Sweet Sorghum Accessions Research Articles

Genetic diversity among Ethiopian sweet sorghum [Sorghum bicolor (L.) Moench] accessions using simple sequence repeat markers

Sweet sorghum (Sorghum bicolor (L.) Moench) is the only grain and stalk crop that can be used for multipurpose. Despite its global significance and potential, it faced genetic erosion. These are due to low productivity and lower farmers' preferences, which is not considered one of the most important cereal crops in Ethiopia. To utilize and popularize these crops, understanding the genetic diversity and population structure is a pre-request. Therefore, this study was aimed to assess the genetic diversity and population structure of selected 82 Ethiopian sweet sorghum accessions using 10 simple sequence repeat (SSR) markers that represent seven geographic regions of Ethiopia. The study revealed a total of 116 alleles with a mean of 11.6 alleles per locus. All used microsatellite loci were highly polymorphic with polymorphic information content (PIC) ranging from 0.75 to 0.90 with an average of 0.82. They showed high gene diversity ranging from 0.59 to 0.81 with an overall mean of 0.70. There was a moderate genetic differentiation (FST = 0.21) showing the presence of high gene flow (Nm = 5.033) where 91 % of the total variation was accounted for within populations genetic variability. The clustering, principal coordinate analysis (PCoA) and population structure did not cluster the studied populations into a separate group according to their geographical origin. In conclusion, the highest intra-population diversity was observed among populations of North Wollo (He = 0.81) and South Wollo (He = 0.79), and hence these areas can be considered as hot spots for the identification of novel traits. Therefore, the present study has generated baseline information for breeders to improve Ethiopian sweet sorghum through breeding, management, and conservation of the available genetic resources.

Genome-Wide Association Study Based on Plant Height and Drought-Tolerance Indices Reveals Two Candidate Drought-Tolerance Genes in Sweet Sorghum

To understand the molecular mechanism of drought tolerance in sweet sorghum [Sorghum bicolor (L.) Moench], we found the genetic loci associated with single nucleotide polymorphism (SNP) markers and explored drought-tolerance candidate genes. A genome-wide association study (GWAS) of sweet sorghum was performed using the general linear model (GLM), mixed linear model (MLM) and the fixed and random model circulating probability unification (FarmCPU) method in R. Mean productivity (MP), relative drought index (RDI) and stress-tolerance index (STI), based on plant height under two water treatments, were obtained from 354 sweet sorghum accessions from home and abroad. These plant-height drought-tolerance indices showed continuous quantitative variation. Except for the RDI, the others were close to normal distribution. A total of 6186 SNPs were obtained from the resequencing data after quality control and filling. The marker densities on chromosomes 9, 10 and 5 were higher than those on other chromosomes, which were 40.4, 16.5 and 10.0 SNPs within 1 Mb, respectively. The GWAS results showed that 49, 5 and 25 significant SNP loci were detected by the GLM, the MLM and FarmCPU, respectively, many of which were detected by two or more models. Two candidate genes of drought tolerance were annotated: Sb08g019720.1, homologous to the gene encoding the early flowering MYB protein transcription factor in Arabidopsis thaliana; and Sb01g037050.1, homologous to the gene encoding the basic leucine zipper transcription factor in maize. The results of this study can facilitate the cultivar development of drought-tolerant sweet sorghum.

Photoperiod Sensitivity and Variability of Agromorphological Traits and Brix Content of Sweet Sorghum Cultivated in Burkina Faso under Two Sowing Dates

Sweet sorghum is mainly cultivated for the sweetness of its stems and the quality of its fodder. Unfortunately, its cultivation is gradually being abandoned in Burkina Faso due to climatic hazards. In a general context of strong variations in the rainfall regime, it is, therefore, important to determine the effect of the sowing period on the expression of agromorphological traits and Brix content. Thus, 29 sweet sorghum accessions were evaluated using 15 quantitative variables in a three-replicate Fisher block design with two sowing dates spaced 25 days apart. The results of the study showed that only stalk length (pr. = 0.519) and internode length (pr. = 0.367) were not significantly influenced by sowing date. Indeed, delayed sowing resulted in an increase in the number of vegetative (+2.44) and useful (+1.3) tillers, as well as Brix (+1.16%). However, a reduction in leaf area (−4.35 cm × 1.43 cm), plant height (−85.69 cm), panicle length (−2.63 cm), and panicle weight (−6.19 g), as well as a reduction in the sowing-to-flowering cycle from 3 to 21 days, was obtained at the second sowing date. Thus, all accessions are sensitive to photoperiod with photoperiodic coefficients varying from 0.19 (GB02) to 0.93 (BSA5). These results could be exploited in the sweet sorghum improvement program.

Evaluation of sweet sorghum genotypes for bioethanol yield and related traits

AbstractThe cultivation of sweet sorghum (Sorghum bicolor (L.) Moench) for bioethanol production is receiving global attention due to the plant's sugar‐rich stalk juice, which can be fermented directly to ethanol. One of the important steps toward the development of a superior sweet sorghum cultivar is proper assessment of bioethanol‐related traits in different environments. This study was conducted to characterize global sweet sorghum accessions for bioethanol yield and related traits. To do this and to obtain a final cultivar suitable for efficient bioethanol production, two different environments were chosen to select for the characteristics studied. In total, 53 genotypes, which were selected from 551 accessions and nine cultivars, were evaluated in two contrasting environments and two consecutive years (2014–2015). The results revealed wide variability among the genotypes for the traits investigated. In all the growing years and locations, the highest values for the extractable stalk juice yield, bioethanol yield, and juice Brix content were recorded for BSS55 (22 740 L ha−1), BSS46 (1569.6 L ha−1), and BSS67 (15.63 °Bx), respectively. The genotypes that originated from the USA showed some of the highest values for bioethanol yield and related traits. Positive and very high correlations were observed between the bioethanol yield and extractable stalk juice yield (r = 0.861**) and fructose and glucose concentration (r = 0.856**). The knowledge obtained in this investigation about the variation in the bioethanol yield and related traits led to potential genotypes that can be used in sweet sorghum breeding programs for bioenergy production. © 2020 Society of Industrial Chemistry and John Wiley & Sons Ltd

Phenotypic variability and correlation estimates for traits of Burkina Faso’ sweet grain sorghum genotypes

Sweet grain sorghum [Sorghum bicolor (L.) Moench] is a neglected crop mainly grown for its sweet grains in the pasty form. Although its taste is the main character of interest, knowledge of protein related content of the grain, especially when linked to its value for infant porridge appears equally important. The objective of this study was to evaluate the status of crude protein content of pasty grains and to determine genetic correlations between morphological and biochemical traits among sweet grain of sorghum genotypes in Burkina Faso. Eight sweet grain sorghum cultivars (BTO2, BZI1, KBZ4, PBO5, PGO3, SBR7, SPI2, STO4) were evaluated through 13 morphological and two biochemical variables. Crude protein content of these genotypes was also compared with the composition of two controls of sweet stalk sorghum (ETS) and ordinary grain sorghum or common sorghum (EBS). The analysis of variance revealed variability within sweet grain sorghum accessions, mainly on the biochemical traits (crude protein and water content) and two morphological traits (peduncle and panicle lengths), which discriminated significantly in the thresholds of 1 and 5%, respectively. In addition, sweet grain sorghum had low crude protein content compared to other types of sorghum, except, two genotypes of sweet grain sorghum (BZI1 and STO4) which recorded higher protein content compared to the common sorghum. An important and negative correlation was noted between sowing-flowering cycle and protein content.

Characterization of semi-arid Chadian sweet sorghum accessions as potential sources for sugar and ethanol production

Sweet sorghum (Sorghum bicolor (L.) Moench) is an important crop in Chad that plays an economic role in the countryside were stalks are produced mainly for human consumption without any processing. Unfortunately, very little information exists on its genetic diversity and brix content. Studies performed in 2014 and 2015 showed that there were significant variations (p < 0.001) for all assessed quantitative traits. Potential grain yield (0.12–1.67 t ha−1), days to 50% flowering (68.3–126.3 days), and plant height (128.9–298.3 cm) were among traits that exhibited broader variability. Brix content range from 5.5 to 16.7% across accessions, was positively correlated to stalk diameter and plant height, but negatively correlated to moisture content in fresh stalk and potential grain yield. Fresh stalk yield range from 16.8 to 115.7 Mg ha−1, with a mean value of 58.3 Mg ha−1 across accession. Moisture content in fresh stalk range from 33.7 to 74.4% but was negatively correlated to fresh stalk yield. Potential sugar yield range from 0.5 to 5.3 Mg ha−1 across accession with an average of 2.2 Mg ha−1. Theoretical ethanol yield range from 279.5 to 3,101.2 L ha−1 across accession with an average of 1,266.3 L ha−1 which is significantly higher than values reported under similar semiarid conditions. Overall, grain yields were comparatively low. However, two accessions had grain yield of more than 1.5 t ha−1; which is greater than the average 1.0 t ha−1 for local grain sorghum varieties in Chad. These could have multi-purpose uses; grains, sugar and bioenergy production.

Coupling phytoremediation of cadmium-contaminated soil with safe crop production based on a sorghum farming system

With increasing environmental pressure and soil pollution, sustainable energy and food production for a steadily growing world population is a grand challenge. Globally, nearly 12 million hectares of croplands are contaminated by cadmium (Cd), and how to develop a production system for the cleaning and utilisation of such contaminated land is essential for sustainability. Herein, a diverse panel of 166 sorghum accessions was grown in typical Cd-contaminated fields in two consecutive years, and the effect of different accessions and organs on the phytoremediation potential was evaluated by analysing the Cd concentrations of stems, leaves and grains at maturity. Both the bioaccumulation factors (BCFs) and the aboveground Cd accumulation varied substantially and the differences were up to 13–24 fold. The aboveground Cd accumulation was positively associated with important bioenergy traits including biomass, stem Brix, internode numbers and plant height, as envisaged by the high Cd concentration in sweet sorghum accessions, while BCF was significantly negatively correlated with relevant agronomic traits except Brix. The genetic regulation of Cd concentration in grains is different from those in leaves and stems, which allowed us to screen for three types of sorghum resources with the potential to couple soil phytoremediation with the production of bioethanol, safe grains and forage. A sorghum farming system was further proposed, which could reduce soil Cd concentration below the safe level within 12 years and obtain economic returns of about 70.5–169.5 million Chinese Yuan (CNY) by producing bioethanol, safe grains and forage in one season in 30% of the Cd-contaminated soil in China.

Molecular and morphological evidence for resistance to sugarcane aphid (Melanaphis sacchari) in sweet sorghum [Sorghum bicolor (L.) Moench

Aphids are one of the devastating pests affecting the productivity of sorghum in many countries. The aim of the present investigation was to identify sweet sorghum genotypes resistant to the sugarcane aphid, Melanaphis sacchari (Zehntner). A Sequence Characterized Amplified Region (SCAR) marker linked to an aphid-resistance gene (RMES1) was first used to prescreen for resistant genotypes in 561 sorghum accessions. Molecular assays indicated that 91 sorghum accessions in the collection had the RMES1 resistance marker allele. Of those, 26 agronomically superior sweet sorghum accessions, along with three commercial cultivars and one susceptible check, were further evaluated in two locations (Antalya, a lowland province, and Konya, a highland province) under field conditions. These accessions were scored for resistance to aphid damage under natural aphid infestations. The number of aphids counted on the plant leaves and stalks in the accessions during the growing seasons was used to score resistant genotypes on a scale of 1-5, where 1 was highly resistant (plants having 0-50 aphids/plant) and 5 was highly sensitive (plants having 1000 + aphids/plant). Fumagine intensity on the leaves was also taken into consideration. Ten accessions from the lowland and one accession from the highland scored "1," indicating a high resistance to aphid infestation. A further 13 accessions scored "1" or "2" in both environments. Only two accessions scored "4," and no accession scored "5," indicating the utility of the RMES1 marker for prescreening purposes. One accession, BSS507, showed outstanding resistance to M. sacchari, with a score of "1" in both environments.

Yield Stability of Sweet Sorghum Genotypes for Bioenergy Production Under Contrasting Temperate and Tropical Environments

Forty-three sweet sorghum accessions were grown in two contrasting environments; Nigeria (tropical environment) and Denmark (temperate environment). The objectives were to determine the interaction between genotype and environment on grain yield, fresh biomass and stem sugar, and to assess yield stability of sweet sorghum and identify the best genotypes for biofuel production. The sweet sorghum originating from a Dutch and ICRISAT collection was grown in randomized complete block design in three replicates for two years (2014 and 2015). The combined analysis of variance of the sweet sorghum genotypes in two years over the two contrasting environments revealed that year (Y), genotype (G), environment (E) and genotype by environment interaction (GEI) were significant in the entire biofuel yield attributes obtained from both Dutch and ICRISAT collections except the degree of Brix and fresh biomass respectively across the year. The year and genotype interaction (Y&amp;times;G) was not significant in all the biofuel attributes of Dutch accessions. Additive main effect and multiplicative interaction (AMMI) analysis of variance showed significant effect of G, E and the GEI. The AMMI was used to identify the best performing, adaptable and more stable genotypes. Twenty-two genotypes of both ICRISAT and Dutch accessions were identified to be stable across the two locations with respect to different biofuel attributes. Nine, seven, and six genotypes were found to be stable for grain yield, biomass yield and brix value, respectively. The best performing genotypes for stem sugar across locations were identified. From the available data collected, the performance of the sweet sorghum was attributed to both genetic and environmental effects. High GE was observed to influence stability, hence will influence the selection criteria of the sweet sorghum genotypes.

Phenotypic and molecular characterization of sweet sorghum accessions for bioenergy production.

Sweet sorghum [Sorghum bicolor (L.) Moench] is a type of cultivated sorghum characterized by the accumulation of high levels of sugar in the stems and high biomass accumulation, making this crop an important feedstock for bioenergy production. Sweet sorghum breeding programs that focus on bioenergy have two main goals: to improve quantity and quality of sugars in the juicy stem and to increase fresh biomass productivity. Genetic diversity studies are very important for the success of a breeding program, especially in the early stages, where understanding the genetic relationship between accessions is essential to identify superior parents for the development of improved breeding lines. The objectives of this study were: to perform phenotypic and molecular characterization of 100 sweet sorghum accessions from the germplasm bank of the Embrapa Maize and Sorghum breeding program; to examine the relationship between the phenotypic and the molecular diversity matrices; and to infer about the population structure in the sweet sorghum accessions. Morphological and agro-industrial traits related to sugar and biomass production were used for phenotypic characterization, and single nucleotide polymorphisms (SNPs) were used for molecular diversity analysis. Both phenotypic and molecular characterizations revealed the existence of considerable genetic diversity among the 100 sweet sorghum accessions. The correlation between the phenotypic and the molecular diversity matrices was low (0.35), which is in agreement with the inconsistencies observed between the clusters formed by the phenotypic and the molecular diversity analyses. Furthermore, the clusters obtained by the molecular diversity analysis were more consistent with the genealogy and the historic background of the sweet sorghum accessions than the clusters obtained through the phenotypic diversity analysis. The low correlation observed between the molecular and the phenotypic diversity matrices highlights the complementarity between the molecular and the phenotypic characterization to assist a breeding program.

Evaluation of sweet sorghum accessions for seedling cold tolerance using both lab and field cold germination test

Objective: Seedling cold tolerance is one of the important traits for sweet sorghum production. This study is to evaluate the method for identification of sweet sorghum accessions with seedling cold tolerance using both lab cold germination and field early-spring cold planting. Methodology: Sorghum seeds were germinated in growth chamber (under lab cold condition) at a constant 12°C for five weeks. After two weeks, germinated seeds and germination rates were counted and calculated at weekly intervals for four times. The same seed lots for lab cold test were also planted 45 days earlier than the normal planting time in the field (early-spring cold planting). In addition to seedling dry weight, germinated seeds and seed germination rates were also counted and calculated at weekly intervals for three times. Results: In this study, a high correlation coefficient between lab germination rate and field germination rate (R2=0.503, p<0.0001) was observed. In general, lab germination rate can predict the field germination performance; but some discrepancies between field and lab tests were also observed for some accessions. Among 212 sweet sorghum accessions tested, several sweet sorghum accessions with seedling cold tolerance were identified from both lab and field tests. These accessions will be useful materials for development of sweet sorghum cultivars with early spring cold tolerance. Conclusion: Compared with the field test, the lab test is less labor intensive. For a large-scale screening of seedling cold tolerance, the lab test may be conducted initially followed by selection of superior accessions from the lab test for further evaluation under field conditions.

Characterization of Ethiopian Sweet Sorghum Accessions for 0Brix, Morphological and Grain Yield Traits

The improvement of sweet sorghum (Sorghum bicolor) for biofuel traits is getting more attention globally due to its sugar-rich stalk that can be used as a renewable energy product. An understanding and proper assessment of biofuel-related traits in sweet sorghum crop is an important step toward the development of superior cultivar. The study was conducted to characterize sweet sorghum collections of Ethiopia for 0Brix degree, some morphological and grain yield traits. A total of 180 accessions were collected and evaluated in two environments. The result revealed wide variability among the accessions collected from different regions. Collections from northern part of Ethiopia (Wello and Tigray) showed significantly high 0Brix mean value while collections from the rest of the regions (Hararge, West Shewa, East Wollega and Gojam) expressed lower 0Brix mean value but higher biomass for stalk sugar yield. Most of the accessions showed higher 0Brix mean value, which is similar to globally known sweet sorghum cultivars. Accessions with high 0Brix degree combined with high biomass traits like stalk diameter and plant height will be an ideal germplasm to be used for biofuel production. Hence, it is imperative to utilize these accessions in sweet sorghum breeding program in order to develop superior sugar-rich sweet sorghum cultivars.

Evaluation of Whorl Damage by Fall Armyworm (Lepidoptera: Noctuidae) on Field- and Greenhouse-Grown Sweet Sorghum Plants

Abstract The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an economically important pest of sorghum, Sorghum bicolor (L.) Moench. However, resistance to fall armyworm in sweet sorghum has not been extensively studied. A collection of primarily sweet sorghum accessions were evaluated in the field for natural fall armyworm infestation. Fall armyworm damage ratings ranged from 1.88 ± 0.35 to 4.75 ± 0.37, suggesting that a range of response to fall armyworm feeding exists in this collection. Based on the results of field data from two planting dates, accessions with the highest and lowest fall armyworm damage ratings were selected for greenhouse evaluations. At 7 d after infestation, the sorghum accessions, excluding BTx623 and Plant Introduction (PI) 147573, had significantly higher fall armyworm damage than resistant control MP708. Furthermore, at 7 d after the infestation, genotype PI 147573 was the most resistant; whereas, genotypes 13, 22, ‘GT-IR8′, and ‘GT-IR6′ were th...

A near infrared spectroscopic assay for stalk soluble sugars, bagasse enzymatic saccharification and wall polymers in sweet sorghum

In this study, 123 sweet sorghum (Sorghum bicolor L.) accessions and 50 mutants were examined with diverse stalk soluble sugars, bagasse enzymatic saccharification and wall polymers, indicating the potential near infrared spectroscopy (NIRS) assay for those three important parameters. Using the calibration and validation sets and modified squares method, nine calibration optimal equations were generated with high determination coefficient on the calibration (R2) (0.81–0.99), cross-validation (R2cv) (0.77–0.98), and the ratio performance deviation (RPD) (2.07–7.45), which were at first time applied by single spectra for simultaneous assay of stalk soluble sugars, bagasse hydrolyzed sugars, and three major wall polymers in bioenergy sweet sorghum.

Tapping the US Sweet Sorghum Collection to Identify Biofuel Germplasm

The narrow genetic base in sweet sorghum [Sorghum bicolor (L.) Moench] breeding programs is limiting the development of new varieties for biofuel production. Therefore, the identification of genetically diverse sweet sorghum germplasm in the U.S. National Plant Germplasm System (NPGS) collection is imperative for biofuel breeding programs as biofuel production expands to new regions. Nine-hundred twenty-five sweet sorghum accessions from the NPGS collection were agronomically evaluated and a subset of 56 accessions selected for further evaluation. A 2 year replicated trial of this subset together with 17 U.S. sweet sorghum varieties were evaluated for agronomic and biofuel traits flowering time, plant height, fresh and dry weight, brix, juice volume, percent of moisture, and fermentable sugars [dinitrosalicylic (DNS) method] and disease response [anthracnose (Colletotricum sublineolum) and rust (Purcina purpurea)]. Nine accessions from the NPGS collection originally from South Africa, Ethiopia, Sudan, Zimbabwe, and the U.S. showed brix values ranging from 10 to 14, with five accessions having a higher amount of fermentable sugars than U.S. references accessions (DNS = 9.86–11.42). Likewise, the total dry matter content of three accessions originally from Ethiopia and U.S. were higher than the U.S. reference accessions (>156.87 g/plant). Multiple new sources of anthracnose and rust resistance were identified; being PI 156424 from Tanzania resistant to both diseases. The results demonstrated that accessions in the NPGS sorghum collection enclose valuable genes/alleles for biofuel traits that are not being used in U.S. biofuel breeding programs. Thus, the integration of these accessions into these programs will aid to increase genetic diversity and development of new biofuel varieties.

Absorption of different sorghum accessions on heavy metals in polluted soil

利用重金属含量较高的污水污染土壤, 以未污染土壤作对照, 种植8个甜高粱品种、2个饲用高粱品种和1个粒用高粱品种, 检测8种重金属在高粱植物体内不同器官的含量, 以研究不同高粱种质对重金属的吸收特性。结果表明: 甜高粱对汞(Hg)、镉(Cd)、锰(Mn)和锌(Zn)的吸收在两种土壤间差异显著, 对钴(Co)、铬(Cr)、铅(Pb)和铜(Cu)的吸收差异不显著。Mn在甜高粱体内含量表现为未污染土壤高于污染土壤; 而Zn含量在不同器官之间存在差异, 未污染土壤叶中含量远高于穗, 穗中含量远高于茎和根。不同重金属在甜高粱体内的储存部位不同, 污染土壤上Hg、Cd、Co、Cr和Zn在根中积累量较高, Cu、Mn和Pb在穗中的积累量较高。甜高粱、饲用高粱和粒用高粱对重金属的吸收、运输及储存在品种之间差异较大, 同一品种对不同重金属的吸收也存在差异。饲用高粱表现为叶部对Cr和Zn的储存量较高, 而粒用高粱'晋中0823'则显示了茎对多种重金属的储存能力。高粱根对土壤中重金属的富集系数较高, 为0.02(Pb)~0.23(Cd), 转移系数变幅为0.21(Co)~3.42(Pb)。对同一种重金属的吸收量品种间差异较大, 甜高粱'西蒙'根对Co、Cr、Cu、Mn、Pb和Zn具有高富集系数, 粒用高粱'晋中0823'茎对Hg、Cd、Mn、Pb和Zn富集系数较高。高粱对重金属的吸收能力与转移能力不同步, 甜高粱'绿能1号'具有对多种重金属的高转移能力, 粒用高粱'晋中0823'只对Zn有较高的转移能力。因此本文认为甜高粱对不同重金属的吸收和转移有选择性。对Zn吸收并转移到地上部后, 首先储存在叶和穗中, 当吸收量足够大时, 茎和根也成为储存器官; 对Mn的吸收与其他重金属的吸收存在竞争作用, Hg吸收后很少向地上部转移; 而对Cu、Mn和Pb吸收后在穗部的储存量较大。饲用高粱与甜高粱相比对重金属的吸收未显示明显的不同, 甜高粱'西蒙'根对多种重金属具有强储存能力, 而粒用高粱'晋中0823'的茎秆显示了比甜高粱更强的储存能力, 甜高粱'绿能1号'对多种重金属的转移能力较强。所以, 选择富集和转移能力均强的高粱品种能更有效地吸收土壤中的重金属, 达到修复污染土壤的目的。

Sugar-rich sweet sorghum is distinctively affected by wall polymer features for biomass digestibility and ethanol fermentation in bagasse

Sweet sorghum has been regarded as a typical species for rich soluble-sugar and high lignocellulose residues, but their effects on biomass digestibility remain unclear. In this study, we examined total 63 representative sweet sorghum accessions that displayed a varied sugar level at stalk and diverse cell wall composition at bagasse. Correlative analysis showed that both soluble-sugar and dry-bagasse could not significantly affect lignocellulose saccharification under chemical pretreatments. Comparative analyses of five typical pairs of samples indicated that DP of crystalline cellulose and arabinose substitution degree of non-KOH-extractable hemicelluloses distinctively affected lignocellulose crystallinity for high biomass digestibility. By comparison, lignin could not alter lignocellulose crystallinity, but the KOH-extractable G-monomer predominately determined lignin negative impacts on biomass digestions, and the G-levels released from pretreatments significantly inhibited yeast fermentation. The results also suggested potential genetic approaches for enhancing soluble-sugar level and lignocellulose digestibility and reducing ethanol conversion inhibition in sweet sorghum.

Identification of Sweet Sorghum Accessions Possessing Multiple Resistance to Shoot Fly (Atherigona soccata Rondani) and Spotted Stem Borer (Chilo partellus Swinhoe)

Thirty-two sweet sorghum genotypes were evaluated for resistance to shoot fly and stem borer during rainy seasons 2009–2012. The parameters viz., seedling vigour, glossiness, dead-hearts caused by shoot fly, stem borer, stem borer leaf damage score, stem borer stalk tunneling, stem borer exit holes and stem borer larvae/stalk were assessed for their contribution in imparting resistance to A. soccata and C. partellus. None of the traits considered could discriminate entries as resistant/ susceptible individually. In view of the complexity of interactions between A. soccata,C. partellus with sorghum, principal component analysis was applied considering seven parameters viz., seedling vigour, seedling glossiness, dead-hearts caused by shoot fly, stem borer, stem borer stalk tunneling, stem borer exit holes/stalk and larvae recovered/stalk. Two principal components were extracted explaining a cumulative variation of 84.6 %. PC1 and PC2 explained 69.5 and 15.1 % of the variations, respectively indicating that seedling vigour, glossiness, dead-hearts caused by both pests, stem borer exit holes/stalk were the most reliable parameters for characterization of multiple resistances to A. soccata and C. partellus. The sweet sorghum lines IS 5353, IS 18164, ICSV 93046, ICSV 700, GGUB 50 were classified as resistant to both the pests. The multiple resistant lines with durable resistance can be employed in future sweet sorghum breeding programs for enhancing levels of resistance to shoot fly and stem borer.

Assessment of Genetic Variability of 142 Sweet Sorghum Germplasm of Diverse Origin with Molecular and Morphological Markers

Sorghum bicolor (L.) Moech is the fifth most important crop in the world. Recently, its agronomics and genetics have drawn interest among scientists. Sweet sorghum, a variety of sorghum, may potentially become a bioenergy source because of the high sugar content in its juicy stems. Exploring the diversity of sweet sorghum around the world is important to the development and improvement of the crop as an energy source. In exploring the diversity of sweet sorghum, three types of markers (simple sequence repeats [SSR], sequence-related amplified polymorphisms [SRAP], and morphological markers) are used on 142 sweet sorghum accessions from around the world. The accessions show a high significance (P < 0.05) for all the morphological traits measured. The morphological markers cluster the accessions into five groups based primarily on plant height (PH), anthesis data (AD), and moisture content (ML), with the principal component analysis (PCA) showing these traits to explain 92.5% of the total variation. The furthest accessions were PI571103 from Sudan, and N99 from the United States. The Nei’s genetic standard distances ranged from 0.024 to 1.135 and 0.078 to 0.866 for SSR and SRAP, respectively. As expected, accessions of the same origin or breeding history had the lowest genetic distance (e.g. Mokula and Marupantse, both from Botswana; NSL83777 and NSL83779 from Cameroon). Neighbor joining clusters the sweet sorghum accessions into five major groups using SSR and four major groups using SRAP, based on their origin, or breeding history. The three marker types complement each other, and the presence of accessions of different origins across clusters indicate similar genetics, and evidence of germplasm movement between countries.

Agro-industrial potential of sweet sorghum accessions grown under semi-arid conditions

The current world-wide interest in alternative and sustainable forms of energy is providing an opportunity for carving new pathways of development in many countries. Plants are particularly attractive vehicles in this regard because of their innate capacity to self-renew and to produce chemical forms of energy every time. Carbohydrates and oils as primary products from plants are attractive raw materials for the production of alternative forms of energy such as bioethanol and biodiesel. Against this background, this study was undertaken to assess the potential of sweet sorghum as a feedstock for bioethanol production. To this end, a comparative analysis of non-structural carbohydrate amounts in mature stems of several local accessions of sweet sorghum was carried out. For comparison, the same products were also determined in mature stems of sugarcane. Sucrose was the predominant sugar in the mature stems of sweet sorghum as was the case with sugarcane. However, the overall carbohydrate profiles of sweet sorghum were markedly different from those of sugarcane. Mature stems of sweet sorghum contain more readily fermentable sugars than mature sugarcane stems. In addition, sweet sorghum also accumulates starch in the stems as well as in the seeds. Through hydrolysis, this serves as an additional source of glucose for fermentation into ethanol. These data clearly demonstrate the renewable energy resource potential of sweet sorghum. Nonetheless, further studies on the basic biology of carbohydrate partitioning in sweet sorghum are warranted. Such studies could provide rational basis for improvement of wet-fermentation substrate yield of this crop. Key words : Metabolism, non-structural carbohydrates, renewable energy, substrates, sucrose, trade-offs, wet fermentation.