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Modifying lignin content and composition of cell walls are key targets for bioenergy feedstock improvement for a range of renewable chemical applications. Sorghum (Sorghum bicolor) is a drought-tolerant C4 grass being developed as a dedicated bioenergy feedstock. The monolignol biosynthetic pathway produces the hydroxycinnamic subunits of lignin, a major target to increase the energy content of sorghum biomass for thermal bioenergy conversion processes. SbMyb60 is a transcription factor linked to the activation of the monolignol biosynthetic pathway and caffeoyl CoA O-methyltransferase (SbCCoAOMT) is a S-adenosyl methionine (SAM)–dependent O-methyltransferase responsible for the methylation of caffeoyl-CoA to generate feruloyl-CoA in this pathway. Overexpression of each gene resulted in increased energy content of biomass and increased levels of several aromatic compounds in previous greenhouse experiments. To assess how SbMyb60 and SbCCoAOMT overexpression lines performed under field conditions, these lines were planted in field trials over two growing seasons, 2017 and 2018, and the effects on lignin composition and content as well as agronomic traits were assessed. Field-grown plants of SbMyb60 and SbCCoAOMT overexpression lines had increased total energy and phenolic compounds. Furthermore, two SbMyb60 transgenic events, SbMyb-10a and SbMyb-15a, with decreased stover yield and seed set were combined with three sorghum lines, N32, N4692, and Tx3118, to investigate whether yield reduction could be rescued. Hybrids improved yield of SbMyb60-15a; however, hybrids were unable to improve performance for SbMyb60-10a. Overall, these results demonstrated that field-grown sorghum overexpressing SbMyb60 or SbCCoAOMT can have biomass with increased phenolic compounds and total energy.

Grain sorghum [Sorghum bicolor (L.) Moench] is an important crop for rainfed production systems with 2.7 million ha grown in the United States in 2013. The brown-midrib (bmr) mutations, especially bmr-12, have resulted in low stover lignin and high fiber digestibility without reducing grain yield in some sorghum lines. However, the effect of the bmr trait on beef cattle (Bos taurus) performance when grazing crop residue is unknown. Our objectives were to validate previous small-plot results reporting no grain yield difference between near-isogenic bmr-12 (BMR) and wild-type control (CON) A Wheatland × R Tx430 sorghum hybrids in a field-scale experiment and to determine if BMR stover enhances beef production in a grazing experiment. Four replicated paddocks (2.3 ha) were planted in 2006 and 2008 near Mead, NE. Crossbred yearling steers (240 ± 17 kg hd⁻¹) grazed (2.6 steers ha⁻¹) paddocks following grain harvest for 72 d in 2006 and 61 d in 2008. Forage was sampled 4, 30, and 60 d after grazing began. Grain yield of BMR was 6% less (P = 0.01) than CON with no difference in stover neutral detergent fiber (NDF) content, but BMR stover had higher in vitro NDF digestibility (IVNDFD) (31%; P < 0.0001), steer average daily gain (ADG; 0.18 kg hd⁻¹ d⁻¹; P = 0.001), and body weight (BW) gain (29 kg ha⁻¹; P = 0.002), resulting in an estimated increase in net return of $133.84 ha⁻¹ due to BMR. Results suggest that the A Wheatland × R Tx430 bmr-12 hybrid is an effective dual-purpose sorghum crop for both grain and beef production.

Four shattercane [ subsp. (Nees ex Steud.) de Wet ex Davidse] genetic stocks—N614 (Reg. No. GS-652, PI 665684), AN615 (Reg. No. GS-651, PI 665683), N616 (Reg. No. GS-653, PI 665685), and N617 (Reg. No. GS-654, PI 665686)—with A cytoplasmic male sterility or the nuclear male sterility gene containing either juicy () or dry () 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 A cytoplasmic male sterility, and genetic (nuclear) male sterility to facilitate crossing. These genetic stocks also contain juicy () or dry () 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 [ (L.) Moench] to shattercane and on the fitness of offspring resulting from such crosses.

Although heterosis is well established in grain and forage sorghum [Sorghum bicolor (L.) Moench], reports of heterosis in sweet sorghum are limited to results from grain sorghum × sweet sorghum hybrids. Recent development of cytoplasmic male-sterile sweet sorghum lines allows creation of sweet sorghum hybrids for research and industry. Male sterility may also affect allocation of photosynthate to plant parts, creating the potential to increase sugar content in stems by eliminating seed as a sink. The objectives of this study were to compare performance of A 3 cytoplasmic male-sterile lines and A 3 cytoplasmic male-sterile hybrids to fertile B 3 counterparts and to each other. A 3 cytoplasmic male-sterile ‘Dale’, ‘Wray’, ‘Sugar Drip’, and N100 were crossed in all combinations to their male-fertile counterparts, resulting in 20 genotypes including the male-fertile lines. The 20 genotypes were grown in a randomized complete block in 2004 and 2005 at Lexington, KY. Male-sterile hybrids and lines had higher brix than male-fertile lines. Hybrids produced greater stalk yield due to taller plants with greater stem diameter. Juice fraction and juice composition remained relatively unchanged. Only six hybrids showed positive heterosis for brix. The greater juice yield and higher sugar content of selected hybrids such as A 3 N100 × Dale could produce more total syrup or ethanol than current pureline sweet sorghum varieties.

Four sorghum [Sorghum bicolor (L.) Moench] genetic stocks, BN611 (Reg. No. GS-140, PI 652943), AN612 (Reg. No. GS-141, PI 652944), BN612 (Reg. No. GS-142, PI 652945), and RN613 (Reg. No. GS-143, PI 652946), with stacked brown midrib genes bmr-6 and bmr-12 were developed jointly by the USDA-ARS and the Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska, and were released in July 2006. The genetic stocks BN611, AN612 and BN612

Although there is growing demand for sorghum [Sorghum bicolor (L.) Moench] with white seed and tan plant color, there is limited information on the overall agronomic fitness of sorghum with these characters. A set of experiments was conducted to evaluate the combined effects of plant color and seed color on sorghum germination, emergence, and agronomic performance. Twenty near-isogenic lines with red seed/tan plant (RT), red seed/purple plant (RP), white seed/ tan plant (WT), white seed/purple plant (WP) phenotypes were tested under field and laboratory conditions. Plant color x seed color interactions were not significant. Purple plant color phenotypes had higher cold germination, higher germination after accelerated aging, and greater seedling elongation at 10 d than tan plant color phenotypes. Plant color did not influence standard warm germination. No differences in standard warm germination or seed vigor test results were attributable to seed color. Seedling emergence under field conditions was higher for the red seed than the white seed phenotype. Grain yield was higher for the white seed than the red seed phenotype, and higher for the purple plant color than the tan plant color phenotype. Grain test weights from purple plant color lines were higher than those from tan plant color lines. All four phenotypes included relatively high yielding lines. There was considerable overlap between WT, WP, RT, RP lines in yield and other indicators of agronomic performance leading to the conclusion that white seed and tan plant color lines with comparable performance to red seed and purple plant color lines can be selected from segregating breeding populations.

A new method of determining in vitro dry matter digestibility (IVDMD) was recently developed in which the digestion is conducted with the forage samples in filter bags. Our objective was to compare the filter bag and conventional IVDMD analysis methods using smooth bromegrass (Bromus inermis Leyss.), switchgrass (Panicum virgatum L), and forage sorghum [Sorghum bicolor (L.) Moench] samples. In addition, the filter bag analysis systems for determining non-sequential neutral and acid detergent fiber (NDF and ADF), respectively, were compared with the non-sequential conventional analysis systems. In the filter bag systems, the forage samples are sealed in filter bags and the analyses are conducted on a batch basis rather than on an individual basis as in the conventional IVDMD and fiber analysis procedures. The filter bag analysis methods produced results similar to the conventional methods and ranked the forage samples in the same relative order.

cross-fertilization in ‘White Milo’ in Texas, and noted differing percentages of cross-fertilization among heads. Amount of natural outcrossing in a species is one of the primary Sieglinger (1921) reported an average of 5% cross-fertildetermining factors in selection of breeding methods. Existing literaization between white and yellow milo in Oklahoma. ture on natural outcrossing of sorghum is dated and limited in geographical reference. Experiments were designed to investigate natural Fewer experiment results are published on natural outcrossing in contemporary sorghum, Sorghum bicolor (L.) Moench, outcrossing of sudangrass. Hogg and Ahlgren (1943) B- and R-lines, and in sudangrass, Sorghum bicolor (L.) Moench. showed an average of 7% natural cross-fertilization of Four R-lines and four B-lines were seeded in rows in isolation at ‘Piper’ sudangrass with ‘Leoti’ sorghum in Wisconsin. Mead, NE, and allowed to intercross in each of 2 yr. Bulked seed Garber and Atwood (1945) reported 18 to 77% outfrom each row was planted and proportion of offtypes recorded. crossing in an experimental line of sudangrass using seed Outcrossing ranged from 0.1 to 13% in R-lines, and from 0.5 to 9% produced in Pennsylvania, with an increase in crossin B-lines. Outcrossing among sudangrass plants with white or green fertilization between 6 and 26 August. midribs transplanted in isolation in each of 2 yr was estimated by Maunder and Sharp (1963) showed outcrossing perutilizing the dominant gene for white midrib as a marker. Panicles centages of sorghum in Texas to be affected by genotype from green midrib plants were tagged to indicate approximate date of pollination. At maturity, the panicles were divided into top, middle, and floret position on the panicle. ‘Combine Kafir and bottom thirds and threshed. Seed from each panicle section was 60-B’ averaged 3% outcrossing on the upper one-fourth planted and proportion of white midrib plants recorded. Outcrossing and 1% outcrossing on the lower three-fourths of the ranged from 0 to near 100% on individual sudangrass plants and was panicle. ‘Double Dwarf White Feterita’ averaged 10% highly variable. Harvest of panicles pollinated during the middle of outcrossing on the upper one-fourth and 4% outcrossing the pollination period should maximize outcrossing in sudangrass, on the lower three-fourths of the panicle. The authors but the use of nuclear male-sterility genes is still recommended for concluded that “for increased purity (selfing), it would improvement of sudangrass through recurrent selection. For sorghum seem justifiable to discard the upper portion of openbreeding procedures requiring a high degree of self-pollination, selfing pollinated panicles at the time of threshing.” One might under pollination bags is recommended. also conclude that percentage of natural outcrossing could be maximized by saving only the upper portion of the panicle. A

Currently, no information is available comparing the agronomic performance of At and A3 cytoplasms in sorghum x sudangrass [Sorghum bicolor (L.) Moenchl hybrids. The objectives of this study were to compare the effects of A1 and A3 cytoplasm on the maturity, fertility, height, forage yield, and forage quality of sorghum x sudangrass hybrids. In 1989, pollen from a bulk of eight sudangrass populations was used to pollinate four sorghum lines that had been male-sterilized in both At and A3 cytoplasm. Hybrids were grown at the Univ. of Nebraska Field Laboratory, Ithaca, NE, in 1990 and 1991, in a split-plot design with inbreds (females) treated as whole plots and cytoplasms treated as subplots. The soil was a Sharpsburg silty clay loam (fine montmorillonitic, mesic Typic Agriudoll). Cytoplasm had no effect on days to 50% anthesis, height, forage yield, in vitro dry matter disappearance (IVDMD), or crude protein. Seed set under selfing bags (fertility restoration) in A3 hybrids was observed, with interaction among A3 cytoplasm sources and lines.

Two field studies involving different groups of germplasm were conducted to compare sorghum-sudangrass, Sorghum bicolor (L.) Moench X S. sudanense (Piper) Stapf, hybrid seed production of male-sterile FI's with their component A·lines. The FI's yielded 45 and 82% more grain than their A·line counterparts in Study I and 2, respectively, with the increase attributable to more seeds per panicle and a greater threshing percentage. Mean values of nine traits measured on nine groups of eight FI's in Study I and seven groups of six FI's in Study 2 were compared with their respective A·lines. All groups of FI's significantly outyielded their A·line counterparts in both studies except for A·line N35 in Study 1. Phenotypic correlations of yield and seeds per panicle were high in both A·lines and FI's in both studies, as were the correlations of yield and threshing percentage except for the FI's in Study 1. Application of these findings should facilitate the production of higher yields of sorghum-sudangrass hybrid seed at reduced cost per unit of seed. The best FI's to use and the magnitude of their superiority over A·lines will be influenced by the location in which seed is produced. Additional indexwords:Sorghum bicolor (L.) Moench, Sorghum sudanense (Piper) Stapf, Single-cross hybrids, Three-way hybrids. SORGHUM-SUDANGRASS, Sorghum bicolor (L.) Moench X S. sudanense (Piper) Stapf, hybrids are grown extensively to provide supplementary forage for animals as pasture, silage, or greenchop. These hybrids play an important role in the management plans of many livestock producers, particularly in drouth-prone regions such as the Great Plains. In a 1977 survey by Harvey (I), 81.5% of the commercially produced sorghum-sudangrass hybrids in the United States were F I 's, with 'Redlan' grain sorghum being the preferred male-sterile and 'Greenleaf sudangrass the most often used pollinator. Also, three-way cross hybrids made up I I% of the total seed production of sorghums and sudangrasses used for forage compared with less than 2% in grain sorghum (I). Despite this rather extensive use of three-way crosses in forage and sudangrass hybrids, only two preliminary reports were found in which the seed production of three-way and single cross hybrids was compared. In a I-year study of seed production of sorghum-sudangrass hybrids in Hungary (3), seed yields of F I male steriles were greater and production was more dependable than for Alines because the F1's matured earlier, but comparative seed yields of three-way and single cross hybrids were not presented. In Japan (6), four grain sorghum A-lines, six grain-sorghum male-sterile F I 's and six sorgo male-sterile F I 's were used in a comparative I Contribution of USDA-ARS and the NebraskaAgric. Exp. Stn. Published asPaper no. 7415, Journal Series, Nebraska Agric. Exp, Stn., Lincoln. Research was conducted under Nebraska Project no. 12-114. Received 29 Feb. 1984. 2 Supervisory research geneticist, USDA-ARS; research technologist inagronomy;George Holmes professorof agronomy; and research geneticist, USDA-ARS, Lincoln, NE68583, respectively. study of seed production of forage sorghum hybrids. Seed weight per head on the grain-sorghum malesterile F I 's was slightly lower than for the A-lines, while seed weight per head on the sorgo male-sterile F I 's was substantially greater than on either of the other two female types. Seed yield per land area was not given. The A-lines used differed in each of the three groups of material, and seed weights of F I 's could not be compared with those of their component A-lines. Although published information on comparisons of three-way with single cross forage-type hybrids is limited, more extensive literature is available for grain sorghums as indicated in a recent report (2). The objectives of this study were to I) compare seed yield and other agronomIC traits between malesterile F I seed parents and their component A-line seed parents in the production of sorghum-sudangrass hybrids in two different groups of germplasm, 2) determine phenotypic correlations among traits within parental groups, and 3) relate the findings to hybrid seed production. Evaluation of the hybrid seed produced in terms of forage production will be reported in a subsequent paper. MA TERIALS AND METHODS The seed parents used in Study 1 were nine combineheight cytoplasmic male-sterile A-lines and their 36 malesterile AX B-line crosses (FI'S) that were identical to those used in a similar study with grain sorghum hybrids (2). The A-lines included KS4, KS23, 'Martin', N30, N35, N36, N38, WD4, and 'Wheatland'. In Study 2, the seed parents were seven A-lines and their 21 male-sterile F t's. The A-lines were KS5 and KS9, described by Ross et al. (4); N38 and N48, described by Ross et al. (5); N4692, described by Webster et al. (7); N50I3, an experimental line; and the cultivar Redlan. The pollen source was produced from a composite of equal seed weights of the sudangrass cultivars Greenleaf and 'Piper', Nebraska 7035, and experimentallow-dhurrin strains of Greenleaf and Piper. This heterogeneous pollen source assured continuous and adequate pollen dispersal to the female parents over the range of their stigma receptivity. The sudangrass composite was seeded in double rows, with six rows of male-sterile sorghums being grouped between each pair of sudangrass rows. The outside rows of each group of six male-steriles were seeded to cytoplasmic male-sterile 'Combine Kafir-60', which served as unharvested border rows to minimize any effect of the taller sudangrass rows on the four randomly assigned male-sterile lines and F I hybrids that were harvested in each group. The experiments were planted 29 May 1979 and 27 May 1980 at the University of Nebraska Field Laboratory, Mead, in a medium textured Sharpsburg silty clay loam soil (fine, montmorillonitic, mesic Typic Argiudoll) to which 112 kg haI of N had been applied. Four replications of singlerow plots 7.6 m long and 0.76 m apart in a randomized complete block design were used each year. All plots were overseeded and thinned to 15 em between plants, giving a plant population of about 87 000 plants ha1• The exper1134 Published in Crop Science (November-December 1984) v.24, no. 6