Targeted sequencing of the \u3ci\u3ePanicum miliaceum\u3c/i\u3e gene space and genotyping of variant sites from population genetics studies, combined in a single assay, as a tool for broomcorn millet assisted breeding

Broomcorn millet (Panicum miliaceum L.) is a prehistorical cereal, today cultivated as a minor crop with low yields but with a renewed interest for its high water use effciency and gluten-free grains. To reverse the downward trend in broomcorn millet cultivation, the crop needs genetic improvement and creation of novel genetic variation to increase productivity. In order to facilitate genomics-assisted breeding, we designed a reduced representation genome-sequencing assay that investigates 1.8% of the nuclear DNA in a targeted and reproducible way, with an intensity of genomic sampling that is a direct function of local recombination rate. We used this tool and set up bioinformatics analyses tailored to the polyploid genome of P. miliaceum for maternity and paternity testing, quantification and genomic distribution of homozygous regions and estimation of parental genome contribution for individual seedlings in advanced inbred lines from a breeding program and compared their genomic composition with registered varieties. We found several clues that suggest that the genetic purifcation process to ensure genetic uniformity is incomplete in varieties of this species. Residual heterozygosity was detected in the genome of three registered varieties ranging from 4.4 to 6.25% of their haploid genome length. Other registered varieties show genome-wide homozygosity. We found, however, evidence of intravarietal genetic variation in three cases that suggest that the breeder seed or commercial seed production had fixed by self-pollination multiple inbred lines with very similar, though not identical, genotypes within each variety

Analysis of Croatian wild and cultivated grapevine diversity by genotyping by sequencing

Minor varieties represent a significant part of the grapevine germplasm (Vitis vinifera L. subsp. vinifera) in Croatia. During the long history of grape cultivation in insular, coastal and continental Croatia, numerous local varieties were cultivated, many of which are still used today. There are also several populations of wild grapevine (Vitis vinifera subsp. sylvestris Hegi Gmel) that have survived until the present in natural sites. Here, we developed a single primer enrichment technology (SPET) panel consisting of 61,308 probes for targeted sequencing of the V. vinifera gene space. In doing so, we examined a total of 28,092 gene models, 88.2% of all predicted genes, interrogating an average of 19 Mb nucleotides per individual genome, which corresponds to 4% of the haploid genome length. This is the first time that SPET-based sequencing has been applied to Croatian grapevine germplasm to generate multilocus genotype data of 126 cultivated accessions and 50 wild specimens. We identified 531,900 variants sites, 208,802 of which reside in coding sequences, 140,836 in introns, 118,416 in UTRs, and 63,424 in the nearby intergenic space that revealed the presence of 33 clonally propagated specimens representing both synonymies and clones within local varieties (22) as well as synonymies between local and international varieties (11), mostly from neighbouring countries. To investigate possible contribution of wild grapevine (Vitis vinifera subsp. sylvestris Hegi Gmel) to the development of present cultivars, four wild grapevine populations were included. None of the cultivated varieties showed close kinship with local wild specimens. This study opens new possibilities for studying the genetic diversity of Croatian grapevine germplasm and provides additional information with respect to SSR genotyping and phenotyping

Grapevine field experiments reveal the contribution of genotype, the influence of environment and the effect of their interaction (GxE) on berry transcriptome

Changes in the performance of genotypes in different environments are defined as genotype x environment (GxE) interactions. In grapevine (Vitis vinifera), complex interactions between different genotypes and climate, soil, and farming practices yield unique berry qualities. However, the molecular basis of this phenomenon remains unclear. To dissect the basis of grapevine GxE interactions, we characterized berry transcriptome plasticity, genome methylation landscape, and within-genotype allelic diversity in two genotypes, cultivated in three different environments, over two vintages. We identified, through a novel data-mining pipeline, genes with expression profiles that were unaffected by genotype or environment, genotype-dependent but unaffected by the environment, environmentally-dependent regardless of genotype, and GxE-related. The GxE-related genes showed different degrees of within-cultivar allelic diversity in the two genotypes and were enriched for stress responses, signal transduction and secondary metabolism categories. Our study unraveled the mutual relationships between genotypic and environmental variables during GxE interaction in a woody perennial species, providing a reference model to explore how cultivated fruit crops respond to diverse environments. Also, the pivotal role of vineyard location in determining the performance of different varieties, by enhancing berry quality traits, was unraveled

A single polyploidization event at the origin of the tetraploid genome of Coffea arabica is responsible for the extremely low genetic variation in wild and cultivated germplasm

The genome of the allotetraploid species Coffea arabica L. was sequenced to assemble independently the two component subgenomes (putatively deriving from C. canephora and C. eugenioides) and to perform a genome-wide analysis of the genetic diversity in cultivated coffee germplasm and in wild populations growing in the center of origin of the species. We assembled a total length of 1.536 Gbp, 444 Mb and 527 Mb of which were assigned to the canephora and eugenioides subgenomes, respectively, and predicted 46,562 gene models, 21,254 and 22,888 of which were assigned to the canephora and to the eugeniodes subgenome, respectively. Through a genome-wide SNP genotyping of 736 C. arabica accessions, we analyzed the genetic diversity in the species and its relationship with geographic distribution and historical records. We observed a weak population structure due to low-frequency derived alleles and highly negative values of Taijma's D, suggesting a recent and severe bottleneck, most likely resulting from a single event of polyploidization, not only for the cultivated germplasm but also for the entire species. This conclusion is strongly supported by forward simulations of mutation accumulation. However, PCA revealed a cline of genetic diversity reflecting a west-to-east geographical distribution from the center of origin in East Africa to the Arabian Peninsula. The extremely low levels of variation observed in the species, as a consequence of the polyploidization event, make the exploitation of diversity within the species for breeding purposes less interesting than in most crop species and stress the need for introgression of new variability from the diploid progenitors

Characterisation of the pan-genome of Vitis vinifera using Next Generation Sequencing

The main objective of the present project is the characterisation of the dispensable portion of Vitis vinifera pan-genome, mostly attributable to Structural Variants (SVs). Single Nucleotide Polymorphism (SNP) markers were used to explore the grapevine population structure and to assess the genetic relationships between individuals. In a subset of 50 varieties, representative of the genetic diversity of the grapevine population, we investigated at genome-wide level the structural variants shaping the V. vinifera pan-genome

Extent of wild–to–crop interspecific introgression in grapevine (Vitis vinifera) as a consequence of resistance breeding and implications for the crop species definition

Over the past two centuries, introgression through repeated backcrossing has introduced disease resistance from wild grape species into the domesticated lineage Vitis vinifera subsp. sativa. Introgression lines are being cultivated over increasing vineyard surface areas, as their wines now rival in quality those obtained from preexisting varieties. There is, however, a lot of debate about whether and how wine laws defining commercial product categories, which are based on the classification of V. vinifera and interspecific hybrid grapes, should be revised to accommodate novel varieties that do not fit either category. Here, we developed a method of multilocus genotype analysis using short–read resequencing to identify haplotypic blocks of wild ancestry in introgression lines and quantify the physical length of chromosome segments free–of–introgression or with monoallelic and biallelic introgression. We used this genomic data to characterize species, hybrids and introgression lines and show that newly released resistant varieties contain 76.5–94.8% of V. vinifera DNA. We found that varietal wine ratings are not always commensurate with the percentage of V. vinifera ancestry and linkage drag of wild alleles around known resistance genes persists over at least 7.1–11.5 Mb, slowing down the recovery of the recurrent parental genome. This method also allowed us to identify the donor species of resistance haplotypes, define the ancestry of wild genetic background in introgression lines with complex pedigrees, validate the ancestry of the historic varieties Concord and Norton, and unravel sample curation errors in public databases

Symptom expression and 'Candidatus Phytoplasma prunorum' concentration in different Prunus species

Abstract A SYBR ® Green I real-time PCR assay has been used for specific detection and quantification of 'Candidatus Phytoplasma prunorum' in different Prunus species such as P. armeniaca, P. salicina, P. persica and P. tomentosa grown in a screenhouse and infected by means of the vector. Infection level of 'Ca. P. prunorum' in plant samples, expressed as 'Ca. P. prunorum' GU per ng of plant DNA, was achieved by the standard curve quantification method choosing rplV (rpl22) gene as target for phytoplasma quantification and plant 18S rDNA to normalize the data. Visual inspections of the plants maintained in the screenhouse and qualitative molecular data demonstrated that the species P. armeniaca and P. salicina are the most susceptible and sensitive, that P. persica is less susceptible but quite sensitive and finally that P. tomentosa is less susceptible and quite tolerant. Quantitative molecular data for the first time demonstrated, for the first time, that 'Ca. P. prunorum' titre increases during the vegetative season, and that symptom expression is correlated with its infection level

ddRAD-seq reveals the genetic structure and detects signals of selection in Italian brown trout

BACKGROUND: Brown trout is one of the most widespread fresh-water fish species in Europe. The evolutionary history of and phylogenetic relationships between brown trout populations are complex, and this is especially true for Italian populations, which are heavily influenced in different ways by stocking practices. The characterization of the genetic structure of Italian brown trout populations may give information on the risk of losing endemic Italian populations due to lack of genetic diversity or to admixture with stocking populations. The identification of signatures of selection, and the information deriving from dense genotyping data will help genotype-informed breeding programs. We used a ddRAD-seq approach to obtain more than 100,000 single nucleotide polymorphisms (SNPs), and to characterize the population structure and signatures of selection in 90 brown trout samples. RESULTS: Italian brown trout populations are genetically differentiated, although the stocking practices have introduced strong admixture in endemic Italian trout, especially with the Atlantic lineage. Most of the analysed populations showed high levels of kinship and inbreeding. We detected putative signatures of selection using different approaches, and investigated if the regions were enriched for functional categories. Several regions putatively under selection and characterized by a reduction in heterozygosity across all the studied populations are enriched for genes involved in the response to viral infections. CONCLUSIONS: Our results, which show evidence of admixture with the Atlantic lineage (commonly used for stocking), confirm the need for controlling stocking practices, in order to avoid the erosion of the endemic gene pool; given the apparently high levels of kinship and inbreeding in local populations, our results also show the need to take action for increasing gene diversity. In addition, we used the genetically-distinct lineages to detect signatures of selection and we identified putative signatures of selection in several regions associated with resistance to infectious diseases. These constitute candidate regions for the study of resistance to infections in wild and farmed trout. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12711-022-00698-7

Genetic, epigenetic and genomic effects on variation of gene expression among grape varieties

The transcriptional regulatory structure of plant genomes is still relatively unexplored, and little is known about factors that influence expression variation in plants. We used a genetic system consisting of 10 heterozygous grape varieties with high consanguinity and high haplotypic diversity to: (i) identify regions of haplotype sharing through whole-genome resequencing and single-nucleotide polymorphism (SNP) genotyping; (ii) analyse gene expression through RNA-seq in four stages of berry development; and (iii) associate gene expression variation with genetic and epigenetic properties. We found that haplotype sharing in and around genes was positively correlated with similarity in expression and was negatively correlated with the fraction of differentially expressed genes. Genetic and epigenetic properties of the gene and the surrounding region showed significant effects on the extent of expression variation, with negative associations for the level of gene body methylation and mean expression level, and with positive associations for nucleotide diversity, structural diversity and ratio of non-synonymous to synonymous nucleotide diversity. We also observed a spatial dependency of covariation of gene expression among varieties. These results highlight relevant roles for cis-acting factors, selective constraints and epigenetic features of the gene, and the regional context in which the gene is located, in the determination of expression variation. Open Research Badges: This article has earned an Open Data Badge for making publicly available the digitally-shareable data necessary to reproduce the reported results. The data is available at https://www.ncbi.nlm.nih.gov/bioproject/PRJNA385116; https://www.ncbi.nlm.nih.gov/bioproject/PRJNA392287; https://www.ncbi.nlm.nih.gov/bioproject/PRJNA373967 (released upon publication); https://www.ncbi.nlm.nih.gov/bioproject/PRJNA490160 (released upon publication); https://www.ncbi.nlm.nih.gov/bioproject/PRJNA265039; https://www.ncbi.nlm.nih.gov/bioproject/PRJNA265040. © 2019 The Authors The Plant Journa