Potential for seed-mediated gene flow in agroecosystems from transgenic safflower (Carthamus tinctorius L.) intended for plant molecular farming

Abstract

Safflower has been transformed for field scale molecular farming of high-value proteins including several pharmaceuticals. Viable safflower seed remaining in the soil seed bank after harvest could facilitate seed and pollen-mediated gene flow. Seeds may germinate in subsequent years and volunteer plants may flower and potentially outcross with commodity safflower and/or produce seed. Seeds from volunteers could become admixed with conventional crops at harvest, and/or replenish the seed bank. Seed in following crops could be transported locally and internationally and facilitate gene flow in locations where regulatory thresholds and public acceptance differ from Canada. Seed-mediated gene flow was examined in three studies. Safflower seed loss and viability following harvest of commercial fields of a non-transgenic cultivar were determined. We assessed seed longevity of transgenic and non-transgenic safflower, on the soil surface and buried at two depths. Finally, we surveyed commercial safflower fields at different sites and measured density and growth stage of safflower volunteers, in other crops the following year and documented volunteer survival and viable seed production. Total seed loss at harvest in commercial fields, ranged from 231 to 1,069 seeds m(-2) and the number of viable seeds ranged from 81 to 518 seeds m(-2). Safflower has a relatively short longevity in the seed bank and no viable seeds were found after 2 years. Based on the seed burial studies it is predicted that winter conditions would reduce safflower seed viability on the soil surface by >50%, leaving between 40 and 260 viable seeds m(-2). The density of safflower volunteers emerging in the early spring of the following year ranged from 3 to 11 seedlings m(-2). Safflower volunteers did not survive in fields under chemical fallow, but in some cereal fields small numbers of volunteers did survive and generate viable seed. Results will be used to make recommendations for best management practices to reduce seed-mediated gene flow from commercial production of plant molecular farming with safflower.

Description of safflower (Carthamus tinctorius) phenological growth stages according to the extended BBCH scale

“…McPherson et al () and Víchová et al () mentioned some BBCH codes for safflower in their works about gene flow and plant disease, respectively. Nevertheless, there are no publications describing safflower growth stages according to the BBCH scale.…”

“…Nevertheless, there are no publications describing safflower growth stages according to the BBCH scale. Furthermore, McPherson et al () explain that safflower growth stages were described using the sunflower BBCH scale. However, growth characteristics of safflower plants are different than sunflower, especially with respect to flowering, fruit development and ripening (Lancashire et al , ).…”

Assessment of Genetic Diversity and Population Structure in a Global Reference Collection of 531 Accessions of Carthamus tinctorius L. (Safflower) Using AFLP Markers

“…However, archaeo-botanical evidence suggests its cultivation as a major oil crop in the Near East dating back to the Bronze Age (Marinova and Riehl 2009). It has also been used as a platform for production of plant-derived pharmaceuticals (McPherson et al 2009;Flider 2013;Carlsson et al 2014), biofuels, and as a source of industrial oil (Velasco et al 2005;Ilkılıç et al 2011). Safflower is cultivated in arid and semi-arid conditions in various agricultural zones across the world (Weiss 1983).…”

Development of Systems for the Production of Plant-Derived Biopharmaceuticals

“…When plant-made pharmaceuticals produced via molecular farming enter the commercial market, their production needs to meet regulatory requirements and address public concerns regarding containment of transgenic crops [79]. Best management practices to reduce seed-mediated gene flow and environment contamination by pollen transmission have been published [80]. Two recent articles indicate that the incidence of pollen transmission ranges from 0.00024% to 0.0087% [81,82].…”