An international breeding project using a wild potato relative Solanum commersonii resulted in two new frost-tolerant native potato cultivars for the Andes and the Altiplano.

This breeding project, initiated at the United States Potato Genebank (USPG) in collaboration with Peruvian partners Instituto Nacional de Innovacion Agraria (INIA), International Potato Center, Peru (CIP), and local farmers, sought to enhance cold hardiness and frost tolerance in native potato cultivars in Peru. The Andes and Altiplano are often affected by frost, which causes significant reduction in yield; creating varieties with superior resilience is a critical undertaking. The goal was to transfer outstanding non-acclimated cold tolerance and acclimation capacity found in wild potato species Solanum commersonii (cmm). Breeding families segregating for cold hardiness were created using (a) a somatic hybrid cmm + haploid Solanum tuberosum (tbr) (cv. Superior, US variety from Wisconsin) as male and (b) seven cultivars native to Peru of the species S. tuberosum sbsp. andigenum (adg) as females. All plant materials were part of the USPG germplasm collection. Sexual seeds of each family were sent to Peru for evaluations under the natural conditions of the Andean highlands and Altiplano. The plants were assessed for their response to frost, and genotypes showing exceptional tolerance were selected. Plants were also evaluated for good tuber traits and yield. Initial planting involving ~2,500 seedlings in five locations resulted in selecting 58 genotypes with exceptional frost tolerance, good recovery capacity after frost, and good tuber traits. Over the years, evaluations continued and were expanded to replicated field trials in the harsher conditions of the Altiplano (Puno). All trials confirmed consistency of frost tolerance over time and location, tuber quality, and yield. After 8 years, two advanced clones were considered for cultivar release because of their exceptional frost tolerance and superior field productivity that outyielded many of the established cultivars in the region. In November 2018, a new native cultivar named Wiñay, a Quechua word meaning "to grow" was released in Peru. In 2022, a second cultivar followed with the name Llapanchispaq (meaning "for all of us"). This project evidenced that a multinational and all-encompassing approach to deploy valuable genetic diversity can work and deliver effective results. This is even more significant when outcomes can promote food security and sustainability in very vulnerable regions of the world.

Evolutionary relationships, hybridization and diversification under domestication of the locoto chile (Capsicum pubescens) and its wild relatives.

Patterns of genetic variation in crops are the result of multiple processes that have occurred during their domestication and improvement, and are influenced by their wild progenitors that often remain understudied. The locoto chile, Capsicum pubescens, is a crop grown mainly in mid-highlands of South-Central America. This species is not known from the wild and exists only as a cultigen. The evolutionary affinities and exact origin of C. pubescens have still not been elucidated, with hypotheses suggesting its genetic relatedness and origin to two wild putative ancestral Capsicum species from the Central Andes, C. eximium and C. cardenasii. In the current study, RAD-sequencing was applied to obtain genome-wide data for 48 individuals of C. pubescens and its wild allies representing different geographical areas. Bayesian, Maximum Likelihood and coalescent-based analytical approaches were used to reconstruct population genetic patterns and phylogenetic relationships of the studied species. The results revealed that C. pubescens forms a well-defined monotypic lineage closely related to wild C. cardenasii and C. eximium, and also to C. eshbaughii. The primary lineages associated with the diversification under domestication of C. pubescens were also identified. Although direct ancestor-descendant relationship could not be inferred within this group of taxa, hybridization events were detected between C. pubescens and both C. cardenasii and C. eximium. Therefore, although hybrid origin of C. pubescens could not be inferred, gene flow involving its wild siblings was shown to be an important factor contributing to its contemporary genetic diversity. The data allowed for the inference of the center of origin of C. pubescens in central-western Bolivia highlands and for better understanding of the dynamics of its gene pool. The results of this study are essential for germplasm conservation and breeding purposes, and provide excellent basis for further research of the locoto chile and its wild relatives.

Population Genomics of Domesticated Cucurbita ficifolia Reveals a Recent Bottleneck and Low Gene Flow with Wild Relatives.

Cucurbita ficifolia is a squash grown from Mexico to Bolivia. Its ancestor is unknown, but it has limited compatibility with wild xerophytic Cucurbita from Mexico's highlands. We assembled the reference genome of C. ficifolia and assessed the genetic diversity and historical demography of the crop in Mexico with 2524 nuclear single nucleotide polymorphisms (SNPs). We also evaluated the gene flow between C. ficifolia and xerophytic taxa with 6292 nuclear and 440 plastome SNPs from 142 individuals sampled in 58 sites across their area of sympatry. Demographic modelling of C. ficifolia supports an eight-fold decrease in effective population size at about 2409 generations ago (95% CI = 464-12,393), whereas plastome SNPs support the expansion of maternal lineages ca. 1906-3635 years ago. Our results suggest a recent spread of C. ficifolia in Mexico, with high genetic diversity (π = 0.225, FST = 0.074) and inbreeding (FIS = 0.233). Coalescent models suggest low rates of gene flow with C. radicans and C. pedatifolia, whereas ABBA-BABA tests did not detect significant gene flow with wild taxa. Despite the ecogeographic proximity of C. ficifolia and its relatives, this crop persists as a highly isolated lineage of puzzling origin.

The ORGAN SIZE (ORG) locus modulates both vegetative and reproductive gigantism in domesticated tomato.

BACKGROUND AND AIMS: Gigantism is a key component of the domestication syndrome, a suite of traits that differentiates crops from their wild relatives. Allometric gigantism is strongly marked in horticultural crops, causing disproportionate increases in the size of edible parts such as stems, leaves or fruits. Tomato (Solanum lycopersicum) has attracted attention as a model for fruit gigantism, and many genes have been described controlling this trait. However, the genetic basis of a corresponding increase in size of vegetative organs contributing to isometric gigantism has remained relatively unexplored. METHODS: Here, we identified a 0.4-Mb region on chromosome 7 in introgression lines (ILs) from the wild species Solanum pennellii in two different tomato genetic backgrounds (cv. 'M82' and cv. 'Micro-Tom') that controls vegetative and reproductive organ size in tomato. The locus, named ORGAN SIZE (ORG), was fine-mapped using genotype-by-sequencing. A survey of the literature revealed that ORG overlaps with previously mapped quantitative trait loci controlling tomato fruit weight during domestication. KEY RESULTS: Alleles from the wild species led to lower cell number in different organs, which was partially compensated by greater cell expansion in leaves, but not in fruits. The result was a proportional reduction in leaf, flower and fruit size in the ILs harbouring the alleles from the wild species. CONCLUSIONS: Our findings suggest that selection for large fruit during domestication also tends to select for increases in leaf size by influencing cell division. Since leaf size is relevant for both source-sink balance and crop adaptation to different environments, the discovery of ORG could allow fine-tuning of these parameters.

Genomic analysis unveils reduced genetic variability but increased proportion of heterozygotic genotypes of the intensively managed mezcal agave, Agave angustifolia.

PREMISE: The central Oaxaca Basin has a century-long history of agave cultivation and is hypothesized to be the region of origin of other cultivated crops. Widely cultivated for mezcal production, the perennial crop known as "espadín" is putatively derived from wild Agave angustifolia. Nevertheless, little is known about its genetic relationship to the wild A. angustifolia or how the decades-long clonal propagation has affected its genetics. METHODS: Using restriction-site-associated DNA sequencing and over 8000 single-nucleotide polymorphisms, we studied aspects of the population genomics of wild and cultivated A. angustifolia in Puebla and Oaxaca, Mexico. We assessed patterns of genetic diversity, inbreeding, distribution of genetic variation, and differentiation among and within wild populations and plantations. RESULTS: Genetic differentiation between wild and cultivated plants was strong, and both gene pools harbored multiple unique alleles. Nevertheless, we found several cultivated individuals with high genetic affinity with wild samples. Higher heterozygosity was observed in the cultivated individuals, while in total, they harbored considerably fewer alleles and presented higher linkage disequilibrium compared to the wild plants. Independently of geographic distance among sampled plantations, the genetic relatedness of the cultivated plants was high, suggesting a common origin and prevalent role of clonal propagation. CONCLUSIONS: The considerable heterozygosity found in espadín is contained within a network of highly related individuals, displaying high linkage disequilibrium generated by decades of clonal propagation and possibly by the accumulation of somatic mutations. Wild A. angustifolia, on the other hand, represents a significant genetic diversity reservoir that should be carefully studied and conserved.

Multiple domestication events explain the origin of Gossypium hirsutum landraces in Mexico.

Several Mesoamerican crops constitute wild-to-domesticated complexes generated by multiple initial domestication events, and continuous gene flow among crop populations and between these populations and their wild relatives. It has been suggested that the domestication of cotton (Gossypium hirsutum) started in the northwest of the Yucatán Peninsula, from where it spread to other regions inside and outside of Mexico. We tested this hypothesis by assembling chloroplast genomes of 23 wild, landraces, and breeding lines (transgene-introgressed and conventional). The phylogenetic analysis showed that the evolutionary history of cotton in Mexico involves multiple events of introgression and genetic divergence. From this, we conclude that Mexican landraces arose from multiple wild populations. Our results also revealed that their structural and functional chloroplast organizations had been preserved. However, genetic diversity decreases as a consequence of domestication, mainly in transgene-introgressed (TI) individuals (π = 0.00020, 0.00001, 0.00016, 0, and 0, of wild, TI-wild, landraces, TI-landraces, and breeding lines, respectively). We identified homologous regions that differentiate wild from domesticated plants and indicate a relationship among the samples. A decrease in genetic diversity associated with transgene introgression in cotton was identified for the first time, and our outcomes are therefore relevant to both biosecurity and agrobiodiversity conservation.

Collecting wild potato species (Solanum sect. Petota) in Peru to enhance genetic representation and fill gaps in ex situ collections.

Crop wild relatives (CWRs) are important sources of novel genes, due to their high variability of response to biotic and abiotic stresses, which can be invaluable for crop genetic improvement programs. Recent studies have shown that CWRs are threatened by several factors, including changes in land-use and climate change. A large proportion of CWRs are underrepresented in genebanks, making it necessary to take action to ensure their long-term ex situ conservation. With this aim, 18 targeted collecting trips were conducted during 2017/2018 in the center of origin of potato (Solanum tuberosum L.), targeting 17 diverse ecological regions of Peru. This was the first comprehensive wild potato collection in Peru in at least 20 years and encompassed most of the unique habitats of potato CWRs in the country. A total of 322 wild potato accessions were collected as seed, tubers, and whole plants for ex situ storage and conservation. They belonged to 36 wild potato species including one accession of S. ayacuchense that was not conserved previously in any genebank. Most accessions required regeneration in the greenhouse prior to long-term conservation as seed. The collected accessions help reduce genetic gaps in ex situ conserved germplasm and will allow further research questions on potato genetic improvement and conservation strategies to be addressed. These potato CWRs are available by request for research, training, and breeding purposes under the terms of the International Treaty for Plant Genetic Resources for Food and Agriculture (ITPGRFA) from the Instituto Nacional de Innovacion Agraria (INIA) and the International Potato Center (CIP) in Lima-Peru.

Corrigendum: How could the use of crop wild relatives in breeding increase the adaptation of crops to marginal environments?

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How Could the Use of Crop Wild Relatives in Breeding Increase the Adaptation of Crops to Marginal Environments?

Alongside the use of fertilizer and chemical control of weeds, pests, and diseases modern breeding has been very successful in generating cultivars that have increased agricultural production several fold in favorable environments. These typically homogeneous cultivars (either homozygous inbreds or hybrids derived from inbred parents) are bred under optimal field conditions and perform well when there is sufficient water and nutrients. However, such optimal conditions are rare globally; indeed, a large proportion of arable land could be considered marginal for agricultural production. Marginal agricultural land typically has poor fertility and/or shallow soil depth, is subject to soil erosion, and often occurs in semi-arid or saline environments. Moreover, these marginal environments are expected to expand with ongoing climate change and progressive degradation of soil and water resources globally. Crop wild relatives (CWRs), most often used in breeding as sources of biotic resistance, often also possess traits adapting them to marginal environments. Wild progenitors have been selected over the course of their evolutionary history to maintain their fitness under a diverse range of stresses. Conversely, modern breeding for broad adaptation has reduced genetic diversity and increased genetic vulnerability to biotic and abiotic challenges. There is potential to exploit genetic heterogeneity, as opposed to genetic uniformity, in breeding for the utilization of marginal lands. This review discusses the adaptive traits that could improve the performance of cultivars in marginal environments and breeding strategies to deploy them.

Phylogenomic analysis points to a South American origin of Manihot and illuminates the primary gene pool of cassava.

The genus Manihot, with around 120 known species, is native to a wide range of habitats and regions in the tropical and subtropical Americas. Its high species richness and recent diversification only c. 6 million years ago have significantly complicated previous phylogenetic analyses. Several basic elements of Manihot evolutionary history therefore remain unresolved. Here, we conduct a comprehensive phylogenomic analysis of Manihot, focusing on exhaustive sampling of South American taxa. We find that two recently described species from northeast Brazil's Atlantic Forest were the earliest to diverge, strongly suggesting a South American common ancestor of Manihot. Ancestral state reconstruction indicates early Manihot diversification in dry forests, with numerous independent episodes of new habitat colonization, including into savannas and rainforests within South America. We identify the closest wild relatives to Manihot esculenta, including the crop cassava, and we quantify extensive wild introgression into the cassava gene pool from at least five wild species, including Manihot glaziovii, a species used widely in breeding programs. Finally, we show that this wild-to-crop introgression substantially shapes the mutation load in cassava. Our findings provide a detailed case study for neotropical evolutionary history in a diverse and widespread group, and a robust phylogenomic framework for future Manihot and cassava research.

Solanum malmeanum, a promising wild relative for potato breeding.

Crop wild relatives are gaining increasing attention. Their use in plant breeding is essential to broaden the genetic basis of crops as well as to meet industrial demands, for global food security and sustainable production. Solanum malmeanum (Solanum sect. Petota, Solanaceae) is a wild relative of potatoes (S. tuberosum) from Southern South America, occurring in Argentina, Brazil, Paraguay and Uruguay. This wild potato has been largely mistaken for or historically considered as conspecific with S. commersonii. Recently, it was reinstated at the species level. Retrieving information on its traits and applied uses is challenging, because the species name has not always been applied correctly and also because species circumscriptions and morphological criteria applied to recognize it have not been consistent. To overcome these difficulties, we performed a thorough literature reference survey, herbaria specimens' identification revision and genebank database queries to review and update the information available on this potato wild relative, contributing to an increase in research on it to fully understand and explore its potential for potato breeding. Scarce studies have been carried out concerning its reproductive biology, resistance against pests and diseases as well as tolerance to abiotic stresses and evaluation of quality traits. The scattered information available makes it less represented in genebanks and genetic studies are missing. We compile, update and present available information for S. malmeanum on taxonomy, geographical distribution, ecology, reproductive biology, relationship with its closest relatives, biotic and abiotic stresses resistance and quality traits and discuss ways to overcome sexual barriers of hybridization and future perspectives for its use in potato breeding. As a final remark, we highlight that this species' potential uses have been neglected and must be unlocked. Thus, further studies on morphological and genetic variability with molecular tools are fundamental for an efficient conservation and applied use of this promising genetic resource.

Crop genetic erosion: understanding and responding to loss of crop diversity.

Crop diversity underpins the productivity, resilience and adaptive capacity of agriculture. Loss of this diversity, termed crop genetic erosion, is therefore concerning. While alarms regarding evident declines in crop diversity have been raised for over a century, the magnitude, trajectory, drivers and significance of these losses remain insufficiently understood. We outline the various definitions, measurements, scales and sources of information on crop genetic erosion. We then provide a synthesis of evidence regarding changes in the diversity of traditional crop landraces on farms, modern crop cultivars in agriculture, crop wild relatives in their natural habitats and crop genetic resources held in conservation repositories. This evidence indicates that marked losses, but also maintenance and increases in diversity, have occurred in all these contexts, the extent depending on species, taxonomic and geographic scale, and region, as well as analytical approach. We discuss steps needed to further advance knowledge around the agricultural and societal significance, as well as conservation implications, of crop genetic erosion. Finally, we propose actions to mitigate, stem and reverse further losses of crop diversity.

Phylogenetic diversity and conservation of crop wild relatives in Colombia.

Crop wild relatives (CWR) are an important agricultural resource as they contain genetic traits not found in cultivated species due to localized adaptation to unique environmental and climatic conditions. Phylogenetic diversity (PD) measures the evolutionary relationship of species using the tree of life. Our knowledge of CWR PD in neotropical regions is in its infancy. We analysed the distribution of CWR PD across Colombia and assessed its conservation status. The areas with the largest concentration of PD were identified as being in the northern part of the central and western Andean mountain ranges and the Pacific region. These centres of high PD were comprised of predominantly short and closely related branches, mostly of species of wild tomatoes and black peppers. In contrast, the CWR PD in the lowland ecosystems of the Amazon and Orinoquia regions had deeply diverging clades predominantly represented by long and distantly related branches (i.e. tuberous roots, grains and cacao). We categorized 50 (52.6%) of the CWR species as 'high priority', 36 as 'medium priority' and nine as 'low priority' for further ex-situ and in situ conservation actions. New areas of high PD and richness with large ex-situ gap collections were identified mainly in the northern part of the Andes of Colombia. We found that 56% of the grid cells with the highest PD values were unprotected. These baseline data could be used to create a comprehensive national strategy of CWR conservation in Colombia.

Response to water deficit of semi-desert wild potato Solanum kurtzianum genotypes collected from different altitudes.

Drought-sensitive crops are threatened as a consequence of limited available water due to climate change. The cultivated potato (Solanum tuberosum) is susceptible to drought and within its wild relative species, Solanum kurtzianum is the Argentinian wild potato species best adapted to arid conditions. However, its physiological responses to water deficit (WD) are still missing. Within the distribution of S. kurtzianum, genotypes could be adapted to differential precipitation regimes. The aim of this work was to evaluate responses of three S. kurtzianum genotypes collected at 1100 (G1), 1900 (G2) and 2100 m a.s.l. (G3) to moderate and severe WD. Treatments were imposed since flowering and lasted 36 days. Yield components, morpho-physiological and biochemical responses; and phenotypic plasticity were evaluated. The three genotypes presented mechanisms to tolerate both WD treatments. G1 presented the lowest yield reduction under moderate WD, mainly through a rapid stomatal closure and a modest vegetative growth. The differences among genotypes suggest that local adaptation is taking place within its natural habitat. Also, G2 presented environmentally induced shifts in plasticity for stomatal length and carotenoids, suggesting that phenotypic plasticity has a role in acclimation of plants to WD until selection works.

Intentional and unintentional selection during plant domestication: herbivore damage, plant defensive traits and nutritional quality of fruit and seed crops.

Greater susceptibility to herbivory can arise as an effect of crop domestication. One proposed explanation is that defenses decreased intentionally or unintentionally during the domestication process, but evidence for this remains elusive. An alternative but nonexclusive explanation is presumed selection for higher nutritional quality. We used a metaanalytical approach to examine susceptibility to herbivores in fruit and seed crops and their wild relatives. Our analyses provide novel insights into the mechanisms of increased susceptibility by evaluating whether it can be attributed to either a reduction in herbivore defensive traits, including direct/indirect and constitutive/inducible defenses, or an increase in the nutritional content of crops. The results confirm higher herbivory and lower levels of all types of defenses in crops compared to wild relatives, although indirect defenses were more affected than direct ones. Contrary to expectations, nutritional quality was lower in crops than in wild relatives, which may enhance biomass loss to herbivores if they increase consumption to meet nutritional requirements. Our findings represent an important advance in our understanding of how changes in defensive and nutritional traits following domestication could influence, in combination or individually, crop susceptibility to herbivore attacks.

Chromosomal introgressions from Oryza meridionalis into domesticated rice Oryza sativa result in iron tolerance.

Iron (Fe) toxicity is one of the most common mineral disorders affecting rice (Oryza sativa) production in flooded lowland fields. Oryza meridionalis is indigenous to northern Australia and grows in regions with Fe-rich soils, making it a candidate for use in adaptive breeding. With the aim of understanding tolerance mechanisms in rice, we screened a population of interspecific introgression lines from a cross between O. sativa and O. meridionalis for the identification of quantitative trait loci (QTLs) contributing to Fe-toxicity tolerance. Six putative QTLs were identified. A line carrying one introgression from O. meridionalis on chromosome 9 associated with one QTL was highly tolerant despite very high shoot Fe concentrations. Physiological, biochemical, ionomic, and transcriptomic analyses showed that the tolerance of the introgression lines could partly be explained by higher relative Fe retention in the leaf sheath and culm. We constructed the interspecific hybrid genome in silico for transcriptomic analysis and identified differentially regulated introgressed genes from O. meridionalis that could be involved in shoot-based Fe tolerance, such as metallothioneins, glutathione S-transferases, and transporters from the ABC and MFS families. This work demonstrates that introgressions of O. meridionalis into the O. sativa genome can confer increased tolerance to excess Fe.

Environmentally induced phenotypic plasticity and DNA methylation changes in a wild potato growing in two contrasting Andean experimental gardens.

DNA methylation can be environmentally modulated and plays a role in phenotypic plasticity. To understand the role of environmentally induced epigenetic variation and its dynamics in natural populations and ecosystems, it is relevant to place studies in a real-world context. Our experimental model is the wild potato Solanum kurtzianum, a close relative of the cultivated potato S. tuberosum. It was evaluated in its natural habitat, an arid Andean region in Argentina characterised by spatial and temporal environmental fluctuations. The dynamics of phenotypic and epigenetic variability (with Methyl Sensitive Amplified Polymorphism markers, MSAP) were assayed in three genotypes across three growing seasons. These genotypes were cultivated permanently and also reciprocally transplanted between experimental gardens (EG) differing in ca. 1000 m of altitude. In two seasons, the genotypes presented differential methylation patterns associated to the EG. In the reciprocal transplants, a rapid epigenomic remodelling occurred according to the growing season. Phenotypic plasticity, both spatial (between EGs within season) and temporal (between seasons), was detected. The epigenetic and phenotypic variability was positively correlated. The lack of an evident mitotic epigenetic memory would be a common response to short-term environmental fluctuations. Thus, the environmentally induced phenotypic and epigenetic variation could contribute to populations persistence through time. These results have implications for understanding the great ecological diversity of wild potatoes.

Contemporary evolution of maize landraces and their wild relatives influenced by gene flow with modern maize varieties.

Mexico is recognized as the center of origin and domestication of maize. Introduction of modern maize varieties (MVs) into Mexico raised concerns regarding the possible effects of gene flow from MVs into maize landraces (LRs) and their wild relatives (WRs), teosintes. However, after more than 60 y from the release of the first MVs, the impact of the sympatry with LRs and their WRs has not been explored with genetic data. In this work, we assessed changes in the genomes of 7 maize LRs and 2 WR subspecies from collections spanning over 70 y. We compared the genotypes obtained by genotyping by sequencing (GBS) for LRs and WRs before and after the adoption of MVs, and observed introgression from sympatric MVs into LRs and into the WR Zea mays ssp. mexicana sampled after the year 2000. We also found a decrease in the paired divergence index (FST ) between MV-LR and MV-WR over the same time frame. Moreover, we determined that LR genetic diversity increased after 2000, probably as a result of gene flow from MVs introduced in the 1990s. Our findings allowed us to identify ongoing changes in the domesticated and wild maize genetic pools, and concur with previous works that have evaluated short-term gene flow from MVs into LRs in other crops. Our approach represents a useful tool for tracking evolutionary change in wild and domesticated genetic resources, as well as for developing strategies for their conservation.

In vitro performance in cotton plants with different genetic backgrounds: the case of Gossypium hirsutum in Mexico, and its implications for germplasm conservation.

One of the best ex situ conservation strategies for wild germplasm is in vitro conservation of genetic banks. The success of in vitro conservation relies heavily on the micropropagation or performance of the species of interest. In the context of global change, crop production challenges and climate change, we face a reality of intensified crop production strategies, including genetic engineering, which can negatively impact biodiversity conservation. However, the possible consequences of transgene presence for the in vitro performance of populations and its implications for biodiversity conservation are poorly documented. In this study we analyzed experimental evidence of the potential effects of transgene presence on the in vitro performance of Gossypium hirsutum L. populations, representing the Mexican genetic diversity of the species, and reflect on the implications of such presence for ex situ genetic conservation of the natural variation of the species. We followed an experimental in vitro performance approach, in which we included individuals from different wild cotton populations as well as individuals from domesticated populations, in order to differentiate the effects of domestication traits dragged into the wild germplasm pool via gene flow from the effects of transgene presence. We evaluated the in vitro performance of five traits related to plant establishment (N = 300): propagation rate, leaf production rate, height increase rate, microbial growth and root development. Then we conducted statistical tests (PERMANOVA, Wilcoxon post-hoc tests, and NMDS multivariate analyses) to evaluate the differences in the in vitro performance of the studied populations. Although direct causality of the transgenes to observed phenotypes requires strict control of genotypes, the overall results suggest detrimental consequences for the in vitro culture performance of wild cotton populations in the presence of transgenes. This provides experimental, statistically sound evidence to support the implementation of transgene screening of plants to reduce time and economic costs in in vitro establishment, thus contributing to the overarching goal of germplasm conservation for future adaptation.

Epigenetic consequences of interploidal hybridisation in synthetic and natural interspecific potato hybrids.

Interploidal hybridisation can generate changes in plant chromosome numbers, which might exert effects additional to the expected due to genome merger per se (that is genetic, epigenetic and phenotypic novelties). Wild potatoes are suitable to address this question in an evolutionary context. To this end, we performed genetic (AFLP and single sequence repeart (SSR)), epigenetic (MSAP), and cytological comparisons in: (1) natural populations of the diploid cytotype of the hybrid taxonomic species Solanum × rechei (2n = 2×, 3×) and its parental species, the triploid cytotype of Solanum microdontum (2n = 2×, 3×) and Solanum kurtzianum (2n = 2×); and (2) newly synthesised intraploidal (2× × 2×) and interploidal (3× × 2×) S. microdontum × S. kurtzianum hybrids. Aneuploidy was detected in S. × rechei and the synthetic interploidal progeny; this phenomenon might have originated the significantly higher number of methylation changes observed in the interploidal vs the intraploidal hybrids. The wide epigenetic variability induced by interploidal hybridisation is consistent with the novel epigenetic pattern established in S. × rechei compared to its parental species in nature. These results suggest that aneuploid potato lineages can persist throughout the short term, and possibly medium term, and that differences in parental ploidy resulting in aneuploidy are an additional source of epigenetic variation.