Charlotte J. Allender

Fitness of hybrids between rapeseed (Brassica napus) and wild Brassica rapa in natural habitats

Fitness of hybrids between genetically modified (GM) crops and wild relatives influences the likelihood of ecological harm. We measured fitness components in spontaneous (non‐GM) rapeseed × Brassica rapa hybrids in natural populations. The F1 hybrids yielded 46.9% seed output of B. rapa, were 16.9% as effective as males on B. rapa and exhibited increased self‐pollination. Assuming 100% GM rapeseed cultivation, we conservatively predict < 7000 second‐generation transgenic hybrids annually in the United Kingdom (i.e. ∼20% of F1 hybrids). Conversely, whilst reduced hybrid fitness improves feasibility of bio‐containment, stage projection matrices suggests broad scope for some transgenes to offset this effect by enhancing fitness.

Genetic structure and domestication of carrot (Daucus carota subsp. sativus) (Apiaceae)

UNLABELLED PREMISE OF THE STUDY Analyses of genetic structure and phylogenetic relationships illuminate the origin and domestication of modern crops. Despite being an important worldwide vegetable, the genetic structure and domestication of carrot (Daucus carota) is poorly understood. We provide the first such study using a large data set of molecular markers and accessions that are widely dispersed around the world. • METHODS Sequencing data from the carrot transcriptome were used to develop 4000 single nucleotide polymorphisms (SNPs). Eighty-four genotypes, including a geographically well-distributed subset of wild and cultivated carrots, were genotyped using the KASPar assay. • KEY RESULTS Analysis of allelic diversity of SNP data revealed no reduction of genetic diversity in cultivated vs. wild accessions. Structure and phylogenetic analysis indicated a clear separation between wild and cultivated accessions as well as between eastern and western cultivated carrot. Among the wild carrots, those from Central Asia were genetically most similar to cultivated accessions. Furthermore, we found that wild carrots from North America were most closely related to European wild accessions. • CONCLUSIONS Comparing the genetic diversity of wild and cultivated accessions suggested the absence of a genetic bottleneck during carrot domestication. In conjunction with historical documents, our results suggest an origin of domesticated carrot in Central Asia. Wild carrots from North America were likely introduced as weeds with European colonization. These results provide answers to long-debated questions of carrot evolution and domestication and inform germplasm curators and breeders on genetic substructure of carrot genetic resources.

Spontaneous gene flow from rapeseed (Brassica napus) to wild Brassica oleracea

Research on the environmental risks of gene flow from genetically modified (GM) crops to wild relatives has traditionally emphasized recipients yielding most hybrids. For GM rapeseed (Brassica napus), interest has centred on the ‘frequently hybridizing’ Brassica rapa over relatives such as Brassica oleracea, where spontaneous hybrids are unreported in the wild. In two sites, where rapeseed and wild B. oleracea grow together, we used flow cytometry and crop-specific microsatellite markers to identify one triploid F1 hybrid, together with nine diploid and two near triploid introgressants. Given the newly discovered capacity for spontaneous introgression into B. oleracea, we then surveyed associated flora and fauna to evaluate the capacity of both recipients to harm cohabitant species with acknowledged conservational importance. Only B. oleracea occupies rich communities containing species afforded legislative protection; these include one rare micromoth species that feeds on B. oleracea and warrants further assessment. We conclude that increased attention should now focus on B. oleracea and similar species that yield few crop-hybrids, but possess scope to affect rare or endangered associates.

Rapeseed cytoplasm gives advantage in wild relatives and complicates genetically modified crop biocontainment

Biocontainment methods for genetically modified crops closest to commercial reality (chloroplast transformation, male sterility) would be compromised (in absolute terms) by seed-mediated gene flow leading to chloroplast capture. Even in these circumstances, however, it can be argued that biocontainment still represses transgene movement, with the efficacy depending on the relative frequency of seed- and pollen-mediated gene flow. In this study, we screened for crop-specific chloroplast markers from rapeseed (Brassica napus) amongst sympatric and allopatric populations of wild B. oleracea in natural cliff-top populations and B. rapa in riverside and weedy populations. We found only modest crop chloroplast presence in wild B. oleracea and in weedy B. rapa, but a surprisingly high incidence in sympatric (but not in allopatric) riverside B. rapa populations. Chloroplast inheritance models indicate that elevated crop chloroplast acquisition is best explained if crop cytoplasm confers selective advantage in riverside B. rapa populations. Our results therefore imply that chloroplast transformation may slow transgene recruitment in two settings, but actually accelerate transgene spread in a third. This finding suggests that the appropriateness of chloroplast transformation for biocontainment policy depends on both context and geographical location.

Development of best practices for ex situ conservation of radish germplasm in the context of the crop genebank knowledge base

Information about crop-specific best practices for ex situ conservation of plant genetic resources has been difficult to find until recently. The CGIAR, together with national and regional partners, started to fill that gap by publishing best practices on the crop genebank knowledge base (CGKB -http://cropgenebank.sgrp.cgiar.org/), a website specifically developed and officially launched in 2010 to provide easy access to knowledge about all aspects of ex situ conservation of specific crops to genebank managers and ex situ conservation researchers. A collaborative study, undertaken by Bioversity International with eight national and international genebanks, utilized the framework provided by the CGKB to develop and publish radish conservation best practices. This paper focuses on two aspects of this study: (1) Differences in procedures and practices in radish conservation currently applied in five key genebank activities, namely, acquisition of germplasm, viability testing and monitoring, seed drying, seed storage, and regeneration. While in a few cases genebanks agreed on a specific best practice to recommend, in others it was not desirable to identify one practice as superior to another, therefore a range of existing practices is described as a variety of equivalent options. The results highlight the importance of proactive genebank management aimed at meeting the standards within the specific context in which a genebank operates. (2) The framework and template provided by the CGKB in guiding the development of genebank best practices, and the CGKB as an excellent resource to widely and freely share best practices with the global community to support the effective management of crop genebanks.

Who is sowing our seeds? A systematic review of the use of plant genetic resources in research

Collections of plant genetic resources managed by genebanks function to conserve the range of genetic diversity present in crop genepools. They can facilitate access to valuable allelic variation for both plant breeders and researchers who are able to request germplasm for use in crop improvement and both basic and applied scientific research. The direct impact of genebank collections is often unclear as downstream uses of germplasm samples may not be reported back to the genebank of origin. This study aims to systematically review scientific use of germplasm using the UK Vegetable Genebank (UKVGB) as a model. Between the years of 1980–2016, a total of 271 publications were identified as using UKVGB material. The frequency of publications and the international nature of use increased significantly over the time period studied. Accessions directly sourced from the UKVGB made up the majority of material used by researchers, but material from research-derived resources such as differential sets and core collections or diversity sets have also been used. Resistance to pests and diseases and genetic diversity were the main topics of study although germplasm was used to address a wide range of other research questions. Genebanks such as UKVGB provide an essential resource of allelic diversity in crop genepools which supports a diverse range of research projects. The utilisation of these plant genetic resources has increased over time, contributing to a substantial number of publications. Developments in sequencing technologies have no doubt played a part as larger numbers of accessions can be utilized in a single experiment, but the increase also no doubt reflects a greater interest in the use of allelic diversity to overcome challenges in crop improvement and research.