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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]

New innovation systems are needed to help agriculture meet its "grand challenges." These systems should integrate the major streams of discovery in agricultural bioscience (biotechnologies and agroecotechnologies) and engage this and other research with private enterprise, civil society, and government sectors, to develop new agricultural systems that meet high standards for performance in economic, social, and environmental terms. To create and sustain such innovation systems, a critical mass of agricultural bioscientists is needed with certain skills, understandings, and inclinations that enable constructive and ongoing participation in innovation systems. To achieve this critical mass, graduate education will play a crucial role. We outline a graduate curriculum for this purpose, similar in scope to a graduate minor program; it features two foundational courses, experientially based short courses and student experiences in cross-sector innovation systems. The curriculum is now being pilot-tested at the University of Minnesota with a cohort of 11 students, but is well suited to multi-institutional implementation. Initial evaluation data suggest that the first year of the curriculum promoted development of certain relevant skills and inclinations in an initial cohort of seven students. [ABSTRACT FROM AUTHOR]

(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]

The article discusses a study which investigated the palatability and nutritive value of native legumes to sheep as well as their importance for prairie restoration and grazing in the Upper Midwest. Materials and methods included the establishment of a Waukegan silt loam soil in Saint Paul, Minnesota in 1997. Several charts are also presented, including one that shows height, growth stage, leafiness and palatability of perennial legumes as determined by sheep in 1998.

The article determines the palatability and nutritive value to sheep of several native perennial legumes of the Fabaceae family based on relative leaf consumption. Some of the native legumes included in the analysis are false indigo, Illinois bundleflower, blue wild indigo and purple prairie clover. The examination has revealed that the most palatable native legumes to sheep are purple prairie clover and Illinois bundleflower. The least palatable native legume among grazing sheep is false indigo.

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 effects of alfalfa, red clover, and perennial ryegrass as cover crops on soybean cyst nematode (SCN) and soybean and corn yields were evaluated in Waseca, Lamberton, and Rosemount, MN. The cover crops were interseeded in soybean at 0 or 2 wks after planting soybean in 2002 and killed with herbicide before planting corn in 2003. As expected, SCN-susceptible soybean supported higher SCN population density than SCN-resistant soybean. Reduction of SCN population density by red clover (up to 40%) and alfalfa (up to 55%) was observed in some sampling occasions at Lamberton and Rosemount, probably due to reduced soybean growth, but the effect was inconsistent. No significant reduction of SCN population by the two crops was detected at Waseca. While perennial ryegrass did not affect SCN population density in most cases, up to 46% higher egg population densities were observed in the perennial ryegrass treatment as compared to the control at Waseca. SCN-resistant soybean produced higher yield than susceptible soybean at all sites. While alfalfa reduced soybean yield at Lamberton (up to 50%) and Rosemount (up to 11%), red clover and perennial ryegrass reduced soybean yield only at Lamberton (up to 38%) and Waseca (up to 34%), respectively. No difference in corn yield was observed at Waseca. At Lamberton, alfalfa and red clover planted at the time of planting soybean reduced corn yield in the following year 17 and 13%, respectively, and perennial ryegrass planted 2 wks after planting soybean reduced corn yield 13%. At Rosemount, significant reduction of corn yield was observed with red clover (15–21%) interseeded in SCN-susceptible soybean and with alfalfa (12%) and red clover (12%) interseeded in SCN-resistant soybean at the time of planting soybean. The results suggest that an even later planting date of cover crops in soybean may reduce yield loss due to competition and make these cover crops more appropriate for use in the soybean-corn rotation in Minnesota. [ABSTRACT FROM AUTHOR]

Perennial flax (Linum spp.) breeding objectives at the University of Minnesota (UMN) are to develop agronomic (oilseed, fiber) and horticultural (cut flower, garden perennial) varieties that are hardy in Minnesota (USDA Plant Hardiness Zones 3 and 4). The objective of this research was to determine the range of cold hardiness in UMN perennial flax breeding populations compared with wild accessions of L. austriacum, L. lewisii, and L. perenne. Fifty‐three genotypes from seven populations were low temperature acclimated, followed by controlled freezing using a programmable freezer. The observed lethal temperature for 50% plant kill (LT50) ranged from >0 °C (0% survival) to <−12 °C (100% survival), for the test temperatures of 0, −4, −8, −10, and −12 °C. Cold damage was measured after 4 wk of regrowth as the proportion of alive shoots and a root damage rating. Significant negative correlations were observed between LT50 and proportion of alive shoots (r = −.918) and root damage rating (r = −.935). Both L. austriacum and L. perenne had significantly less cold damage than L. lewisii and the breeding populations. This study establishes methods of screening perennial flax cold tolerance that are more cost effective, rapid, and repeatable compared to field evaluations. Core Ideas: Controlled freezing tests were useful to identify hardy perennial flax species and genotypes.Lethal temperatures for 50% plant kill (LT50) were as low as ‐12 °C (hardy in MN USDA Z3–4).Linum austriacum and L. perenne had significantly less cold damage than L. lewisii and hybrids. [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]

Highlights • Variation was significant for fatty acid profile, oil, and hundred seed weight. • High estimates for broad sense heritability suggests selection will be effective. • More extreme variation is likely required for large changes in erucic acid or oil. • Overall and relative performance of accessions is variable across locations. Abstract Increasing oil content and altering the fatty acid profile of the oilseed cover crop, field pennycress (Thlaspi arvense L.), would improve its profitability and functionality as a biodiesel, and possibly allow its entry into the industrial and edible oil markets. However, plant breeders know little about the amount of existing variation for these traits. To make gains in selection using traditional plant breeding to meet these objectives, heritable variation is required for traits of interest. Reported here is the characterization of a collection of 41 winter type pennycress accessions from the United States Department of Agriculture (USDA) National Plant Germplasm System (NPGS) and wild selections. The collection was grown at three Minnesota locations in 2014–2015 and surveyed for total oil percentage, fatty acid profile, and hundred seed weight. Significant variation (p < 0.001) was detected among the accessions for all traits surveyed. Coupled with high broad sense heritability (average for all traits: H p l o t 2 = 0.62 and H e n t r y 2 = 0.88), results indicate potential for effective selection within this collection in the environments tested. Although significant, no extreme variation was found, suggesting that mutagenesis or additional germplasm may be necessary to make desired alterations. The effect of location was significant for nine of twelve traits, and accession by location interaction in eight of twelve, showing that both overall and relative performance of the accessions were variable across locations. [ABSTRACT FROM AUTHOR]

Agricultural management practices can produce changes in soil microbial populations whose functions are crucial to crop production and may be detectable using high-throughput sequencing of bacterial 16S rRNA. To apply sequencing-derived bacterial community structure data to on-farm decision-making will require a better understanding of the complex associations between soil microbial community structure and soil function. Here 16S rRNA sequencing was used to profile soil bacterial communities following application of cover crops and organic fertilizer treatments in certified organic field cropping systems. Amendment treatments were hairy vetch ( Vicia villosa ), winter rye ( Secale cereale ), oilseed radish ( Raphanus sativus ), buckwheat ( Fagopyrum esculentum ), beef manure, pelleted poultry manure, Sustane ® 8-2-4, and a no-amendment control. Enzyme activities, net N mineralization, soil respiration, and soil physicochemical properties including nutrient levels, organic matter (OM) and pH were measured. Relationships between these functional and physicochemical parameters and soil bacterial community structure were assessed using multivariate methods including redundancy analysis, discriminant analysis, and Bayesian inference. Several cover crops and fertilizers affected soil functions including N -acetyl-β- d -glucosaminidase and β-glucosidase activity. Effects, however, were not consistent across locations and sampling timepoints. Correlations were observed among functional parameters and relative abundances of individual bacterial families and phyla. Bayesian analysis inferred no directional relationships between functional activities, bacterial families, and physicochemical parameters. Soil functional profiles were more strongly predicted by location than by treatment, and differences were largely explained by soil physicochemical parameters. Composition of soil bacterial communities was predictive of soil functional profiles. Differences in soil function were better explained using both soil physicochemical test values and bacterial community structure data than using soil tests alone. Pursuing a better understanding of bacterial community composition and how it is affected by farming practices is a promising avenue for increasing our ability to predict the impact of management practices on important soil functions. [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]

Rotation with non-host crops can be an effective method for reducing soybean cyst nematode (Heterodera glycines) populations in soybean cropping systems. Sunn hemp, Illinois bundleflower, oilseed rape, perennial ryegrass, red clover, corn and H. glycines-susceptible soybean were compared for their effects on H. glycines hatch, viability and development in laboratory and glasshouse experiments. In the laboratory experiments, root exudates in soil leachates, extracts from fresh plant tissues, and extracts from residues of sunn hemp, red clover and soybean stimulated hatch of second-stage juveniles (J2) of H. glycines. All crops appeared to contain hatch inhibitors as well. There was no apparent effect of the root exudates and extracts from any of the crops on egg viability in vitro. When the H. glycines J2 were exposed to root exudates and extracts for 72 h, only the extracts of fresh plants and plant residue from sunn hemp, red clover and soybean, and the extract of plant residue from oilseed rape reduced viability of J2. In glasshouse experiments, residues of all crops, except Illinois bundleflower, reduced egg population density, with sunn hemp providing the greatest reduction. Residues of sunn hemp, red clover, and perennial ryegrass added to soil reduced the reproduction factor, suggesting the residues not only reduced egg population density but also reduced nematode infectivity. While all crops allowed penetration by J2, minimal development (to third- or fourth-stage juveniles only) occurred only in sunn hemp, red clover, oilseed rape and Illinois bundleflower, and full development occurred only in soybean. The results suggest that sunn hemp and red clover were the most effective rotation crops for managing H. glycines, and that stimulating hatch of H. glycines J2 was the main mechanism involved in reducing the H. glycines population density. [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]

Highlights • NO 3 -N leaching was two orders of magnitude less below a perennial grain than maize. • Soil solution NO 3 -N was lower beneath a perennial grain than maize and switchgrass. • N fertilizer increased perennial grain yield without increasing NO 3 -N leaching. Abstract Global expansion of high-input annual grain crops and associated nitrogen (N) fertilizer use can have negative consequences for the environment and human health. Nitrate nitrogen (NO 3 -N) leaching from fertilized annual crops can contaminate groundwater and pollute natural aquatic ecosystems and rural drinking water sources. Intermediate wheatgrass (IWG; Thinopyrum intermedium) is a perennial grass being domesticated to serve as the world's first widely available perennial grain crop. Our objective was to measure water quality variables and crop yields in order to model NO 3 -N leaching beneath IWG, maize, and switchgrass under three N fertilizer treatments; low N (0 kg N ha−1), medium N (maize = 80, switchgrass and IWG = 40 kg N ha−1), and high N (maize = 160, switchgrass and IWG = 120 or 160 kg N ha−1). The switchgrass and IWG medium N treatments also included alfalfa as an intercrop. The NO 3 -N concentration in soil solution 50 cm below the surface was one and two orders of magnitude lower in high N fertilized IWG compared to switchgrass and maize, respectively. Soil solution NO 3 -N increased with N fertilizer in all crops. Soil water content was less at 50 and 100 cm depths in IWG compared to switchgrass and maize but was unaffected by N fertilizer treatment. Using the Denitrification and Decomposition (DNDC) model, average annual NO 3 -N leaching estimates in the high N treatments were 21.7 kg N ha−1 for maize and 3.7 and 0.2 kg N ha−1 for switchgrass and IWG, respectively. Despite consistent biomass yields through time, IWG grain yields decreased with stand age at all N fertilizer treatments. Alfalfa did not persist in the IWG and switchgrass medium N treatments, thus other legumes should be tested for intercropping with perennial grain crops. Intermediate wheatgrass has great potential to provide food-quality grain and biomass while preventing NO 3 -N leaching. [ABSTRACT FROM AUTHOR]

Highlights • Brassica NIRS calibration equations successfully used for pennycress mutant germplasm evaluations. • Pennycress mutants facilitate identification of traits for rapid domestication. • Differences in seed composition traits create new industrial opportunities. Abstract Pennycress is being domesticated as a new winter oilseed crop to be grown between corn harvest and soybean planting the following year in the Upper Midwestern United States. The aim of this research was to evaluate seed composition traits in a large pennycress mutant population using near-infrared spectroscopy (NIRS). We tested the hypothesis that Brassica NIRS calibration equations could be used rapidly and cost effectively to evaluate pennycress seeds for protein, oil, glucosinolate, and fatty acid contents. Using calibration equations developed for Brassica , we identified a broad range for each of the traits evaluated in this study. Wet lab analyses were conducted on selected subsets of the mutant families to confirm the predicted variation for each trait using NIRS. Supporting our hypothesis, moderate to strong correlations were observed between the wet lab analyses and NIRS predictions for seven of the eight traits evaluated. For protein, oil and glucosinolate content, correlations between the NIRS predictions and wet lab values were 0.82, 0.92 and 0.78 respectively. For fatty acid content, moderate correlations for oleic acid (0.68), linoleic acid (0.78), linolenic acid (0.60) and erucic acid (0.74) were observed. These findings allowed us to use NIRS to quickly evaluate large heterogenous mutant families and identify pennycress lines harboring desirable traits required for adoption as a cover crop and to create several industrial opportunities. [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]

Historically, agroecosystems have been designed to produce food. Modern societies now demand more from food systems-not only food, fuel, and fiber, but also a variety of ecosystem services. And although today's farming practices are producing unprecedented yields, they are also contributing to ecosystem problems such as soil erosion, greenhouse gas emissions, and water pollution. This review highlights the potential benefits of perennial grains and oilseeds and discusses recent progress in their development. Because of perennials' extended growing season and deep root systems, they may require less fertilizer, help prevent runoff, and be more drought tolerant than annuals. Their production is expected to reduce tillage, which could positively affect biodiversity. End-use possibilities involve food, feed, fuel, and nonfood bioproducts. Fostering multidisciplinary collaborations will be essential for the successful integration of perennials into commercial cropping and food-processing systems. [ABSTRACT FROM AUTHOR]

The management of the soybean aphid Aphis glycines Matsumara is a major challenge to soybean production in the north-central United States. The identification and characterization of the insect predator community has informed integrated pest management strategies by providing insight on predators that can suppress soybean aphid populations. Hoverflies (Diptera: Syrphidae) are known predators of A. glycines, but more information is needed on their diversity, abundance, and performance to evaluate their importance as biological control agents of A. glycines. In this study, syrphid abundance was evaluated across two growing seasons in four soybean fields in east-central Minnesota. Six methods were used to quantify syrphid abundance at the larval, pupal, and adult life stages; describe species composition and richness for adults; and directly compare larval abundance to aphid abundance. The syrphid community comprised eight species, dominated by Toxomerus marginatus (Say) and Toxomerus geminatus (Say). Syrphid abundance was relatively low in soybean fields. Feeding trials were conducted to compare the performance of the most common syrphid (T. marginatus) on a diet of A. glycines with two native aphids, Aphis nerii Boyer de Fonscolombe and Aphis monardae Oestlund. Despite their low abundance in soybeans, T. marginatus larvae perform well on A. glycines, A. nerii, and A. monardae in laboratory feeding trials, implying that factors other than host suitability are limiting their potential to exert biological control on soybean aphids. [ABSTRACT FROM PUBLISHER]

Over the last half-century, crop breeding and agronomic advances have dramatically enhanced yields in temperate summer-annual cropping systems. Now, diversification of these cropping systems is emerging as a strategy for sustainable intensification, potentially increasing both crop production and resource conservation. In temperate zones, diversification is largely based on the introduction of winter-annual and perennial crops at spatial and temporal locations in annual-crop production systems that efficiently increase production and resource conservation. Germplasm development will be critical to this strategy, but we contend that to be feasible and efficient, germplasm improvement must be closely integrated with commercialization of these crops. To accomplish this integration, we propose a novel approach to germplasm development: the reflective plant breeding paradigm (RPBP). Our approach is enabled by developments in genomics, agroecosystem management, and innovation theory and practice. These developments and new plant-breeding technologies (e.g., low-cost sequencing, phenotyping, and spatial modeling of agroecosystems) now enable germplasm development to proceed on a time scale that enables close coordination of breeding and commercialization (i.e, development of cost-effective production systems and supply-value chains for end-use markets). The RPBP approach is based on close coordination of germplasm development with enterprise development. In addition to supporting strategic diversification of current annual-cropping systems, the RPBP may be useful in rapid adaptation of agriculture to climate change. Finally, the RPBP may offer a novel and distinctive pathway for future development of the public plant-breeding programs of land-grant universities with implications for graduate education for public- and privatesector plant breeders. [ABSTRACT FROM AUTHOR]

In the Upper Midwest, corn (Zea mays L.) and soybean (Glycine max [L.] Merr.) dominate the landscape, but only for six to seven months of the year. Thus, opportunities exist to establish crops that can utilize the remainder of the growing season and contribute to overall farm profitability. One species of interest is pennycress (Thlaspi arvense L.), but a lack of established agronomic best management practices is a barrier to successful crop production. The objectives of this study were to identify a range of cumulative growing degree days (CGDD) corresponding to pennycress physiological maturity, determine the optimal harvest window that maximizes pennycress seed yield and oil content, and characterize changes in pennycress seed attributes over seed maturation. This study was conducted over the 2016–2017 and 2017–2018 growing seasons with 'MN106' pennycress at two locations in Minnesota, USA. Seed dry weight stabilized within the window of maximum seed yield, but oil content did not maximize until after this period. However, there was minimal loss of oil content when pennycress was harvested within the seed yield maximization window. Based on these parameters, as well as seed moisture, it was estimated that pennycress reached physiological maturity between 2230 and 2250 °C d CGDD, or about a week prior to harvest maturity in terms of crop phenology. Delaying harvest to harvest maturity resulted in a 26% loss in harvestable seed due to seed shatter compared with the average maximum seed yield of 928 kg ha−1. Ensuring maximum pennycress seed yield and oil content at harvest is imperative to successful production and contribution to farm economic viability. • Parameters indicating pennycress physiological maturity maximized in a similar order, regardless of site-year. • Pennycress reached physiological maturity between 2230 and 2250 °C CGDD. • Seed moisture was too high at physiological maturity for mechanical harvest, so moisture reduction will be necessary to facilitate the earliest possible pennycress harvest. [ABSTRACT FROM AUTHOR]

Abstract: Intermediate wheatgrass (Thinopyrum intermedium) is a perennial crop that possesses desirable agronomic traits and provides environmental services, e.g., reducing soil erosion, nitrate leaching and inputs of energy and pesticide. Thus, intermediate wheatgrass is currently being domesticated as a perennial grain crop. However, the genetic information for molecular breeding is quite limited. Here we report a molecular analysis of high-molecular-weight glutenin subunits (HMW-GS) in intermediate wheatgrass using gene cloning and protein biochemistry. Five HMW-GS genes were isolated from individual intermediate wheatgrass plants: two x-type genes TiHGS1 and TiHGS4, and three y-type genes TiHGS2, TiHGS3 and TiHGS5. Among them, TiHGS5 was novel and possessed an additional cysteine residue at the N-terminal domain or repetitive domain. Sequence alignments showed that TiHGS1 and TiHGS2 genes shared high identities (>96%) with the Glu-1Dx and Glu-1Dy genes, respectively, in common wheat and Aegilops species, TiHGS3 with HMW-GS genes from Dasypyrum or Pseudoroegneria, and TiHGS4 and TiHGS5 with HMW-GS genes from Thinopyrum elongatum. This work provides substantial new insights into the gene compositions and protein profiles of HMW-GS in intermediate wheatgrass, and also gives evidence about the genome components of intermediate wheatgrass. [Copyright &y& Elsevier]

Highlights: [•] We examine an interspecific Helianthus annuus × Helianthus tuberosus population. [•] We can easily identify true interspecific hybrids. [•] Intermated F1 (IM1F1) have increased flower size (up to 20%) compared to the F1. [•] Perennial habit segregates in a simple fashion even if the genetics are complex. [•] The best improvement strategy is a recurrent selection program focusing on yield. [ABSTRACT FROM AUTHOR]

Efforts are underway to domesticate the winter annual oilseed cover crop, pennycress (Thlaspi arvense L.), to aid in overcoming global food security and ecosystem challenges. Several key alleles for domestication have already been introgressed; however, the weedy trait of seed dormancy remains. To make pennycress attractive for growers, any traits that could contribute to weed pressure on their fields must be removed. In this study, we have performed multi-faceted experiments to understand and dissect challenges associated with seed dormancy and germination in wild pennycress. Lines were derived by chemical mutagenesis to provide a possible genetic solution. Laboratory and field-based experiments were performed to understand the role of light, seed priming, and gibberellic acid in the wild-type pennycress. These experiments were followed by incorporation of a genotype with a mutation in the TRANSPARENT TESTA 2 gene that could potentially overcome problem of seed dormancy in wild-type pennycress. Subsequent laboratory and field-based comparison of the wild-type and tt2 mutant over three seasons suggested that the tt2 line can germinate at a faster rate than wild-type and is comparable to the germination of wild-type treated with gibberellic acid. These experiments validated the hypothesis of using transparent testa mutants to solve seed dormancy and germination challenges. Further characterization of the transparent testa mutant indicated that this genotype can be susceptible to abiotic stress conditions such as NaCl, polyethylene glycol, coarse growth medium (sand), and abscisic acid. Future work is required to understand the issues related to the abiotic stress response in these lines. • The germination rate of the tt2 mutant was ≥ 89% versus ≤ 63% for wild-type. • Soil texture and precipitation greatly influenced germination of the tt2 mutant. • Salt, water, and ABA stress reduced tt2 germination compared to wild-type. [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]

Iron‐deficiency chlorosis (IDC) and soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) are important factors limiting soybean [Glycine max (L.) Merr.] yield. Vesicular‐arbuscular mycorrhizal fungi (MF) are generally beneficial to crops. The effect of preceding crops with known variation in MF colonization was tested in two SCN‐infested fields in Waseca and Lamberton in Minnesota to determine the effect of MF and other soil biotic and abiotic factors on IDC. No crop effect on soybean yield was detected. There was no difference in SCN population density following nonhost crops at Lamberton, but sunn hemp (Crotalaria juncea L.) resulted in lower SCN population density than corn (Zea mays L.) at Waseca. Chlorosis rating and colonization frequency of soybean roots by MF were lowest following canola (Brassica napus L.) and sugar beet (Beta vulgaris L.), the two nonmycorrhizal crops. Soybean had lowest number and weight of N‐fixing nodules following soybean, highest following corn, and intermediate following other crops. Iron‐deficiency chlorosis was positively correlated with MF and negatively correlated with nodulation and soil Fe at both sites. The correlations of SCN, other soil elements, and soil penetration resistance with IDC were either insignificant at both sites or inconsistent across the sites. No consistent correlation of soil factors with MF was detected. This study suggests that a causal relationship between MF and IDC might exist, but it requires further exploration. [ABSTRACT FROM AUTHOR]

Abstract: Perennial vegetation can provide multiple ecosystem services essential for sustainable production more effectively than production systems based on annual crops. However, the ability of annually harvested, unfertilized perennial systems to sustain long-term yields while also maintaining ecosystem services has not been widely studied. Here we compare the impacts of harvested perennial grass and annual crop fields on ecosystem functioning in KS, USA. Despite the lack of mineral fertilizer applications, the aboveground harvests of perennial fields yielded similar levels of N compared to those of conventional high-input wheat (Triticum aestivum) fields and at only 8% of the in-field energy costs. Their 75-yr cumulative N yield per ha was approximately 23% greater than that from the region''s wheat fields. In terms of aboveground food webs, perennial fields harboured greater numbers and/or diversity of insect pollinators, herbivores and detritivores. Belowground, perennial grass fields maintained 43Mgha−1 more soil carbon and 4Mgha−1 more soil nitrogen than annual crop fields in the surface 1m. Soil food webs in perennial fields, as indicated by nematode communities, exhibited greater food web complexity and stability than did those in annual crop fields. In surrounding watersheds, increased annual cropland was correlated with higher riverine nitrate-nitrogen levels. Given their benefits, harvested perennial grasslands provide valuable ecological benchmarks for agricultural sustainability. [Copyright &y& Elsevier]

Restoration of native plant communities requires adapted germplasm; thus, information is needed to guide native seed collection and production. Analysis of genetic variation has potential to provide insight into diversity and relatedness of natural populations. Our objectives were to examine genetic diversity of native species in Minnesota to discover if variation is related to biomes or distance, and possibly to develop seed collection zones. Our study included prairie cordgrass (Spartina pectinata), purple prairie clover (Dalea purpurea), and spotted joe-pye weed (Eupatorium maculatum). Using amplified fragment length polymorphisms, we analyzed 100 samples from eight populations for prairie cordgrass, 152 samples from nine populations for purple prairie clover, and 127 samples from 10 populations for spotted joe-pye weed. We found moderate to high levels of genetic diversity within each species. Small populations were not necessarily lower in diversity than larger ones. Analysis of molecular variance results indicate clear population differentiation. However, rather than displaying geographic or ecological associations, the variation had discontinuous patterns. Therefore, we were not able to develop unambiguous recommendations for seed collection. We discuss the applicability of molecular markers in detecting adaptive potential. [ABSTRACT FROM AUTHOR]

The article presents a study of seeding rate that affects the establishment of native perennial legumes or Fabaceae in the upper western U.S., conducted at Rosemount, Minnesota in 1999 and 2000. The species differed in population and yield response to seeding rates, with seeds cultivated of little bluestem or Poaceae. Illinois bundleflower and wild senna have the potential for biomass use than the purple prairie clover. The seeding-year populations increased linearly with the rise of seeding rate.

Symbiotic N2 fixation capacity may affect productivity of the perennial legume Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. & Fernald]. Our objective was to estimate N2 fixation of three Illinois bundleflower accessions managed for forage. Herbage yield ranged from 1.02 Mg ha-1 to 3.69 Mg ha-1 in Year 1, and 2.99 Mg ha-1 to 8.27 Mg ha-1 in Year 2. Accessions differed in herbage yield, aboveground N yield, and N2 fixed at certain locations in Year 1, but not in Year 2. Percentage of N derived from the atmosphere (%Ndfa) varied with location but not with accession in either year. The 15N natural abundance method gave lower estimates of %Ndfa than the 15N enrichment method. In yr 1, N2 fixation ranged from 0 to 30 kg ha-1 N (51N natural abundance method), 11 to 43 kg ha-1 (15N enrichment method), and 0 to 50 kg ha-1 N (total N difference method), and in Year 2 these estimates at two locations were 60 to 67 kg ha-1 N, 79 to 127 kg ha-1 N, and 67 to 142 kg ha-1 N, respectively. Differences in N2 fixation among locations could have been due to rhizobial strains. At the high-yielding location with the greatest N2 fixation, over one-half of the nodules were occupied by indigenous rhizobial strains, whereas at other locations, strains from commercial inoculant accounted for most nodules. Symbiotic N2 fixation by Illinois bundleflower could be enhanced by new rhizobial inoculums. [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]