented to highlight the risks associated with informal seed systems and wild collected seeds in particular. Additionally, suggestions on how to address phytosanitary issues are presented including awareness raising measures aimed at improving biosecurity procedures during collection and before long-term storage of seed accessions.
Highlights
Most horticulturists view seeds as naturally occurring, convenient packages for the movement of ‘starter material’, i.e. plentiful, small, robust and, in the case of orthodox seed, offering good ‘shelf life’
From the black rot bacteria (Xanthomonas campestris pv. campestris) of brassica crops (Shekhawat et al, 1982) and tomato brown rugose fruit virus (ToBRFV) on tomatoes (Davino et al, 2020; Dombrovsky & Smith, 2017) to Megastigmus sp. seed chalcids associated with wild-origin native and exotic Rosa species growing at Royal Botanic Gardens (RBG), Kew (UK) and the Muséum National d’Histoire Naturelle (MNHN) in Paris (Roques & Auger-Rozenberg, 2016), a growing body of evidence demonstrates very clearly that seed from any source has the potential to act as an important pathway for the introduction of pests and pathogens to new areas
The commercial seed trade is regulated and, risks such as that highlighted with ToBRFV are present, there are both visual and diagnostic checks during production and in trade to mitigate against the risks of importing seed with damaging viruses or other pathogens
Summary
Most horticulturists view seeds as naturally occurring, convenient packages for the movement of ‘starter material’, i.e. plentiful, small, robust and, in the case of orthodox seed, offering good ‘shelf life’. In traded seed lots, provided infection levels are below a threshold estimated to be sufficiently low as to not pose a significant threat to the productivity and quality of any resulting crop, seed will usually be distributed for cultivation. Seed chalcids (wasp) associated with wild-origin native and exotic Rosa species growing at Royal Botanic Gardens (RBG), Kew (UK) and the Muséum National d’Histoire Naturelle (MNHN) in Paris (Roques & Auger-Rozenberg, 2016), a growing body of evidence demonstrates very clearly that seed from any source has the potential to act as an important pathway for the introduction of pests and pathogens to new areas. Botanic garden staff involved in biosecurity have been raising concerns about the potential for seeds from trade and botanic gardens to act as a pathway for the distribution of non-native organisms, including plant pests and pathogens (Symes, 2011). Additional measures which could be implemented for improving procedures to enhance biosecurity at a local level are discussed
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