Molecular biogeography of prickly lettuce (lactuca serriola l.) shows traces of recent range expansion

Prickly lettuce (Lactuca serriola L., Asteraceae), a wild relative of cultivated lettuce, is an autogamous species which greatly expanded throughout Western and Northern Europe during the last 2 centuries. Here, we present a large-scale biogeographic genetic analysis performed on a dataset represented by 2622 individuals from 110 wild European populations. Thirty-two maternally inherited chloroplast RFLP-markers and 10 nuclear microsatellite loci were used. Microsatellites revealed low genetic variation and high inbreeding coefficients within populations, as well as strong genetic differentiation between populations, which was in accordance with the autogamous breeding system. Analysis of molecular variance based clustering indicated the presence of 3 population clusters, which showed strong geographical patterns. One cluster occupied United Kingdom and part of Northern Europe, and characterized populations with a single predominant genotype. The second mostly combined populations from Northern Europe, while the third cluster grouped populations particularly from Southern Europe. Kriging of gene diversity for L. serriola corroborated northwards and westwards spread from Central (Eastern) Europe. Significant lower genetic diversity characterized the newly colonized parts of the range compared to the historical ones, confirming the importance of founder effects. Stronger pattern of isolation by distance was assessed in the newly colonized areas than in the historical areas (Mantel’s r = 0.20). In the newly colonized areas, populations at short geographic distances were genetically more similar than those in the historical areas. Our results corroborate the species’ recent and rapid northward and westward colonization from Eastern Europe, as well as a decrease of genetic diversity in recently established populations

Genomic regions in crop-wild hybrids of lettuce are affected differently in different environments: implications for crop breeding

Many crops contain domestication genes that are generally considered to lower fitness of crop–wild hybrids in the wild environment. Transgenes placed in close linkage with such genes would be less likely to spread into a wild population. Therefore, for environmental risk assessment of GM crops, it is important to know whether genomic regions with such genes exist, and how they affect fitness. We performed quantitative trait loci (QTL) analyses on fitness(-related) traits in two different field environments employing recombinant inbred lines from a cross between cultivated Lactuca sativa and its wild relative Lactuca serriola. We identified a region on linkage group 5 where the crop allele consistently conferred a selective advantage (increasing fitness to 212% and 214%), whereas on linkage group 7, a region conferred a selective disadvantage (reducing fitness to 26% and 5%), mainly through delaying flowering. The probability for a putative transgene spreading would therefore depend strongly on the insertion location. Comparison of these field results with greenhouse data from a previous study using the same lines showed considerable differences in QTL patterns. This indicates that care should be taken when extrapolating experiments from the greenhouse, and that the impact of domestication genes has to be assessed under field conditions

How to Assure That Farmers Apply New Technology According to Good Agricultural Practice: Lessons From Dutch Initiatives

The application of Good Agricultural Practice (GAP) contributes to many aspects of sustainable farming, including integrated control of weeds, diseases, and pests, and optimization of fertilization and irrigation. It is a relatively neglected issue in debates regarding the application of new technology, such as genetic modification (GM), which often revolve around the intrinsic properties of a GM crop allegedly leading to unsatisfactory performance. However, the performance largely depends on the agronomic and institutional embedding of applying new technology, which generally applies to all crops, whether conventional or GM. We describe and discuss four cases in which the government or private partners in the production chain regulate this, using legal measures, incentives, or mutual agreements, or a combination thereof. These cases serve as a starting point for a discussion on how GAP can be stimulated, organized, and guaranteed. We argue that next to the government, also seed suppliers, NGOs, and buyers, as well as farmers can be drivers for the application of GAP when tools are available that enable farmers to make optimal farming choices

Abiotic stress QTL in lettuce crop–wild hybrids: comparing greenhouse and field experiments

The development of stress-tolerant crops is an increasingly important goal of current crop breeding. A higher abiotic stress tolerance could increase the probability of introgression of genes from crops to wild relatives. This is particularly relevant to the discussion on the risks of new GM crops that may be engineered to increase abiotic stress resistance. We investigated abiotic stress QTL in greenhouse and field experiments in which we subjected Recombinant Inbred Lines from a cross between cultivated Lactuca sativa cv. Salinas and its wild relative L. serriola to drought, low nutrients, salt stress, and above ground competition. Aboveground biomass at the end of the rosette stage was used as a proxy for the performance of plants under a particular stress. We detected a mosaic of abiotic stress QTL over the entire genome with little overlap between QTL from different stresses. The two QTL clusters that were identified reflected general growth rather than specific stress responses and co-located with clusters found in earlier studies for leaf shape and flowering time. Genetic correlations across treatments were often higher among different stress treatments within the same experiment (greenhouse or field), than among the same type of stress applied in different experiments. Moreover, the effects of the field stress treatments were more correlated to those of the greenhouse competition treatments than to those of the other greenhouse stress experiments, suggesting that competition rather than abiotic stress is a major factor in the field. In conclusion, the introgression risk of stress tolerance (trans-)genes under field conditions cannot easily be predicted based on genomic background selection patterns from controlled QTL experiments in greenhouses. Especially field data will be needed to assess potential (negative) ecological effects of introgression of these transgenes into wild relatives

Crop to wild introgression in lettuce: following the fate of crop genome segments in backcross populations

Background: After crop-wild hybridization, some of the crop genomic segments may become established in wild populations through selfing of the hybrids or through backcrosses to the wild parent. This constitutes a possible route through which crop (trans)genes could become established in natural populations. The likelihood of introgression of transgenes will not only be determined by fitness effects from the transgene itself but also by the crop genes linked to it. Although lettuce is generally regarded as self-pollinating, outbreeding does occur at a low frequency. Backcrossing to wild lettuce is a likely pathway to introgression along with selfing, due to the high frequency of wild individuals relative to the rarely occurring crop-wild hybrids. To test the effect of backcrossing on the vigour of inter-specific hybrids, Lactuca serriola, the closest wild relative of cultivated lettuce, was crossed with L. sativa and the F1 hybrid was backcrossed to L. serriola to generate BC1 and BC2 populations. Experiments were conducted on progeny from selfed plants of the backcrossing families (BC1S1 and BC2S1). Plant vigour of these two backcrossing populations was determined in the greenhouse under non-stress and abiotic stress conditions (salinity, drought, and nutrient deficiency). Results: Despite the decreasing contribution of crop genomic blocks in the backcross populations, the BC1S1 and BC2S1 hybrids were characterized by a substantial genetic variation under both non-stress and stress conditions. Hybrids were identified that performed equally or better than the wild genotypes, indicating that two backcrossing events did not eliminate the effect of the crop genomic segments that contributed to the vigour of the BC1 and BC2 hybrids. QTLs for plant vigour under non-stress and the various stress conditions were detected in the two populations with positive as well as negative effects from the crop. Conclusion: As it was shown that the crop contributed QTLs with either a positive or a negative effect on plant vigour, we hypothesize that genomic regions exist where transgenes could preferentially be located in order to mitigate their persistence in natural populations through genetic hitchhiking

Veredeling voor de ecosysteemdiensten plaagonderdrukking en bestuiving in voedingsgewassen

Natuurinclusieve teelten kunnen bijdragen aan het verduurzamen van de landbouw. Een belangrijk element daarin is het optimaal gebruik maken van ecosysteemdiensten. Een divers agro-ecosysteem is daarvoor een basisvoorwaarde. Vanuit veredelingsperspectief roept dit de vraag op of gewassen ook verbeterd kunnen worden voor het ondersteunen van ecosysteemdiensten. Om hier zicht op te krijgen is voor deze deskstudie gekeken naar wat erover gerapporteerd is in de wetenschappelijke literatuur voor twee voorbeelden van ecosysteemdiensten, bestuiving en plaagonderdrukking. Zonder volledigheid na te streven is een globale inventarisatie gemaakt, aangevuld met een aantal voorbeelden met relevantie voor de biologische teelt in Nederland. Interessant voor veredeling is dat voor bestuiving zowel als plaagonderdrukking variatie beschreven is in genetische bronnen van gewassen voor eigenschappen van belang voor het aantrekken van bestuivers dan wel natuurlijke vijanden van plaaginsecten; zoals de productie van vluchtige stoffen, het verschaffen van beloningen, zoals nectar en de toegankelijkheid van de bloem. Tegelijkertijd gaat het echter om voor de veredeling relatief complexe systemen. De te veredelen bloemkenmerken zijn slechts een onderdeel voor een succesvolle bestuiving. Bij plaagonderdrukking komt bovenop een klassieke aanpak via resistentieveredeling op de directe interactie tussen plant en plaaginsect, ook de interactie met parasitoïden en/of predatoren via complexe mengsels van signaalstoffen en beloningen door de plant. Tegelijkertijd is de wijdere omgeving van de teelten van bijzonder belang voor continuïteit in het verschaffen van voeding en schuilplaatsen voor bestuivers en natuurlijke vijanden. Ten dele kan dit ondervangen worden via intercropping en bloemenranden. Voor slechts een beperkt aantal combinaties van gewas en plaaginsecten zijn uitgebreider relaties met natuurlijke vijanden beschreven, inclusief voor veredeling belangrijke variatie in de betrokken planteigenschappen. Bij bestuiving is de informatie over de relatie tussen bloemeigenschappen en het aantrekken en ondersteunen van bestuivers onvolledig en soms inconsistent. Voor het optimaliseren van ecosysteemdiensten via gewasveredeling zal meer onderzoek gedaan moeten worden naar deze eigenschappen en hun interacties met het teeltsysteem en de omringende landschapselementen. Concluderend wordt gesteld dat er mogelijkheden zijn om natuurlijke plaagonderdrukking en bestuiving mee te nemen in de ontwikkeling van nieuwe rassen. Dit opent een nieuw perspectief op de ontwikkeling van een natuurinclusieve landbouw

Invloed van gewassen op bodemkwaliteit: Variatie tussen genotypen : een verkennende literatuurstudie voor ruwvoedergewassen

Gewassen beïnvloeden de bodem waarop ze geteeld worden. In deze verkennende literatuurstudie is onderzocht wat er bekend is over variatie tussen verschillende genotypen/plantenrassen met betrekking tot hun effect op bodemkwaliteit voor een aantal ruwvoedergewassen, in het bijzonder Maïs (Zea mays), Engels raaigras (Lolium perenne) en Witte klaver (Trifolium repens). Dergelijke variatie zou mogelijkheden kunnen bieden om via veredeling en het inzetten van specifieke rassen de bodemkwaliteit te verbeteren. Er is betrekkelijk weinig onderzoek vanuit deze invalshoek gedaan. De focus van de studie was gericht op variatie in wortelarchitectuur, en wortelexudatie en wortelafsterving/nieuwvorming in relatie tot het organische stof gehalte en beschikbaarheid van nutriënten, en de bodem biota, met name mycorrhiza

Genetic engineering at the heart of agroecology

We discuss whether genetic engineering and agroecology are compatible. For this, we investigated three cases of genetically engineered crops and considered agroecology as scientific discipline as well as a social movement. One case was the use of cisgenic modifications to make potato durably resistant to late blight, the second was the use of CRISPR/Cas to make rice resistant to bacterial blight and as a third case, we evaluated experiences with cultivating transgenic Bt crops. These cases demonstrated that genetic engineering offers opportunities to grow crops in novel integrated pest management (IPM) systems with, as direct benefit, a decrease in the use of chemical crop protection agents, and as indirect effect that the role of predators and biological control agents can become more important than in present conventional systems based on pesticides. We used a framework based on four concerns (both cons and pros) that were gathered from an extensive societal interaction organized around the Dutch research project DuRPh, which produced a proof-of-concept of a cisgenic late blight-resistant potato. We concluded that genetic engineering and agroecology certainly have synergy in the context of agroecology as science, when applied to making crops less vulnerable to pests and diseases and when combined with cultivation using IPM. By contrast, within the movement context, genetically engineered varieties may be welcomed if they include traits that contribute to successful IPM schemes and are socially benign. Whether they would actually be deemed desirable or acceptable will, however, vary depending on the norms and values of the social movements. We propose that some concerns may be reconcilable in a dialogue. Deontological arguments such as naturalness are more difficult to reconcile, as they relate to deeply felt ethical or cultural values. A step forward would be when also for these arguments everyone can make an informed choice and when these choices can coexist in a respectful manner.</p