Author: Alejandro Zamora-Melendez
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

Get Book Here

Book Description
Several studies have shown that disease resistance genes diverge under recurrent positive selection as a result of a molecular arms-race between hosts and pathogens. However, these studies have been conducted mainly in animals and few plant genes have been shown to evolve adaptively. The study of plant molecular adaptation for disease resistance is fundamental to our understanding of plant-microbe interactions and to the development of novel plant breeding strategies. Here, we combined information from the expression pattern of Sorghum bicolor genes and their divergence to rice in order to identify candidate disease response genes (DRGs). We used evolutionary analyses of orthologous DRG sets from grass species to identify positively selected genes and the targeted residues. Six genes showed a pattern of substitution consistent with positive selection: a thaumatin, a peroxidase and a barley mlo homolog, all known antifungal proteins; and a MADS box gene, an eIF5 gene and a gene of unknown function: SESPY. All adaptive sites mapped to the surface of the crystal structures of peroxidase and thaumatin and several are close to the active sites. This information provides a basis for functional validation studies, the identification of accessions having variation at important residues and the rational design of DRGs. Rapid divergence through positive selection should correlate to reduced intraspecific polymorphism. Here we compare the macroevolution and intraspecific polymorphism of positively selected disease response genes and show that the patterns of polymorphism found are consistent with both selective sweeps and balancing selection. The sorghum mlo homolog and SESPY, have old, divergent alleles, while a peroxidase and a gene with a RNA binding domain have significantly reduced diversity suggesting a recent selective sweep. Finally, we show that sorghum DRGs are significantly closer to the telomere and have more exons than a control set of evenly expressed genes. The evidence from gene location; structure; macro-evolution and polymorphism of these DRGs point to the great selective pressure produced by pathogens which has driven the evolution of cereal genome content, order and function.

Author: Yi-Hong Wang
Publisher: CRC Press
ISBN: 1482210096
Category : Science
Languages : en
Pages : 366

Get Book Here

Book Description
Sorghum is one of the hardiest crop plants in modern agriculture and also one of the most versatile. Its seeds provide calorie for food and feed, stalks for building and industrial materials and its juice for syrup. This book provides an in-depth review of the cutting-edge knowledge in sorghum genetics and its applications in sorghum breeding. Each

Author: Bin Liu
Publisher:
ISBN:
Category :
Languages : en
Pages :

Get Book Here

Book Description
Sorghum (Sorghum bicolor L. Moench) is an important member of the Poaceae family. It is a highly resilient crop that is drought and cold tolerant, and capable of surviving in the areas that would otherwise not support other cereal crops like maize. One of the major challenges in sorghum production is anthracnose leaf blight caused by Colletotrichum sublineolum. Understanding the mechanisms by which sorghum combat anthracnose is key to breeding for resistant cultivars. Plants combat disease infection through several ways: Passive defense mechanisms are thickening of cell wall, growth of waxy layers, epidermal outgrowth etc. Active defense mechanisms leading to hypersensitive response, which appears as localized cell death, synthesis of phytoalexins and antibiotic compounds. Sorghum is unique in the Poaceae family in its ability to synthesize 3-deoxyanthocyanidins (3-DAs), a sub-class of flavonoids. These compounds have been shown to act as phytoalexins that accumulate as brick red pigments at the primary site of attempted penetration by the fungus. Because of their anti-fungal properties, 3-DA phytoalexins can limit fungal progression. Sorghum phytoalexins include luteolinidin, apigeninidin and their methoxylated derivatives. We are interested in investigating detailed biosynthetic pathways of 3-DAs in sorghum as well as signal transduction events that lead to the resistance responses imparted via the 3-DAs. Following are my thesis objectives: 1. Interaction of sorghum Y1 transcription factor with maize flavonoid structural genes during pathogen defense response. Based on the structural similarities of 3-DAs and flavan-4-ols (see Figure 1 in Chapter 1), it has been hypothesized that 3-DAs are also synthesized via the flavonoid pathway branch which leads to the production of phlobaphenes in sorghum. An R2R3 MYB transcription factor encoded by yellow seed1 (y1) has been shown to be required for the biosynthesis of flavan-4-ols and phlobaphenes in the pericarp and leaf tissues. Using a transposon insertion mutant in y1, our lab has shown that the y1 gene is also required for the accumulation of 3-DAs in Colletotrichum sublineolum challenged sorghum leaves. Further, transformation of sorghum y1 gene into maize showed induced disease resistance response to Colletotrichum graminicola, establishing that the y1 gene can induce maize structural genes to accumulate 3-DAs in maize. In addition, that study indicated the y1 promoter contains cis- regulatory elements that are possibly involved in regulation of y1 during fungal challenges. Despite the above-mentioned results, we do not exactly know the flavonoid branch and the structural genes that are required for the biosynthesis of 3-DAs. It is also possible that 3-DAs either originate from a separate branch from naringenin, or these are simply derived from flavan-4-ols as a precursor. To identify the flavonoid branch leading to 3-DAs, we first transferred sorghum y1 to maize and then used maize mutants of flavonoid structural genes because of the non-availability of such mutants in sorghum. Our results showed that y1 transgene can regulate the expression of all the maize flavonoid genes tested. We also found that this induced expression was correlated with the observed disease resistance phenotype. This study indicates that the anthocyanidin synthase encoded by a2 in maize also have novel influence on flavan-4-ols and 3-DAs accumulation. Furthermore, through the accumulation of total phenolics, we have found that the y1-driven flavonoid pathway as a whole promoted the total phenolic accumulation. 2. Expression of phytohormones salicylic acid and jasmonic acid genes during the 3-DA biosynthesis in sorghum and maize. Currently, the upstream regulation of y1 remains relatively unclear. We attempted to understand signal transduction events upstream of y1 by measuring phytohormones that may have a role in early signaling events. Two phytohormones particularly important in plant defense are jasmonic acid (JA) and salicylic acid (SA). Previous studies focusing on the effect of exogenous phytohormones on 3-DA pathway have yielded conflicting results. In this work, sorghum mesocotyls and transgenic y1 maize lines were inoculated to study the internal interactions between the transcription of key genes in the SA and JA phytohormonal pathways and the accumulation of 3-DAs. Our results indicate a dual mode of 3-DAs regulation: JA is involved in disease triggered 3-DAs accumulation, and SA is involved in wounding triggered 3-DAs accumulation. 3. Cell wall component profiling for biomass improvement in sorghum using Fourier-Transform Near-infrared Spectroscopy. Cell wall composition plays a major role in the plant immune system, both as a source of primary, and secondary defenses. It is also the basis for lignocellulose biomass. This objective of my thesis was to explore biomass diversity cell wall composition in sorghum. My goal is to correlate this information with anthracnose resistance in sorghum. Currently, we have a collection of over 800 sorghum lines, representing a wide variety of grain, forage, bioenergy, and sweet sorghum in diversity. To fully exploit these lines and to understand the genetic variation contributing to sorghum lignocellulosic biomass accumulation, we developed and tested a high throughput method. In collaboration with Dr. Seong Kim's Laboratory, Fourier-transform Near Infrared (FT-NIR) Spectroscopy was used to characterize the cell wall composition in sorghum. Cell wall content assayed by FT-NIR showed high fidelity compared to that produced by wet chemistry laboratory while reducing both analysis time and sample size needed by order of magnitudes. Our results show FT-NIR is a useful method to fully exploit the large number of germplasm lines available in our collection. In conclusion, by understanding the regulatory role of y1 transcription factor in phytoalexins biosynthesis, and the role of phytohormones synthesized during 3-DAs accumulation, we will gain a clearer picture of the active defense responses in sorghum. By quantifying cell wall component in a vast library of available germplasm, we can gain a better understanding of passive defense mechanisms. Breeding for increased defense against plant pathogens should be a holistic approach that combines both passive and active defense mechanisms.

Author: Davina Rhodes
Publisher:
ISBN:
Category : Anti-inflammatory agents
Languages : en
Pages : 167

Get Book Here

Book Description
Staple cereal crops provide the majority of nutrients to the world's population, and thus, can significantly impact human nutrition and health. Phenotypic and genetic diversity within a crop can be useful for biofortification and crop improvement, but quantitative phenotyping is needed to identify varieties with high or low concentrations of a nutrient of interest, and to identify alleles responsible for quantitative trait variation of the nutrient. Sorghum (Sorghum bicolor (L.) Moench) is a diverse and widely adapted cereal crop that provides food for more than 500 million people in sub-Saharan Africa and Asia, and is becoming increasingly popular in specialty grain products in the United States. Sorghum is a valuable resource for nutrient diversity, as adaptation to different environments has led to extensive phenotypic and genetic diversity in the crop. Many sorghum varieties are rich in flavonoids, primarily 3-deoxyanthocyanidins and proanthocyanidins, which appear to protect against chronic inflammatory diseases. Most studies have only explored the health benefits of a small number of sorghum accessions, but over 45,000 sorghum accessions exist in crop gene banks. A large genetically diverse sorghum panel can be used to identify varieties with high concentrations of flavonoids and to explore the effects of natural variation of sorghum flavonoids on inflammation. This same resource can also be used to identify varieties with high concentrations of protein, fat, or starch, which can lead to improved nutritional value of sorghum grain. The overall aim of my dissertation project was to quantify sorghum flavonoids and identify allelic variants controlling them; quantify grain composition more broadly (protein, fat, and starch) and identify allelic variants controlling them; and investigate anti-inflammatory properties of sorghum extracts with contrasting levels of flavonoids. Using a large germplasm resource (USDA National Plant Germplasm System), highthroughput methods of phenotyping (near-infrared spectroscopy) and genotyping (genotyping-by-sequencing), association mapping (genome-wide association studies), and in vitro inflammation models, the work presented here provides new insights into the diversity, genetics, and anti-inflammatory properties of sorghum nutrients that are important to human health. It provides a survey of grain nutrient diversity in a large global panel of sorghum, identifies quantitative trait loci and candidate genes for underlying controls of these nutrients, and demonstrates that a larger variety of sorghum accessions than previously thought have anti-inflammatory properties.

Author: R. Madhusudhana
Publisher: Springer
ISBN: 8132224221
Category : Technology & Engineering
Languages : en
Pages : 231

Get Book Here

Book Description
This book provides an up-to-date overview of international research work on sorghum. Its comprehensive coverage of our current understanding of transgenic development in sorghum and the strategies that are being applied in molecular breeding make this book unique. Important areas such as genetic diversity, QTL mapping, heterosis prediction, genomic and bioinformatics resources, post-genome sequencing developments, molecular markers development using bioinformatics tools, genetic transformation and transgenic research are also addressed. The availability of the genome sequence along with other recent developments in sequencing and genotyping technologies has resulted in considerable advances in the area of sorghum genomics. These in turn have led to the generation of a large number of DNA-based markers and resulted in the identification and fine mapping of QTL associated with grain yield, its component traits, biotic and abiotic stress tolerance as well as grain quality traits in sorghum. Though a large volume of information has accumulated over the years, especially following the sequencing of the sorghum genome, until now it was not available in a single reference resource. This book fills that gap by documenting advances in the genomics and transgenic research in sorghum and presenting critical reviews and future prospects. “Sorghum Molecular Breeding” is an essential guide for students, researchers and managers who are involved in the area of molecular breeding and transgenic research in sorghum and plant biologists in general.

Author: Kahiu Ngugi
Publisher: LAP Lambert Academic Publishing
ISBN: 9783846544365
Category :
Languages : en
Pages : 92

Get Book Here

Book Description
Sorghum bicolor (L) Moench is the fifth most important cereal crop globally and in Africa, it is the second most important after Maize. In Kenya, Sorghum is an important food security crop mainly cultivated in semi-arid agro-ecological zones on area of about 150,000 ha where annual rainfall is about 250mm . The major constraint to low yields is due to prolonged drought stress and frequent drought occurrence. In order to alleviate the low yields in the face of continuing climate change, there is need to identify germ-plasm that possesses drought tolerance genes/alleles and that can be harnessed to improve sorghum adaptation to drought stress. This study assessed the phenotypic and genotypic performance of sorghum local land-races grown in Kenya and characterized their genetic diversity under drought stress conditions. The results reported here showed that Kenyan sorghum germ-plasm is highly polymorphic and genetically diverse.The land-races can be categorized as having been selected for earliness or drought escape, drought tolerance as represented by the many newly identified stay-green genotypes and has also been selected for high yielding but drought susceptible alleles.

Author: Sarah June Schloss
Publisher:
ISBN:
Category :
Languages : en
Pages : 256

Get Book Here

Book Description

Author: Mohammad Shafiqurrahaman
Publisher:
ISBN:
Category :
Languages : en
Pages : 6

Get Book Here

Book Description

Author: Lydia Ndinelao Nghishikungu-Horn
Publisher:
ISBN:
Category : Sorghum
Languages : en
Pages : 236

Get Book Here

Book Description

Author: Jhansi Rani
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659437717
Category :
Languages : en
Pages : 268

Get Book Here

Book Description
Post rainy sorghum is unique to India, which is mostly grown on residual soil moisture in southern states, subjected to various biotic and abiotic stresses. Keeping in view the low heterosis in post rainy hybrids compared to rainy season hybrids, the study was taken up with 41 genotypes to enumerate the approaches for enhancing the level of heterosis. There was a positive relationship between heterosis for grain yield and major yield components. Genetic diversity analysis showed importance of inter as well as intra group divergence in expression of heterosis. There was a general positive trend between hybrid yield and sca effect but at least one general combiner was involved in highest yielding crosses and there was positive relationship between heterosis and mean gca of parents. Major yield components were controlled by non additive gene effects hence it is proposed to breed parental lines with high gca effect with capability to produce high sca effect in hybrid combination to enhance the level of heterosis and productivity. The information in this book is useful for sorghum breeders and geneticists for formulating effective crop improvement programme.