Seed bank, seed bank, seed bank: the population persistence of Brassica hybrids as influenced by crop rotations

Hooftman, Danny; Bullock, James; Hails, Rosemary. 2011 Seed bank, seed bank, seed bank: the population persistence of Brassica hybrids as influenced by crop rotations. [Speech] In: Environmental impact of genetically modified crops: European experience. IOBC / WPRS 5th EIGMO MEETING, Ceske Budejovice, June 22 – 25, 2011. (Unpublished)

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The interest in the possible persistence of crop x wild relative hybrids in agricultural fields is two-fold. Firstly, in-field weed populations could become introgressed with crop genes, including transgenes. Secondly, hybrids could serve as a temporal bridge, linking sequential crops. Although many studies have studied hybrid fitness, very few have tested all life stage transitions within one single experiment. Here, we tested the fitness of hybrids between Brassica napus (Oilseed Rape) and B. rapa in an agricultural habitat. Our analyses include matrix elasticities, LTRE and periodic matrices, including crop rotations. We found no differences in survival or germination rate between parental species and hybrids, but hybrids had a lower number of pods, seeds per pod and seed viability. This difference in fecundity leads to a large difference in λ between parents (56 and 96 for B. rapa and B. napus) and hybrids (0.58), using conventional matrices. However, by including crop rotations and a constant ability for outcrossing, this difference becomes small: B. rapa λ = 0.88, B. napus 1.00 and hybrids 0.88. All classes are fully dependent on survival in the seed bank in the years without B. napus cultivation. Hence, seed bank survival becomes the dominant component of the life-cycle. Our results highlight that hybrids can persist within crop fields for over 20 years, leaving ample opportunity for unintended stacking of transgenic constructs to occur. Novel combinations of traits could trigger as yet unanticipated enhanced weediness of hybrid plants, forcing weed management to become more elaborate and expensive. Moreover, the high dependence on, and elasticity of, seed bank survival, suggests the need for future research into management efforts that would increase seed mortality, such as depth and timing of tillage.

Item Type: Publication - Conference Item (Speech)
Programmes: CEH Topics & Objectives 2009 - 2012 > Biodiversity
UKCEH and CEH Sections/Science Areas: Hails
NORA Subject Terms: Ecology and Environment
Agriculture and Soil Science
Related URLs:
Date made live: 11 Sep 2013 14:47 +0 (UTC)

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