Sweet Sorghum Cultivars Research Articles

Chemical composition, kinetics of degradation, and digestibility of forage of different purpose sorghum cultivars

The aim of the study was to identify suitability of different purpose sorghum cultivars for silage production and for green chopping, at the first and second season, based on the chemical composition and degradation kinetics. The experiment was based on a randomized block design with four replicates, with sowing in the months of November and March, as the first and second season, respectively. The trial was conducted at the Plant Production Sector of the Federal Institute of Education, Science and Technology of Rondonia, Colorado do Oeste campus, and chemical analyses were performed at the Animal Nutrition Laboratory of the Federal University of Mato Grosso, Cuiaba campus. The treatments comprised six sorghum hybrids of different purposes (BRS 308 and BRS 310, grain sorghum; BRS 655 and BRS 610, forage sorghum; BRS 506 and CMSXS 647, sweet sorghum). The chemical composition, digestibility, and kinetic parameters were evaluated. At the first season, there was a higher digestibility (P < 0.0001) for sweet sorghum BRS 506, while for the second season, both grain sorghum BRS 308 and sweet sorghum cultivars BRS 506 and CMSXS 647 presented higher digestibility (P = 0.0005). Considering the nutritional value, all sorghum cultivars have the potential to produce silage, or to be used as green chop, at the first and second season.

Metabolite Profiling of Sorghum Seeds of Different Colors from Different Sweet Sorghum Cultivars Using a Widely Targeted Metabolomics Approach.

Sweet sorghum (Sorghum bicolor) is one of the most important cereal crops in the world with colorful seeds. To study the diversity and cultivar-specificity of phytochemicals in sweet sorghum seeds, widely targeted metabolomics was used to analyze the metabolic profiles of the white, red, and purple seeds from three sweet sorghum cultivars Z6, Z27, and HC4. We identified 651 metabolites that were divided into 24 categories, including fatty acids, glycerolipids, flavonoids, benzoic acid derivatives, anthocyanins, and nucleotides and its derivatives. Among them, 217 metabolites were selected as significantly differential metabolites which could be related to the seed color by clustering analysis, principal component analysis (PCA), and orthogonal signal correction and partial least squares-discriminant analysis (OPLS-DA). A significant difference was shown between the red seed and purple seed samples, Z27 and HC4, in which 106 were downregulated and 111 were upregulated. The result indicated that 240 metabolites were significantly different, which could be related to the purple color with 58 metabolites downregulated and 182 metabolites upregulated. And 199 metabolites might be involved in the red phenotype with 54 downregulated and 135 upregulated. There were 45 metabolites that were common to all three cultivars, while cyanidin O-malonyl-malonyl hexoside, cyanidin O-acetylhexoside, and cyanidin 3-O-glucosyl-malonylglucoside were significantly upregulated red seeds, which could be the basis for the variety of seed colors. Generally, our findings provide a comprehensive comparison of the metabolites between the three phenotypes of S. bicolor and an interpretation of phenotypic differences from the point of metabolomics.

The increased hydrocyanic acid in drought-stressed sorghums could be alleviated by plant growth regulators

Droughts not only reduce the biomass of sorghum (Sorghum bicolor (L.) Moench) but also increase the risk of hydrogen cyanide (HCN) toxicity to animals, mainly due to increased HCN content in drought-stressed plants. In the present study, the variations of HCN contents in 12 sorghum genotypes (10 sweet sorghum cultivars, one Sudangrass and one forage sorghum) were investigated at jointing, filling and ripening stages under rainfed conditions. Next, three genotypes – one sweet sorghum, one Sudangrass and one forage sorghum – were further selected to elucidate the physiological mechanisms of plant growth regulators (PGRs) (abscisic acid (ABA) and methyl jasmonate (MeJA)) in mitigating the concentrations of HCN in drought-stressed plants in a pot experiment. About 100 µg/L ABA and 100 µg/L MeJA were sprayed separately or together twice on drought-stressed (50 and 75% field water capacity) plant leaf. The drought lasted for 15 days. In the field experiment the HCN content in plants reduced from jointing to filling stages then increased from filling to ripening stages in several cultivars. In the pot experiment, drought increased the HCN accumulation and soluble protein content in leaves of all three genotypes. PGRs overall reduced the HCN contents in drought-stressed sweet sorghum and Sudangrass but not in forage sorghum (except in the ABA+MeJA treatment). However, the soluble protein contents were reduced by PGRs in drought-stressed forage sorghum but not in sweet sorghum (except in the ABA+MeJA treatment) and Sudangrass. Both ABA and MeJA increased the plant weights, whereas only MeJA enhanced net photosynthetic rate (PN) in all three genotypes. PGRs reduced release rate of superoxide and hydrogen peroxide and malondialdehyde in all drought-stressed plants, and reduced the activities of peroxidase, superoxide dismutase, catalase, and ascorbate peroxidase in sweet sorghum but not in other two genotypes. These results suggest that exogenous ABA and MeJA could increase plant weight and reduce HCN content in drought-stressed sorghums, with varying physiological responsive mechanisms among sorghum genotypes.

Accumulation of Carboxylate and Aromatic Fluorophores by a Pest-Resistant Sweet Sorghum [Sorghum bicolor (L.) Moench] Genotype.

The sugary juice from sweet sorghum [Sorghum bicolor (L.) Moench] stalks can be used to produce edible syrup, biofuels, or bio-based chemical feedstock. The current cultivars are highly susceptible to damage from sugarcane aphids [Melanaphis sacchari (Zehntner)], but development of new cultivars is hindered by a lack of rapid analytical methods to screen for juice quality traits. The mechanism of aphid resistance/tolerance is also largely unknown, though the importance of defense phytochemicals has been suggested. The purpose of this study was to develop low-cost methods sensitive to fluorescent fingerprints in sweet sorghum juice, which is a complex mixture of saccharides, carboxylates, polyphenols, and metal ions. Of primary juice components, tryptophan and trans-aconitic acid were the highest intensity contributors to the overall fluorescence and UV/visible absorbance, respectively, while tyrosine and polyphenols contributed to a less extent. In a test of 24 sweet sorghum cultivars, tryptophan and tyrosine contents were the highest in the aphid-susceptible hybrid N109A x Chinese, while sucrose, trans-aconitic acid, and polyphenols were the highest in the resistant line No. 5 Gambela. This suggests that the accumulation of carboxylate (trans-aconitic acid) and polyphenolic secondary products in No. 5 Gambela may contribute to its aphid resistance, thus allowing it to maintain sucrose production. Rapid detection of these chemical signatures could be used to prescreen the breeding material for potential resistance and juice quality traits, without analytical separation required for metabolomics.

Nitrogen Content and Use Efficiency of Sweet Sorghum Grown in the Lower Midwest

Optimizing N fertilizer inputs is imperative for improving sweet sorghum [Sorghum bicolor (L.) Moench] yields and biofuel feedstock system efficiency. A 2‐yr study was conducted to determine the physiological N‐use efficiency (NUE) response in sweet sorghum's ethanol yield of stem juice, bagasse, and total ethanol yield (TEY). Two sweet sorghum cultivars (‘Dale’ and ‘Top 76–6’) were fertilized at five N fertilizer rates (0, 56, 112, 168, and 224 kg ha−1). At harvest, the stem juice and bagasse yields were measured then analyzed for the corresponding N concentrations and N contents. Whole‐plant N recovery efficiency ranged from −1.5 to 57.6% across both years, with a significant N rate effect only in one study year. The NUE of juice ethanol yield only demonstrated an N response in the second year, whereas the NUE of lignocellulosic ethanol yield was greatest at the 56 kg ha−1 fertilizer rate each year. The NUE of total theoretical ethanol yield, determined as the sum of juice and bagasse conversion to ethanol, averaged 169 L EtOH kg−1 N across both years and was greatest at the 56 kg N ha−1 fertilizer rate in both years, and decreased at N rates exceeding 56 kg ha−1 in only one of the years. This study revealed that although sweet sorghum ethanol yields increased with N fertilizer application, NUE was greatest with low N fertilizer rates, consistent with previous research indicating that sweet sorghum is an appropriate biofuel feedstock for production in low‐input systems or on marginal lands.Core Ideas Nitrogen recovery and use efficiencies of sweet sorghum juice and bagasse were measured for two years in Missouri. Nitrogen recovery efficiency was greatest in one study year when 224 kg N ha−1 was applied, with no differences in recovery in the second year. The N use efficiency of estimated total ethanol yield was greatest at 56 kg N ha−1.

Arbuscular Mycorrhiza Enhances Biomass Production and Salt Tolerance of Sweet Sorghum.

Arbuscular mycorrhizal (AM) fungi (AMF) are widely known to form a symbiosis with most higher plants and enhance plant adaptation to a series of environmental stresses. Sweet sorghum (Sorghum bicolor (L.) Moench) is considered a promising alternative feedstock for bioalcohol production because of its sugar-rich stalk and high biomass. However, little is known of AMF benefit for biomass production and salt tolerance of sweet sorghum. Here, we investigated the effects of Acaulospora mellea ZZ on growth and salt tolerance in two sweet sorghum cultivars (Liaotian5 and Yajin2) under different NaCl addition levels (0, 0.5, 1, 2, and 3 g NaCl/kg soil). Results showed AMF colonized the two cultivars well under all NaCl addition levels. NaCl addition increased mycorrhizal colonization rates in Yajin2, but the effects on Liaotian5 ranged from stimulatory at 0.5 and 1 g/kg to insignificant at 2 g/kg, and even inhibitory at 3 g/kg. High NaCl addition levels produced negative effects on both AM and non-AM plants, leading to lower biomass production, poorer mineral nutrition (N, P, K), higher Na+ uptake, and lower soluble sugar content in leaves. Compared with non-AM plants, AM plants of both cultivars had improved plant biomass and mineral uptake, as well as higher K+/Na+ ratio, but only Yajin2 plants had a low shoot/root Na ratio. AM inoculation increased the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and soluble sugar content in leaves. Overall, both cultivars benefited from mycorrhization, and Yajin2 with less salt tolerance showed higher mycorrhizal response. In conclusion, AMF could help to alleviate the negative effects caused by salinity, and thus showed potential in biomass production of sweet sorghum in saline soil.

CHEMICAL AND ENERGETIC CHARACTERISTICS OF AFRICAN SWEET SORGHUM AS A SOURCE OF BIOENERGY

ABSTRACT The aim of this study was to evaluate the energetic potential achieved by the application of phyto-regulators to sweet sorghum cultivars. A randomized complete block design was used. Experiments were conducted using two sweet sorghum cultivars (BRS 508 and BRS 509), fourphyto-regulators (ethephon, ethyl-trinexapac, glyphosate, and sulfometuron-methyl), and a control; four replicates were performed 70 days after sowing, at the beginning of the flowering phase of the plants, with the aid of a CO2-pressurized coastal sprayer. The plants were harvested after 40 days, with the stems being cleared at the height of the apical bud, and were subjected to grinding for the extraction of broth. The following analyses were carried out: chemical (total extractives, lignin, and holocellulose contents), proximate (volatile matter, fixed carbon, and ash contents), and energetic (higher heating value). Multiple comparison (Tukey) and linear correlation (Pearson) analyses were carried out at a 5% significance level. The phyto-regulators positively and significantly influenced the chemical attributes and contents of lignin and fixed carbon. It was concluded that glyphosate, sulfometuron-methyl, and ethephon enhanced the biomass/bioenergy potential of sweet sorghum cultivars.

Resistance of bioenergy sorghum to Diatraea saccharalis (Lepidoptera: Crambidae)

This study evaluated the effects of the sugarcane borer Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) on cultivars of sweet and biomass sorghum for the selection of resistant cultivars. The present work consisted of two trials, with natural pest infestation. In the first one, 10 sweet sorghum cultivars were analyzed for the following variables: plant height, number of healthy and damaged internodes, gallery position and size, stem infestation level and soluble solids content (°Brix). In the second trial, it was analyzed 16 genotypes of high biomass sorghum, with the same variables above mentioned, in addition to the lignin, cellulose and hemicellulose contents. Among sweet sorghum genotypes evaluated, the genotype CMSXS647 stood out due to the traits: plant height, infestation level, gallery size and soluble solids content. Among the sorghum genotypes evaluated, CMSXS7030, CMSXS7012 and CMSXS7028 presented ideal characteristics for infestation level, plant height and number of lignocellulosic compounds. Such information, in addition to supporting the bioenergy sorghum breeding program, will assist in integrated pest management for sorghum cultivation.

Effect of Sink Removal and Magnesium Spraying on Photosynthetic Pigments and Sugar Yield of Two Sweet Sorghum Cultivars

Effect of Sink Removal and Magnesium Spraying on Photosynthetic Pigments and Sugar Yield of Two Sweet Sorghum Cultivars

Rapid Data Analytics to Relate Sugarcane Aphid [(Melanaphis sacchari (Zehntner)] Population and Damage on Sorghum (Sorghum bicolor (L.) Moench)

Sugarcane aphid [(Melanaphis sacchari (Zehntner)] emerged in the United States in 2013 as a new pest infesting sorghum (Sorghum bicolor (L.) Moench). Aphid population and plant damage are assessed by field scouting with mean comparison tests or repeated regression analysis. Because of inherently large replication errors from the field and interactions between treatments, new data analytics are needed to rapidly visualize the pest emergence trend and its impact on plant damage. This study utilized variable importance in the projection (VIP) and regression vector statistics of partial least squares (PLS) modeling to deduce directional relationships between aphid population and leaf damage from biweekly field monitoring (independent variable) and chemical composition (dependent variable) of 24 sweet sorghum cultivars. Regardless of environment, aphid population increase preceded the maximum damage rating. Greater damage rating at earlier growth stage in 2015 than 2016 led to an overall higher damage rating in 2015 than 2016. This trend in damage coincided with higher concentrations of trans-aconitic acid and polyphenolic secondary products in stem juice in 2016 than 2015, at the expense of primary sugar production. Developed rapid data analytics could be extended to link phenotypes to perturbation parameters (e.g., cultivar and growth stage), enabling integrated pest management.

Sweet sorghum for ethanol production in the semi-arid: response to potassium silicate and maturation

The sweet sorghum is an important alternative source to ethanol production, and in a function of its rusticity and tolerance to adverse environment present high potential to Brazilian semi-arid region. With the purpose of seeking recommendations to improvements in agronomic performance, the objective of this study was to assess the biomass yield and juice quality of sweet sorghum cultivars as a function of foliar fertilization with potassium silicate and determine the optimal harvest time. The experiment was conducted in the semi-arid region (Pentecoste, CE, Brazil) in 2014 and 2015, using three genotypes (BRS 506, BRS 511 and EJX 7C30) fertilized with potassium silicate (0, 500, 1000 and 1500 mL ha-1) and harvested at 90, 97, 104 and 111 days after sowing (DAS). The experiment was arranged in randomized blocks with four replications in a split-split-plot design (3 x 4 x 4). The total biomass and juice yield, total soluble solids (oBrix), total soluble carbohydrates and estimated ethanol production were determined for each year. In 2014, the mean biomass yield for BRS 506, BRS 511 and EJX 7C30 were 58.6, 64.9 and 24.5 Mg ha-1, respectively. As for 2015, the biomass yield of BRS 506 and BRS 511 decreased by 8.5 and 21 %. The juice of BRS 506 and BRS 511 showed a high quality standard, and the latter cultivar stood out with 157 g L-1 of total soluble carbohydrates at 111 DAS. The cultivars BRS 506 and BRS 511 showed high juice quality when harvested at 111 DAS.

Establishing sustainable sweet sorghum-based cropping systems for forage and bioenergy feedstock in North China Plain

Sweet sorghum [Sorghum bicolor (L.) Moench] offers a sustainable and renewable bioenergy resource for feed and biomass production. Two separate field experiments were conducted on arable land at Shangzhuang Station and on saline-alkali land at Quzhou Station in the North China Plain. Three cultivars of sweet sorghum including early- (ZS1) (114 days), medium- (CT2) (138 days), and late-maturity (LN3) (160 days), were sole cropped on arable land in 2006–2007. Using the same cultivars, sweet sorghum based - double cropping systems with winter wheat rotation were analyzed on saline-alkali land in 2009–2011. This study aims to determine the planting potential of three sweet sorghum cultivars and develop an optimized sweet sorghum - based double cropping system on saline-alkali land to maximize the production outputs. The aboveground biomass yield, energy output, theoretical ethanol yield (TEY), and chemical composition of three sweet sorghum cultivars - based cropping systems were assessed. Results indicate that: (1) the annual average dry biomass yield and dry matter content of the three sweet sorghum cultivars showed an overall uptrend with the increasing crop growth length. The average dry biomass yield of three sorghum maturity groups on arable land were 48.9% higher than that on saline-alkali land. (2) Sweet sorghum cultivars of late- (LN3) and medium- maturity (CT2) displayed better chemical composition for both bioenergy utilization (higher starch, soluble sugar, cellulose and hemicellulose and lower ash) and forage quality (better relative feed value (RFV) and lower acid detergent fiber (ADF) and neutral detergent fiber (NDF)). (3) The double cropping system of medium-maturity sweet sorghum (CT2) and winter wheat presented the best total dry biomass yield (24.9 t ha−1), energy output (394.6 GJ ha−1), and theoretical ethanol yield (6857 L ha−1). Therefore, this double cropping system can be recommended for extensive planting in the North China Plain for bioenergy or forage production.

Physical fractionation of sweet sorghum and forage/energy sorghum for optimal processing in a biorefinery

Sorghum offers enormous potential as a feedstock for the production of fuels and chemicals from both water-extractable sugars and the cell wall biopolymers, while its within-plant structural and compositional heterogeneity may allow for physical fractionations to tailor feedstock properties to a biorefining process. In this study, the stem internodes of two sorghum (Sorghum bicolor L. Moench) genotypes, a sweet sorghum (‘Della’) and a forage/energy sorghum (‘TX08001’), were first subjected to fractionation by manual classification by stem anatomy and internode proximity to the ground to yield 18 fractions. These fractions exhibited substantial differences in cell wall morphology, composition, and recalcitrance to mild alkaline pretreatment and enzymatic hydrolysis. While the sweet sorghum cultivar held nearly 70% more water-extractable sugar (sucrose, glucose, fructose, starch) in the stems than the forage/energy sorghum hybrid, both cultivars exhibited comparable diversity of composition and these compositions were remarkably similar in similar tissues and stem regions between the two cultivars. The fractions isolated from the pith parenchyma were the least recalcitrant to mild alkaline pretreatment and enzymatic hydrolysis and contained less lignin than fractions isolated from the epidermis, outer and inner rind, and internal vascular bundles. The pith samples isolated from the lowest region of the stem from both cultivars exhibited near-theoretical sugar hydrolysis yields when no pretreatment was employed and exhibited the lowest lignin contents of any of the fractions. Next, a physical fractionation approach approximating a commercial “de-pithing” process utilizing wet disintegration and sieving was applied to the forage/energy sorghum. A pith-rich fraction representing approximately 20% of the extractives-free mass of the stem could be isolated with this approach and, relative to the other fractions, was low in lignin, high in ash, highly hygroscopic, and showed an improved response to mild alkaline pretreatment and enzymatic hydrolysis at low enzyme loadings. Overall, these results demonstrate how heterogeneity within sorghum stems can be exploited using physical fractionation approaches to yield fractions enriched in desired properties that may allow for more streamlined processing.

First and Second Generation of Ethanol Production for Five Sweet Sorghum Cultivars during Soft Dough Grain

This study we aimed to identify how the harvest period of the stems from 5 sweet sorghum cultivars influences the production of sugar and ethanol under rainfed conditions in the municipality of Itambe, state of Pernambuco. Subsequently we evaluated the ethanol production from juice and bagasse of the different cultivars. The field experiment was evaluated in a factorial arrangement with two factors (5 cultivars and 3 harvest periods) and fours replications. The fermentation experiments, pretreatment and enzymatic hydrolysis were delineated in a completely randomized design in quadruplicate. Data obtained for all variables evaluated were submitted to an Analysis of Variance and the means compared by the Tukey test at 5% of probability. Results showed that the harvest period influenced the total soluble solids, and the harvest period of soft dough was chosen for assessments of ethanol production of first and second generation. Ethanol production from juice differed among cultivars with the best performance by cultivar SF 15. Significant differences were observed for the chemical composition of bagasses between cultivars, but there where no difference in efficiencies of enzymatic hydrolysis. The average conversion of cellulose in glucose was 64.87%. The cultivars of sweet sorghum biomass developed and adapted for the Northeastern region of Brazil showed potential for ethanol production from the juice and bagasse.

Competitive Interaction Between Sweet Sorghum with Weeds

ABSTRACT: The objective of this work was to determine the competitive interaction of sweet sorghum cultivars BRS 506, BRS509, and BRS 511 with biotypes of Alexandergrass and wild poinsettia. The adopted experimental design was the randomized block one, with four replications. Treatments were arranged in a substitution series by proportions of 100:0, 75:25, 50:50, 25:75, and 0:100%, corresponding to 20:0, 15:5, 10:10, 5:15 and 0:20 plant per pot of sweet sorghum (cultivars BRS 506, BRS 509 and BRS 511) withweeds (Alexander grass/wild poinsettia). The leaf area (LA) and dry matter (DM) of sweet sorghum, Alexandergrass and wild poinsettia plants were determined 50 days after emergence. Data about competitive abilities were analysed through the graphical analysis method, constructing diagrams based on yield or relative and total variations. Indices of relative competitiveness, clustering coefficient and aggressiveness were also determined; all of them were relative indices. There was competition for the same environmental resources between sweet sorghum cultivars and weeds, with mutual injury to the species involved in the community. Wild poinsettia and Alexandergrass negatively modified the LA and DM of the crop, demonstrating a greater competitive ability for the resources that are available in the environment. Wild poinsettia was less competitive than sweet sorghum cultivars, while Alexandergrass showed higher competitive ability than them. The highest losses for the LA and DM variables were observed when species were in interspecies competition rather than intraspecies competition.

Genetic interrelationship of sweet stem sorghum genotypes assessed with simple sequence repeat markers

Knowledge of genetic diversity within and among populations provides essential information in employing appropriate management strategies for germplasm conservation and for establishing a successful breeding program. The objective of this study was to evaluate the genetic interrelationships among phenotypically selected sweet stem sorghum genotypes using polymorphic simple sequence repeat (SSR) markers. Eighteen sweet sorghum cultivars were genotyped using 25 selected SSR markers. The number of alleles detected per marker ranged from 1 to 10 with a mean of 4.64 per locus. The number of effective alleles varied from 1 to 6.75 with a mean of 2.9. The observed heterozygosity varied from 0.00 to 0.39 with a mean of 0.16. The inbreeding coefficient varied from 0.11 to 1.00 with a mean of 0.7. The polymorphism information content (PIC) values for all markers ranged from 0.00 to 0.85 with a mean value of 0.56. Sixty-eight percent of the markers used had a PIC value > 0.50. Analysis of molecular variance revealed highly significant differences (p < 0.001) among the test population. Among and within individual variances contributed to 78% and 21% of total genetic variance, respectively. Based on SSR analysis and agronomic traits, genotypes AS391, SS27, AS204 and AS244 were selected to breed for biofuel production.

Diversity of Endophytic Bacteria in Sweet Sorghum (Sorghum bicolor (L.) Moench) and Their Potential for Promoting Plant Growth

Objectives: To isolate endophytic bacteria of sweet sorghum cv. FS501 adapted to two locations in Bunder and Mulo, Indonesia and characterize their properties including fixing nitrogen, solubilizing phosphate, and producing (Indole -3-Acetic Acid)IAA. Methods/Statistical Analysis: The bacteria were isolated from roots, stems, and shoots and followed by repetitive element PCR (rep-PCR) for endophyte determination. The 16S rRNA genes amplifications were sequenced using ABI Prism 3730. Sequence’s similarity was evaluated using BLAST then analyzed with MEGA 5.0. Bacteria properties including nitrogen-fixation ability, dissolving phosphate and IAA production was performed in a semisolid LGI medium, Pikovskaya media and colorimetric method, respectively. Findings: Forty-eight isolates of endophytic bacteria were isolated from roots, stems, and shoots of sweet sorghum. The rep-PCR resulted the isolated bacteria belonged to 23 groups consisted of 9 isolates from Bunder and 14 isolates from Mulo. Sequences from the 23 isolates were determined and aligned with those of reference strains in GenBank. BLAST analysis indicated that the isolated endophytic bacteria belonged to 10 different genera: Beijerinckia, Ralstonia, Microbacterium, Curtobacterium, Brevibacterium, Leifsonia, Bacillus, Staphylococcus, Lysinibacillus, and Fictibacillus. Of the total 23 endophytic bacterial isolates acquired the five diazotrophic isolates were from the genera Beijerinckia, Microbacterium, Curtobacterium, Bacillus, and Staphylococcus; the four isolates capable of dissolving the phosphate from the genera Microbacteriumand Brevibacterium; and nine isolates were able to produce IAA from the genera Microbacterium, Brevibacterium, and Bacillus. Isolates BA3 (Microbacterium testaceum), BA8 (Microbacterium oleivorans), BA14 (Brevibacterium iodinum), and MA24 (Microbacterium arborescens) positive for more than one mechanism promoting plant growth. Application/Improvements: The four isolates having more than one mechanism promoting plant growth would be of commercial interest to biotechnology companies with a goal of producing an inoculant for sweet sorghum cultivars. Keywords: Endophytic bacteria, sweet sorghum, nitrogen fixation, IAA production, phosphate solubilization

The Environment Strongly Affects Estimates of Heterosis in Hybrid Sweet Sorghum

Sweet sorghum [Sorghum bicolor (L.) Moench] has potential as a biofuel feedstock, but hybrid cultivars are needed to support an industry based on this crop. The purpose of this study was to compare five inbred sweet sorghum lines and 15 hybrids derived from them and to determine the extent of environmental effects on estimates of hybrid vigor (heterosis) and heritability for various agronomic traits. The test was repeated across 2 years (2013 and 2015) and three planting dates each year (April, May, and June) at Tifton, GA, USA. Environmental conditions were highly variable, and thus, estimates of heterosis for various traits, as well as correlations between hybrids and midparents (average of the inbred parents), were also variable. In the 2015 season, a new insect pest, sugarcane aphid (Melanaphis sacchari Zehntner), appeared to cause reduced juice Brix in the April planting. Hybrids generally flowered earlier than their inbred male-parent lines, and flowering time was highly correlated between midparents and hybrids. Hybrids frequently had greater lodging percentage than inbreds, but lodging was also correlated between midparents and hybrids in four environments. Heterosis for juice Brix and sugar yield was uncommon, while heterosis for panicle (grain) yield was frequently observed. Based on this study, it will be difficult to predict hybrid performance for juice Brix, sugar yield, and panicle yield based on inbred performance. Testing in multiple environments will be essential for the development of sweet sorghum hybrids, and there is a critical need for sweet sorghum cultivars with resistance to sugarcane aphids.

Evaluation of three cultivars of sweet sorghum as feedstocks for ethanol production in the Southeast United States

Sweet sorghum has become a promising alternative feedstock for biofuel production because it can be grown under reduced inputs, responds to stress more efficiently than traditional crops, and has large biomass production potential. A three-year field study was conducted to evaluate three cultivars of sweet sorghum as bioenergy crops in the Southeast United States (Fort Valley, Georgia): Dale, M81 E and Theis. Parameters evaluated were: plant density, stalk height, and diameter, number of nodes, biomass yield, juice yield, °Bx, sugar production, and theoretical ethanol yields. Yields were measured at 85, 99, and 113 days after planting. Plant fresh weight was the highest for Theis (1096 g) and the lowest for Dale (896 g). M81 E reported the highest stalk dry weight (27 Mg ha−1) and Theis reported the lowest (21 Mg ha−1). Theis ranked the highest °Bx (14.9), whereas M81 E was the lowest (13.2). Juice yield was the greatest for M81 E (10915 L ha−1) and the lowest for Dale (6724 L ha−1). Theoretical conservative sugar yield was the greatest for Theis (13 Mg ha−1) and the lowest for Dale (9 Mg ha−1). Theoretical ethanol yield was the greatest for Theis (7619 L ha−1) and the lowest for Dale (5077 L ha−1).

QTL mapping of agronomically important traits in sorghum (Sorghum bicolor L.)

Sorghum is one of the most important cereal crops; it is used to produce feed, sugar, and biofuel. To investigate genetic tradeoffs between grain and stem sugar production, we evaluated plant height, Brix (the percentage of soluble solids in stalk juice), 100-grain weight and flowering time over 3 years in a recombinant inbred line (RIL) population consisting of 189 individuals derived from a cross between the sweet sorghum cultivar ‘Rio’ and grain sorghum ‘BTx623’. We constructed a genetic linkage map (total length, 1418.71 cM; average distance between markers, 11.26 cM), which consisted of 118 simple sequence repeat (SSR) and 8 insertion-deletion (INDEL) markers. A total of 14 QTLs were detected on chromosomes 1, 3, 6, 7, and 9, which included 6 QTLs for plant height; 4 for Brix; and 2 QTLs for each 100-grain weight and flowering time. Eight QTLs were detected at least in 2 years. These results will be useful for future QTL fine mapping and gene mining for these traits, and useful for the improvement of sorghum through molecular marker-assisted selection.