Switchgrass ( Panicum virgatum L.) has been identified as a “model” herbaceous species for bioenergy production by the United States Department of Energy. Switchgrass can provide several ecosystem services, including biodiversity support, soil erosion control, runoff filtering, and reclamation of marginal land. In addition to the reduction in greenhouse gas emissions from switchgrass‐derived biofuel, soil carbon sequestration is of particular importance. The objective of this study was to evaluate the variability in soil carbon sequestration, particularly in response to water limitation, and to investigate the relationship between soil carbon sequestration and switchgrass yield. For this purpose, dry aboveground biomass yield and soil reactive carbon—specifically, permanganate oxidizable carbon (POXC)—content at three depths (0–15, 15–30, and 30–60 cm) were measured for 150 different switchgrass genotypes for three consecutive years. We found that drought significantly reduced yield compared to control plots, reduced the amount of soil POXC, and that POXC decreased with soil depth. A positive correlation ( r = 0.27, p < 0.05) between POXC and yield was observed in the drought‐stressed plots. This study provides insight into the impact of switchgrass on soil POXC over time and at different depths, offering a framework for future evaluation of root‐related traits in switchgrass, particularly in relation to drought stress.

Economically viable production of biobased products and fuels requires high-yielding, high-quality, sustainable process-advantaged crops, developed using bioengineering or advanced breeding approaches. Understanding which crop phenotypic traits have the largest impact on biofuel economics and sustainability outcomes is important for the targeted feedstock crop development. Here, we evaluated biomass yield and cell-wall composition traits across a large natural variant population of switchgrass (Panicum virgatum L.) grown across three common garden sites. Samples from 331 switchgrass genotypes were collected and analyzed for carbohydrate and lignin components. Considering plant survival and biomass after multiple years of growth, we found that 84 of the genotypes analyzed may be suited for commercial production in the southeastern U.S. These genotypes show a range of growth and compositional traits across the population that are apparently independent of each other. We used these data to conduct techno-economic analyses and life cycle assessments evaluating the performance of each switchgrass genotype under a standard cellulosic ethanol process model with pretreatment, added enzymes, and fermentation. We find that switchgrass yield per area is the largest economic driver of the minimum fuel selling price (MSFP), ethanol yield per hectare, global warming potential (GWP), and cumulative energy demand (CED). At any yield, the carbohydrate content is significant but of secondary importance. Water use follows similar trends but has more variability due to an increased dependence on the biorefinery model. Analyses presented here highlight the primary importance of plant yield and the secondary importance of carbohydrate content when selecting a feedstock that is both economical and sustainable.

Cold stress (CS) affects the survivability, geographical distribution, and yield stability of crops. Suitable management and agronomic practices can minimize the crop losses associated with cooler environments. However, agronomic practices alone can't support plants adequately to withstand the harsh cold. Therefore, exploring plants cold stress-responsive factors such as genetic, epigenetic, physiological, and cellular is crucial. This report discusses on cold stress effect, signal perception, signal transduction, gene expression, and associated molecular phenomena in plants. Three cold acclimation response pathways: Ca2+ mediated ICE1- CBF/ DREB1, hormonal, and reactive oxygen species (ROS), are elucidated. Also, this report summarizes the latest research work on genetics and genomics of forage species from the perspectives of cold tolerance improvement. In several instances, our hypotheses have been supported by a recent research output from our genetic analysis experiment on alfalfa (Medicago sativa L.) cold tolerance. We further review the importance of high-throughput genomics and phenomics for cold tolerance improvement in forage species and recommended implementing widely recognized techniques such as genomic selection (GS) and genome-wide association studies (GWAS) to develop climate-resilient cultivars. The transgenics and genome-edited cold-tolerant forage cultivars with low or no yield penalty must be the goals of future research.

The major forces driving farm-level production for the ever-growing global population have relied upon mechanized farming techniques, synthetic inputs, and developing high-yielding crop varieties. Recently, however, there has been a gradual shift toward developing sustainable approaches addressing the potential use of beneficial traits of the soil-plant microbiome to establish a sustainable food supply as well as to maintain soil and plant health. The intricate relationship of the soil-plant microbiome complex often faces difficulty in the efficient translation for the broad spectrum of audiences across society. In recent years, there has been a growing need to formulate strategies and streamline the global sharing of the generated information on plant microbiome interactions. In this review, we discuss novel and emerging strategies to use indigenous microbial consortia and engineered exogenous microbial inoculants for rhizosphere engineering. In addition, this review also details the use of these microbial consortia to improve crop yields and environmental protection that are currently in practice.

Switchgrass ( Panicum virgatum L.) is a perennial warm-season grass that can serve dual purposes, forage and biofuel feedstock. Because the cell wall accounts for more than half the dry matter weight, breeding for both objectives will largely depend on cell wall components which include cellulose, hemicellulose, and lignin. We used NIRS to measure crude protein, neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose, and Klason lignin to conduct QTL mapping in an F1 population derived from a cross between tetraploid lowlands AP13 and B6 with 285 progenies. Of the three major cell wall components of the dry matter, cellulose was the highest (34.51–41.40%), followed by hemicellulose (25.48–33.55%), and Klason lignin (9.70–13.23%). Mapping of biomass and forage quality traits was done using two linkage maps with 2772 SNP markers. We identified 37 significant QTL for all six traits with the highest percentage variance explained by individual QTL in all traits ranging from 4.89 to 8.57%. There are 9 chromosome regions with colocalized QTL of different traits, indicating either pleiotropic gene action or tight linkage between the genes. Improvement of switchgrass for forage and biofuel feedstock quality would benefit from the selection of QTL that contribute directly to the target phenotypes. The frequency of favorable QTL alleles can be enhanced through Genomic Selection.

Switchgrass (Panicum virgatum L.) has gained wider attention due to its recognition and use as a model herbaceous crop species for bioenergy production. Genetic diversity information in lowland switchgrass cultivars can help to specify cultivars to be used in the breeding programs aiming for hybrid vigor. The objective of this research was to analyze genetic variation within and among five lowland switchgrass cultivars using amplified fragment length polymorphism (AFLP) markers. AFLP polymorphisms indicated the presence of high genetic variation within lowland switchgrass cultivars with ‘Alamo’ exhibiting the highest genetic variation and ‘Performer’ the lowest. The Nei’s genetic diversity parameters revealed the lowest genetic distance between cultivars ‘Alamo’ and ‘Cimarron’ and the highest value between cultivars ‘Alamo’ and ‘Kanlow’. ‘Alamo’ and ‘Cimarron’ were clustered together while ‘BoMaster’, ‘Kanlow’, and ‘Performer’ were grouped into the other cluster. In addition, there were clusters with mixed genotypes. The findings of this study can be used to select diverse lines as parents for heterosis and inbreeding studies.

Quantitative trait loci (QTLs) refer to a specific region on chromosomes, which harbors gene(s) controlling the traits. QTL mapping tries to identify stretches of DNA closely linked to genes underlying a specific trait by performing statistical analysis of molecular markers and traits in populations of controlled crosses. QTL mapping provides a starting point for dissecting complex traits into its component alleles. It helps to quantify the relative effects of alleles on the traits and locates genomic regions responsible for marker–trait association. Finally, it provides a foundation of marker-assisted selection (MAS) that expedites the breeding process given the proper estimation of position and the effects of QTLs. QTLs that are detected in multiple environments are called stable QTL and are reliable QTL for MAS. Mapping loci in genome requires a population that segregates for the target traits. QTL analysis is performed by estimating the correlation between phenotype data with genotype (markers) data of segregating populations. The primary types of segregating population for QTL mapping include F2, recombinant inbred lines, BC1, double haploid lines, near-isogenic lines, and full-sib F1 (pseudo-testcross).

In agroecosystems, nitrogen is one of the major nutrients limiting plant growth. To meet the increased nitrogen demand in agriculture, synthetic fertilizers have been used extensively in the latter part of the twentieth century, which have led to environmental challenges such as nitrate pollution. Biological nitrogen fixation (BNF) in plants is an essential mechanism for sustainable agricultural production and healthy ecosystem functioning. BNF by legumes and associative, endosymbiotic, and endophytic nitrogen fixation in non-legumes play major roles in reducing the use of synthetic nitrogen fertilizer in agriculture, increased plant nutrient content, and soil health reclamation. This review discusses the process of nitrogen-fixation in plants, nodule formation, the genes involved in plant-rhizobia interaction, and nitrogen-fixing legume and non-legume plants. This review also elaborates on current research efforts involved in transferring nitrogen-fixing mechanisms from legumes to non-legumes, especially to economically important crops such as rice, maize, and wheat at the molecular level and relevant other techniques involving the manipulation of soil microbiome for plant benefits in the non-legume root environment.

In the article [1], in 'Methods' section and 'G x E and heritability' subsection, there is an error in the formula of heritability (H2).

Switchgrass (Panicum virgatum L.), as a model herbaceous crop species for bioenergy production, is targeted to improve biomass yield and feedstock quality. Plant height is a major component contributing to biomass yield. Accordingly, the objectives of this research were to analyze phenotypic variation for biomass and plant height and the association between them and to localize associated plant height QTLs. Two lowland switchgrass mapping populations, one selfed and another hybrid population established in the field at Perkins and Stillwater, Oklahoma, were deployed in the experiment for two years post establishment. Large genetic variation existed for plant biomass and height within the two populations. Plant height was positively correlated with biomass yield in the selfed population (r = 0.39, P<0.0001) and the hybrid population (r = 0.41, P<0.0001). In the selfed population, a joint analysis across all environments revealed 10 QTLs and separate analysis for each environment, collectively revealed 39 QTLs related to plant height. In the hybrid population, the joint analysis across overall environments revealed 35 QTLs and the separate analysis for each environment revealed 38 QTLs. The findings of this research contribute new information about the genetic control for plant height and will be useful for future plant breeding and genetic improvement programs in lowland switchgrass.

Plant tillering and related traits are morphologically important components contributing to switchgrass ( L.) biomass yield. The objectives of this study were to estimate broad-sense heritabilities for tillering-related traits, to analyze correlations between biomass yield and the traits, and to identify quantitative trait loci (QTL) for them. A first-generation selfed population of NL94 plant and a hybrid population between NL94 and SL93 plants were field established in a randomized complete block design with three replications in Stillwater and Perkins, OK. Phenotypic data were collected in 2 yr and genotypic data were obtained by genotyping simple-sequence repeat (SSR) markers in the two populations on the basis of two preexisting genetic maps. Plant base size (PBS), plant girth (PG), tillering ability (TA), tiller diameter (TD), and tiller dry weight (TDW) were positively correlated with biomass yield in both populations. Consistently, PBS had the largest correlation coefficients for biomass yield, suggesting its value as an indirect selection criterion for biomass yield. Twenty and 26 QTL for six tillering-related traits were detected in the hybrid and selfed population, respectively. Among the QTL, one on linkage group (LG) 5a between sww-2387/PVCAG-2197/2198 and PVGA-1649/1650 for PBS, PG, and TA and another on LG 2a between sww-2640/sww-2545 and PVCA-765/766 for TD and TDW were stably detected in multiple environments in the two populations. The findings add to the knowledge base regarding the genetics of tillering-related traits that could be used in accelerating the development of high-yielding cultivars through marker-assisted selection.

Annual ryegrass (Lolium multiflorum Lam.) is a highly nutritive, fast-growing, C3 cool-season annual forage. Blast or gray leaf spot is a fungal disease of ryegrass caused by Magnaporthe orygae (anamporph Pyricularia oryzae). The disease kills seedlings as well as adult plants. Blast-resistant annual ryegrass cultivars are not available at present. Therefore, identifying sources of resistance and developing blast-resistant germplasm are priorities to circumvent the devastating disease. Incorporation of germplasm screening in a breeding program requires an efficient, low-cost, and high-throughput evaluation system. Screening methods reported in literature lack both efficiency and throughput capabilities suitable for breeding. The aims in this work were to develop a low-cost, high-throughput phenotyping system, and to screen the annual ryegrass National Plant Germplasm System (NPGS) collection with a highly aggressive, newly isolated M. oryzae strain from naturally infected annual ryegrass plants, which was named MoGA1. Host specificity was tested on four species in addition to annual ryegrass. Extensive damage was caused to perennial ryegrass (Lolium perenne L.) and tall fescue (Lolium arundinaceum (Schreb.) Darbysh), whereas rice (Oryza sativa L.) and orchard grass (Dactylis glomerata L.) exhibited a hypersensitivity response and resisted the infection, suggesting that pathogenicity of the strain was limited to the Lolium genus. A portable low-cost, high-throughput screening system capable of screening 1,536 plants per unit was developed and used to screen 138 ryegrass accessions with MoGA1. Two accessions showed resistance to the pathogen and produced seed. These two entries can be used to incorporate blast resistance in annual ryegrass germplasm.

Turfgrass varietal identification is critical and allows turfgrass professionals to manage the turf based on the cultural requirements of the variety. On the Oklahoma State University (OSU) Baseball Field (OSUBF) in Stillwater, OK, some bermudagrass ( Cynodon sp.) plants exhibited desirable traits but their exact identities were unknown due to the installation of multiple varieties over time. Accordingly, the major objective of this study was to identify if the desirable bermudagrass plants were from commercially available known varieties. Recently, the OSU turf bermudagrass breeding program developed and entered three fairway-type clonal bermudagrasses in the 2013 National Turfgrass Evaluation Program (NTEP) bermudagrass trial: OKC 1131, OKC 1163, and OKC 1302. The secondary objective was to create molecular marker profiles for these three experimental lines. Five OSUBF samples were analyzed using simple sequence repeat (SSR) markers, along with 24 clonal, commercially available turf bermudagrass varieties widely used in Oklahoma, the three OSU experimental clones, six randomly selected single plants from ‘Riviera’, and two controls for common bermudagrass ( Cynodon dactylon ) and african bermudagrass ( Cynodon transvaalensis ). SSR marker genotyping data indicated that the five OSUBF plants were clones of an identical bermudagrass. The OSUBF bermudagrass had the same fingerprint as ‘Astro-DLM’ bermudagrass for 14 out of 16 SSRs genotyped. Fifteen out of 30 additional SSR markers also showed differences between the OSUBF bermudagrass and ‘Astro-DLM’. The three OSU experimental clones were different from each other and had different fingerprints from the other tested varieties based on SSR profiles, indicating they are new breeding lines. These four distinct lines have potential to be released as new varieties if they demonstrate superior turf quality traits and adaptation over time.

Timing of biomass removal from stands of switchgrass ( Panicum virgatum L.) impacts the nutrient content of harvested material and fertilizer requirements for subsequent growing seasons. This study was conducted to determine the change in N, P, and K content of harvested switchgrass biomass as a function of the harvest date and to determine the economic consequences of an extended harvest window. Data were produced in a randomized complete block study conducted at the Oklahoma Agricultural Experiment Station, Stillwater, with six replications over three harvest seasons from November of 2007 to March of 2010. Treatments on the established stand of cultivar Kanlow consisted of five harvest dates separated by about 30 d beginning in late November. Regression equations were used to fit yield and N, P, and K concentration response to the harvest date. Delaying harvest beyond December resulted in an average 5.4% decline in harvested biomass per month. Delaying harvest beyond November did not result in a significant change in the N concentration in the harvested biomass. However, delaying harvest did result in a significant decrease in both P and K content in the harvested biomass. Point estimates from the response functions were used to estimate production cost for each of five harvest dates beginning with 30 November and ending with 30 March. The quantities of P 2 O 5 and K 2 O fertilizer that would be required to replace the P and K removed with the biomass were used in the budgets. Biomass production cost was similar across harvest dates.

If switchgrass harvest is delayed until after senescence, some nutrients will translocate to the plant’s crown and roots. Biomass yield and fertilizer requirements depend on harvest date. The objective is to determine switchgrass biomass yield, nutrient concentration in biomass, fertilizer requirements, and expected production cost by month of harvest.

The maximum biomass yield of switchgrass ( Panicum virgatum L.) usually is achieved with one seasonal autumn harvest. However, information is limited on the influences of winter harvesting on annual biomass yield and on quality parameters impacting conversion into bioethanol. Accordingly, the objectives of this study were to assess: (i) yield of standing field cured biomass at monthly intervals through winter, (ii) year‐round elemental composition of biomass, and (iii) associated year‐round soil nutrient status. An unfertilized ‘Kanlow’ switchgrass planting established in 1998 was used for this study conducted from November 2007 to October 2010. The experimental treatment was monthly harvest from November to the following March and year‐round monthly sampling of biomass (except April) and soil for chemical analyses. The 3‐yr mean dry matter yield of winter harvests was 5.94Mg ha −1 , ranging from 3.88 Mg ha −1 in the winter of 2007–2008 to 7.55 Mg ha −1 in 2009–2010. Monthly biomass yield differences were significant in Years 1 and 3 but not in Year 2. Concentrations of biomass elements and soil nutrients changed with various degrees over the 3 yr. Concentrations of ash, cell wall components, and mineral nutrients, except P, K, and S, did not change appreciably across winter months. Early winter harvests resulted in less yield loss compared to late winter harvests. These findings will be valuable in harvest management for switchgrass biomass production.