Switchgrass Biomass Yield Research Articles

Empirical comparison of genomic selection to phenotypic selection for biomass yield of switchgrass

AbstractSwitchgrass (Panicum virgatum L.) is one of several grass species being bred for use as a biomass crop to support the biofuel industry. Increases in biomass yield are imperative to ensure that crops such as switchgrass can sustainably meet the needs of this industry. Genomic selection is one strategy that can accelerate breeding gains for complex traits such as biomass yield. The goal of this study was to conduct three cycles of genomic selection in a previously trained Liberty switchgrass population and compare that to one cycle of phenotypic selection, both of which required 3 years to complete. The advanced lines were tested across five locations and three hardiness zones in the Central United States using a randomized complete block design with four replicates. There were strong genotype × location interactions, but the first two generations of genomic selection were superior to Liberty at four of the five evaluation locations. Conversely, phenotypic selection failed to result in significant gains in biomass yield for any of the five evaluation locations. Based on these results from Liberty switchgrass, genomic selection methods are expected to at least double the rates of gain in biomass yield relative to previous estimates using phenotypic selection methods.

Economic and energy efficiency of resource-saving technology for switchgrass cultivation

Purpose. The study aimed to compare the efficiency of the resource-saving technology with the conventional technology for switchgrass cultivation using the developed methodology for assessing the economic and energy efficiency. Methodology / approach. The study used general and special methods, including the methodology of scientific research in agronomy, laboratory determination of dry matter content in biomass, quantitative-weight analysis to establish crop yield, and the authors’ improved methodology for assessing economic and energy efficiency. The research results were statistically processed using variance and comparative analysis. Results. The results of the research on the use of resource-saving cultivation technology in comparison with conventional technology show an increase in switchgrass biomass yield from 14.6 to 15.7 t/ha, an increase in economic efficiency with profitability growth from 73.8 to 79.0 %, and an increase in energy efficiency with a growth of the energy efficiency coefficient by 0.7 – from 4 to 4.7 (average level of energy efficiency) when applying a specific complex of agrotechnical measures. When using resource-saving technology, the average full cost of cultivating switchgrass for six years is 8305.6 UAH/ha, compared to 7952.8 UAH/ha with conventional technology. However, resource-saving technology generates an average sales revenue of 14867.5 UAH/t, which is 1045 UAH/t more than conventional technology (13822.5 UAH/t). Originality / scientific novelty. For the first time, a field experiment was conducted to compare switchgrass cultivation using resource-saving and conventional technologies. The authors have developed a methodology to assess the economic and energy efficiency of cultivating switchgrass. The results indicate that the efficiency of switchgrass biomass production is influenced by improved cultivation technology. The authors have developed a three-dimensional econometric model that demonstrates how the profitability level depends on the chosen switchgrass cultivation technology. Practical value / implications. The research results have practical significance as they have led to the development of a methodology and evaluate the economic and energy efficiency of switchgrass cultivation. These results will be useful for agrarian enterprises to save resources.

Blocking miR396 activity by overexpression MIM396 improved switchgrass tiller number and biomass yield.

MicroRNA396 (miR396) plays an important role in the regulation of plant growth and development by repressing the expression level of its target growth-regulating factor (GRF) family genes. In our previous study, we found that overexpression of miR396 negatively regulated both tillering and biomass yield in switchgrass (Panicum virgatum L.). We, therefore, speculated that blocking the expression of miR396 could enhance switchgrass tillering and biomass yield. Here, we produced transgenic switchgrass plants overexpressing a target mimicry form of miR396 (MIM396) in wild type (WT) and Os-MIR319b overexpressing switchgrass plant (with higher enzymatic hydrolysis efficiency, but reduced tillering), in which the expression of miR396 was blocked. The phenotype and biological yields of these plants were analyzed. Blocking miR396 to improve its target PvGRFs expression in switchgrass improved the tiller number and dry weight of transgenic plants. Further morphological analysis revealed that MIM396 plants increased the number of aerial branches and basal tillers compared to those of wild-type plants. The enzymatic efficiency of MIM396 plants was reduced; however, the total sugar production per plant was still significantly higher than that of wild-type plants due to the increase in biomass. In addition, blocking miR396 in a transgenic switchgrass plant overexpressing Os-MIR319b (TG21-Ms) significantly increased the PvGRF1/3/5 expression level and tiller number and biomass yield. The miR156-target gene PvSPL4, playing a negative role in aerial and basal buds outgrowth, showed significant downregulated in MIM396 and TG21-Ms. Those results indicate that miR396-PvGRFs, through disrupting the PvSPL4 expression, are involved in miR319-PvPCFs in regulating tiller number, at least partly. MIM396 could be used as a molecular tool to improving tiller number and biomass yield in switchgrass wild type and miR319b transgenic plants. This finding may be applied to other graminaceous plants to regulate plant biological yield.

PvARL1 Increases Biomass Yield and Enhances Alkaline Tolerance in Switchgrass (Panicum virgatum L.).

Switchgrass is an important bioenergy crop valued for its biomass yield and abiotic tolerance. Alkali stress is a major abiotic stress that significantly impedes plant growth and yield due to high salinity and pH; however, the response mechanism of switchgrass to alkali stress remains limited. Here, we characterized PvARL1, an ARF-like gene, which was up-regulated in both the shoot and root tissues under alkali stress conditions. Overexpression of PvARL1 not only improved alkali tolerance but also promoted biomass yield with more tiller and higher plant height in switchgrass. Moreover, PvARL1 overexpression lines displayed higher capacities in the maintenance of water content and photosynthetic stability compared with the controls under alkali treatments. A significant reduction in the ratio of electrolyte leakage, MDA content, and reactive oxygen species (ROS) showed that PvARL1 plays a positive role in protecting cell membrane integrity. In addition, PvARL1 also negatively affected the K+ efflux or uptake in roots to alleviate ion toxicity under alkali treatments. Overall, our results suggest that PvARL1 functions as a positive regulator in plant growth as well as in the plant response to alkali stress, which could be used to improve switchgrass biomass yield and alkali tolerance genetically.

Antagonistic Activity of Streptomyces alfalfae 11F against Fusarium Wilt of Watermelon and Transcriptome Analysis Provides Insights into the Synthesis of Phenazine-1-Carboxamide.

Streptomyces alfalfa strain 11F has inhibitory effects on many phytopathogenic fungi and improves the establishment and biomass yield of switchgrass. However, the antagonistic effects of strain 11F on Fusarium wilt of watermelon and its secondary metabolites that contribute to its biocontrol activity are poorly understood. We evaluated the antagonistic and growth-promoting effects of strain 11F and conducted a transcriptome analysis to identify the metabolites contributing to antifungal activity. Strain 11F had marked inhibitory effects on six fungal pathogens. The incidence of Fusarium wilt of watermelon seedlings was decreased by 46.02%, while watermelon seedling growth was promoted, as indicated by plant height (8.7%), fresh weight (23.1%), and dry weight (60.0%). Clean RNA-sequencing data were annotated with 7553 functional genes. The 2582 differentially expressed genes (DEGs) detected in the Control vs. Case 2 comparison were divided into 42 subcategories of the biological process, cellular component, and molecular function Gene Ontology categories. Seven hundred and forty functional genes (55.47% of the DEGs) were assigned to Kyoto Encyclopedia of Genes and Genomes metabolic pathways, reflecting the complexity of the strain 11F metabolic regulatory system. The expression level of the gene phzF, which encodes an enzyme essential for phenazine-1-carboxylic acid (PCA) synthesis, was downregulated 3.7-fold between the 24 h and 48 h fermentation time points, suggesting that strain 11F can produce phenazine compounds. A phenazine compound from 11F was isolated and identified as phenazine-1-carboxamide (PCN), which contributed to the antagonistic activity against Fusarium oxysporum f. sp. niveum. PCA was speculated to be the synthetic precursor of PCN. The downregulation in phzF expression might be associated with the decrease in PCA accumulation and the increase in PCN synthesis in strain 11F from 24 to 48 h. Streptomyces alfalfae 11F protects watermelon seedlings from Fusarium wilt of watermelon and promotes seedling growth. The transcriptome analysis of strain 11F provides insights into the synthesis of PCN, which has antifungal activity against F. oxysporum f. sp. niveum of watermelon.

Mapping quantitative trait loci for biomass yield and yield-related traits in lowland switchgrass (Panicum virgatum L.) multiple populations.

Switchgrass can be used as an alternative source for bioenergy production. Many breeding programs focus on the genetic improvement of switchgrass for increasing biomass yield. Quantitative trait loci (QTL) mapping can help to discover marker-trait associations and accelerate the breeding process through marker-assisted selection. To identify significant QTL, this study mapped seven hybrid populations and one combined of two hybrid populations (30 to 96 F1s) derived from Alamo and Kanlow genotypes. The populations were evaluated for biomass yield, plant height, and crown size in a simulated-sward plot with two replications at two locations in Tennessee from 2019 to 2021. The populations showed significant genetic variation for the evaluated traits and exhibited transgressive segregation. The 17,251 single nucleotide polymorphisms (SNPs) generated through genotyping-by-sequencing (GBS) were used to construct a linkage map using a fast algorithm for multiple outbred families. The linkage map spanned 1,941 cM with an average interval of 0.11 cM between SNPs. The QTL analysis was performed on evaluated traits for each and across environments (year and location) that identified five QTL for biomass yield (Logarithm of the odds, LOD 3.12 to 4.34), four QTL for plant height (LOD 3.01 to 5.64), and seven QTL for crown size (LOD 3.0 to 4.46) (P ≤ 0.05). The major QTL for biomass yield, plant height, and crown size resided on chromosomes 8N, 6N, and 8 K explained phenotypic variations of 5.6, 5.1, and 6.6%, respectively. SNPs linked to QTL could be incorporated into marker-assisted breeding to maximize the selection gain in switchgrass breeding.

Local adaptation of switchgrass drives trait relations to yield and differential responses to climate and soil environments

AbstractSwitchgrass, a potential biofuel crop, is a genetically diverse species with phenotypic plasticity enabling it to grow in a range of environments. Two primary divergent ecotypes, uplands and lowlands, exhibit trait combinations representative of acquisitive and conservative growth allocation strategies, respectively. Whether these ecotypes respond differently to various types of environmental drivers remains unclear but is crucial to understanding how switchgrass varieties will respond to climate change. We grew two upland, two lowland, and two intermediate/hybrid cultivars of switchgrass at three sites along a latitudinal gradient in the central United States. Over a 4‐year period, we measured plant functional traits and biomass yields and evaluated genotype‐by‐environment (G × E) interaction effects by analyzing switchgrass responses to soil and climate variables. We found substantial evidence of G × E interactions on biomass yield, primarily due to deviations in the response of the southern lowland cultivar Alamo, which produced more biomass in hotter and drier environments relative to other cultivars. While lowland cultivars had the highest potential for yield, their yields were more variable year‐to‐year compared to other cultivars, suggesting greater sensitivity to environmental perturbations. Models comparing soil and climate principal components as explanatory variables revealed soil properties, especially nutrients, to be most effective at predicting switchgrass biomass yield. Also, positive correlations between biomass yield and conservative plant traits, such as high stem mass and tiller height, became stronger at lower latitudes where the climate is hotter and drier, regardless of ecotype. Lowland cultivars, however, showed a greater predisposition to exhibit these conservative traits. These results suggest switchgrass trait allocation trade‐offs that prioritize aboveground biomass production are more tightly associated in hot, dry environments and that lowland cultivars may exhibit a more specialized strategy relative to other cultivars. Altogether, this research provides essential knowledge for improving the viability of switchgrass as a biofuel crop.

Overexpression of PvBiP2 improved biomass yield and cadmium tolerance in switchgrass (Panicum virgatum L.)

Switchgrass (Panicum virgatum L.), the prime bioenergy feedstock crop, is one ideal candidate for phytoremediation of cadmium (Cd). The absorption of Cd imposes severe endoplasmic reticulum (ER)-stress in plants. ER chaperone binding proteins (BiPs) are important modulators in ER-stress responses. The objective of this study was to characterize one Cd-responsive BiP gene, PvBiP2, in switchgrass for its roles in Cd tolerance and plant growth. PvBiP2 was up-regulated by Cd and the ER-stress inducer, dithiothreitol (DTT) and could be trans-activated by one Cd-responsive heat shock transcription factor PvHsfA4. Overexpression of PvBiP2 in switchgrass significantly increased its plant growth with higher height, stem diameter, leaf width, internode length, and tiller numbers than those of the wildtype (WT) plants under non-stress conditions. After 30 days of Cd treatment, the PvBiP2 over-expression transgenic lines showed 40–45% higher dry biomass accumulation with net photosynthesis rate (Pn), but lower electrolyte leakage (EL), malondialdehyde (MDA), and glutathione (GSH) levels than WT. Moreover, over-expressing PvBiP2 led to ∼90–140% Cd accumulation in plants but 46–57% lower Cd translocation rates to shoots. Together, the PvHSFA4-PvBiP2 module acted as positive regulators in plant Cd tolerance, and over-expressing PvBiP2 promoted plant vegetative growth as well as Cd tolerance making it an ideal molecular target for genetic improvement in switchgrass in the future.

Impact of ploidy on biomass yield of upland switchgrass (Panicum virgatum L.) : a meta-analysis

Impact of ploidy on biomass yield of upland switchgrass (Panicum virgatum L.) : a meta-analysis

Harvest frequency and harvest timing following a freeze event effects on yield and composition of switchgrass

AbstractConstant supply of biomass from the field is limited by the seasonality of production of warm‐season grasses in the transition U.S. region. Delaying harvest after occurrence of freeze may be an alternative to extend the biomass supply period of switchgrass (Panicum virgatum L.) in North Carolina. The objectives of this study were to evaluate the effects of harvest frequency (HF) and harvest timing at the end of the growing season (HT) on switchgrass biomass yield, nutrient (N, P, and K) removal, and dry matter (DM) and ash concentrations. Treatments were the factorial combination of two HF (clipped once [1X] or twice [2X] per season) and three HT (before freeze in October, after first freeze in November, and late winter in February). Delaying harvest after occurrence of freeze did not affect total annual biomass yield for the 2X treatment (average of 15.5 Mg ha−1), whereas for 1X yield declined from 14.4 to 10.1 Mg ha−1 when harvest was delayed from October to February. Ash concentration declined from 29 g kg−1 in October to 14 g kg−1 in February. The DM concentration level reached in February was lowest (893 g kg−1) and it would be considered safe for storage of biomass. Nutrient removal was consistently greater for 2X than 1X (ranging from 43 to 137, 3.6 to 25.1, and 54 to 213 kg ha−1 for N, P, K, respectively). Delaying harvest of switchgrass after a freeze event is feasible when clipping twice a year to extend the window of biomass supply.

Comparative Genome Analyses of Plant Rust Pathogen Genomes Reveal a Confluence of Pathogenicity Factors to Quell Host Plant Defense Responses.

Switchgrass rust caused by Puccinia novopanici (P. novopanici) has the ability to significantly affect the biomass yield of switchgrass, an important biofuel crop in the United States. A comparative genome analysis of P. novopanici with rust pathogen genomes infecting monocot cereal crops wheat, barley, oats, maize and sorghum revealed the presence of larger structural variations contributing to their genome sizes. A comparative alignment of the rust pathogen genomes resulted in the identification of collinear and syntenic relationships between P. novopanici and P. sorghi; P. graminis tritici 21–0 (Pgt 21) and P. graminis tritici Ug99 (Pgt Ug99) and between Pgt 21 and P. triticina (Pt). Repeat element analysis indicated a strong presence of retro elements among different Puccinia genomes, contributing to the genome size variation between ~1 and 3%. A comparative look at the enriched protein families of Puccinia spp. revealed a predominant role of restriction of telomere capping proteins (RTC), disulfide isomerases, polysaccharide deacetylases, glycoside hydrolases, superoxide dismutases and multi-copper oxidases (MCOs). All the proteomes of Puccinia spp. share in common a repertoire of 75 secretory and 24 effector proteins, including glycoside hydrolases cellobiohydrolases, peptidyl-propyl isomerases, polysaccharide deacetylases and protein disulfide-isomerases, that remain central to their pathogenicity. Comparison of the predicted effector proteins from Puccinia spp. genomes to the validated proteins from the Pathogen–Host Interactions database (PHI-base) resulted in the identification of validated effector proteins PgtSR1 (PGTG_09586) from P. graminis and Mlp124478 from Melampsora laricis across all the rust pathogen genomes.

Overexpression of PvSTK1 gene from Switchgrass (Panicum virgatum L.) affects flowering time and development of floral organ in transgenic Arabidopsis thaliana

Flowering means that the plant enters the reproductive growth stage, which is a crucial stage in the plant life cycle. Delaying flowering time to prolong vegetative growth is an important method to increase biomass yield and saccharification efficiency in switchgrass, It is of great significance to study the molecular mechanism of plant flowering and regulate the process of plant flowering in the process of biomass production. In this study, we identified 55 serine/threonine-protein kinase genes related to flower development from the switchgrass transcriptome database. Simultaneously, we cloned one of them, PvSTK1, whose expression level and differential fold were significantly higher than other members. PvSTK1 is located on chromosome 8N and its protein was in the cell membrane, cytoplasm, and nucleus. The spatio-temporal expression analysis of the PvSTK1 in switchgrass displayed that the PvSTK1 is crucial in vegetative period, however, not in the transition to reproductive period. Overexpression of PvSTK1 in Arabidopsis resulted in down-regulation of flower-promoting genes and up-regulation of flower-suppressing genes, thereby delaying flowering. In addition, PvSTK1 caused atrophy of the ovules of the florets at the base of the inflorescence, leading to sterility of the florets. The function of PvSTK1 is to inhibit the development of floral organs, and its overexpression can prolong its vegetative period. In the future, overexpression of the PvSTK1 gene in switchgrass will change the flowering time and increase yield and utilization efficiency of biomass.

Rust (Puccinia emaculata) Management and Impact on Biomass Yield in Switchgrass.

Rust, putatively caused by Puccinia emaculata, is a widespread and potentially damaging disease of switchgrass, a crop produced as feedstock for livestock and bioenergy. Azoxystrobin, chlorothalonil, and myclobutanil were applied at 1-, 2-, 3-, or 4-week intervals for 12 to 14 weeks to the vegetatively propagated switchgrass cultivar Cloud Nine to assess fungicide selection and application interval for the control of rust as well as the impact of this disease on switchgrass biomass yield. Although rust severity significantly differed among study years, azoxystrobin and myclobutanil were often equally and more effective than chlorothalonil at controlling rust, with superior disease control coming at shorter application intervals compared with extended application intervals. Year, product, application interval, and product × interval significantly impacted dry biomass yield, which was greatest in 2016 and lowest in 2014. Dry biomass yield protection was significantly better with azoxystrobin and myclobutanil applications than with chlorothalonil or no fungicide. Linear regression models with the final disease rating, as well as with the area under disease progress curve in each year, were significant, but coefficients of determination were low to moderate (0.21 < R2 < 0.60), indicating that rust response and subsequent disease impact on dry biomass yield were impacted by other factors. From our models, an estimated 3 to 5% biomass decline was calculated for each 10% increment in rust-related leaf necrosis observed at the final September rating date. With rust-related leaf necrosis ≥80% by 1 September in each of 4 study years, biomass yield may be reduced by 24 to 40% if rust problems are not managed in switchgrass crops.

The characterization of Streptomyces alfalfae strain 11F and its effect on seed germination and growth promotion in switchgrass

As an important bioenergy crop, switchgrass (Panicum virgatum L.) can produce high biomass yield. However, its biomass yield could be further increased by using beneficial microbe inoculation methods. In this study, a plant beneficial symbiotic microbe strain 11F was isolated and identified as Streptomyces alfalfae, which can produce IAA and siderophore. It is also known to have phosphate-solubilizing and N2 fixing abilities. In addition, the promoting effects of strain 11F on seed germination and plant growth were evaluated. The results indicated that seeds treated with 11F showed higher germination rates, which observed an increase of 21.9%. Compared with the control, the switchgrass plants treated with strain 11F were found to have longer leaf lengths; greater plant heights, shoot fresh weights and root fresh weights; longer overall total lengths; and larger total plant root surface areas, which were significantly increased, by 30.7%, 25.8%, 49.5%, 42.9%, 39.3%, and 44.8%, respectively. Moreover, an egfp-tagged 11F strain was constructed and the mycelium of the 11F strain was observed on the surfaces of the switchgrass root hairs. The colonization dynamics of the egfp-tagged 11F strain to the rhizosphere soil of the switchgrass showed that it remained stable up to 30 days at 2.65 × 105 CFU g−1 dry weight from the initial inoculums. All of the aforementioned observational results suggest the potential of the S. alfalfae 11F strain in improving establishment and biomass yield of switchgrass.

High-throughput phenotyping for plant growth and biomass yield of switchgrass under a controlled environment

Switchgrass (<italic>Panicum virgatum</italic> L.) is a native and prominent perennial grass species used for feedstocks. High-throughput phenotyping of biomass component traits is desirable for switchgrass improvement and production. The objective of this study was to establish correlations between the manually measured traits and image-extracted measurements in switchgrass grown in a controlled environment. Red-green-blue (RGB) images from side- and top-views were automatically collected from the plants varying in growth stages for assessing their relationships with manually measured traits. Plant height, tiller number, crown diameter, and shoot dry weight were all significantly correlated with RGB image-based measurements including side-view height (SHT), side convex hull (SCH), side projected area (SPA), top convex hull (TCH), and top projected area (TPA). For a particular plant trait, a good prediction was observed based on an image-based measurement, including plant height and SHT (R² = 0.992), tiller number and SPA (R² = 0.86), crown diameter and SCH (R² = 0.72), and shoot dry weight and SPA (R² = 0.88). Plant height was also well predicted by SCH (R² = 0.94) and SPA (R² = 0.88). Overall, SHT, SCH, and SPA extracted from RGB images well predicted plant height, tiller number and shoot dry weight. The results demonstrated that the image-based parameters could be leveraged in quantifying the growth and development of switchgrass.

Improved ALMANAC simulations of upland switchgrass ecotypes in the northern United States

AbstractThis investigation used a modified parameterization of the Agricultural Land Management Alternative with Numerical Assessment Criteria (ALMANAC) model to improve simulated growth and biomass yield of upland switchgrass (Panicum virgatum L.) ecotypes in northern U.S. locations. Leaf area development, biomass accumulation, and N utilization of upland ecotypes were parameterized by field evaluations from Montreal, QC, Canada, and sites throughout the northern U.S. Great Plains. Resulting ALMANAC simulations were validated against measured yields from 66 location–years of switchgrass production across 13 sites in Minnesota, North Dakota, and South Dakota. As contrasted to the model defaults, the modified parameterization reduced RMSE of annual simulated yields from 3.77 to 2.62 Mg ha−1 and improved percentage bias from −16 to 13%. Model performance was most improved in environments with no N fertilization, where ALMANAC simulated annual yields with an RMSE of 1.73 Mg ha−1 and percentage bias of −0.5%. Relative to the default ALMANAC parameterization, the modified parameterization also simulated a longer growing season and extended the median simulated maturity date from 1 to 28 August, greatly improving the estimation of switchgrass phenology within the study region. Sensitivity analyses revealed that simulated switchgrass yield was unaffected by modifications of runoff curve number and was most affected by modifications of radiation use efficiency. The other seven parameter modifications each had a median yield impact of 0.57–1.4 Mg ha−1. This work provides an improved characterization of upland switchgrass ecotypes in northern U.S. locations for future ALMANAC users.

Genomic regions associated with salinity tolerance in lowland switchgrass

AbstractSwitchgrass (Panicum virgatum L.) is a promising candidate species for sustainable biofuel feedstock production on marginal land. Soil salinity is one of the significant factors that limits sustainable agricultural production worldwide including a substantial reduction in biomass yield of switchgrass. This study was designed to assess genetic variation in lowland switchgrass and identify genomic regions contributing to an increased level of salinity tolerance using a subset (550 pseudo F2) of a nested association mapping (NAM) population. Salinity tolerance was evaluated based on salt injury score (SIS) using a 1 to 9 scale (1 = the most tolerant, 9 = the most sensitive) and stress tolerance index (STI) calculated from plant height measurements. Substantial variation among NAM families and genotypes within families was observed (p &lt; .05) for SIS. However, no variation was evident among NAM families and genotypes within families for STI. The switchgrass plant accessions EG 1104–1, and EG 1104–2 displayed a high level of salinity tolerance based on SIS which can be used as source material for cultivar development. A total of five quantitative trait loci (QTL) associated with SIS were detected by composite interval mapping on four chromosomes 2B, 6B, 7B, and 9B. The phenotypic variation explained by an individual QTL ranged from 1.4 to 6.5%. The additive genetic effects of individual QTL ranged from −0.07 to 0.63. Homologs of five candidate genes were identified, which were reported to be associated with salinity tolerance.

Genetic loci associated with winter survivorship in diverse lowland switchgrass populations.

High winter mortality limits biomass yield of lowland switchgrass (Panicum virgatumL.) planted in the northern latitudes of North America. Breeding of cold tolerant switchgrass cultivars requires many years due to its perennial growth habit and the unpredictable winter selection pressure that is required to identify winter-hardy individuals. Identification of causal genetic variants for winter survivorship would accelerate the improvement of switchgrass biomass production. The objective of this study was to identify allelic variation associated with winter survivorship in lowland switchgrass populations using bulk segregant analysis (BSA). Twenty-nine lowland switchgrass populations were evaluated for winter survival at two locations in southern Wisconsin and 21 populations with differential winter survivorship were used for BSA. A maximum of 10% of the individuals (8-20) were bulked to create survivor and nonsurvivor DNA pools from each population and location. The DNA pools were evaluated using exome capture sequencing, and allele frequencies were used to conduct statistical tests. The BSA tests revealed nine quatitative trait loci (QTL) from tetraploid populations and seven QTL from octoploid populations. Many QTL were population-specific, but some were identified in multiple populations that originated across a broad geographic landscape. Four QTL (at positions 88 Mb on chromosome 2N, 115 Mb on chromosome 5K, and 1 and 100 Mb on chromosome 9N) were potentially the most useful QTL. Markers associated with winter survivorship in this study can be used to accelerate breeding cycles of lowland switchgrass populations and should lead to improvements in adaptation within USDA hardiness zones 4 and 5.

Determination of Biomass Yield and Other Agricultural Characteristics of Switchgrass (Panicum virgatum L.) Varieties in Rainfed Conditions in 4th and 5th Years

Bu çalışma Konya - Karapınar lokasyonunda yağışa bağlı sulamasız şartlarda çok yıllık bir bitki olan altı adet dallı darı çeşidinin plantasyondan sonraki 4. ve 5. yılına ait biyokütle verimi ve diğer özelliklerinin belirlenmesi amacıyla iki yıl süreyle (2018 ve 2019) yürütülmüştür. Tesadüf blokları deneme desenine göre üç tekerrürlü olarak yürütülen çalışmada altı çeşit (Alamo, Shawnee, Kanlow, Shelter, Cave in rock ve Trailblazer) kullanılmıştır. Çalışmada iki yıllık verilere göre yeşil biyokütle verimi 734 kg da-1 (Cave in rock)-1499 kg da-1 (Alamo), kuru biyokütle verimi 343 kg da-1 (Cave in rock)-774 kg da-1 (Trailblazer), bitki boyu 47.8 cm (Cave in rock)- 70 cm (Alamo), metrede sap sayısı 229.8 adet (Cave in rock)- 448.5 adet (Trailblazer), sap ağırlığı 0.78 g (Trailblazer)- 1.24 g (Kanlow), klorofil içeriği % 29.6 (Shawnee)- % 44.3 (Kanlow), stomal iletkenlik 22.4 mmol H2O m -2 s -1 (Shawnee)- 34.3 mmol H2O m-2 s-1 (Alamo) mmol H2O m-2 s-1 ve bitki örtüsü sıcaklığı 37.7 oC (Kanlow) – 43.9 oC (Shawnee) aralığında belirlenmiştir. Çalışmada biyokütle verimlerinin beşinci yılda azaldığı ve Kanlow, Alamo, Trailblazer ile Shelter çeşitlerinin en yüksek verime sahip olduğu belirlenmiştir.

Switchgrass biomass yield and composition and soil quality as affected by treated wastewater irrigation in an arid environment

Freshwater (FW) scarcity as a result of prolonged drought has reduced FW availability to agriculture in the arid west Texas region in order to meet demands from other sectors. Alternatively, there is enormous potential to utilize treated urban wastewater (TWW) for agricultural irrigation. However, the soil salinization potential of TWW is a concern as it can be detrimental to crops and soil quality. Alternative crops that are both less water-intensive and salt-tolerant are therefore needed to sustain this region's agriculture. Switchgrass is a perennial grass that is well adapted to grow on marginal lands and is a novel crop for lignocellulosic bioenergy feedstock. However, its performance when irrigated with TWW on arid soils of far west Texas is largely unknown. This field study evaluated the yield potential and composition of switchgrass biomass as affected by TWW along with soil quality changes, using a split-plot experimental design. Results indicate that biomass yields were not affected by TWW irrigation and there were no significant differences between TWW and FW across years. With respect to biomass composition, cellulose and lignin contents were lower, while ash content was significantly higher in TWW treatment. Theoretical ethanol production was not affected. Soil salinity and sodicity increased overtime but this increase was more prominent under TWW irrigation. However, application of gypsum and sulfur significantly reduced soil sodicity. These results indicate that switchgrass can tolerate soil salinity induced by TWW application and therefore can be successfully grown on these marginal arid soils as a bioenergy feedstock.