No abstract

Understanding the mechanisms underlying biological invasions and rapid adaptation to global change remains a fundamental challenge, particularly in small populations lacking in genetic variation. Two understudied mechanisms that could facilitate adaptive evolution and adaptive plasticity are the increased genetic variation due to transposable elements (TEs), and associated or independent modification of gene expression through epigenetic changes. Here, we focus on the potential role of these genetic and non‐genetic mechanisms for facilitating invasion success. Because novel or stressful environments are known to induce both epigenetic changes and TE activity, these mechanisms may play an underappreciated role in generating phenotypic and genetic variation for selection to act on. We review how these mechanisms operate, the evidence for how they respond to novel or stressful environments, and how these mechanisms can contribute to the success of biological invasions by facilitating adaptive evolution and phenotypic plasticity. Because genetic and phenotypic variations due to TEs and epigenetic changes are often well regulated or “hidden” in the native environment, the independent and combined contribution of these mechanisms may only become important when populations colonize novel environments. A focus on the mechanisms that generate and control the expression of this variation in new environments may provide insights into biological invasions that would otherwise not be obvious. Global changes and human activities impact on ecosystems and allow new opportunities for biological invasions. Invasive species succeed by adapting rapidly to new environments. The degree to which rapid responses to environmental change could be mediated by the epigenome—the regulatory system that integrates how environmental and genomic variation jointly shape phenotypic variation—requires greater attention if we want to understand the mechanisms by which populations successfully colonize and adapt to new environments. A free Plain Language Summary can be found within the Supporting Information of this article.

Fruit-set and seed-set depend on environmental conditions and reproductive systems. They are important components of sexual reproductive success in plants. They also control the ecological success and adaptation of invasive plants within their nonnative ecosystems. We studied which factors bring about fruit-set and seed-set in invasive populations of the aquatic plant Ludwigia grandiflora subsp. hexapetala. We analyzed fruit set and seed set in 37 populations growing under variable climatic conditions in Western Europe. Sub-samples of seven fruitful and fruitless populations were grown in common controlled conditions. We carried out self-and crosspollinations, and measured the floral morphometry. Environmental conditions did not affect fruit-set and seed-set in-situ and in common controlled environments. Handpollinations showed that individuals from fruitful populations exhibited fruit and seed production whatever the pollen donor, whereas individuals from fruitless populations only did so when pollen came from fruitful populations. Floral morphometry evidenced the existence of two floral morphs that fully overlapped with fruitfulness, and individual incompatibility. Our results rebutted the hypothesis that environmental variations control fruit set and seed set in these invasive populations. We instead showed that fruit set and seed set were controlled by a heteromorphic reproductive system involving a self-incompatible and inter-morph compatible morph (long-styled morph), and a self-and inter-morph compatible reverse morph (short-styled morph).We collected morphs and fruit set records of this species worldwide and found the same relationship: fruitless populations were all composed only of individuals with long-styled floral morph. Our study constitutes the first evidence of a heteromorphic self-incompatible system in Ludwigia genus and Onagraceae family. K E Y W O R D Sheteromorphic self-incompatible system, freshwater invasion, climate impact, management plan, Ludwigia grandiflora subsp. HexapetalaThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

The homogeneity of anther culture-derived lines of maize has been evaluated by means of field observations and molecular markers. The homogeneity of the doubled haploid (DH) lines was shown by the absence of segregation for morphological oligogenic traits. The intravariance for polygenic traits for 42 DH and two conventionally derived lines was similar, which confirmed the homozygosity of the DH lines. More than 100 RFLP markers were tested on 189 DH lines derived from two crosses, DH5 x DH7 and A188 x DH7, and 60 single-seed descent (SSD, F6) lines derived from A188 x DH7. The overall rate of heterozygosity for all of the DH lines was approximatively 1% and pertained to 6 lines out of 189, while it was 8.5% for the SSD lines after four selfings. A precise description of the material used suggested that the events which led to this unexpected heterozygozity in DH lines were more likely to have occurred after rather than during the androgenetic process. Nine duplicated pairs of genotypes were found within the DH lines, indicating that a single microspore-derived structure can fragment to give two identical plantlets. Despite the extensive screening with more than 100 markers, only 2 lines showed unexpected banding profiles, and these were probably gametoclonal variants. The use of a direct regeneration system that avoids any callus phase might explain this low frequency of gametoclonal variation.

Powdery mildew is one of the major diseases of wheat in regions with a maritime or semi-continental climate which can strongly affect grain yield. The objective of the study was to identify and compare quantitative resistance to powdery mildew of line RE9001 at the adult plant and vernalized seedling stages. RE9001 has no known Pm gene and shows a high level of adult plant resistance in the field. Using 104 recombinant inbred lines (RILs) of an RE9001 · 'Courtot' F8 population, a genetic map was developed with 363 markers distributed over 26 linkage groups and covering 3825 cM. The global map density was 1 locus/10.3 cM. RILs were assessed under field and tunnel greenhouse conditions for 2 years in two locations. Eleven quantitative trait loci (QTL) were detected at the adult stage and they explained 63% of the variation, depending on the environment. Three QTLs were found, at least, in the two environments. One QTL from RE9001, mapped on chromosome 2B, was stable in each environment. This QTL, QPm.inra.2B, explained 10.3-36.6% of the variation and could be mapped in the vicinity of the Pm6 gene. At the vernalized seedling stage, one QTL detected by the isolate 93-27 could be an allele of the Pm3g gene present in 'Courtot'. No residual effect of the Pm3g gene was detected at either stage. Markers flanking the QTL 2B could be useful tools to combine resistance to powdery mildew in wheat cultivars.

The Pm3 resistance locus, located on chromosome 1A in wheat, confers race-specific resistance to the obligate biotrophic fungus Blumeria graminis (DC) E.O. Speer f. sp. tritici, the causal agent of powdery mildew. Several Pm3 alleles are still effective in controlling the disease in Europe. A genetic map was constructed to map the Pm3g allele in the recombinant inbred line progeny from the cross ÔRE9001Õ (susceptible) · ÔCourtotÕ (resistant). Two microsatellite markers were closely mapped to Pm3g. The PSP2999 marker, which cosegregates with this allele, was shown to detect the presence of the Pm3g resistance allele in other cultivars. A collection of 56 wheat cultivars or advanced lines carrying one Pm3 allele was used to assess the allelespecific amplification of the PSP2999 marker. The same amplification pattern was obtained for lines with Pm3a, Pm3b, Pm3e, Pm3f and Pm3g alleles. Twenty genotypes carrying Pm3d showed a specific amplification pattern. This marker allowed the detection of the Pm3d allele in highly resistant lines whose resistance gene combinations were unknown. It was concluded that PSP2999 is a useful marker to detect Pm3 alleles in parents and to manage them in breeding programmes.

In the context of expansion of invasive species, survival of invasive plants is conditioned by their ability to adapt. In France, the water primrose Ludwigia grandiflora, an aquatic invasive species, invades yet wet meadows, leading to a depreciation of their fodder value. Understanding its potential adaption is necessary to its management, strong differences between both morphotypes were expected. So morphological and metabolic responses to terrestrial environment were analyzed for aquatic and terrestrial morphotypes. All morphological and biomass variables were greater in the terrestrial morphotype than the aquatic morphotype, independent of conditions. In terrestrial condition, both morphotypes showed a high production of sugars in root tissues, especially in the terrestrial morphotype and both morphotypes produced a low level of amino acids in shoot tissues. All results demonstrate that the terrestrial condition seems a stressful situation for both morphotypes, which activates glycolysis and fermentation pathways to improve their survival under hypoxic stress. But, only the terrestrial morphotype has been able to adjust its metabolism and maintain efficient growth. In the future, a differential transcriptomic analysis will be carried out to confirm this result.

Sourdille, P., Charmet, G., Trottet, M., Tixier, M. H. Boeuf, C., Negre, S., Barloy, D. and Bernard, M. 1998. Linkage between RFLP molecular markers and the dwarfing genes Rht-B1 and Rht-Dl in wheat. -Hereditas 128: 41-46. Lund, Sweden. Identifying genotypes carrying the dwarfing genes Rht-BZ and Rht-DZ would be of great interest for wheat (Triticum aestiuum L. em Thell) breeding. Two RFLP loci were found to be linked to those two genes, Xpsr 1 4 -4 8 with Rht-Bl on chromosome 4BS and Xglk578-4D with Rht-Dl on chromosome 4DS, by genotyping two F, populations, Renan (Rht-Blb) x Camp-Rimy and Rendez-Vous (Rht-Dlb) x Roazon. Utilisation of these markers in breeding schemes is discussed.