Registration of N614, A3N615, N616, and N617 Shattercane Genetic Stocks with Cytoplasmic or Nuclear Male Sterility and Juicy or Dry Midribs

Four shattercane [Sorghum bicolor subsp. drummondii (Nees ex Steud.) de Wet ex Davidse] genetic stocks—N614 (Reg. No. GS-652, PI 665684), A3N615 (Reg. No. GS-651, PI 665683), N616 (Reg. No. GS-653, PI 665685), and N617 (Reg. No. GS-654, PI 665686)—with A3 cytoplasmic male sterility or the nuclear male sterility gene ms3 containing either juicy (dd) or dry (DD) culms were developed jointly by the USDA-ARS; the Iowa Agricultural and Home Economics Experiment Station, College of Agriculture and Life Sciences, Iowa State University; and the Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska. The stocks were released in July 2011. The source material for these genetic stocks was isolated from an archetypical shattercane population found near Lincoln, NE. Release of these genetic stocks makes available shattercane lines with both A3 cytoplasmic male sterility, and ms3 genetic (nuclear) male sterility to facilitate crossing. These genetic stocks also contain juicy (dd) or dry (DD) culms, a visible genetic marker to facilitate screening progeny resulting from crosses. The genetic stocks have immediate application for basic research involving gene flow from cultivated sorghum [Sorghum bicolor (L.) Moench] to shattercane and on the fitness of offspring resulting from such crosses

Field damage of sorghum (\u3ci\u3eSorghum bicolor\u3c/i\u3e) with reduced lignin levels by naturally occurring insect pests and pathogens

Sorghum (Sorghum bicolor (L.) Moench) brown midrib (bmr) mutant lines have reduced levels of lignin, which is a potentially useful trait for bioenergy production, but the effects of this trait on insect and plant pathogen interactions are unknown under field conditions. Field-grown bmr6, bmr12, and wild-type (WT) plants were examined for insect and disease damage. In most cases, observed frequency, population, or leaf area damage caused by insects or pathogens on bmr6 or bmr12 plants were not greater than those observed on WT plants in the field or laboratory assays. European corn borers [Ostrinia nubilalis (Hübner)(Lepidoptera: Pyralidae)] often caused lower amounts of leaf damage to bmr6 leaves compared to bmr12 and sometimes WT leaves in the field study. Leaf damage by corn earworms [Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae)] and fall armyworms [Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)] in laboratory assays was often lower for bmr versus WT leaves. Incidence of disease lesions was significantly higher on bmr6 compared to WT plants for one of three samplings in 2011, but the opposite trend was observed overall in 2012 and no significant differences were noted in 2013. When corn earworms and fall armyworms were fed the excised pith, bmr6 and/or bmr12 pith caused significant morality to one or both insect species in all 3 years. Damage variability between the 3 years may have been due to hotter and drier than normal conditions in 2012. Thus, bmr lines of sorghum suitable for bioenergy production have potential for sustainable production in the field

Efficacy of Singular and Stacked \u3ci\u3ebrown midrib 6\u3c/i\u3e and \u3ci\u3e12\u3c/i\u3e in the Modification of Lignocellulose and Grain Chemistry

In sorghum, brown midrib (bmr) 6 and 12 impair the last two steps of monolignol synthesis. bmr genes were introduced into grain sorghum to improve the digestibility of lignocellulosic tissues for grazing or bioenergy uses following grain harvest. Near-isogenic grain sorghum hybrids (AWheatland X RTx430) were developed containing bmr6, bmr12, and the bmr6 bmr12 double mutant (stacked), and their impacts were assessed in a two-year field study. The bmr genes did not significantly impact grain or lignocellulosic tissue yield. Lignocellulosic tissue from bmr6, bmr12, and stacked hybrids had reduced lignin content and increased in vitro dry matter digestibility (IVDMD) compared to those of the wild type (WT). The lignin content of the stacked lignocellulosic tissue was further reduced compared to that of bmr6 or bmr12. Surprisingly, bmr12 modestly increased carbohydrates in lignocellulosic tissue, and bmr6 increased fiber and lignin content in grain. These data indicate that bmr6 and bmr12 have broader effects on plant composition than merely lignin content, which has promising implications for both livestock utilization and bioenergy conversion

Efficacy of Singular and Stacked \u3ci\u3ebrown midrib 6\u3c/i\u3e and \u3ci\u3e12\u3c/i\u3e in the Modification of Lignocellulose and Grain Chemistry

In sorghum, brown midrib (bmr) 6 and 12 impair the last two steps of monolignol synthesis. bmr genes were introduced into grain sorghum to improve the digestibility of lignocellulosic tissues for grazing or bioenergy uses following grain harvest. Near-isogenic grain sorghum hybrids (AWheatland X RTx430) were developed containing bmr6, bmr12, and the bmr6 bmr12 double mutant (stacked), and their impacts were assessed in a two-year field study. The bmr genes did not significantly impact grain or lignocellulosic tissue yield. Lignocellulosic tissue from bmr6, bmr12, and stacked hybrids had reduced lignin content and increased in vitro dry matter digestibility (IVDMD) compared to those of the wild type (WT). The lignin content of the stacked lignocellulosic tissue was further reduced compared to that of bmr6 or bmr12. Surprisingly, bmr12 modestly increased carbohydrates in lignocellulosic tissue, and bmr6 increased fiber and lignin content in grain. These data indicate that bmr6 and bmr12 have broader effects on plant composition than merely lignin content, which has promising implications for both livestock utilization and bioenergy conversion

Field damage of sorghum (\u3ci\u3eSorghum bicolor\u3c/i\u3e) with reduced lignin levels by naturally occurring insect pests and pathogens

Sorghum (Sorghum bicolor (L.) Moench) brown midrib (bmr) mutant lines have reduced levels of lignin, which is a potentially useful trait for bioenergy production, but the effects of this trait on insect and plant pathogen interactions are unknown under field conditions. Field-grown bmr6, bmr12, and wild-type (WT) plants were examined for insect and disease damage. In most cases, observed frequency, population, or leaf area damage caused by insects or pathogens on bmr6 or bmr12 plants were not greater than those observed on WT plants in the field or laboratory assays. European corn borers [Ostrinia nubilalis (Hübner)(Lepidoptera: Pyralidae)] often caused lower amounts of leaf damage to bmr6 leaves compared to bmr12 and sometimes WT leaves in the field study. Leaf damage by corn earworms [Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae)] and fall armyworms [Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)] in laboratory assays was often lower for bmr versus WT leaves. Incidence of disease lesions was significantly higher on bmr6 compared to WT plants for one of three samplings in 2011, but the opposite trend was observed overall in 2012 and no significant differences were noted in 2013. When corn earworms and fall armyworms were fed the excised pith, bmr6 and/or bmr12 pith caused significant morality to one or both insect species in all 3 years. Damage variability between the 3 years may have been due to hotter and drier than normal conditions in 2012. Thus, bmr lines of sorghum suitable for bioenergy production have potential for sustainable production in the field

Temporal transcriptomic profiling elucidates sorghum defense mechanisms against sugarcane aphids

Background The sugarcane aphid (SCA; Melanaphis sacchari) has emerged as a key pest on sorghum in the United States that feeds from the phloem tissue, drains nutrients, and inflicts physical damage to plants. Previously, it has been shown that SCA reproduction was low and high on sorghum SC265 and SC1345 plants, respectively, compared to RTx430, an elite sorghum male parental line (reference line). In this study, we focused on identifying the defense-related genes that confer resistance to SCA at early and late time points in sorghum plants with varied levels of SCA resistance. Results We used RNA-sequencing approach to identify the global transcriptomic responses to aphid infestation on RTx430, SC265, and SC1345 plants at early time points 6, 24, and 48 h post infestation (hpi) and after extended period of SCA feeding for 7 days. Aphid feeding on the SCA-resistant line upregulated the expression of 3827 and 2076 genes at early and late time points, respectively, which was relatively higher compared to RTx430 and SC1345 plants. Co-expression network analysis revealed that aphid infestation modulates sorghum defenses by regulating genes corresponding to phenylpropanoid metabolic pathways, secondary metabolic process, oxidoreductase activity, phytohormones, sugar metabolism and cell wall-related genes. There were 187 genes that were highly expressed during the early time of aphid infestation in the SCA-resistant line, including genes encoding leucine-rich repeat (LRR) proteins, ethylene response factors, cell wall-related, pathogenesis-related proteins, and disease resistance-responsive dirigent-like proteins. At 7 days post infestation (dpi), 173 genes had elevated expression levels in the SCA-resistant line and were involved in sucrose metabolism, callose formation, phospholipid metabolism, and proteinase inhibitors. Conclusions In summary, our results indicate that the SCA-resistant line is better adapted to activate early defense signaling mechanisms in response to SCA infestation because of the rapid activation of the defense mechanisms by regulating genes involved in monolignol biosynthesis pathway, oxidoreductase activity, biosynthesis of phytohormones, and cell wall composition. This study offers further insights to better understand sorghum defenses against aphid herbivory

Resistance to greenbugs in the sorghum nested association mapping population

The greenbug, Schizaphis graminum, is a serious pest of sorghum (Sorghum bicolor). For the past several decades, resistant sorghum hybrids have been used to control greenbug populations. However, the durability of plant resistance is frequently challenged by evolution of new greenbug biotypes, and there is a continuous need for screening of resistant germplasm for its effective management in the field. Natural variation in sorghum plants/populations provides distinct approaches to identify novel sources of resistance against greenbugs. In this study, we used the recently developed sorghum nested association mapping (NAM) population parental lines to understand sources of sorghum resistance to greenbugs. Using choice and no-choice assays, we have identified SC265 and Segaolane as the resistant and susceptible lines, respectively, to greenbugs compared to the wild-type plants. The Electrical Penetration Graph (EPG) analysis revealed that the greenbugs spent significantly lesser time in the xylem and sieve element phases while feeding on the resistant NAM parental line, SC265, compared to the susceptible (Segaolane) and wild-type (RTx430) sorghum lines. In addition, the EPG results indicated that there is no significant difference in the time to first probe, time to reach first sieve element, pathway phase, and non-probing phase among the three sorghum plants, which suggests that the resistance factors present in the vascular tissues of the resistant line (SC265) potentially contribute to the resistance mechanisms against greenbugs. Overall, SC265 NAM parental line showed a combination of antixenotic and antibiotic-mediated resistance mechanisms against greenbugs, whereas the susceptible line Segaolane displayed the least resistance to greenbugs

Elucidation of the Structure and Reaction Mechanism of Sorghum Hydroxycinnamoyltransferase and Its Structural Relationship to Other Coenzyme A-Dependent Transferases and Synthases

Hydroxycinnamoyltransferase (HCT) from sorghum (Sorghum bicolor) participates in an early step of the phenylpropanoid pathway, exchanging coenzyme A (CoA) esterified to p-coumaric acid with shikimic or quinic acid as intermediates in the biosynthesis of the monolignols coniferyl alcohol and sinapyl alcohol. In order to elucidate the mode of action of this enzyme, we have determined the crystal structures of SbHCT in its apo-form and ternary complex with shikimate and p-coumaroyl-CoA, which was converted to its product during crystal soaking. The structure revealed the roles of threonine-36, serine-38, tyrosine- 40, histidine-162, arginine-371, and threonine-384 in catalysis and specificity. Based on the exact chemistry of p-coumaroyl-CoA and shikimic acid in the active site and an analysis of kinetic and thermodynamic data of the wild type and mutants, we propose a role for histidine-162 and threonine-36 in the catalytic mechanism of HCT. Considering the calorimetric data, substrate binding of SbHCT should occur sequentially, with p-coumaroyl-CoA binding prior to the acyl acceptor molecule. While some HCTs can use both shikimate and quinate as an acyl acceptor, SbHCT displays low activity toward quinate. Comparison of the structure of sorghum HCT with the HCT involved in chlorogenic acid synthesis in coffee (Coffea canephora) revealed many shared features. Taken together, these observations explain how CoA-dependent transferases with similar structural features can participate in different biochemical pathways across species

Registration of N619 to N640 Grain Sorghum Lines with Waxy or Wild-Type Endosperm

Sorghum [Sorghum bicolor (L.) Moench] lines N619 to N636 (A lines; Reg. No. GS-699 to GS-716, PI 670134 to PI 670151); N619 to N636 (B lines; Reg. No. GS-721 to GS-738, PI 671777 to PI 671794); and N637 to N640 (R lines; Reg. No. GS-717 to GS-720, PI 670152 to PI 670155) comprise nine pairs of seed parent (A/B) lines, and two pairs of pollinator (R) lines (11 pairs total) that are near-isogenic for waxy (low-amylose) or wildtype endosperm. Breeding work was conducted jointly by the USDA–ARS and the Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska, and the lines were released in May 2014. Release of these lines makes available two different waxy (wx) alleles (wxa and wxb) for development of grain sorghum as a source of lowamylose starch, whose end use is targeted to the ethanol and food industries. In particular, the release of wx and wild-type near-isogenic pairs facilitates the evaluation of agronomic performance of wx genotypes, and the release of both A/B and R lines facilitates the production of waxy grain hybrids