Faba bean (Vicia faba L.) is a facultative cross-pollinating legume crop with a great importance for food and feed due to its high protein content as well as the important role in soil fertility and nitrogen fixation. In this work we evaluated genetic diversity and population structure of faba bean accessions from the Western Mediterranean basin and wild related species. For that purpose we screened 53 V. faba, 2 V. johannis and 7 V. narbonensis accessions from Portugal, Spain and Morocco with 28 faba bean Single Sequence Repeats (SSR). SSR genotyping showed that the number of alleles detected per locus for the polymorphic markers ranged between 2 and 10, with Polymorphic Information Content (PIC) values between 0.662 and 0.071, and heterozygosity (H_O) between 0–0.467. Heterozygosity and inbreeding coefficient levels indicate a higher level of inbreeding in wild related species than in cultivated Vicia. The analysis of molecular variance (AMOVA) showed a superior genetic diversity within accessions than between accessions even from distant regions. These results are in accordance to population structure analysis showing that individuals from the same accession can be genetically more similar to individuals from far away accessions, than from individuals from the same accession. In all three levels of analysis (whole panel of cultivated and wild accessions, cultivated faba bean accessions and Portuguese accessions) no population structure was observed based on geography or climatic factors. Differences between V. narbonensis and V. johannis are undetectable although these wild taxa are clearly distinct from V. faba accessions. Thus, a limited gene flow occurred between cultivated accessions and wild relatives. Contrastingly, the lack of population structure seems to indicate a high degree of gene flow between V. faba accessions, possibly explained by the partially allogamous habit in association with frequent seed exchange/introduction.

Genomic diversity of Portuguese accessions of Avena species—diploid A. strigosa and hexaploids A. sativa and A. sterilis—was evaluated through molecular and cytological analysis of 45S rDNA, and other repetitive sequences previously studied in cereal species—rye subtelomeric sequence (pSc200) and cereal centromeric sequence (CCS1). Additionally, retrotransposons and microsatellites targeting methodologies—IRAP (inter-retrotransposon amplified polymorphism) and REMAP (retrotransposon-microsatellite amplified polymorphism)—were performed. A very high homology was detected for ribosomal internal transcribed sequences (ITS1 and ITS2) between the species analyzed, although nucleolar organizing regions (NOR) fluorescent in situ hybridization (FISH) analysis revealed distinct number of Nor loci between diploid and hexaploid species. Moreover, morphological diversity, evidenced by FISH signals with different sizes, was observed between distinct accessions within each species. pSc200 sequences were for the first time isolated from Avena species but proven to be highly similar in all genotypes analyzed. The use of primers designed for CCS1 unraveled a sequence homologous to the Ty3/gypsy retrotransposon Cereba, that was mapped to centromeric regions of diploid and hexaploid species, being however restricted to the more related A and D haplomes. Retrotransposon-based methodologies disclosed species- and accessions-specific bands essential for the accurate discrimination of all genotypes studied. Centromeric, IRAP and REMAP profiles therefore allowed accurate assessment of inter and intraspecific variability, demonstrating the potential of these molecular markers on future oat breeding programs.

Wheat is one of the most important cereals for food and feed, and it is, therefore, necessary to determine the effects of short-term high temperature events (heatwaves) during grain filling. These heatwave events are increasingly common, especially in Portugal. In this work, seven commercial varieties recommended for production in Portugal were submitted to one-week high temperature (HT) treatment ten days after anthesis to evaluate heat effects on grain yield and quality. Grain yield parameters, such as grain number and weight, were evaluated as well as grain composition through attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Variation in HT response between varieties was detected. Grain number and weight tended to decrease in most varieties analyzed. However, two varieties proved to be more resilient since grain number and weight remain unaltered in the Bancal variety, which is the one with better yield results, and even increased in the Pata Negra variety. Regarding grain composition, the comparison between ATR-FTIR spectra of milled grains from control and HT plants revealed alterations in peaks assigned to polysaccharides and proteins. Additionally, a model was built based on nitrogen elemental analysis to predict protein content in flour samples through spectral data that corroborated the differences identified by spectra profile comparison. Moreover, both analyses showed that the intervarietal diversity observed in control conditions was significantly reduced in HT treated plants. The results obtained highlight the intervarietal diversity of wheat response to HT, regarding grain yield parameters, grain composition, and particularly, protein content.

Understanding how increased genome size and diversity within polyploid genomes impacts plant evolution and breeding continues to be challenging. Although historical studies by McClintock suggested the importance of transposable elements mediated by polyploidisation on genomic changes, data from plant crosses remain scarce. Despite the absence of a conclusive proof regarding autonomous retrotransposon movement in synthetic allopolyploids, the transposition of retrotransposons and their ubiquitous dispersion in all plant species might explain the positive correlation between the genome size of plants and the prevalence of retrotransposons. Here, we address polyploidisation-mediated rearrangements of retrotransposon-associated sequences and discuss a tendency for a preferential restructuring of large ancestral genomes after polyploidisation. A comparative analysis of the frequency of modifications of retrotransposon-associated sequences in synthetic polyploids with marked differences in genome sizes is presented. Such analyses suggest the absence of a significant difference in the rates of rearrangements despite vast dissimilarities in the retrotransposon copy number between species, which emphasises the high plasticity of this genomic feature. See also the sister article focusing on animals by Arkhipova and Rodriguez in this themed issue.

The plant stress response has been extensively characterized at the biochemical and physiological levels. However, knowledge concerning repetitive sequence genome fraction modulation during extreme temperature conditions is scarce. We studied high-temperature effects on subtelomeric repetitive sequences (pSc200) and 45S rDNA in rye seedlings submitted to 40°C during 4 h. Chromatin organization patterns were evaluated through fluorescent in situ hybridization and transcription levels were assessed using quantitative real-time PCR. Additionally, the nucleolar dynamics were evaluated through fibrillarin immunodetection in interphase nuclei. The results obtained clearly demonstrated that the pSc200 sequence organization is not affected by high-temperature stress (HTS) and proved for the first time that this noncoding subtelomeric sequence is stably transcribed. Conversely, it was demonstrated that HTS treatment induces marked rDNA chromatin decondensation along with nucleolar enlargement and a significant increase in ribosomal gene transcription. The role of noncoding and coding repetitive rye sequences in the plant stress response that are suggested by their clearly distinct behaviors is discussed. While the heterochromatic conformation of pSc200 sequences seems to be involved in the stabilization of the interphase chromatin architecture under stress conditions, the dynamic modulation of nucleolar and rDNA topology and transcription suggest their role in plant stress response pathways.

Wheat is undoubtedly one of the most important crops worldwide and it is essential to study how the distinct varieties answer to heat waves associated with climatic changes, in order to design adequate wheat breeding strategies. To assess high temperature (HT) impact in wheat grain characteristics, seven commercial varieties, which have been recommended for production in Portugal, were submitted for one-week HT treatment ten days after anthesis. Firstly, predicted grain technological quality was determined by giving high scores for all varieties studied, based on the allelic compositions of genes encoding high molecular weight glutenins, granule-bound starch synthase and puroindolines. The effects of HT on transcription levels of those genes were, for the first time, evaluated in distinct wheat genotypes, in comparison with control plants. Finally, protein fraction content in mature grains were also estimated in untreated and treated plants. Immature grains from plants, maintained in control conditions, showed significant intervarietal differences in transcription levels of genes associated with grain quality traits, a variability that was significantly reduced in grains from HT treated plants. On the other hand, the influence of HT in mature grain protein-fractions and in gliadin/glutenin ratios revealed intervarietal diversity, even with opposite effects in some varieties. The present study, therefore, discloses marked variability in parameters associated with flour quality between the wheat varieties analyzed, which are differentially affected by HT treatments, similar to heat waves frequently observed in climate change scenarios.