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Flat thin-film magnesium oxide-chitosan nanocomposite membranes were synthesized with polyethylene terephthalate (PET) and employed for natural gas dehydration. The water vapor permeation was most pronounced with a nanocomposite membrane doped with 0.9 g MgO nanoparticles (NP) as a result of a significant upsurge in the permeability of water vapor in the membrane (0.87). With the increase in MgO NP, large macro-voids are created, substratum pore size, and thickness together with the water vapor permeation were upsurged. The dehydration of natural gas performance of magnesium oxide-chitosan nanocomposite membranes synthesized with PET was enhanced with the increase in MgO NP embedded in the membrane. Though water vapor permeation was restricted by the polyester non-woven material used as a support for the nano composite membranes, as the three membranes did not reach the permeation coefficient of 1. However, the permeation coefficient increased with an increased MgO NP, with three mambrane samples (M1, M2 and M3) having permeation coefficient of 0.763, 0.77 and 0.87 respectively. The gas reduced with an increase MgO NP, with M1, M2 and M3 having 3.46×10−2, 3.17×10−2 and 3.88×10−3 kg/m3 respectively. From the adsorption study, the discrepancy observed between CH4 and vapor with isotherm models was ascribed to the different adsorption behavior of CH4 and vapor on the membrane-active area. The cost of making the membrane cannot be considered as a terminal criterion because most of the cost-effective option is not always the optimum one. The membranes confirmed their suitability for the dehydration of natural gas.

Sorghum is an important food and feed crop globally; its production is hampered by anthracnose disease caused by the fungal pathogen Colletotrichum sublineola (Cs). Here, we report identification and characterization of ANTHRACNOSE RESISTANCE GENE 2 (ARG2) encoding a nucleotide-binding leucine-rich repeat (NLR) protein that confers race-specific resistance to Cs strains. ARG2 is one of a cluster of several NLR genes initially identified in the sorghum differential line SC328C that is resistant to some Cs strains. This cluster shows structural and copy number variations in different sorghum genotypes. Different sorghum lines carrying independent ARG2 alleles provided the genetic validation for the identity of the ARG2 gene. ARG2 expression is induced by Cs, and chitin induces ARG2 expression in resistant but not in susceptible lines. ARG2-mediated resistance is accompanied by higher expression of defense and secondary metabolite genes at early stages of infection, and anthocyanin and zeatin metabolisms are upregulated in resistant plants. Interestingly, ARG2 localizes to the plasma membrane when transiently expressed in Nicotiana benthamiana. Importantly, ARG2 plants produced higher shoot dry matter than near-isogenic lines carrying the susceptible allele suggesting absence of an ARG2 associated growth trade-off. Further, ARG2-mediated resistance is stable at a wide range of temperatures. Our observations open avenues for resistance breeding and for dissecting mechanisms of resistance.

Sorghum is an important food and feed crop globally; its production is hampered by anthracnose disease caused by the fungal pathogenColletotrichum sublineola(Cs). Here, we report identification and characterization ofANTHRACNOSE RESISTANCE GENE 2(ARG2) encoding a nucleotide-binding leucine-rich repeat (NLR) protein that confers race-specific resistance toCsstrains.ARG2is one of a cluster of severalNLRgenes in the sorghum differential line SC328C that is resistant to someCsstrains. This cluster shows structural and copy number variations in different sorghum genotypes. Different sorghum variants carrying independentARG2alleles provided the genetic validation for the identity of theARG2gene.ARG2expression is induced byCs, and chitin induceARG2expression in resistant but not in susceptible lines. ARG2-mediated resistance is accompanied by higher expression of defense and secondary metabolite genes at early stages of infection, and anthocyanin and zeatin metabolisms are upregulated in resistant plants. Interestingly, ARG2 localizes to the plasma membrane when transiently expressed inNicotiana benthamiana. Importantly,ARG2plants produced higher shoot dry matter than near-isogenic lines carrying the susceptible allele suggesting absence of anARG2associated growth trade-off. Further, ARG2-mediated resistance is stable at a wide range of temperatures. Our observations open avenues for resistance breeding and for dissecting mechanisms of resistance.

Sorghum (Sorghum bicolor), the fifth most widely grown cereal crop globally, provides food security for millions of people. Anthracnose caused by the fungus Colletotrichum sublineola is a major disease of sorghum worldwide. We discovered a major fungal resistance locus in sorghum composed of the nucleotide-binding leucine-rich repeat receptor gene ANTHRACNOSE RESISTANCE GENE1 (ARG1) that is completely nested in an intron of a cis-natural antisense transcript (NAT) gene designated CARRIER OF ARG1 (CARG). Susceptible genotypes express CARG and two alternatively spliced ARG1 transcripts encoding truncated proteins lacking the leucine-rich repeat domains. In resistant genotypes, elevated expression of an intact allele of ARG1, attributed to the loss of CARG transcription and the presence of miniature inverted-repeat transposable element sequences, resulted in broad-spectrum resistance to fungal pathogens with distinct virulence strategies. Increased ARG1 expression in resistant genotypes is also associated with higher histone H3K4 and H3K36 methylation. In susceptible genotypes, lower ARG1 expression is associated with reduced H3K4 and H3K36 methylation and increased expression of NATs of CARG. The repressive chromatin state associated with H3K9me2 is low in CARG-expressing genotypes within the CARG exon and higher in genotypes with low CARG expression. Thus, ARG1 is regulated by multiple mechanisms and confers broad-spectrum, strong resistance to fungal pathogens.

Key messageSeven novel alleles ofSBEIIband one allele ofSSIIaco-segregated with the ASV phenotype and contributed to distinct starch quality traits important for food-processing applications.AbstractSorghum is an important food crop for millions of people in Africa and Asia. Whole-genome re-sequencing of sorghum EMS mutants exhibiting an alkali spreading value (ASV) phenotype revealed candidate SNPs inSobic.004G163700andSobic.010G093400. Comparative genomics identifiedSobic.010G093400as astarch synthase IIaandSobic.004G163700as astarch branching enzyme IIb. Segregation analyses showed that mutations inSobic.010G093400orSobic.004G163700co-segregated with the ASV phenotype. Mutants inSSIIaexhibited no change in amylose content but expressed lower final viscosity and lower starch gelatinization temperature (GT) than starches from non-mutant plants. ThesbeIIbmutants exhibited significantly higher amylose levels and starch GT and lower viscosity compared to non-mutant starches andssIIamutants. Mutations inSBEIIbhad a dosage-dependent effect on amylose content. Double mutants ofsbeIIbandssIIaresembled theirsbeIIbparent in amylose content, starch thermal properties and viscosity profiles. These variants will provide opportunities to produce sorghum varieties with modified starch end-use qualities important for the beer brewing and baking industries and specialty foods for humans with diabetes.

The eastern Africa region, Ethiopia and its surroundings, is considered as the center of origin and diversity for sorghum, and has contributed to global sorghum genetic improvement. The germplasm from this region harbors enormous genetic variation for various traits but little is known regarding the genetic architecture of most traits. Here, 1425 Ethiopian landrace accessions were phenotyped under field conditions for presence or absence of awns, panicle compactness and shape, panicle exsertion, pericarp color, glume cover, plant height and smut resistance under diverse environmental conditions in Ethiopia. In addition, F1 hybrids obtained from a subset of 1341 accessions crossed to an A1 cytoplasmic male sterile line, ATx623, were scored for fertility/sterility reactions. Subsequently, genotyping-by-sequencing generated a total of 879,407 SNPs from which 72,190 robust SNP markers were selected after stringent quality control (QC). Pairwise distance-based hierarchical clustering identified 11 distinct groups. Of the genotypes assigned to either one of the 11 sub-populations, 65% had high ancestry membership coefficient with the likelihood of more than 0.60 and the remaining 35% represented highly admixed accessions. A genome-wide association study (GWAS) identified loci and SNPs associated with aforementioned traits. GWAS based on compressed mixed linear model (CMLM) identified SNPs with significant association (FDR ≤ 0.05) to the different traits studied. The percentage of total phenotypic variation explained with significant SNPs across traits ranged from 2 to 43%. Candidate genes showing significant association with different traits were identified. The sorghum bHLH transcription factor, ABORTED MICROSPORES was identified as a strong candidate gene conditioning male fertility. Notably, sorghum CLAVATA1 receptor like kinase, known for regulation of plant growth, and the ETHYLENE RESPONSIVE TRANSCRIPTION FACTOR gene RAP2-7, known to suppress transition to flowering, were significantly associated with plant height. In addition, the YELLOW SEED1 like MYB transcription factor and TANNIN1 showed strong association with pericarp color validating previous observations. Overall, the genetic architecture of natural variation representing the complex Ethiopian sorghum germplasm was established. The study contributes to the characterization of genes and alleles controlling agronomic traits, and will serve as a source of markers for molecular breeding.

Genetic analysis of brown midrib sorghum (Sorghum bicolor) mutant lines assembled in our program has previously shown that the mutations fall into four allelic groups, bmr2, bmr6, bmr12 or bmr19. Causal genes for allelic groups bmr2, bmr6 and bmr12, have since been identified. In this report, we provide evidence for the nature of the bmr19 mutation. This was accomplished by introgressing each of the four bmr alleles into nine different genetic backgrounds. Polymorphisms from four resequenced bulks of sorghum introgression lines containing either mutation, relative to those of a resequenced bulk of the nine normal midrib recurrent parent lines, were used to locate their respective causal mutations. The analysis confirmed the previously reported causal mutations for bmr2 and bmr6 but failed in the case of bmr12-bulk due to a mixture of mutant alleles at the locus among members of that mutant bulk. In the bmr19-bulk, a common G → A mutation was found among all members in Sobic.001G535500. This gene encodes a putative folylpolyglutamate synthase with high homology to maize Bm4. The brown midrib phenotype co-segregated with this point mutation in two separate F2 populations. Furthermore, an additional variant allele at this locus obtained from a TILLING population also showed a brown midrib phenotype, confirming this locus as Bmr19.

Stalk rots are important biotic constraints to sorghum production worldwide. Several pathogens may be associated with the disease, but Macrophomina phaseolina and Fusarium thapsinum are recognized as the major causal organisms. The diseases become more aggressive when drought and high-temperature stress occur during grain filling. Progress in genetic improvement efforts has been slow due to lack of effective phenotyping protocol and the strong environmental effect on disease incidence and severity. Deployment of modern molecular tools is expected to accelerate efforts to develop resistant hybrids. This study was aimed at identifying genomic regions associated with resistance to both causal organisms. A sorghum diversity panel consisting of 300 genotypes assembled from different parts of the world was evaluated for response to infection by both pathogens. Community resources of 79,132 single nucleotide polymorphic (SNP) markers developed on the panel were used in association studies using a multi-locus mixed model to map loci associated with stalk rot resistance. Adequate genetic variation was observed for resistance to both pathogens. Structure analysis grouped the genotypes into five subpopulations primarily based on the racial category of the genotypes. Fourteen loci and a set of candidate genes appear to be involved in connected functions controlling plant defense response. However, each associated SNP had relatively small effect on the traits, accounting for 19–30% of phenotypic variation. Linkage disequilibrium analyses suggest that significant SNPs are genetically independent. Estimation of frequencies of associated alleles revealed that durra and caudatum subpopulations were enriched for resistant alleles, but the results suggest complex molecular mechanisms underlying resistance to both pathogens.

The ease with which seeds are detached from panicles is one of the early domestication traits. Genotypes with sticky panicles are hard to thresh, and whenever threshed, the grain tends to remain attached to the glume which reduces market value and processability. This study was conducted to determine the genetic mechanisms underlying the threshability trait in sorghum. Four seed parents and eleven pollinators differing for threshability were intercrossed in Design II mating scheme and the resulting hybrids and the parents were grown in four environments. Threshability was estimated as the ratio of seed yield to panicle weight (TW) and proportion of seeds without sticky glumes (TG). Variation was significant among the entries, inbreds and hybrids with GCA for TG and TW varying markedly. Mean TG for inbred and hybrids of low threshable genotypes was not markedly different indicating that threshability trait is under the control of additive genes with dominant or partially dominant effects. Segregation analysis indicates that the TG trait may be under the control of few major genes with approximately one to three loci affecting the trait.

The Existence and Distribution of Jatropha curcas L. germplasms in the Northwest zone of Nigeria is hereby reported with coordinates and point mapping. Fifty seven (57) accessions were collected from the seven States of the zone which spans across the Sahel, Sudan and Guinea Savannas. The collection was made from 18th to 22nd of August 2009. A plantation was established from these collections and the seeds from 39 different provenances of the seven States were analyzed for their oil content. The mean oil content ranged from 20.29% to 61.83% (CV 29.11%). The 100-seed weight ranged from 28.558g to 80.046g. There was a positive correlation between 100 seed weight and oil content (r = 0.235). The accessions from Kaduna State, spanning through the Sudan and Northern Guinea Savanna, had the highest mean oil content followed by those from Kano and Katsina States in the Sudan Savanna ecology. There were no significant differences (p < 0.5) in the accessions from Jigawa, Kebbi, Sokoto and Zamfara States which are mainly located in the Sudano-Sahelian Savanna agro-ecological zone. Most of the provenances visited were more than 50 yrs old as reported by the locals, implying that Jatropha has been a long existing crop in Nigeria. The existence of Jatropha in almost all the visited locations, and the impressive intensity of fruiting as sighted on the trees and their oil contents show that the potential for adopting it into the farming systems of these localities as source of renewable energy exists. (C) 2011 Elsevier Ltd. All rights reserved.

Genetics of harvest index and leaf-yield index in cowpea (Vigna unguiculata [L.] Walp) were studied via generation mean analysis to understand the gene action controlling the two traits and to identify the most appropriate breeding strategies for improving these traits. Three cultivars involving IAR-00-1074 with good fodder yield and IT93K-499-35 and IT93K-452-1 with high grain yield were used during 2005 at the Institute for Agricultural Research (IAR), Samaru, Nigeria. The parents, their F1, F2 and two backcross generations were evaluated using a randomized complete-block design. Highly significant differences were observed among the five generations for harvest index and leaf-yield index. F1 means were closer to the parent with higher harvest index for both crosses. This suggested that dominance was involved in expression of harvest index. The same trend was observed for leaf-yield index. Backcrossing to both parents showed good convergence of genes on the recurrent parent in the cross IAR-00-1074 × IT...