Volume 6 Special Issue 1 2012
Sorghum

ISBN 978-4-903313-93-1

How to reference: Liang Y (2012) Sorghum: Genetic Improvement for Biofuel. In: Dobránszki J (Ed) Sorghum. The European Journal of Plant Science and Biotechnology 6 (Special Issue 1), 1-9

Guest Editor

Judit Dobránszki

Research Institute of University of Debrecen, Centre for Agricultural and Applied Economic Sciences, Hungary

CONTENTS AND ABSTRACTS

Yanna Liang (USA) Sorghum: Genetic Improvement for Biofuel (pp 1-9)

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Invited Review: During recent years, sorghum has drawn intensive attention from the scientific community and policy decision-makers. Three categories of sorghum, grain, forage, and sweet sorghum can be used differently for producing bioethanol and other kinds of biofuels. While grains from grain sorghum and juice from sweet sorghum are readily fermentable, the sorghum stalk which is a lignocellulosic material is recalcitrant. To utilize sorghum as a bioenergy crop, however, the biomass quality and yield must be enhanced. Highly fermentable and highly digestable lines are extremely desirable but research on this aspect is lagging behind those of other crops, such as maize. With numerous genes affecting sorghum quality being known, it is reasonable to expect that sorghum can be improved to serve as a biomass plant well through genetic and molecular breeding. Over the years, genetic modification of sorghum has been mainly conducted in three areas: 1) reducing lignin content by establishing brown midrib mutants and understanding the genetic mechanisms for lignin reduction; 2) developing cold tolerant progenies and identifying quantitative trait loci (QTL) related to cold tolerance; and 3) investigating sugar related traits with the aim of increasing contents of sugar and nonstructural carbohydrates. This review provides detailed information on how these studies are carried out. Future research directions are also recommended for transforming sorghum from a promising crop to a truly invaluable plant in the biofuel arena.

Christopher R. Little, Ramasamy Perumal, Tesfaye Tesso, Louis K. Prom, Gary N. Odvody, Clint W. Magill (USA) Sorghum Pathology and Biotechnology - A Fungal Disease Perspective: Part I. Grain Mold, Head Smut, and Ergot (pp 10-30)

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Invited Review: Three common sorghum diseases, grain mold, head smut and ergot, each of which is directly related to seed production and quality are covered in this review. Each is described with respect to the causal organism or organisms, infection process, global distribution, pathogen variability and effects on grain production. In addition, screening methods for identifying resistant cultivars and the genetic basis for host resistance including molecular tags for resistance genes are described where possible.

Tesfaye Tesso, Ramasamy Perumal, Christopher R. Little, Adedayo Adeyanju, Ghada L. Radwan, Louis K. Prom, Clint W. Magill (USA) Sorghum Pathology and Biotechnology - A Fungal Disease Perspective: Part II. Anthracnose, Stalk Rot, and Downy Mildew (pp 31-44)

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Invited Review: Foliar diseases and stalk rots are among the most damaging diseases of sorghum in terms of lost production potential, thus commanding considerable research time and expenditure. This review will focus on anthracnose, a fungal disease that causes both foliar symptoms and stalk rots along with the stalk rots caused by Fusarium spp. and Macrophomina phaseolina. Although the downy mildews are caused by oomycetes rather than true fungi, recent outbreaks have revealed resistance to previously effective chemical seed treatments and the evolution of new pathogenic races, once again pointing out the need for continuous vigilance. Sorghum diseases are described with respect to the causal organism or organisms, infection process, global distribution, pathogen variability and effects on grain production. In addition, screening methods for identifying resistant cultivars and the genetic basis for host resistance including molecular tags for resistance genes are described where possible along with prospects for future advances in more stable disease control.

I. K. Das, S. Audilakshmi, J. V. Patil (India) Fusarium Grain Mold:The Major Component of Grain Mold Disease Complex in Sorghum (Sorghum bicolor L. Moench) (pp 45-55)

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Invited Review: Sorghum grain mold, particularly Fusarium and Curvularia grain mold, are important on improved, short- and medium-duration sorghum cultivars worldwide. There is hardly any literature that deals with Fusarium grain mold as a component of sorghum grain mold disease complex in detail. This review summarizes many aspects related to Fusarium grain mold: typical symptoms, causal organisms in relation to mold development phases, colonization processes, nature of damage and its significance on yield and quality and management options. The review also attempts to shortlist probable mechanisms that might be useful for developing resistance against early infection events. There are three major and proven pathogenic species of Fusarium (F. andiyazi, F. proliferatum and F. thapsinum) that are capable of infecting sorghum flower. Others are predominantly saprophytes. Some strains of these species are highly toxigenic and responsible for Fusarial-toxicoses in human beings, animals and poultry birds. There is necessity to identify resistance against Fusarium grain mold in general and toxigenic strains in particular and incorporate the resistance in new varieties and hybrids of sorghum.

Joshua H. Wong, Jeffrey F. Pedersen, Bob B. Buchanan, Peggy G. Lemaux (USA) Western Blot Analysis Uncovers Clues to Prolamin Digestibility in Raw and Cooked Meal from Sorghum and Corn (pp 56-65)

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Original Research Paper: Digestibility of cereal grain protein is conventionally expressed as percentage of protein digested by pepsin in a defined period. Sorghum has the lowest protein digestibility among cereals especially after wet cooking. If additional details were known as to which proteins are resistant to digestion, it should be possible to find means to improve this property. In this paper, two approaches are described to extract and identify proteins undigested by pepsin in uncooked and cooked meal from numerous sorghum and corn varieties. The first, one-solvent approach involves extracting residues undigested after 2 h with Borate-SDS-ME and separating by PAGE. Improved separation of undigested sorghum proteins was achieved using NuPAGE Bis-Tris gels. Western blots with antibodies against particular zeins and kafirins, used to monitor fates of different kafirins, revealed differential digestion rates. A second approach involved extracting undigested residues sequentially with 60% t-butanol, 60% t-butanol-ME and Borate-SDS-ME. The second, three-solvent approach, coupled with western analysis, revealed the following. (i) Oligomeric forms of certain kafirins exist that differ in the degree of their susceptibility to pepsin digestion. (ii) Effect of cooking on the formation and digestion of the oligomers. (iii) Cross-linked forms of most α-kafirins became more resistant to digestion after cooking. (iv) Most α-kafirins are preferentially extracted in 60% t-butanol-ME while most γ-kafirins are extracted in Borate-SDS-ME buffer. (v) Monomeric γ-kafirins are resistant to pepsin digestion. (vi) γ-Kafirins form a series of oligomers that exhibit differential resistance to digestion. Our results suggest that the presently described systematic approach to analyzing the digestion by pepsin of sorghum prolamins should lead to greater insights into the digestion of specific types of sorghum grain proteins.

A. Ashok Kumar, Belum V. S. Reddy, B. Ramaiah, K. L. Sahrawat (India), Wolfgang H. Pfeiffer (Colombia) Genetic Variability and Character Association for Grain Iron and Zinc Contents in Sorghum Germplasm Accessions and Commercial Cultivars (pp 66-70)

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Original Research Paper: Sorghum a widely consumed cereal stapled in sub-tropical and semi-arid regions of Africa and Asia. Sorghum is the second cheapest source of energy and micronutrients (after pearl millet). Micronutrient malnutrition, primarily the result of diets poor in bio-available vitamins and minerals, causes blindness and anemia (even death) in more than half of the world’s population, especially among women and children. Biofortification wherever possible, is a cost effective and sustainable solution for tackling the micronutrient deficiencies as the intake of micronutrients is on a continuing basis with no additional costs to the consumer. ICRISAT is working on sorghum biofortification for enhancing Fe and Zn contents of the grain. Large variability for grain Fe and Zn contents was found from assessment of core germplasm collections (>2200), and from these, promising donors were identified for further improvement. Significant positive association observed between grain Fe and Zn contents indicated that it is feasible to develop high Fe and Zn containing cultivars with high yielding and different maturity backgrounds. The commercial sorghum cultivars (66) currently being cultivated by the farmers in India, were evaluated to identify high Fe and Zn cultivars in adapted backgrounds. Identification of commercial cultivars with high grain Fe and Zn content would help in wider dissemination of the cultivars to complement the on-going efforts for combating the micronutrient malnutrition.

Pinnamaneni Srinivasa Rao, Santosh Deshpande, Michael Blümmel, Belum V. S. Reddy, Tom Hash (India) Characterization of Brown Midrib Mutants of Sorghum (Sorghum bicolor (L.) Moench) (pp 71-75)

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Original Research Paper: Twenty brown midrib (bmr) mutants of sorghum (Sorghum bicolor (L.) Moench) were evaluated for agronomic traits, forage quality traits and the relationships between these traits. Potential fodder quality was assessed by laboratory analysis. Significant differences were observed among the bmr mutants (bmr1, 3, 6, 7, 8 and two new mutants) for stover yield, plant height, stover nitrogen (N) content, in vitro organic matter digestibility (IVOMD), metabolizable energy (ME) content and acid detergent lignin (ADL) content. The bmr mutants such as IS 23253, IS 21549, IS 23789 and IS 23787 had high stover yield coupled with better forage quality, hence these mutants can be exploited in future bmr hybrid breeding programs. All of these had reduced cinnamyl alcohol dehydrogenase (CAD) activity except for the new and uncharacterized bmr mutant, IS 23253, whose allelic relationship is yet to be determined.

Pinnamaneni Srinivasa Rao, Michael Blümmel, Belum V. S. Reddy (India) Enhancement of in Vitro Digestibility of Sorghum (Sorghum bicolor (L) Moench) in Brown Midrib (bmr) Mutant Derivatives of bmr1 and bmr7 (pp 76-80)

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Original Research Paper: Ten sorghum derivatives with brown midrib alleles (bmr1 and bmr7) were investigated for stover fodder quality traits, grain yield and the relationships between these productive traits. Potential fodder quality was assessed by laboratory analysis. Significant differences were observed among the tested derivatives of bmr1 allele for stover nitrogen (N) content, in vitro organic matter digestibility (IVOMD), and acid detergent lignin (ADL) content. In contrast, no significant genotypic differences were observed among bmr7derivatives. In the bmr1gene derivatives stover N content ranged from 0.63 to 0.81%, ADL content varied from 2.6 to 3.2% and IVOMD ranged from 52.9 to 55.4%. Two lines have recorded over 55% IVOMD and higher grain yield than the bmr1 source. In bmr7 derivatives IVOMD ranged between 52.9 and 54.4%. The enhanced IVOMD coupled with improved grain and biomass yield in bmr1 and bmr7 derivatives will increase overall benefits from sorghum in mixed crop livestock systems. This is the first study on utilization of bmr1and bmr7mutants in improving the forage quality of tropical sorghums with perceptible genetic enhancement of candidate biomass and grain yield traits.

Dariush Minai-Tehrani, Aidin Tavakoli Tameh, Ali Rashidfarokhi, Alireza Noormohammadi, Amirabbas Khodakarami, Majid Talebi (Iran) The Effect of Light Crude Oil-Contaminated Soil on the Growth and Germination of Sorghum bicolor (pp 81-84)

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Original Research Paper: Light crude oil has volatile components that can be toxic to living organisms when spilled to the soil and water. The use of plants for treatment of crude oil-contaminated soil has been of particular interest in environmental cleansing. Some plants have demonstrated to have a good capacity for biodegrading oil in soil. In this study the growth and germination of Sorghum bicolor was studied in the presence of different concentrations of light crude oil (1-10%) in the soil. Root and shoot biomass, leaf length and germination percentage decreased as crude oil concentration increased. Light crude oil delayed germination and affected the normal growth of S. bicolor, inducing chlorosis in plants. The measurement of total petroleum hydrocarbons (TPHs) of soil at the end of treatment (45 days) showed that TPH was more reduced in the 1% sample than in the 7 and 10% samples. S. bicolor can be a good plant for phytoremediation of oil-contaminated soil when the concentration of crude oil is lower than 3% in the soil.

László Radics, Izóra Gál, Imre Kádár (Hungary) Effect of Rising Dose of NPK Fertilizers on Weeds of Grain Sorghum (Sorghum bicolor) on a Calcareous Loamy Chernozem Soil (pp 85-89)

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Original Research Paper: The effect of different NPK levels (poor, satisfactory, excessive and toxic) and combinations of these on the soil cover percentage of natural weed flora of grain sorghum (Sorghum bicolor) was studied on a loamy chernozem soil with lime deposit. The N levels were 0 (poor), 100 (satisfactory), 200 (excessive) and 300 (toxic) kg ha^-1 year^-1; P and K fertilizing was done with 0 (poor), 500 (satisfactory), 1000 (excessive), 1500 (toxic) kg ha^-1 P₂O₅ and K₂O refilling doses. Later only sustaining of PK levels were targeted, reapplication was repeated every 5-10 years. P and K fertilizer and half of the N fertilizer was spread in autumn before ploughing the plots, the other half of N was spread in spring in the form of 25-28% calcium ammonium nitrate, 18% superphosphate and 40-60% potassium chloride. The mineral fertilization experiment series was initiated in autumn 1973. Different crops were produced on these plots annually. Grain sorghum was sown in 1992. This long-term experiment series consisted of 4N × 4P × 4K= 64 treatments, or nutritional levels, in two replications, giving a total of 128 plots. The plot size was 6 × 6 = 36 m² in mixed factorial design. Weed surveys were done in 4 m² quadrats in two replications and contained not only weed flora but crop cover, too. The number of weed species, the weed and crop soil cover were highly dependent upon the doses and ratio of different fertilizers.

Éva B. Ábrahám, Nóra Őri, Sándor Szabó, Lajos Blaskó, György Zsigrai (Hungary) Effects of Whitening Process on the Quality of Different Grain Sorghum Hybrids (pp 90-93)

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Short Communication: The effect of whitening on the nutritional profile of grain sorghum was examined in this work. Three commercial hybrids, the white seeded ‘Albita’ and the red seeded ‘Zador’ along with another red-seeded hybrid check were examined. Grain samples drawn from the grain sorghum crop were whitened using the whitener part of a laboratory rice mill. Tannin content, total scavenger capacity, and total phenol content were determined in the whole grain sample, the whitened grains and the bran fraction. The concentration of essential mineral elements (N, P, K, Mg, Ca, Cu, Mn, Fe, Zn) was also measured in whole grains and whitened grains. Tannin content, scavenging capacity and phenol concentration were significantly different among the hybrids and between grain sample fractions; bran had the highest proportion of these compounds in all genotypes. Differences among hybrids with respect to mineral content were not significant in most of the examined elements. Larger differences between the hybrids were only found for N and Fe content. Whitening did not change the element content of the hybrids.