Cultivated Sorghum Research Articles

High rhizospheric ammonium levels in Sorghum halepense (johnsongrass) suggests nitrification inhibition potential

AbstractPlants, such as sorghum (Sorghum bicolor), have been shown to secrete root exudates involved in biological nitrification inhibition (BNI), an ability to suppress the conversion of ammonium to nitrate and thereby minimize its loss. Johnsongrass (Sorghum halepense), a weedy relative of cultivated sorghum, may also possess BNI potential, but little is known in this regard. Here, we conducted a field survey at seven different sites in Southeast Texas to determine this evolutionary trait of johnsongrass in different soil environments. It was found that johnsongrass rhizosphere retains high levels (>60%) of ammonium within the total available N (ammonium + nitrate). Furthermore, the degree of ammonium retention by johnsongrass rhizosphere was significantly greater (up to 40%) in the roadside habitat compared to cultivated fields. The high ammonium retention potential by johnsongrass may explain, in part, their persistence and dominance, especially in marginal environments.Core Ideas Nitrogen is a limiting nutrient for plant growth, and nitrification causes loss of nitrogen. Ammonium retention was higher in roadside johnsongrass biotypes compared to that of cropland biotypes. The high rhizoshpheric ammonium retention by johnsongrass may explain, at least in part, its invasiveness. This trait could be further investigated and integrated into modern sorghum cultivars.

Post-synthetic modification of nano-chitosan using gibberellic acid: Foliar application on sorghum under salt stress conditions and estimation of biochemical parameters

The challenge of desert farming with a high salt level has become an ecological task due to salt stress negatively affecting plant growth and reproduction. The current study deals with the cultivation of sorghum under salt stress conditions to counteract the effect of chitosan and gibberellic acid (GA3). Here, the effects of chitosan, GA3 and nano-composite (GA3@chitosan) on biochemical contents, growth and seed yield of sorghum under salinity stress conditions were studied. The results showed that spraying with GA3@chitosan increased sorghum grain yield by 2.07, 1.81 and 1.64 fold higher than salinity stressed plants, chitosan treatment and GA3 treatment, respectively. Additionally, compared to the control of the same variety, the GA3@chitosan spraying treatment improved the concentration of microelements in the grains of the Shandweel-1 and Dorado by 24.51% and 18.39%, respectively for each variety. Furthermore, spraying GA3@chitosan on sorghum varieties increased the accumulation of the macroelements N, P, and K by 34.03%, 47.61%, and 8.67% higher than salt-stressed plants, respectively. On the other hand, the proline and glycinebetaine content in sorghum leaves sprayed with nano-composite were drop by 51.04% and 11.98% less than stressed plants, respectively. The results showed that, in Ras Sudr, the Shandweel-1 variety produced more grain per feddan than the Dorado variety. These findings suggest that GA3@chitosan improves the chemical and biochemical components leading to a decrease in the negative effect of salt stress on the plant which reflects in the high-yield production of cultivated sorghum plants in salt conditions.

Overview of Cyanide Poisoning in Cattle from Sorghum halepense and S. bicolor Cultivars in Northwest Italy.

Sorghum plants naturally produce dhurrin, a cyanogenic glycoside that may be hydrolysed to cyanide, resulting in often-lethal toxicoses. Ruminants are particularly sensitive to cyanogenic glycosides due to the active role of rumen microbiota in dhurrin hydrolysis. This work provides an overview of a poisoning outbreak that occurred in 5 farms in Northwest Italy in August 2022; a total of 66 cows died, and many others developed acute toxicosis after being fed on either cultivated (Sorghum bicolor) or wild Sorghum (Sorghum halepense). Clinical signs were recorded, and all cows received antidotal/supportive therapy. Dead animals were subjected to necropsy, and dhurrin content was determined in Sorghum specimens using an LC-MS/MS method. Rapid onset, severe respiratory distress, recumbency and convulsions were the main clinical features; bright red blood, a bitter almond smell and lung emphysema were consistently observed on necropsy. The combined i.v. and oral administration of sodium thiosulphate resulted in a rapid improvement of clinical signs. Dhurrin concentrations corresponding to cyanide levels higher than the tolerated threshold of 200 mg/kg were detected in sorghum specimens from 4 out of 5 involved farms; thereafter, such levels declined, reaching tolerable concentrations in September-October. Feeding cattle with wild or cultivated Sorghum as green fodder is a common practice in Northern Italy, especially in summer. However, care should be taken in case of adverse climatic conditions, such as severe drought and tropical temperatures (characterising summer 2022), which are reported to increase dhurrin synthesis and storage.

Phenolic compounds of sorghum [Sorghum bicolor (L.) Moench] and their allelopathic effect

Purpose. To establish the quantitative composition of phytochemicals containing in vegetative and generative organs of sugar sorghum hybrids with high and medium sugar content ‘Sugargraze ARG’ (Argentina), ‘Sioux’ and ‘Mohawk’ (USA) and ‘Ananas’ and ‘Medovyi’ (Ukraine) and their allelopathic effect
 Methods. Allelopathic, physiological-biochemical, agrochemical and statistical methods were used. The content of phytochemicals in the vegetative and generative organs of the studied sugar sorghum hybrids was determined by the extraction method.
 Results. A high concentration of sorghum phenolic substances in the seeds at the mature plant stage was found. However, their concentration was species specific and depended on their quantitative component in the process of morphogenesis of vegetative and generative organs of sorghum of different genetic origin. The analysis of the total content of phytochemical compounds in the studied hybrids showed an increase in their number at the end of the vegetation season. The research was conducted in vitro. The manifestation of phenolic compounds was observed through manifestation of the allelopathic effect of cultivated sorghum plants. It was found that on the 7th day of cultivation, the plants actively secreted phenolic compounds; the increase in the number of leaves and the height of plants in hybrids did not change and amounted to 3–5 and 1.6–2.0 cm, respectively. On the 14th day of the experiment, the phenolic spots grew significantly, and yellowing of the lower leaves appeared. In the process of morphogenesis of sorghum plants (during 21 days), a more intense release of phenolic compounds led to suppression and slowing down of growth and subsequently to the death of the clone, regardless of the genetic origin of the hybrids. Phenolic compositions also influenced the formation of the root system of cultivated sorghum plants. A significant decrease in the number of lateral roots and the length of the root system was noted in all studied hybrids.
 Conclusions. The highest content of phenolic compounds was found in the seeds (grain) and stems of the studied sorghum hybrids. Thus, the quantitative composition of glycosides and tannins was 34–39 and 5.5–6.9 %, respectively, in the seeds and 25–29 and 0.3–1.4 %, respectively, in the stems of the studied hybrids. The highest content of hydroxycinnamic acids (from 7 % to 14 %) was found in the leaves of the studied sorghum hybrids. Phenolic compositions under in vitro conditions cause stress, which slows down the growth and development of cultivated plants, and subsequently lead to the death of clones.

Chemical Composition, Antioxidant Potential, and Nutritional Evaluation of Cultivated Sorghum Grains: A Combined Experimental, Theoretical, and Multivariate Analysis.

Sorghum grain (Sorghum bicolor L. Moench) is a gluten-free cereal with excellent nutritional value and is a good source of antioxidants, including polyphenols, as well as minerals with proven health benefits. Herein, the phenolic composition, elemental profile, and antioxidant activity of sixteen food-grade sorghum grains (S1-S16) grown under agroecological conditions in Serbia were determined. Nine phenolic compounds characteristic of sorghum grains, such as luteolinidin, 5-methoxyluteolinidin, luteolidin derivative, luteolidin glucoside, apigeninidin, 7-methoxyapigeninidin, apigeninidin glucoside, and cyanidin derivative, were quantified. The antioxidant potential of the analyzed sorghum grains was evaluated by UV/Vis (DPPH, ABTS, and FRAP) and Electron Paramagnetic Resonance spectroscopy (hydroxyl and ascorbyl radical scavenging assays). The content of macro- and microelements was determined by Inductively Coupled Plasma Optical Emission spectroscopy. Theoretical daily intakes of selected major and trace elements were assessed and compared with the Recommended Daily Allowance or Adequate Intake. Sample S8 had the highest amount of phenolic compounds, while S4, S6, and S8 exhibited the strongest antioxidative potential. The sorghum studied could completely satisfy the daily needs of macro- (K, Mg, and P) and microelements (Se, Zn, Fe). Pattern recognition techniques confirmed the discrimination of samples based on phenolic profile and elemental analysis and recognized the main markers responsible for differences between the investigated samples. The reaction between hydroxyl radicals and luteolinidin/apigeninidin was investigated by Density Functional Theory and thermodynamically preferred mechanism was determined.

Genetic Diversity and Population Structure of African Sorghum (Sorghum bicolor L. Moench) Accessions Assessed through Single Nucleotide Polymorphisms Markers.

Assessing the genetic diversity and population structure of cultivated sorghum is important for heterotic grouping, breeding population development, marker-assisted cultivar development, and release. The objectives of the present study were to assess the genetic diversity and deduce the population structure of 200 sorghum accessions using diversity arrays technology (DArT)-derived single nucleotide polymorphism (SNP) markers. The expected heterozygosity values ranged from 0.10 to 0.50 with an average of 0.32, while the average observed heterozygosity (0.15) was relatively low, which is a typical value for autogamous crops species like sorghum. Moderate polymorphic information content (PIC) values were identified with a mean of 0.26, which indicates the informativeness of the chosen SNP markers. The population structure and cluster analyses revealed four main clusters with a high level of genetic diversity among the accessions studied. The variation within populations (41.5%) was significantly higher than that among populations (30.8%) and between samples within the structure (27.7%). The study identified distantly related sorghum accessions such as SAMSORG 48, KAURA RED GLUME; Gadam, AS 152; CSRO1, ICNSL2014-062; and YALAI, KAFI MORI. The accessions exhibited wide genetic diversity that will be useful in developing new gene pools and novel genotypes for West Africa sorghum breeding programs.

A chromosome-scale genome sequence of sudangrass (Sorghum sudanense) highlights the genome evolution and regulation of dhurrin biosynthesis.

Sudangrass is more similar to US commercial sorghums than to cultivated sorghums from Africa sequence-wise and contain significantly lower dhurrin than sorghums. CYP79A1 is linked to dhurrin content in sorghum. Sudangrass [Sorghum sudanense (Piper) Stapf] is a hybrid between grain sorghum and its wild relative S. bicolor ssp. verticilliflorum and is grown as a forage crop due to its high biomass production and low dhurrin content compared to sorghum. In this study, we sequenced the sudangrass genome and showed that the assembled genome was 715.95Mb with 35,243 protein-coding genes. Phylogenetic analysis with whole genome proteomes demonstrated that the sudangrass genome was more similar to US commercial sorghums than to its wild relatives and cultivated sorghums from Africa. We confirmed that at seedling stage, sudangrass accessions contained significantly lower dhurrin as measured by hydrocyanic acid potential (HCN-p) than cultivated sorghum accessions. Genome-wide association study identified a QTL most tightly associated with HCN-p and the linked SNPs were located in the 3' UTR of Sobic.001G012300 which encodes CYP79A1, the enzyme that catalyzes the first step of dhurrin biosynthesis. As in other grasses such as maize and rice, we also found that copia/gypsy long terminal repeat (LTR) retrotransposons were more abundant in cultivated than in wild sorghums, implying that crop domestication in the grasses was accompanied by increased copia/gypsy LTR retrotransposon insertions in the genomes.

Mobilizing sorghum genetic diversity: Biochemical and histological‐assisted design of a stem ideotype for biomethane production

AbstractSorghum currently contributes to the species portfolio that is supporting bioenergy production including anaerobic digestion. Although agro‐morphological ideotypes maximizing biogas production have been recently proposed, there is a crucial need to refine our understanding of the impacts of the stem composition and structure on this processing trait in order to ensure genetic gains in the mid to long terms. This study aims to assess the potential of Sorghum bicolor ssp bicolor stem genetic diversity to maximize genetic gains for biogas production and define a biogas stem ideotype. In this context, a panel of 57 genotypes, encompassing most of the stem composition variability available in cultivated sorghum, was characterized over five sites. Simultaneous histological and biochemical characterizations were performed. A high broad sense heritability associated with a moderate genetic variability was detected for stem biogas potential ensuring significant genetic gains in the future. In addition, the development of a stem histological phenotyping pipeline made it possible to describe the genetic diversity available for the internode anatomy and the repartition of key cell wall components. Consistently with previous studies, moderate to high heritability was observed for stem biochemical components. Genetic correlation, hierarchical clustering, and multiple stepwise regression analyses identified soluble sugar content as the first main driver of biogas potential genetic variability. Nevertheless, breeding programs should anticipate that biogas yield improvement will also rely on the monitoring of the cell wall components and their distribution in the stem jointly with the soluble sugar content. According to the assets of sorghum in terms of adaptation to environmental stresses and the present results regarding the identification of stem ideotypes suitable for different value chains, this species will surely play a key role to optimize the economic and environmental sustainability of the agrosystems that are currently facing the effects of climate change.

Extensive variation within the pan-genome of cultivated and wild sorghum.

Sorghum is a drought-tolerant staple crop for half a billion people in Africa and Asia, an important source of animal feed throughout the world and a biofuel feedstock of growing importance. Cultivated sorghum and its inter-fertile wild relatives constitute the primary gene pool for sorghum. Understanding and characterizing the diversity within this valuable resource is fundamental for its effective utilization in crop improvement. Here, we report analysis of a sorghum pan-genome to explore genetic diversity within the sorghum primary gene pool. We assembled 13 genomes representing cultivated sorghum and its wild relatives, and integrated them with 3 other published genomes to generate a pan-genome of 44,079 gene families with 222.6 Mb of new sequence identified. The pan-genome displays substantial gene-content variation, with 64% of gene families showing presence/absence variation among genomes. Comparisons between core genes and dispensable genes suggest that dispensable genes are important for sorghum adaptation. Extensive genetic variation was uncovered within the pan-genome, and the distribution of these variations was influenced by variation of recombination rate and transposable element content across the genome. We identified presence/absence variants that were under selection during sorghum domestication and improvement, and demonstrated that such variation had important phenotypic outcomes that could contribute to crop improvement. The constructed sorghum pan-genome represents an important resource for sorghum improvement and gene discovery.

Field Efficacy of Synthetic and Botanical-Derived Insecticides Against Melanaphis sacchari1, and Non-Target and Beneficial Species Associated with Cultivated Sorghum

The purpose of the study was to investigate the field efficacy of commercial insecticides against Melanaphis sacchari (Zehntner) and determine the diversity of non-target species associated before and after treatment. Treatments were applied at 35 and 50 days after germination, and associated insects were sampled with yellow traps 48 hours after application of each product. Insect abundance differed significantly from the control that had 1,006 and 3,750 aphids on the first and second days of evaluation, with fewer aphids at the first sampling (35 days). The most effective products were flupyradifurone (Sivanto®), imidacloprid (Uniprid®), acephate (Unifate®), and Chenopodium ambrosioides botanical extract (Requiem®), with efficacies of 99.95% (0.5 aphids/plant), 99.05 (9.5 aphids/plant), 99.41% (6.0 aphids/plant), and 76.78% (233.5 aphids/plant) (Fn,3 = 19.78; df = 5,12; p < 0.001, r2 = 0.8918), respectively. At the second sampling (50 days), efficacy of flupyradifurone was 100%, and Ch. ambrosioides plant-derived product and spinetoram (Palgus®) were opposite (Fn,3 = 43.14; df = 5,12; p < 0.001, r2 = 0.9473). We collected 980 insects associated with sorghum, in five orders, 26 families, and 53 species of Coleoptera, Diptera, Hemiptera, Hymenoptera, and Neuroptera. Species richness increased as abundance decreased. Species richness and abundance were greatest at the first assessment. The Shannon-Wiener diversity index was between 1.2 and 1.6 for the first assessment and 1.8 and 2.4 for the second evaluation. Flupyradifurone, imidacloprid and acephate should be included in integrated management of M. sacchari, considering adequate use of the product.

Local Taxonomy and Diversity of Chadian Sorghum [&amp;lt;i&amp;gt;Sorghum bicolor&amp;lt;/i&amp;gt; (L.) Moench] Accessions

The integration of local plant genetic resources into the breeding program is an asset for research. The objective of this study is to assess the diversity and analyze the management practices of cultivated sorghum. A questionnaire following a participatory approach was submitted to 675 producers in 45 villages. The cultivars collected were characterized using 9 qualitative descriptors. In total, 151 accessions and 191 names were inventoried. On average, 25.17 accessions per department and 3.36 accessions per village. Local taxonomy is based on many criteria expressed in different local languages. The most common method of naming is that to the word sorghum is added either the color of the grain, the precocity, or any element deemed relevant by the farmers. Significant variability in grain and panicle traits was observed within the collection, except the color of the endosperm. The rate of diversity loss is 11.52% and red grain sorghums are the most threatened with extinction. Five accessions groups are differentiated by the presence or absence of awns, the color of glumes, and amount of grain covered by glumes, grain plumpness, and form. Based on productivity, precocity, plant size, seed shape, and color, the farmers identified seven promising accessions. This potential will be preserved and developed in the sorghum varietal improvement program in Chad.

EVALUASI KESESUAIAN LAHAN TANAMAN SORGUM (Shorgum bicolor) DI KECAMATAN BILAH BARAT, KABUPATEN LABUHANBATU

Sorghum has great potential to be cultivated and developed commercially because it has wide adaptability, high productivity, is resistant to plant pests and is more resistant to marginal conditions. Land evaluation is useful as a basis for sector development in an area that is useful for reorganizing the existing land use to assist in making land use planning decisions. This study that was aimed to evaluate land suitability for sorghum was conducted descriptively using the survey method. The sampling method used was based on a land map unit with a free grid system. The land evaluation was carried out by matching and comparing land characteristics with land suitability class criteria to obtain land suitability classes for sorghum plants in Bilah Barat District, Labuhanbatu Regency. There were six soil sample points collected at a depth of 0-60 cm to determine the value of soil characteristics. The results showed that the cultivated sorghum in Bilah Barat District, Labuhanbatu Regency of 12,829 ha which has the actual land suitability class for sorghum is Nwa with the potential land suitability class is S2tcwa.

Genetic diversity of Ethiopian sorghum reveals signatures of climatic adaptation.

A large collection of Ethiopian sorghum landraces, characterized by agro-ecology and racial-group, was found to contain high levels of diversity and admixture, with significant SNP associations identified for environmental adaptation. Sorghum [Sorghum bicolor L. (Moench)] is a major staple food crop in Ethiopia, exhibiting extensive genetic diversity with adaptations to diverse agroecologies. The environmental and climatic drivers, as well as the genomic basis of adaptation, are poorly understood in Ethiopian sorghum and are critical elements for the development of climate-resilient crops. Exploration of the genome-environment association (GEA) is important for identifying adaptive loci and predicting phenotypic variation. The current study aimed to better understand the GEA of a large collection of Ethiopian sorghum landraces (n = 940), characterized with genome-wide SNP markers, to investigate key traits related to adaptation to temperature, precipitation and altitude. The Ethiopian sorghum landrace collection was found to consist of 12 subpopulations with high levels of admixture (47%), representing all the major racial groups of cultivated sorghum with the exception of kafir. Redundancy analysis indicated that agroecology explained up to 10% of the total SNP variation, and geographical location up to 6%. GEA identified 18 significant SNP markers for environmental variables. These SNPs were found to be significantly enriched (P < 0.05) for a priori QTL for drought and cold adaptation. The findings from this study improve our understanding of the genetic control of adaptive traits in Ethiopian sorghum. Further, the Ethiopian sorghum germplasm collection provides sources of adaptation to harsh environments (cold and/or drought) that could be deployed in breeding programs globally for abiotic stress adaptation.

Leaf angle distribution in Johnsongrass, leaf thickness in sorghum and Johnsongrass, and association with response to Colletotrichum sublineola

Basal leaf angle distribution was surveyed in twenty-one Johnsongrass cultivars near the end of the vegetative stage. The angles increased from the top to the bottom leaves, and compared to cultivated grain sorghums, the average angle was larger in Johnsongrass. When basal leaf angle distribution data were correlated with pathogenicity test data from excised-leaf assays for three isolates of Colletotrichum sublineola, the results showed a weak positive correlation between basal leaf angle and pathogenicity level in Johnsongrass. In order to investigate a protective role of leaf thickness to C. sublineola, leaf thickness was measured in three sorghum cultivars and one Johnsongrass cultivar at the 8-leaf-stage. Leaf thickness near the apex, near the base, and half-way between the two points were measured in the top four leaves of each plant. Thickness of leaf blade and midrib were recorded separately. Using an excised-leaf-assay, the three points were inoculated with C. sublineola, and pathogenicity level was recorded 4-days-post-inoculation. Results showed strong negative correlations between leaf midrib thickness and pathogenicity level in sorghum and Johnsongrass but not in leaf blades.

Wild Sorghum as a Promising Resource for Crop Improvement.

Sorghum bicolor (L.) Moench is a multipurpose food crop which is ranked among the top five cereal crops in the world, and is used as a source of food, fodder, feed, and fuel. The genus Sorghum consists of 24 diverse species. Cultivated sorghum was derived from the wild progenitor S. bicolor subsp. verticilliflorum, which is commonly distributed in Africa. Archeological evidence has identified regions in Sudan, Ethiopia, and West Africa as centers of origin of sorghum, with evidence for more than one domestication event. The taxonomy of the genus is not fully resolved, with alternative classifications that should be resolved by further molecular analysis. Sorghum can withstand severe droughts which makes it suitable to grow in regions where other major crops cannot be grown. Wild relatives of many crops have played significant roles as genetic resources for crop improvement. Although there have been many studies of domesticated sorghum, few studies have reported on its wild relatives. In Sorghum, some species are widely distributed while others are very restricted. Of the 17 native sorghum species found in Australia, none have been cultivated. Isolation of these wild species from domesticated crops makes them a highly valuable system for studying the evolution of adaptive traits such as biotic and abiotic stress tolerance. The diversity of the genus Sorghum has probably arisen as a result of the extensive variability of the habitats over which they are distributed. The wild gene pool of sorghum may, therefore, harbor many useful genes for abiotic and biotic stress tolerance. While there are many examples of successful examples of introgression of novel alleles from the wild relatives of other species from Poaceae, such as rice, wheat, maize, and sugarcane, studies of introgression from wild sorghum are limited. An improved understanding of wild sorghums will better allow us to exploit this previously underutilized gene pool for the production of more resilient crops.

Genetic Diversity of C4 Photosynthesis Pathway Genes in Sorghum bicolor (L.).

C4 photosynthesis has evolved in over 60 different plant taxa and is an excellent example of convergent evolution. Plants using the C4 photosynthetic pathway have an efficiency advantage, particularly in hot and dry environments. They account for 23% of global primary production and include some of our most productive cereals. While previous genetic studies comparing phylogenetically related C3 and C4 species have elucidated the genetic diversity underpinning the C4 photosynthetic pathway, no previous studies have described the genetic diversity of the genes involved in this pathway within a C4 crop species. Enhanced understanding of the allelic diversity and selection signatures of genes in this pathway may present opportunities to improve photosynthetic efficiency, and ultimately yield, by exploiting natural variation. Here, we present the first genetic diversity survey of 8 known C4 gene families in an important C4 crop, Sorghum bicolor (L.) Moench, using sequence data of 48 genotypes covering wild and domesticated sorghum accessions. Average nucleotide diversity of C4 gene families varied more than 20-fold from the NADP-malate dehydrogenase (MDH) gene family (θπ = 0.2 × 10−3) to the pyruvate orthophosphate dikinase (PPDK) gene family (θπ = 5.21 × 10−3). Genetic diversity of C4 genes was reduced by 22.43% in cultivated sorghum compared to wild and weedy sorghum, indicating that the group of wild and weedy sorghum may constitute an untapped reservoir for alleles related to the C4 photosynthetic pathway. A SNP-level analysis identified purifying selection signals on C4 PPDK and carbonic anhydrase (CA) genes, and balancing selection signals on C4 PPDK-regulatory protein (RP) and phosphoenolpyruvate carboxylase (PEPC) genes. Allelic distribution of these C4 genes was consistent with selection signals detected. A better understanding of the genetic diversity of C4 pathway in sorghum paves the way for mining the natural allelic variation for the improvement of photosynthesis.

The Evolution of an Invasive Plant, Sorghum halepense L. ('Johnsongrass').

From noble beginnings as a prospective forage, polyploid Sorghum halepense (‘Johnsongrass’) is both an invasive species and one of the world’s worst agricultural weeds. Formed by S. bicolor x S. propinquum hybridization, we show S. halepense to have S. bicolor-enriched allele composition and striking mutations in 5,957 genes that differentiate it from representatives of its progenitor species and an outgroup. The spread of S. halepense may have been facilitated by introgression from closely-related cultivated sorghum near genetic loci affecting rhizome development, seed size, and levels of lutein, a photochemical protectant and abscisic acid precursor. Rhizomes, subterranean stems that store carbohydrates and spawn clonal propagules, have growth correlated with reproductive rather than other vegetative tissues, and increase survival of both temperate cold seasons and tropical dry seasons. Rhizomes of S. halepense are more extensive than those of its rhizomatous progenitor S. propinquum, with gene expression including many alleles from its non-rhizomatous S. bicolor progenitor. The first surviving polyploid in its lineage in ∼96 million years, its post-Columbian spread across six continents carried rich genetic diversity that in the United States has facilitated transition from agricultural to non-agricultural niches. Projected to spread another 200–600 km northward in the coming century, despite its drawbacks S. halepense may offer novel alleles and traits of value to improvement of sorghum.

Transmission Genetics of a Sorghum bicolor × S. halepense Backcross Populations.

Despite a “ploidy barrier,” interspecific crosses to wild and/or cultivated sorghum (Sorghum bicolor, 2n = 2x = 20) may have aided the spread across six continents of Sorghum halepense, also exemplifying risks of “transgene escape” from crops that could make weeds more difficult to control. Genetic maps of two BC1F1 populations derived from crosses of S. bicolor (sorghum) and S. halepense with totals of 722 and 795 single nucleotide polymorphism (SNP) markers span 37 and 35 linkage groups, with 2–6 for each of the 10 basic sorghum chromosomes due to fragments covering different chromosomal portions or independent segregation from different S. halepense homologs. Segregation distortion favored S. halepense alleles on chromosomes 2 (1.06–4.68 Mb, near a fertility restoration gene), 7 (1.20–6.16 Mb), 8 (1.81–5.33 Mb, associated with gene conversion), and 9 (47.5–50.1 Mb); and S. bicolor alleles on chromosome 6 (0–40 Mb), which contains both a large heterochromatin block and the Ma1 gene. Regions of the S. halepense genome that are recalcitrant to gene flow from sorghum might be exploited as part a multi-component system to reduce the likelihood of spread of transgenes or other modified genes. Its SNP profile suggests that chromosome segments from its respective progenitors S. bicolor and Sorghum propinquum have extensively recombined in S. halepense. This study reveals genomic regions that might discourage crop-to-weed gene escape, and provides a foundation for marker-trait association analysis to determine the genetic control of traits contributing to weediness, invasiveness, and perenniality of S. halepense.

Post-translational regulation of plasma membrane H+-ATPase is involved in the release of biological nitrification inhibitors from sorghum roots

It is an integral property of sorghum (Sorghum bicolor L.) to extensively release biological nitrification inhibitors (BNIs) under NH4+ nutrition, in comparison to NO3− nutrition. Our previous research indicated that plasma membrane (PM) H+-ATPase activity was stimulated by NH4+ and low rhizosphere pH, which in turn provided the driving force for BNIs release from sorghum roots. However, the regulatory mechanism of PM H+-ATPase itself in this regard is not fully elucidated. The present study thus aims at post-translational regulation of PM H+-ATPase via phosphorylation in response to NH4+ nutrition and its functional link to the release of BNIs from sorghum roots. A hydroponic system is used to grow sorghum with 1 mM NH4+ or NO3− as N source at pH 3.0 or pH 7.0 in root medium for the analysis of PM H+-ATPase and BNIs release. The effect of NH4+ on the regulation of PM H+-ATPase was further evaluated by the treatment of NO3−cultivated sorghum roots with different NH4+ concentrations (0.1~1 mM). In addition, fusicoccin (a stimulator of PM H+-ATPase) and vanadate (an inhibitor of PM H+-ATPase) were added to check the effect of PM H+-ATPase phosphorylation on BNIs release. Further, methionine sulphoximine (MSX), which inhibits glutamine synthetase, is used to analyze the effect of ammonium transport/assimilation process on the PM H+-ATPase and BNIs release. Microsomal membrane protein isolated from these roots was used for the test of PM H+-ATPase phosphorylation level by western blot technique. Meanwhile, the root exudates were collected for the analysis of BNIs. Higher amount of PM H+-ATPase protein with higher phosphorylation level were detected in sorghum roots in response to NH4+ and low rhizosphere pH, as compared to NO3− and high pH. Further, PM H+-ATPase protein amount and phosporylation level were dependent on the local supplement of NH4+ (from 0.1 ~ 1 mM) to roots. Nevertheless, the enhanced posphorylation level under all of these treatments was significantly higher than the enhanced protein level of PM H+ ATPase. Unlike protein level, phosphorylation level is closely correlated to the release of BNIs from sorghum roots. In addition, phosphorylation level of PM H+-ATPase adjusted by fusicoccin or vanadate directly affected the release of BNIs, irrespective of the protein level. In addition, ammonium assimilation inhibitor MSX caused decreased phosphorylation level of PM H+-ATPase without affecting the protein level, meanwhile inhibited the release of BNIs from sorghum roots. Our research suggests that phosphorylation of PM H+-ATPase is one of the important regulation mechanisms involved in the release of BNIs from sorghum roots. NH4+ stimulated PM H+-ATPase phosphorylation via excessive H+ generated by NH4+ assimilation in cytoplasm. The up regulation of PM H+-ATPase at post-translational level thus activated the H+ pumping activity to provide the driving force for BNIs release. A new hypothesis is proposed to elucidate the interplay of these functionally inter-linked processes involving ammonium-uptake, −assimilation, and H+-pumps activation in PM on the release of BNIs from sorghum roots.

Genetic diversity among elite sorghum (Sorghum bicolor L.) accessions genotyped with SSR markers to enhance use of global genetic resources

Analysis of genetic diversity, selection of parents with diverse genetic base having contrasting phenotype is an important step in developing mapping populations for QTL detection, association mapping and MAS studies. To elucidate the diversity among Marathwada (Maharashtra) region cultivated sorghum accessions we studied genetic diversity in 20 sorghum accessions using SSR markers. The polymorphism information content (PIC), a measure of gene diversity present in the selected population, varied from 0.38 to 0.72 with an average of 0.55 and was significantly correlated with number of alleles. Clustering analysis based on the unrooted phylogeny using neighbour-joining (NJ) method, bootstrapping of the data (10,000 permutations) as implemented in POWERMARKER grouped the 20 accessions into three clusters and grouping was in good agreement with biological status and some important traits of sorghum accessions. The SSR loci msbCIR306, Xtxp321, msbCIR329, Xcup02 and Xisep0310 were rich in allelic diversity exhibiting highest PIC value.