Russell W. Jessup

Development and Status of Dedicated Energy Crops in the United States

The biofuel industry is rapidly growing because of increasing energy demand and diminishing petroleum reserves on a global scale. A multitude of biomass resources have been investigated, with high-yielding, perennial feedstocks showing the greatest potential for utilization as advanced biofuels. Government policy and economic drivers have promoted the development and commercialization of biofuel feedstocks, conversion technologies, and supply chain logistics. Research and regulations have focused on the environmental consequences of biofuels, greatly promoting systems that reduce greenhouse gas emissions and life-cycle impacts. Numerous biofuel refineries using lignocellulosic feedstocks and biomass-based triglycerides are either in production or pre-commercial development phases. Leading candidate energy crops have been identified, yet require additional efforts to realize their full potential. Advanced biofuels, complementing conventional biofuels and other renewable energy sources such as wind and solar, provide the means to substantially displace humanity’s reliance on petroleum-based energy.

Interploid St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze) hybrids recovered by embryo rescue

St. Augustinegrass is one of the most important warm season turfgrasses in the southern United States because of its shade tolerance. Most cultivars are diploids (2n = 2x = 18) and are susceptible to various diseases and insects. Polyploid cultivars in the species have some resistance to pests, but most lack cold tolerance. In this study, eight polyploid genotypes were crossed with six diploid cultivars to transfer pest resistance to the diploids. Because interploid crosses often result in aborted seed, it was necessary to use in vitro techniques. Using embryo rescue, 268 plants were recovered from 2,463 emasculated and pollinated florets (10.88% crossability). Because of the heterogeneous nature of the species, these purported hybrids could not be verified by phenotype. DNA markers were used for hybrid identification. A subset of 25 plants from crosses between the aneuploid cultivar Floratam (2n = 4x = 32) and five diploid cultivars were analyzed using 144 expressed sequence tags–simple sequence repeats (EST-SSRs) developed from buffelgrass cDNA sequence data. Chi-square tests for paternal-specific markers revealed that all analyzed progeny were true F1 hybrids and none originated from self-fertilization or unintended outcrossing. In addition to identifying DNA polymorphism, the EST-SSRs revealed that genetic variation exists among all analyzed cultivars and is not partitioned between ploidy levels. The findings demonstrate that these embryo rescue techniques will enable the entire spectrum of St. Augustinegrass genetic variation to be better used through the recovery of interploid hybrids.

Nutritive value, fermentation characteristics, and in situ disappearance kinetics of sorghum silage treated with inoculants

Fibrolytic enzymes and microbial inoculants have the potential to improve the value of sorghum feedstuff and feedstock. An experiment was conducted to determine nutritive value, ensiling characteristics, and in situ disappearance kinetics of 4 sorghum (Sorghum bicolor L.) silage varieties: Dairy Master BMR (DBMR; brown midrib; Richardson Seed, Vega, TX), PS 747 (PS; photoperiod sensitive; Pogue Seed, Kenedy, TX), Silo 700D (S700D; conventional forage type; Richardson Seed), and MMR 381/73 (MMR; conventional forage type; Richardson Seed) pretreated with fibrolytic enzyme (xylanase plus cellulase, XC; 50:50 mixture of Cellulase Plus and Xylanase Plus; Dyadic, Juniper, FL) or microbial [Promote ASB (Lactobacillus buchneri and Lactobacillus plantarum); Cargill Animal Nutrition, Indianapolis, IN; PRO] inoculants. The greatest yield was for cultivar PS and the least for MMR. Neutral detergent fiber (NDF) concentration was least for XC-treated silage, and acid detergent fiber (ADF) concentration was least for XC- and PRO-treated silage. When silage was treated with XC, concentrations of NDF concentrations decreased, on average, 4.81% across all cultivars and ADF concentrations decreased, on average, 3.23% in all cultivars except MMR. Inoculant PRO reduced the NDF concentration of DBMR by 6.47%. The ADF concentrations of DBMR and PS treated with PRO were decreased by 3.25%. Treating sorghum silage with XC or PRO reduced the NDF and ADF fractions, which increased cell wall degradability. In vitro true digestibility was greatest for PRO-treated DBMR, whereas acid detergent lignin was least for PRO-treated DBMR. Aerobic stability was not improved by PRO; however, aerobic stability of XC-treated MMR was 63 h greater than that of the control. Acetate concentrations were greatest for XC-treated MMR, which explains the 63-h improvement in aerobic stability due to the inhibition of fungi. However, inoculant PRO did not improve yeast and mold counts or aerobic stability of sorghum silage compared with the control, which may be due to the lesser acetate concentrations, especially of PRO-treated S700D silage. Generally, in situ disappearance kinetics were improved with the application of XC and PRO, and XC had the greatest effect on silage with greater NDF and ADF concentrations.

Molecular characterization of non-flowering perennial Sorghum spp. hybrids.

Aims: The goal of this study was to characterize recently identified, non-flowering, putative tetraploid Sorghum spp. hybrids utilizing bulked segregant analysis with SSRs and compare them to S. bicolor, S. halepense, and triploid putative Sorghum spp. hybrids. Confirmed species hybrids between S. bicolor and S. halepense would provide resources for investigating risks of invasiveness and transgene escape alongside potential for identifying novel perennial Sorghum feedstocks of value. Study design: Bulked segregant analysis of Sorghum species and S. species hybrids. Place and Duration of Study: Department of Soil & Crop Sciences; Texas AM College Station, TX, USA; 2009 2011 Methodology: A bulked segregant analysis approach was conducted using SSRs mined from the S. bicolor genome sequence. Bulked samples of S. bicolor, typical flowering S. halepense, non-flowering tetraploid putative Sorghum spp. hybrids, and triploid putative Sorghum spp. hybrids were surveyed to identify both unique markers specific to each bulk and markers indicative of S. bicolor genetic material introgressed into the Sorghum spp. hybrids. Results: Thirty-nine and 23 markers were found to be unique to the S. bicolor and typical flowering S. halepense bulks, respectively. These unique markers could be utilized in breeding programs to identify interspecific hybrids. A subset of 23 unique SSRs were found in the non-flowering tetraploid putative Sorghum spp. hybrid, and they may be useful in the characterization of the non-flowering phenotype. Conclusion: Markers identified in this study provide: 1) species-specific tools for confirmation of interspecific Sorghum spp. hybrids and quantification of gene flow between Sorghum spp., 2) candidate gene and genomic region resources for dissection of the nonResearch Article American Journal of Experimental Agriculture, 2(1): 9-20, 2012 10 flowering phenotype, and 3) Sorghum spp. hybrid-specific markers suitable towards development of perennial biofuel and forage sorghum feedstocks.

Estimation of Rhizome Composition and Overwintering Ability in Perennial Sorghum spp. Using Near-Infrared Spectroscopy (NIRS)

Temperately adapted perennial sorghum feedstocks have recently begun to receive increasing interest as candidate energy crops, producing significant biomass and contributing agroecological benefits including increased soil organic carbon, reduced soil erosion, reduced input requirements, and higher net energy return. Rhizomes are the primary morphological feature facilitating overwintering in Sorghum species; however, underlying physiological mechanisms governing rhizome overwintering remain poorly characterized. In this study, we investigated the composition of sorghum rhizomes from diverse germplasm before and after overwintering at two locations and three experimental environments. Significant positive correlations were found between rhizome overwintering and water-soluble carbohydrates, ethanol soluble carbohydrates, and fructan concentrations, while significant negative correlations were found between rhizome overwintering and both crude fat and starch. Near-infrared spectroscopy (NIRS) calibration equations were developed to quickly and efficiently predict the concentrations of each of these assimilates in rhizomes.

Seeded-yet-sterile perennial grasses: towards sustainable and non-invasive biofuel feedstocks.

Sustainable cropping systems for leading candidate biofuel crops currently focus predominantly on perennial grasses for which assessments of invasiveness potential remain incomplete. Perennial C 4 grasses have signifi cant capacity for biomass accumulation across diverse environments, providing intrinsic value towards protection and restoration of underutilized, marginal, and degraded lands. Varied seed and vegetative reproduction mechanisms, however, contribute to their invasive potential. Th e development of feedstocks possessing the minimum vegetative propagules required for perennial life habit, combined with seed sterility, would therefore greatly reduce the risk of perennial biofuel crops becoming biological invaders. Pearl millet-napiergrass (“PMN”; Pennisetum glaucum [L.] R. Br. × Pennisetum purpureum Schumach.) and kinggrass (P. purpureum × P. glaucum ) are examples of such feedstocks, being “seeded-yet-sterile” crops in which fertile parents allow seeded production of hybrids that are subsequently both seed-sterile and devoid of rhizomes in biomass production fi elds. Th e use of genomics tools provide further tools suitable for both characterizing genetic mechanisms governing weediness and deploying markerassisted breeding programs for biofuel crops with reduced risk of negative environmental impacts.

Inoculants to Enhance the Ruminal Degradation of Small-Grain Forage

Abstract Fibrolytic enzymes and microbial inoculants have the potential to improve fiber degradability. A 2 × 2 × 2 factorial experiment was conducted to determine the nutritive value, ruminal degradability, and degradation rates of wheat ( Triticum aestivum L.) and oat ( Avena sativa L.) pretreated with fibrolytic enzyme (xylanase plus cellulase: XC) or bacterial [Promote ASB ( Lactobacillus buchneri and L. plantarum ); PRO] inoculants at two maturities. Forage was harvested twice during the tillering stage (H1 and H2) and a third time as stover (H3). Forage from H1 had less neutral detergent fiber (NDF; 43.8% dry-matter [DM] basis) and acid detergent fiber (ADF; 31.2% DM basis) and greater in vitro true digestibility (IVTD; 78.5%) concentrations than H3 (69.0 and 45.3% DM basis, and 51.9%, respectively). The IVTD was greater for oat (55.0%) than wheat (50.7%). Chemical composition was not affected by inoculant; however, inoculant did affect ruminal degradability and degradation rates. Potentially degradable DM, NDF, and ADF and effective ruminal degradability were greater for wheat and oat at tillering. Treatment of oat or wheat with XC or PRO enhanced potential degradability and reduced undegradable fractions. Both XC and PRO may be used to degrade the fiber fractions of small-grain forage.

Perennialism and Weediness in the Saccharinae

The apparent contrast in demands for sustainability and productivity in modern agriculture may be reconcilable via the genetic difference in degree between perennialism and weediness. Effective use of genomic tools may soon allow precise metering of the genetic components required to ensure perennial life status, minimize weediness, and maximize crop yields. The Saccharinae includes both model genomic species and leading food, feed, forage, fuel, and industrial crops upon which translational technologies can be evaluated and deployed. In particular, a balance between the high agricultural productivity demanded in order to minimize land requirements and perennial growth habits necessary to ensure sustainable cropping systems is sought.