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Flaxseed has gained popularity as a health food. Wild, perennial Linum relatives of annual flax (L. usitatissimum) possess similar oil compositions, making them perennial oilseed (OS) alternatives. The objective of this study was to phenotype 25 OS and 17 cut flower (CF) breeding populations with 137 wild Linum species' accessions in a common garden over three years (Y1–3) to quantify the impact of selection and identify top candidates. This study was intercepted by COVID-19, which prevented the same detailed phenotyping of Y1 from occurring in Y2–3. Traits measured from the perennial flax OS, in comparison with the CF ideotypes: weekly seed germination (Y1), yield per plant (Y1–3), seed weight (Y1–2), shattering (Y1–2), and seed capsule diameter (Y1). In Y1, OS selections had the highest yield per plant, followed by L. austriacum and then CF selections. The 1000 seed weights in Y1 were highest in annual flax, followed by L. grandiflorum and L. baicalense. Seed numbers/capsule were low in Y1–2, possibly due to shattering. Average yield per plant increased across Y1–3 indicating that, once plant establishment had occurred along with the potential for two harvests/year in Y2 onwards, significant OS yield can be realized. Harvest 1 yields were significantly higher than in harvest 2. In Y1–3, OS selections had the highest average seed yield. In Y1, OS and CF populations had smaller seeds, higher shattering, smaller capsule diameters, and lower germination than wild species. Significant breeding efforts are needed to increase perennial flax yield, using the multiple crop ideotypes. [ABSTRACT FROM AUTHOR]

Abstract: The use of perennial biomass crops is expected to increase and will likely be part of a diversified approach to cropping system design that focuses on multiple economic, ecological, and environmental benefits. Field experiments were conducted from 2006 to 2011 at three locations in Minnesota to quantify biomass production across a diverse set of perennial herbaceous and woody crops. Herbaceous crops were harvested annually in the fall while the woody crops were harvested once following five years of growth. Willow produced more total biomass than all other woody and herbaceous biomass crops across all locations. However, miscanthus biomass yield was similar to ‘SX67’ willow at St. Paul and Waseca, but was dependent on the cultivar of miscanthus. Prairie cordgrass cultivars were among the highest and most consistent yielding herbaceous biomass crops across locations. Miscanthus cultivars produced the highest annual dry matter yield of 35 Mg ha−1 yr−1 biomass, but only during the final year of the study. Other herbaceous crops such as switchgrass performed well in certain locations and may offer flexibility in cropping choice. This unique information on comparative biomass yield across a diversity of perennial crops will inform the overall decision-making process in a way that reduces risk and optimizes productivity in specific environments. This study shows that several biomass crop species can be successfully grown as part of a diversified biomass cropping enterprise. [Copyright &y& Elsevier]

(1) Background: Annual flax (Linum usitatissimum) and many wild relatives possess showy blue flowers and finely textured foliage. To promote the use of blue-flowered flax as ornamentals, an herbaceous perennial flax breeding program was initiated to develop ideotypes and test their effectiveness. The objectives of this study were to (a) compare traits of interest for herbaceous perennials in breeding populations (CF, oilseed) and accessions of annual/perennial species in a common garden; (b) quantify the impact of selection (direct, indirect) for traits of interest; (c) identify top candidate species for continued breeding using the herbaceous perennial flax crop ideotype; (2) Methods: Recorded traits, based on the perennial flax ideotype, included: flower diameter, flowering period, stem length and diameter, plant width and height, summer and winter survival; (3) Results: OS and CF populations had smaller stem diameters, longer flowering periods, larger plant size, more uniform growth, and improved winter survival compared to wild species. Linum austriacum was the top wild species for the CF breeding ideotype but comparable in performance with L. perenne for the herbaceous perennial flax ideotype; (4) Conclusions: The effect of 1–5 yrs. on selection for target/non-target traits in wild species for future R&D is exemplified with selection and release of an herbaceous/garden ornamental perennial flax for the market. [ABSTRACT FROM AUTHOR]

Gene flow between crop fields and wild populations often results in hybrids with reduced fitness compared to their wild counterparts due to characteristics imparted by the crop genome. But the specifics of the evolutionary outcome of crop-wild gene flow may depend on context, varying due to local environmental conditions and genetic variation within and among wild populations and among crop lines. To evaluate context-dependence of fitness of Fl hybrids, sunflower crop lines were crossed with nine wild populations from across the northern United States. These crop-wild hybrids and their wild counterparts were grown under agricultural conditions in the field with and without wheat competition. Hybrids were far less fecund than wild plants, yet more likely to survive to reproduce. There was considerable variability among wild populations for fecundity and the specific crop line used to generate the crop-wild hybrid significantly affected fecundity. The fitness deficit suffered by crop-wild hybrids varied by population, as did the rankings of the crop-wild hybrids from three different crop lines. Wheat competition decreased fecundity and survival considerably and hampered seed production of wild plants more than that of hybrids. Genotype x environment interactions indicated that the response of fitness to competition differed by population. Consequently, the fitness of hybrids relative to wild plants varied considerably among wild populations and was not consistent across environments. Notably, relative fitness of hybrids was greater under competitive conditions. This research is the first study of its kind to demonstrate that the consequences of crop-wild gene flow are context dependent and contingent on the genetics of the specific wild populations and the local biotic and abiotic conditions. [ABSTRACT FROM AUTHOR]

The genus Linum L. contains ≈200 primarily blue-flowered species, including several ornamentals, yet no reports exist regarding the cut flower potential of this genus. The objective of this study was to evaluate the cut flower potential of perennial flax cultivars (L. perenne L. 'Blue Flax' and 'Sapphire'; Expt. 1, 2018) and accessions (L. austriacum L., L. lewisii Pursh., and L. perenne; Expt. 2, 2019), and record traits that will enable breeding and selection for improved cut flower performance. The mean vase life across both cultivars in Expt. 1 was 9.2 days. In Expt. 2, L. perenne had the longest average vase life (9.3 days), followed by L. austriacum (9.1 days) and L. lewisii (8.3 days). The floral preservative (Floralife 300) significantly increased vase life by an average of 1.7 days in Expt. 1, and 1.6 days in Expt. 2, and resulted in a significantly greater number of flowers (≈2x) in both experiments. Significant variation was observed among genotypes for most traits, including vase life (6.2 to 11.3 days) and number of flowers (1.3 to 10.5), highlighting the opportunities for improving the potential of cut flower perennial flax through breeding. [ABSTRACT FROM AUTHOR]

Summary: Thlaspi arvense (field pennycress) is being domesticated as a winter annual oilseed crop capable of improving ecosystems and intensifying agricultural productivity without increasing land use. It is a selfing diploid with a short life cycle and is amenable to genetic manipulations, making it an accessible field‐based model species for genetics and epigenetics. The availability of a high‐quality reference genome is vital for understanding pennycress physiology and for clarifying its evolutionary history within the Brassicaceae. Here, we present a chromosome‐level genome assembly of var. MN106‐Ref with improved gene annotation and use it to investigate gene structure differences between two accessions (MN108 and Spring32‐10) that are highly amenable to genetic transformation. We describe non‐coding RNAs, pseudogenes and transposable elements, and highlight tissue‐specific expression and methylation patterns. Resequencing of forty wild accessions provided insights into genome‐wide genetic variation, and QTL regions were identified for a seedling colour phenotype. Altogether, these data will serve as a tool for pennycress improvement in general and for translational research across the Brassicaceae. [ABSTRACT FROM AUTHOR]

Field pennycress ( Thlaspi arvense L.) has potential as an oilseed crop that may be grown during fall (autumn) and winter months in the Midwestern United States and harvested in the early spring as a biodiesel feedstock. There has been little agronomic improvement in pennycress through traditional breeding. Recent advances in genomic technologies allow for the development of genomic tools to enable rapid improvements to be made through genomic assisted breeding. Here we report an annotated transcriptome assembly for pennycress. RNA was isolated from representative plant tissues, and 203 million unique Illumina RNA-seq reads were produced and used in the transcriptome assembly. The draft transcriptome assembly consists of 33 873 contigs with a mean length of 1242 bp. A global comparison of homology between the pennycress and Arabidopsis transcriptomes, along with four other Brassicaceae species, revealed a high level of global sequence conservation within the family. The final assembly was functionally annotated, allowing for the identification of putative genes controlling important agronomic traits such as flowering and glucosinolate metabolism. Identification of these genes leads to testable hypotheses concerning their conserved function and to rational strategies to improve agronomic properties in pennycress. Future work to characterize isoform variation between diverse pennycress lines and develop a draft genome sequence for pennycress will further direct trait improvement. [ABSTRACT FROM AUTHOR]

Winter annual cover crops, winter rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth), can reduce weed density and build soil quality in organic production systems. There is interest in integrating cover crops and reduced tillage with organic vegetable production, but few studies have been conducted in regions with short growing seasons and cool soils such as the upper Midwest. We evaluated no-tillage production of tomato (Solamon lycopersicum L.), zucchini (Cucurbita pepo L.), and bell pepper (Capsicum annuum L.) planted into winter rye, hairy vetch, and a winter rye/hairy vetch (WR/HV) mixture that were mechanically suppressed with a roller-crimper at two locations in Minnesota. Average marketable yields of tomato, zucchini, and bell pepper in the rolled cover crops were reduced 89%, 77%, and 92% in 2008 and 65%, 41%, and 79% in 2009, respectively, compared with a no-cover control. Winter rye and the WR/ HV mixture reduced average annual weed density at St. Paul by 96% for 8 to 10 weeks after rolling (WAR) and hairy vetch mulch reduced weeds 80% for 2 to 8 WAR, whereas at Lamberton, there was no consistent effect of cover treatments on weed populations. Winter rye and the WR/HV mixture had higher average residue biomass (5.3 and 5.7 Mg⋅ha-1, respectively) than hairy vetch (3.0 Mg⋅ha-1) throughout the season. Soil growing degree-days (SGDD) were lower in cover crop treatments compared with the no-cover control, which could have delayed early vegetable growth and contributed to reduced yields. All cover crop mulches were associated with low levels of soil nitrogen (N) (less than 10 mg⋅kg-1 N) in the upper 15 cm. Rolled winter annual cover crops show promise for controlling annual weeds in organic no-tillage systems, but additional research is needed on methods to increase vegetable crop yields in rolled cover crops. [ABSTRACT FROM AUTHOR]

Many winter stresses affect the ability of a perennial grass to overwinter in cold, temperate climates. Freezing tolerance is one of the major component traits affecting winterhardiness. Although effective freezing tolerance assessment procedures have long been available for perennial ryegrass ( Lolium perenne L.), no work has been done to characterize plant collections in the United States that may possess novel variation for freezing tolerance and winterhardiness. In this study, 21 accessions sampled from a larger set of 300 accessions with known winterhardiness and 3 check varieties were subjected to environmentally-controlled, low temperature acclimation, followed by controlled freezing using a programmable laboratory freezer. Eight freezing treatments from −2 to −16°C were used to determine survival across the known spectrum of freezing tolerance in perennial ryegrass. LT50 values were estimated based on whole plant survival, as well as tiller survival at each of the temperature treatments in the evaluation. LT50 values for the accessions and checks ranged from −10.31 to −13.95°C, with 3 accessions possessing significantly greater freezing tolerance than the most freeze-tolerant check, ‘NK200’. LT50 values were well correlated with winterhardiness in St. Paul during the winters of 2004–2005 and 2005–2006. Lower LT50 values in this experiment were associated with greater spring growth following the stressful winter of 2004–2005 and upright growth habit. The lack of negative biological association between freezing tolerance and turf quality components indicates that freezing tolerance testing could be a useful tool in breeding and selection with landrace germplasm. [ABSTRACT FROM AUTHOR]

After a decade of transgenic crop production, the dynamics of gene introgression into wild relatives remain unclear. Taking an ecological genetics approach to investigating fitness in crop–wild hybrid zones, we uncovered both conditions and characteristics that may promote introgression. We compared diverse crop–wild hybrid genotypes relative to wild Helianthus annuus under one benign and three stressful agricultural environments. Whereas relative fitness of crop–wild hybrids averaged 0.25 under benign conditions, with herbicide application or competition it reached 0.45 and was more variable. In some instances, hybrid fitness matched wild fitness (≈ 1). Thus, wild populations under agronomic stress may be more susceptible to introgression. Although ‘domestication’ traits are typically considered unlikely to persist in wild populations, we found some (e.g. rapid growth and early flowering) that may enhance hybrid fitness, especially in stressful environments. Rigorous assessment of how particular genotypes, phenotypes, and environments affect introgression will improve risk assessment for transgenic crops. [ABSTRACT FROM AUTHOR]

Flaxseed (Linum usitatissimum) has recently grown in popularity as a health food due to its high levels of omega-3 fatty acids. Many undomesticated Linum species possess a similar oil profile, in addition to perenniality, and could, therefore, provide similar products in addition to ecosystem services such as soil retention, improvements in water quality, and pollinator services. Many Linum species also possess ornamental qualities, e.g., blue flowers, which could provide added value as a new cut flower crop or garden herbaceous perennial. A perennial flax breeding program will be initiated by screening of Linum accessions for key agronomic and horticultural traits. Herein, we outline an ideotype approach which will enable identification of top herbaceous perennial candidates for domestication based on qualities relevant to oilseed, cut flower, and garden herbaceous perennial crop uses. In this review, we summarize the concept of ideotype breeding as it relates to perennial crop domestication and outline considerations for ideotype design. The tools outlined herein should prove useful to other breeders and especially for undomesticated crops. Whether the ideotype concept is applied as a framework for selection or simply as a means of generating hypotheses, applying this approach can provide structure to breeding programs with complex objectives. [ABSTRACT FROM AUTHOR]

Summary: Thlaspi arvense (pennycress) has the potential for domestication as a new oilseed crop. Information from an extensive body of research on the related plant species Arabidopsis can be used to greatly speed this process. Genome‐scale comparisons in this paper documented that pennycress and Arabidopsis share similar gene duplication. This finding led to the hypothesis that it should be possible to isolate Arabidopsis‐like mutants in pennycress. This proved to be true, as forward genetic screens identified floral and vegetative pennycress mutants that were similar to mutants found in Arabidopsis. Extending this approach, it was shown that most of the pennycress genes responsible for the formation of oxidized tannins could be rapidly identified. The causative mutations in the pennycress mutants could be identified either by PCR amplification of candidate genes or through whole‐genome sequencing (WGS) analysis. In all, WGS was used to characterize 95 ethyl methane sulfonate mutants, which revealed a mutation rate of 4.09 mutations per megabase. A sufficient number of non‐synonymous mutations were identified to create a mutant gene index that could be used for reverse genetic approaches to identify pennycress mutants of interest. As proof of concept, a Ta‐max3‐like dwarf mutant and Ta‐kcs5/cer60‐like wax mutants deficient in the biosynthesis of long chain fatty acids were identified. Overall, these studies demonstrate that translational genomics can be used to promote the domestication of pennycress. Furthermore, the ease with which important findings could be made in pennycress makes this species a new potential model plant. Significance statement: The domestication of pennycress has the potential to create a new oilseed cash/cover crop that can be grown during the fallow period between traditional summer crops, such as between the >80 million acres undergoing corn/soybean rotation in the Upper Midwest of the USA. This report demonstrates that translational genomics using Arabidopsis can serve as a tool to help greatly speed up the domestication process. [ABSTRACT FROM AUTHOR]

Native perennial bioenergy crops can mitigate greenhouse gases ( GHG) by displacing fossil fuels with renewable energy and sequestering atmospheric carbon (C) in soil and roots. The relative contribution of root C to net GHG mitigation potential has not been compared in perennial bioenergy crops ranging in species diversity and N fertility. We measured root biomass, C, nitrogen (N), and soil organic carbon ( SOC) in the upper 90 cm of soil for five native perennial bioenergy crops managed with and without N fertilizer. Bioenergy crops ranged in species composition and were annually harvested for 6 (one location) and 7 years (three locations) following the seeding year. Total root biomass was 84% greater in switchgrass ( Panicum virgatum L.) and a four-species grass polyculture compared to high-diversity polycultures; the difference was driven by more biomass at shallow soil depth (0-30 cm). Total root C (0-90 cm) ranged from 3.7 Mg C ha−1 for a 12-species mixture to 7.6 Mg C ha−1 for switchgrass. On average, standing root C accounted for 41% of net GHG mitigation potential. After accounting for farm and ethanol production emissions, net GHG mitigation potential from fossil fuel offsets and root C was greatest for switchgrass (−8.4 Mg CO2e ha−1 yr−1) and lowest for high-diversity mixtures (−4.5 Mg CO2e ha−1 yr−1). Nitrogen fertilizer did not affect net GHG mitigation potential or the contribution of roots to GHG mitigation for any bioenergy crop. SOC did not change and therefore did not contribute to GHG mitigation potential. However, associations among SOC, root biomass, and root C : N ratio suggest greater long-term C storage in diverse polycultures vs. switchgrass. Carbon pools in roots have a greater effect on net GHG mitigation than SOC in the short-term, yet variation in root characteristics may alter patterns in long-term C storage among bioenergy crops. [ABSTRACT FROM AUTHOR]

Perennial biomass from grasslands managed for conservation of soil and biodiversity can be harvested for bioenergy. Until now, the quantity and quality of harvestable biomass from conservation grasslands in Minnesota, USA, was not known, and the factors that affect bioenergy potential from these systems have not been identified. We measured biomass yield, theoretical ethanol conversion efficiency, and plant tissue nitrogen (N) as metrics of bioenergy potential from mixed-species conservation grasslands harvested with commercial-scale equipment. With three years of data, we used mixed-effects models to determine factors that influence bioenergy potential. Sixty conservation grassland plots, each about 8 ha in size, were distributed among three locations in Minnesota. Harvest treatments were applied annually in autumn as a completely randomized block design. Biomass yield ranged from 0.5 to 5.7 Mg ha−1. May precipitation increased biomass yield while precipitation in all other growing season months showed no affect. Averaged across all locations and years, theoretical ethanol conversion efficiency was 450 l Mg−1 and the concentration of plant N was 7.1 g kg−1, both similar to dedicated herbaceous bioenergy crops such as switchgrass. Biomass yield did not decline in the second or third year of harvest. Across years, biomass yields fluctuated 23% around the average. Surprisingly, forb cover was a better predictor of biomass yield than warm-season grass with a positive correlation with biomass yield in the south and a negative correlation at other locations. Variation in land ethanol yield was almost exclusively due to variation in biomass yield rather than biomass quality; therefore, efforts to increase biomass yield might be more economical than altering biomass composition when managing conservation grasslands for ethanol production. Our measurements of bioenergy potential, and the factors that control it, can serve as parameters for assessing the economic viability of harvesting conservation grasslands for bioenergy. [ABSTRACT FROM AUTHOR]

This study chronicles the ongoing process to domesticate an interspecific trigenomic tetraploid hybrid sunflower derived from a series of interspecific crosses between Helianthus annuus and Helianthus tuberosus. The goal of this process is to develop a perennial oilseed crop that can produce both high value vegetable oil and continuous ground-cover. Selection has focused on developing an ideotype with the domesticated morphology of H. annuus and the below-ground perennial features of H. tuberosus. The overarching challenge in the process of breeding and domesticating this interspecific perennial sunflower is overcoming obstacles associated with interploid meiosis in order to resolve a chromosomally stable hybrid population. As selection progresses through generations of intermating, there are improvements toward the desired ideotype, but selection efficiency is slowed by apparent antagonisms between annual- and perennial morphological targets and irregular meiosis which is especially problematic in a trigenomic tetraploid. This shows that keys toward perennial crop development through interspecific hybridization will be to capitalize on the abundant phenotypic variation within our population, achieve meiotic stability in order to maximize selection efficiency, and to break genetic correlations between annual and perennial traits. [ABSTRACT FROM AUTHOR]

Evaluation of genetic diversity within wild populations is an essential process for improvement and domestication of new crop species. This process involves evaluation of population structure and individual accessions based on genetic markers, growth habits, and geographic collection area. In this study, accessions of field pennycress were analyzed to identify population structure and variation in germplasm available for breeding. A total of 9157 genome-wide single nucleotide polymorphisms (SNPs) were identified among the 121 accessions analyzed, and linkage disequilibrium based pruning resulted in 3497 SNPs. Bayesian cluster analysis was implemented in STRUCTURE v2.3.4 to identify four population groups. These groups were confirmed based on principal components analysis and geographic origins. Pairwise diversity among accessions was evaluated and revealed considerable genetic variation. Notably, a subset of accessions from Armenia with exceptional genetic variation was identified. This survey is the first to report significant genetic diversity among pennycress accessions and explain some of the phenotypic differences previously observed in the germplasm. Understanding variation in pennycress accessions will be a crucial step for selection, breeding, and domestication of a new cash cover crop for cold climates. [ABSTRACT FROM AUTHOR]