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Silphium integrifolium (Asteraceae) has been identified as a candidate for domestication as a perennial oilseed crop and is assumed to have sporophytic self-incompatibility system-the genetic basis of which is not well understood in the Asteraceae. To address this gap, we sought to map the genomic location of the self-recognition locus (S-locus) in this species. We used a biparental population and genotyping-by-sequencing to create the first genetic linkage map for this species, which contained 198 SNP markers and resolved into the correct number of linkage groups. Then we developed a novel crossing scheme and set of analysis methods in order to infer S-locus genotypes for a subset of these individuals, allowing us to map the trait. Finally, we evaluated potential genes of interest using synteny analysis with the annual sunflower (Helianthus annuus) and lettuce (Lactuca sativa) genomes. Our results confirm that S. integrifolium does indeed have a sporophytic self-incompatibility system. Our method is effective and efficient, allowed us to map the S. integrifolium S-locus using fewer resources than existing methods, and could be readily applied to other species.

Current food systems are challenged by relying on a few input-intensive, staple crops. The prioritization of yield and the loss of diversity during the recent history of domestication has created contemporary crops and cropping systems that are ecologically unsustainable, vulnerable to climate change, nutrient poor, and socially inequitable. For decades, scientists have proposed diversity as a solution to address these challenges to global food security. Here, we outline the possibilities for a new era of crop domestication, focused on broadening the palette of crop diversity, that engages and benefits the three elements of domestication: crops, ecosystems, and humans. We explore how the suite of tools and technologies at hand can be applied to renew diversity in existing crops, improve underutilized crops, and domesticate new crops to bolster genetic, agroecosystem, and food system diversity. Implementing the new era of domestication requires that researchers, funders, and policymakers boldly invest in basic and translational research. Humans need more diverse food systems in the Anthropocene—the process of domestication can help build them.

Silphium spp. have garnered interest in Europe as a bioenergy crop and in North America as a perennial oilseed crop. However, very little has been done at this early stage of domestication to characterize wild collections for many key characteristics, including important oilseed traits. The objective of this work was to develop a basic understanding of how biogeography and associated population genetic forces have shaped seed phenotypes in plant collections across the native range of Silphium integrifolium Michx. (Asteraceae: Heliantheae), the primary domestication candidate for oilseed use. A collection of 53 accessions was grown in a common environment in Salina, KS, which is a location well within the native range of the species in central North America. Plants from each collection site were randomly mated by hand to produce seed representative of each accession, and the seeds subjected to seed dimensional trait, oil content and oil composition analyses. Kernel width varied along a latitudinal cline of collection site, while kernel length varied across a longitudinal cline. Palmitic and linoleic acids were inversely correlated with each other and varied along a longitudinal cline of the collection site. The results indicate that accessions collected from more southwesterly sites tended to have larger seed and those from more westerly sites had higher linoleic acid content and lower palmitic and myristic acids, which are all desirable phenotypes for an oilseed Silphium.

SUMMARYSilphium integrifolium(Asteraceae) has been identified as a candidate for domestication as a perennial oilseed crop and has a sporophytic self-incompatibility system—the genetic basis of which is not well understood in theAsteraceae. To address this gap, we sought to map the genomic location of the self-recognition locus (S-locus) in this species.We used a biparental population and genotyping-by-sequencing to create the first genetic linkage map for this species. Then we developed a novel crossing scheme and set of analysis methods in order to infer S-locus genotypes for a subset of these individuals, allowing us to map the trait. Finally, we identified potential gene candidates using synteny analysis with the annual sunflower (Helianthus annuus) genome.Our linkage map contains 198 SNP markers and resolved into the correct number of linkage groups. We were able to successfully map the S-locus and identify several potential gene candidates in the sunflower syntenic region.Our method is effective and efficient, allowed us to map theS. integrifoliumS-locus using fewer resources than previous studies, and could be readily be applied to other species. Our best gene candidate appears to be worthy of future work inS. integrifoliumand otherAsteraceaespecies.

The perennial sunflower Silphium integrifolium Michx. (Asteraceae), also known as silflower, is a prospective dual-purpose forage plus grain crop. Pre-flowering biomass harvest for animal feed and the subsequent delay in plant growth and anthesis has the potential to benefit seed yield and/or offset yield loss from native pests, such as the native North American Eucosma giganteana (Lepidopera: Tortricidae). The aim of this study was to develop a cropping technology for silflower to (A) balance forage and grain production and (B) minimize seed loss. Silflower produced high-quality forage, but biomass harvest in early spring reduced same-season seed production by 45%. Despite significantly delaying flowering, forage harvest alone did not effectively reduce Eucosma colonization, although treating plants with the insecticide permethrin did reduce colonization. Our results do not support the proposal that S. integrifolium could be profitably harvested for both high quality forage and as an oilseed grain within the same season. Nevertheless, our findings suggest the possibility of developing a strategy of alternating between forage or seed production, depending on their differential economic values. The choice between harvesting biomass vs. seed could be made much later in the season for this perennial crop than the choice of planting an annual forage vs. annual grain crop.

The emerging bioeconomy will increase the need for plant biomass. We call for a third-generation of bioenergy crops, or biomass crops, to help move society towards a sustainable bioeconomy and global food security. Third-generation biomass crops should be capable of producing both food and raw materials. Such flexibility would allow farmers to respond to global markets and buffer global food security. At the same time, third-generation biomass crops need to increase the sustainability of agriculture. To reach such ambitious goals, new biomass crops have to develop de novo from promising perennial wild species.

International audience; De novo domestication has received recent attention because of the potential to produce new crop species with additional agroecosystem functions and useful products for climate-resilient agricultural systems of the future. However, there are often traits in wild species that make them difficult to domesticate. One key domestication trait selected by early farmers and modern plant breeders in many crops is the ability to self-pollinate. Benefits include higher seed set and more reliable seed production, as well as more efficient selection during breeding because it allows for unmasking of recessive traits and enforcement of favorable gene interactions. Similarly, interspecific hybridization has been used to add to the genetic diversity of many crop species. We evaluated self-pollination and interspecific hybridization in Silphium integrifolium and S. perfoliatum to learn the extent of possible gene flow between the species and its usefulness in cultivar development and the potential for fixation of favorable domestication genes by self-pollination. Our results indicate that Silphium interspecific hybrids can be easily developed, potentially facilitating movement of otherwise invariable traits from one species to another. Further, we showed, for the first time, that self-pollination is also possible in both species and their interspecific hybrids, but the rate varies among genotypes. This has profound implications in optimizing plant breeding methods for the study and improvement of these species and adds more evidence to our understanding of mating systems in Asteraceae, an underutilized family of plants with great potential for additional domesticated species.

PremiseUnderstanding the relationship between genetic structure and geography provides information about a species’ evolutionary history and can be useful to breeders interested in de novo domestication. The North American prairie is especially interesting because of its relatively recent origin and subsequent dramatic fragmentation and degradation. Silphium integrifolium is an iconic perennial American prairie wildflower targeted for domestication as an oilseed crop. Germplasm in the existing breeding program is derived from accessions collected in restricted geographic regions. We present the first application of population genetic data in this species to address the following goals (1) improve breeding programs by characterizing genetic structure and (2) identify the species geographic origin and potential targets and drivers of selection during range expansion.MethodsWe developed a reference transcriptome as a genotyping reference for samples from throughout the species range. Population genetic analyses were used to describe the distribution of genetic variation and demographic modeling was used to characterize potential processes that shaped variation. Outlier scans for selection and associations with environmental variables were used to identify loci linked to putative targets and drivers of selection.Key resultsGenetic variation partitions samples into three geographic clusters. Patterns of variation and demographic modeling suggest that the species origin is in the American southeast. Breeding program accessions are from the region with lowest observed genetic variation.ConclusionsThis iconic prairie species did not originate within the modern prairie. Breeding programs can be improved by including accessions from outside of the germplasm founding region, which has relatively little variation. The geographic structuring coupled with the identified targets and drivers of adaptation can guide collecting efforts towards populations with beneficial agronomic traits.

Parallels exist between the domestication of new species and the improvement of various crops through selection on traits which favor the sowing, harvest and retention of yield potential and the directed efforts to improve their agronomics, disease resistance and quality characteristics. Common selection pressures may result in the parallel selection of orthologs underlying these traits and homologies between crop species can be exploited by plant breeders to improve germplasm. Perennial grains and oilseeds are a class of proposed crops for improving the diversity and sustainability of agricultural systems. Maximilian sunflower (Helianthus maximiliani Schrad.) is a perennial crop wild relative of sunflower (Helianthus annuus L.) and a candidate perennial oilseed species. Understanding parallels between cultivated H. annuus and H. maximiliani may provide new tools for the development of Maximilian sunflower and other wild relatives of sunflower as crops to enhance functional diversity in cropping systems. F2 populations of Maximilian sunflower segregating for traits associated with the domestication ideotype of cultivated sunflower including branching architecture, capitulum morphology and flowering time were developed to investigate parallels between H. maximiliani and H. annuus. Genotype-by-sequencing (GBS) was employed to genotype novel Maximilian sunflower populations and perform quantitative-trait-loci (QTL) analysis. A total of 11 QTL in five regions were identified across 21 linkage groups using 4142 GBS derived single nucleotide polymorphism markers called using the sunflower reference genome as a guide. A major QTL on linkage group 17b, associated with aspects of floral development and apical dominance, was discovered and corresponds with a known domestication QTL hotspot in H. annuus and candidate genes were identified. This suggests the potential to exploit orthologs for neo-domestication of H. maximiliani for traits such as branching architecture, timing of anthesis, and capitulum size and morphology for the development of a perennial oilseed crop from wild relatives of cultivated sunflower.

The classic domestication scenario for grains and fruits has been portrayed as the lucky fixation of major-effect "domestication genes." Characterization of these genes plus recent improvements in generating novel alleles (e.g., by gene editing) have created great interest in de novo domestication of new crops from wild species. While new gene editing technologies may accelerate some genetic aspects of domestication, we caution that de novo domestication should be understood as an iterative process rather than a singular event. Changes in human social preferences and relationships and ongoing agronomic innovation, along with broad genetic changes, may be foundational. Allele frequency changes at many loci controlling quantitative traits not normally included in the domestication syndrome may be required to achieve sufficient yield, quality, defense, and broad adaptation. The environments, practices and tools developed and maintained by farmers and researchers over generations contribute to crop yield and success, yet those may not be appropriate for new crops without a history of agronomy. New crops must compete with crops that benefit from long-standing participation in human cultural evolution; adoption of new crops may require accelerating the evolution of new crops' culinary and cultural significance, the emergence of markets and trade, and the formation and support of agricultural and scholarly institutions. We provide a practical framework that highlights and integrates these genetic, agronomic, and cultural drivers of change to conceptualize de novo domestication for communities of new crop domesticators, growers and consumers. Major gene-focused domestication may be valuable in creating allele variants that are critical to domestication but will not alone result in widespread and ongoing cultivation of new crops. Gene editing does not bypass or diminish the need for classical breeding, ethnobotanical and horticultural knowledge, local agronomy and crop protection research and extension, farmer participation, and social and cultural research and outreach. To realize the ecological and social benefits that a new era of de novo domestication could offer, we call on funding agencies, proposal reviewers and authors, and research communities to value and support these disciplines and approaches as essential to the success of the breakthroughs that are expected from gene editing techniques.

Herbaceous perennial species are receiving increased attention for their potential to provide both edible products and ecosystem services in agricultural systems. Many legumes (Fabaceae Lindl.) are of special interest due to nitrogen fixation carried out by bacteria in their roots and their production of protein-rich, edible seeds. However, herbaceous perennial legumes have yet to enter widespread use as pulse crops, and the response of wild, herbaceous perennial species to artificial selection for increased seed yield remains under investigation. Here we compare cultivated and wild accessions of congeneric annual and herbaceous perennial legume species to investigate associations of lifespan and cultivation with early life stage traits including seed size, germination, and first year vegetative growth patterns, and to assess variation and covariation in these traits. We use "cultivated" to describe accessions with a history of human planting and use, which encompasses a continuum of domestication. Analyses focused on three annual and four perennial species of the economically important genus Phaseolus. We found a significant association of both lifespan and cultivation status with seed size (weight, two-dimensional lateral area, length), node number, and most biomass traits (with cultivation alone showing additional significant associations). Wild annual and perennial accessions primarily showed only slight differences in trait values. Relative to wild forms, both cultivated annual and cultivated perennial accessions exhibited greater seed size and larger overall vegetative size, with cultivated perennials showing greater mean trait differences relative to wild accessions than cultivated annuals. Germination proportion was significantly lower in cultivated relative to wild annual accessions, while no significant difference was observed between cultivated and wild perennial germination. Regardless of lifespan and cultivation status, seed size traits were positively correlated with most vegetative traits, and all biomass traits examined here were positively correlated. This study highlights some fundamental similarities and differences between annual and herbaceous perennial legumes and provides insights into how perennial legumes might respond to artificial selection compared to annual species.

De novo domestication is an exciting option for increasing species diversity and ecosystem service functionality of agricultural landscapes. Genomic selection (GS), the application of genomic markers to predict phenotypic traits in a breeding population, offers the possibility of rapid genetic improvement, making GS especially attractive for modifying traits of long-lived species. However, for some wild species just entering the domestication pipeline, especially those with large and complex genomes, a lack of funding and/or prior genome characterization, GS is often out of reach. High throughput phenomics has the potential to augment traditional pedigree selection, reduce costs and amplify impacts of genomic selection, and even create new predictive selection approaches independent of sequencing or pedigrees.

Silflower (Silphium integrifolium Michx.) is a potential perennial oilseed crop that can provide ecosystem services; however, its seed, oil, and biomass yield potential are unknown. Our objectives were to determine the effects of planting density and N fertilizer on silflower seed, oil, and biomass yields and seed yield components for 3 yr after establishment. Experiments tested six planting densities on two soil types, and five N rates and two planting densities on one soil type. Averaged over years and soil types, increasing planting density from 11,954 to 53,792 plants ha−1 increased biomass yield (BY), but decreased seed heads plant−1 and seeds plant−1. Planting density had no effect on seed yield (SY) or oil yield (OY), other seed related variables, or harvest index. On a sandy soil, SY and OY increased linearly with N rates from 0 to 180 kg ha−1 in the year after seeding but were not affected by N fertilization rates in subsequent years. At 180 kg N ha−1, SY, OY, and BY were 1,651 kg ha−1, 381 kg ha−1, and 10.5 Mg ha−1, respectively, in the year following seeding but declined thereafter. Over both experiments SY and OY were positively correlated (r = .99) and together associated with seed heads plant−1, seeds head−1, and seeds plant−1. Relative to annual oilseed crops, seed and oil yields for this new perennial species are low. Germplasm improvement for seed and oil yield and agronomic research to maintain yields as stands age are critical to develop this new perennial oilseed crop.

In the interest of diversifying the global food system, improving human nutrition, and making agriculture more sustainable, there have been many proposals to domesticate wild plants or complete the domestication of semidomesticated orphan crops. However, very few new crops have recently been fully domesticated. Many wild plants have traits limiting their production or consumption that could be costly and slow to change. Others may have fortuitous preadaptations that make them easier to develop or feasible as high-value, albeit low-yielding, crops. To increase success in contemporary domestication of new crops, we propose a pipeline approach, with attrition expected as species advance through the pipeline. We list criteria for ranking domestication candidates to help enrich the starting pool with more preadapted, promising species. We also discuss strategies for prioritizing initial research efforts once the candidates have been selected: developing higher value products and services from the crop, increasing yield potential, and focusing on overcoming undesirable traits. Finally, we present new-crop case studies that demonstrate that wild species’ limitations and potential (in agronomic culture, shattering, seed size, harvest, cleaning, hybridization, etc.) are often only revealed during the early phases of domestication. When nearly insurmountable barriers were reached in some species, they have been (at least temporarily) eliminated from the pipeline. Conversely, a few species have moved quickly through the pipeline as hurdles, such as low seed weight or low seed number per head, were rapidly overcome, leading to increased confidence, farmer collaboration, and program expansion. Fil: DeHaan, Lee R.. The Land Institute; Estados Unidos Fil: Van Tassel, David L.. The Land Institute; Estados Unidos Fil: Anderson, James A.. University of Minnesota; Estados Unidos Fil: Asselin, Sean R.. University of Manitoba; Canadá Fil: Barnes, Richard. University of Minnesota; Estados Unidos Fil: Baute, Gregory J.. University of British Columbia; Canadá Fil: Cattani, Douglas J.. University of Manitoba; Canadá Fil: Culman, Steve W.. Ohio State University; Estados Unidos Fil: Dorn, Kevin M.. University of Minnesota; Estados Unidos Fil: Hulke, Brent S.. United States Department of Agriculture. Agriculture Research Service; Estados Unidos Fil: Kantar, Michael. University of British Columbia; Canadá Fil: Larson, Steve. Forage and Range Research Laboratory; Estados Unidos Fil: David Marks, M.. University of Minnesota; Estados Unidos Fil: Miller, Allison J.. Saint Louis University; Estados Unidos Fil: Poland, Jesse. Kansas State University; Estados Unidos Fil: Ravetta, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina Fil: Rude, Emily. University of Wisconsin; Estados Unidos Fil: Ryan, Matthew R.. Cornell University; Estados Unidos Fil: Wyse, Don. University of Minnesota; Estados Unidos Fil: Zhang, Xiaofei. University of Minnesota; Estados Unidos

SummaryConcerns about soil health and stability are focusing attention on crops that deliver both agricultural products and ecological services. Deep rooted, perennial plants that build soil organic matter, support diverse below-ground microbial communities, and produce edible seeds are key components underpinning ecological intensification; however few perennial, herbaceous crops have been domesticated for food.To facilitate development of edible, perennial, herbaceous crops, including perennial grains, we constructed an online resource of wild, perennial, herbaceous species – the Perennial Agriculture Project Global Inventory (PAPGI; http://www.tropicos.org/Project/PAPGI). The first component of this project focuses on wild, perennial, herbaceous Fabaceae species. We extracted taxonomic names and descriptors from the International Legume Database and Information Service. Names were added to PAPGI, a special project within the botanical database TROPICOS, where they link to specimen records and ethnobotanical and toxicological data. PAPGI includes 6,644 perennial, herbaceous Fabaceae species. We built a searchable database of more than 60 agriculturally important traits. Here we highlight food and forage uses for 314 legume species, and toxicological data for 278 species.The novel contribution of PAPGI is its focus on wild, perennial herbaceous species that generally have not entered the domestication process but that hold promise for development as perennial food crops. By extracting botanical information relevant for agriculture we provide a dynamic resource for breeders and plant scientists working to advance ecological intensification of agriculture, and for conservation managers working to preserve wild species of potential agricultural importance.Societal Impact StatementAgroecosystems are constantly evolving to meet the needs of a growing population in a sustainable manner. Perennial, herbaceous crops deliver both agricultural products and ecological services. Until recently, edible, perennial, herbaceous crops, including perennial grains, were absent from agriculture. Perennial, herbaceous crops can be developed through wide hybridization between annual crops and perennial relatives or by de novo domestication of wild species. The diversity of wild, perennial, herbaceous legume species documented by the PAPGI increases resources available to breeders of perennial, herbaceous legumes, and raises awareness about previously untapped wild plant diversity in future crop development.

Climatic change will seriously impact Mediterranean areas. Palestine, which has given forth annual grain based agriculture, is particularly vulnerable given its political and economic situation. Research is needed to build climate adaptation and resilience into agroecosystems within the same landscape that gave forth agriculture. A primary step in achieving that adaptation is to develop polycultures composed of perennial crops to protect and rebuild the soil. Our preliminary research shows that agrobiodiversity and genetic material for this deep adaptation is already present within the landscape, and if developed could produce the new crops used to build perennial polycultures.

Organic dormancy, the inability to germinate under favorable conditions, is a common problem in many crop species and their wild relatives, leading to more variable emergence, plant density, and growth rates, thus increasing costs, and lowering yield. To overcome these problems, several different methods have been developed for various crop and model plants. However, in the emerging crop being bred from wild and semi-domesticated Silphium, no such method has been established thus far. The objective of this study was to identify a dormancy-breaking assay to increase the seed germination rate. Seeds of three different Silphium integrifolium Michx. genotypes were treated with five chemical and one cold treatment, and dried before or after the treatment at 27 °C or 40 °C. Untreated, dried seeds were taken as control. Seeds soaked for 24 h in a ethephon/potassium nitrate solution followed by a 72 h drying step at 40 °C showed an increase of germination to up to 90 ± 2% compared to control seeds (3 ± 0% and 5 ± 1%). We identified the minimum time frame of cold stratification needed to enhance seed germination in Silphium, and found that cold stratification was nearly as good as the chemical treatment. Our results provide two alternate ways to treat S. integrifolium seeds for breaking organic dormancy, which will help to facilitate future research in the Silphium domestication community. The fact that our optimal treatments were similar to protocols developed for sunflower suggests that these methods may also be applicable to many related economically important Asteraceae species.

New crops with greater capacity for delivering ecosystem services are needed to increase agricultural sustainability. However, even in these crops, seed yield is usually the main criteria for grain domestication. This focus on yield can cause unintended structural and functional changes. Leaves of selected plants tend to be more vulnerable to infection, which can reduce performance, assimilates, and ultimately yield. Our objectives were to determine the impact of rust (caused by Puccinia silphii) on yield and leaf function in selected Silphium integrifolium (Asteraceae) plants. We tested the effect of a fungicide treatment on rust severity and yield, compared the rust infection of individuals in a population selected for yield, and related this to chemical changes at the leaf level. We also estimated heritability for rust resistance. We found that productivity indicators (head number and weight, leaf weight) and leaf processes (photosynthetic capacity, water use efficiency) were reduced when silphium leaves and stems were more heavily infected by P. silphii. Leaf resin content increased when susceptible plants were infected. Fungicide treatments were effective at reducing rust infection severity, but were ineffective at preventing yield losses. We propose that disease resistance should be included early in the selection process of new perennial crops. Fil: Turner, M. Kathryn. The Land Insitute; Estados Unidos Fil: Ravetta, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Van Tassel, David. The Land Insitute; Estados Unidos

Silflower (Silphium integrifolium Michx.) is in the early stages of domestication as a perennial version of oilseed sunflower, its close relative. Grain crops with deep perennial root systems will provide farmers with new alternatives for managing soil moisture and limiting or remediating soil erosion, fertilizer leaching, and loss of soil biota. Several cycles of selection for increased seed production potential following initial germplasm evaluation in 2002 have provided opportunities to document the botany and ecology of this relatively obscure species, to compare agronomic practices for improving its propagation and management, and to evaluate the differences between semi-domesticated and wild accessions that have accrued over this time through intentional and unintentional genetic processes. Key findings include: domestication has increased aboveground biomass at seedling and adult stages; seed yield has increased more, achieving modest improvement in harvest index. Harvest index decreases with nitrogen fertilization. Silflower acquires nitrogen and water from greater depth than typical crops. In agricultural silflower stands within its native range, we found that Puccinia silphii (rust) and Eucosma giganteana (moth) populations build up to unacceptable levels, but we also found genetic variation for traits contributing to resistance or tolerance. Breeding or management for reduced height and vegetative plasticity should be top priorities for future silflower research outside its native range. Fil: Vilela, Alejandra Elena. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: González Paleo, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina Fil: Turner, Kathryn. The Land Institute; Estados Unidos Fil: Peterson, Kelsey. The Land Institute; Estados Unidos Fil: Ravetta, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina Fil: Crews, Timothy E.. The Land Institute; Estados Unidos Fil: Van Tassel, David. The Land Institute; Estados Unidos

Silphium perfoliatum L. (cup plant, silphie) and S. integrifolium Michx. (rosinweed, silflower) are in the same subfamily and tribe as sunflower (Helianthus annuus L.). Silphium perfoliatum has been grown in many countries as a forage or bioenergy crop with forage quality approaching that of alfalfa (Medicago sativa L.) and biomass yield close to maize (Zea mays L.) in some environments. Silphium integrifolium has large seeds with taste and oil quality similar to traditional oilseed sunflower. Silphium species are all long-lived, diploid perennials. Crops from this genus could improve the yield stability, soil, and biodiversity of agricultural landscapes because, in their wild state, they are deep rooted and support a wide diversity of pollinators. In contrast with premodern domestication, de novo domestication should be intentional and scientific. We have the luxury and obligation at this moment in history to expand the domestication ideotype from food and energy production to include (i) crop-driven ecosystem services important for sustainability, (ii) genetic diversity to enable breeding progress for centuries, (iii) natural adaptations and microbiome associations conferring resource use efficiency and stress tolerance, and (iv) improving domestication theory itself by monitoring genetic and ecophysiological changes from predomestication baselines. Achieving these goals rapidly will require the use of next-generation sequencing for marker development and an international, interdisciplinary team committed to collaboration and strategic planning. Fil: Van Tassel, David. Land Institute; Estados Unidos Fil: Albrecht, Kenneth A.. University Of Wisconsin Madison; Fil: Bever, James D.. University of Kansas; Estados Unidos Fil: Boe, Arvid A.. South Dakota State University; Estados Unidos Fil: Brandvain, Yaniv. University of Minnesota; Estados Unidos Fil: Crews, Timothy E.. Land Institute; Estados Unidos Fil: Gansberger, Markus. Austrian Agency For Health And Food Safety; Austria Fil: Gerstberger, Pedro. University of Bayreuth; Alemania Fil: González Paleo, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina Fil: Hulke, Brent S.. United States Department of Agriculture. Agriculture Research Service; Estados Unidos Fil: Kane, Nolan C.. University of Colorado; Estados Unidos Fil: Johnson, Paul J.. Insect Biodiversity Laboratory; Estados Unidos Fil: Pestsova, Elena G.. Heinrich Heine Universitat; Fil: Picasso Risso, Valentín D.. University of Wisconsin; Estados Unidos Fil: Prasifka, Jarrad R.. United States Department of Agriculture. Agriculture Research Service; Estados Unidos Fil: Ravetta, Damián Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; Argentina Fil: Schlautman, Brandon. Land Institute; Estados Unidos Fil: Sheaffer, Craig C.. University of Minnesota; Estados Unidos Fil: Smith, Kevin P.. University of Minnesota; Estados Unidos Fil: Speranza, Pablo R.. Universidad de la República; Uruguay

Annual grain crops dominate agricultural landscapes and provide the majority of calories consumed by humanity. Perennial grain crops could potentially ameliorate the land degradation and off-site impacts associated with annual grain cropping. However, herbaceous perennial plants with constitutively high allocation to harvestable seeds are rare to absent in nature. Recent trade-off theory models suggest that rugged fitness landscapes may explain the absence of this form better than sink competition models. Artificial selection for both grain production and multiyear lifespan can lead to more rapid progress in the face of fitness and genetic trade-offs than natural selection but is likely to result in plant types that differ substantially from all current domestic crops. Perennial grain domestication is also likely to require the development of selection strategies that differ from published crop breeding methods, despite their success in improving long-domesticated crops; for this purpose, we have reviewed literature in the areas of population and evolutionary genetics, domestication, and molecular biology. Rapid domestication will likely require genes with large effect that are expected to exhibit strong pleiotropy and epistasis. Cryptic genetic variation will need to be deliberately exposed both to purge mildly deleterious alleles and to generate novel agronomic phenotypes. We predict that perennial grain domestication programs will benefit from population subdivision followed by selection for simple traits in each subpopulation, the evaluation of very large populations, high selection intensity, rapid cycling through generations, and heterosis. The latter may be particularly beneficial in the development of varieties with stable yield and tolerance to crowding.

In the course of their evolution, the angiosperms have radiated into most known plant forms and life histories. Their adaptation to a recently created habitat, the crop field, produced a novel form: the plant that allocates an unprecedented 30–60% of its net productivity to sexual structures. Long-lived trees, shrubs and vines of this form evolved, as did annual herbs. Perennial herb forms with increased allocation to asexual reproduction evolved, but there are no examples of perennial herbs with high sexual effort. We suggest that sowing seed into annually tilled fields favored shorter-lived herbs because of trade-offs between first-year seed production and relative growth rate and/or persistence. By propagating cuttings, people quickly domesticated tuber crops and large woody plants. Perennial herbs were too small to be efficiently propagated by cuttings, and the association between longevity, allogamy and genetic load made rapid domestication by sexual cycles unlikely. Perennial grain crops do not exist because they could not have evolved under the original set of conditions; however, they can be deliberately developed today through artificial phenotypic and genotypic selection.

Annual grain crops dominate agricultural landscapes and provide the majority of calories consumed by humanity. Perennial grain crops could potentially ameliorate the land degradation and off-site impacts associated with annual grain cropping. However, herbaceous perennial plants with constitutively high allocation to harvestable seeds are rare to absent in nature. Recent trade-off theory models suggest that rugged fitness landscapes may explain the absence of this form better than sink competition models. Artificial selection for both grain production and multiyear lifespan can lead to more rapid progress in the face of fitness and genetic trade-offs than natural selection but is likely to result in plant types that differ substantially from all current domestic crops. Perennial grain domestication is also likely to require the development of selection strategies that differ from published crop breeding methods, despite their success in improving long-domesticated crops; for this purpose, we have reviewed literature in the areas of population and evolutionary genetics, domestication, and molecular biology. Rapid domestication will likely require genes with large effect that are expected to exhibit strong pleiotropy and epistasis. Cryptic genetic variation will need to be deliberately exposed both to purge mildly deleterious alleles and to generate novel agronomic phenotypes. We predict that perennial grain domestication programs will benefit from population subdivision followed by selection for simple traits in each subpopulation, the evaluation of very large populations, high selection intensity, rapid cycling through generations, and heterosis. The latter may be particularly beneficial in the development of varieties with stable yield and tolerance to crowding.

Numerous classes of chemicals have been considered as regulators of various aspects of plant growth and development. In evaluating these putative regulatory molecules, plant biologists have encountered a number of challenges, including: the problem of quantifying substances present at trace levels in extremely complex mixtures; difficulty in obtaining and interpreting phenotypic responses to exogenous applications; and, until recently, the inability to selectively alter endogenous levels of these substances. Melatonin (N-acetyl 5-methoxytryptamine), a methoxylated indoleamine, is a potential regulatory molecule found in plants. Although no specific phenotype is currently associated with melatonin or its analogs in higher plants, it has important and unique biological activity in many other taxa, from algae to primates. In these organisms, melatonin functions as a night signal, coordinating responses to diurnal and photoperiodic environmental cues. We assess the process by which melatonin has been evaluated in plants so far and find that many of the methods for melatonin analysis, which have been adopted from animal studies, are inappropriate for use with plant materials. Thus, despite some interesting preliminary reports, research supporting the case for melatonin as a plant regulator is still in its infancy.

The indoleamine melatonin, a well-known animal chemical, has been identified in extracts from several plant species. The function of melatonin in plants is unknown. Two major functions of melatonin in animals are dark signaling and antioxidant protection. Fruit ripening was used as a model physiological process that involves changes in the oxidative status of an organ. Tomato fruits at various stages of ripeness were sampled. Morning glory (Pharbitis nil Choisy, cv. Violet) and tomato (Lycopersicon esculentum Mill., cv. T5 and Castlemart) organs were collected throughout a light/dark cycle to determine whether melatonin levels increased during the night. No consistent evidence was found that melatonin increased significantly in organs of these plants during the night, as it does in many animals. The melatonin content of the fruits generally increased during ripening up to the mature ripe stage and thereafter as the fruit became over ripe.

Humanity depends on fewer than a dozen of the approximately 300,000 species of flowering plants for 80% of its caloric intake. And we capitalize on only a fraction of the genetic diversity that resides within each of these species. This is not enough to support our food system in the future. Food availability must double in the next 25 years to keep pace with population and income growth around the world. Already, food-production systems are precarious in the face of intensifying demand, climate change, soil degradation and water and land shortages. Farmers have saved the seeds of hundreds of crop species and hundreds of thousands of ‘primitive’ varieties (local domesticates called landraces), as well as the wild relatives of crop species and modern varieties no longer in use. These are stored in more than 1,700 gene banks worldwide. Maintaining the 11 international gene-bank collections alone costs about US$18 million a year.

Perennial plants, growing in mixtures, make up most of the world's natural terrestrial biomes. In contrast, monocultures of annual crops are sown on more than two-thirds of global cropland. Grain and oilseed crops are the foundation of the human diet, but to date there are no perennial species that produce adequate grain harvests. Yet perennial plant communities store more carbon, maintain better soil and water quality, and manage nutrients more conservatively than do annual plant communities, and they have greater biomass and resource management capacity. These advantages provide a base from which to begin hybridization and selection for increased resource allocation to developing seeds, a decades-long process that must overcome or circumvent genetic complications. Breeding programs aimed at developing perennial grain crops have been initiated in wheat, sorghum, sunflower, intermediate wheatgrass, and other species.