Haplotypes at the sorghum ARG4 and ARG5 NLR loci confer resistance to anthracnose.

Sorghum anthracnose caused by the fungus Colletotrichum sublineola (Cs) is a damaging disease of the crop. Here, we describe the identification of ANTHRACNOSE RESISTANCE GENES (ARG4 and ARG5) encoding canonical nucleotide-binding leucine-rich repeat (NLR) receptors. ARG4 and ARG5 are dominant resistance genes identified in the sorghum lines SAP135 and P9830, respectively, that show broad-spectrum resistance to Cs. Independent genetic studies using populations generated by crossing SAP135 and P9830 with TAM428, fine mapping using molecular markers, comparative genomics and gene expression studies determined that ARG4 and ARG5 are resistance genes against Cs strains. Interestingly, ARG4 and ARG5 are both located within clusters of duplicate NLR genes at linked loci separated by ~1 Mb genomic region. SAP135 and P9830 each carry only one of the ARG genes while having the recessive allele at the second locus. Only two copies of the ARG5 candidate genes were present in the resistant P9830 line while five non-functional copies were identified in the susceptible line. The resistant parents and their recombinant inbred lines carrying either ARG4 or ARG5 are resistant to strains Csgl1 and Csgrg suggesting that these genes have overlapping specificities. The role of ARG4 and ARG5 in resistance was validated through sorghum lines carrying independent recessive alleles that show increased susceptibility. ARG4 and ARG5 are located within complex loci displaying interesting haplotype structures and copy number variation that may have resulted from duplication. Overall, the identification of anthracnose resistance genes with unique haplotype stucture provides a foundation for genetic studies and resistance breeding.

Broad-spectrum fungal resistance in sorghum is conferred through the complex regulation of an immune receptor gene embedded in a natural antisense transcript.

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.

Sorghum Brown Midrib19 (Bmr19) Gene Links Lignin Biosynthesis to Folate Metabolism.

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.

Genome-wide association analysis reveals seed protein loci as determinants of variations in grain mold resistance in sorghum.

KEY MESSAGE: GWAS analysis revealed variations at loci harboring seed storage, late embryogenesis abundant protein, and a tannin biosynthesis gene associated with sorghum grain mold resistance. Grain mold is the most important disease of sorghum [Sorghum bicolor (L.) Moench]. It starts at the early stages of grain development due to concurrent infection by multiple fungal species. The genetic architecture of resistance to grain mold is poorly understood. Using a diverse set of 635 Ethiopian sorghum accessions, we conducted a multi-stage disease rating for resistance to grain mold under natural infestation in the field. Through genome-wide association analyses with 173,666 SNPs and multiple models, two novel loci were identified that were consistently associated with grain mold resistance across environments. Sequence variation at new loci containing sorghum KAFIRIN gene encoding a seed storage protein affecting seed texture and LATE EMBRYOGENESIS ABUNDANT 3 (LEA3) gene encoding a protein that accumulates in seeds, previously implicated in stress tolerance, were significantly associated with grain mold resistance. The KAFIRIN and LEA3 loci were also significant factors in grain mold resistance in accessions with non-pigmented grains. Moreover, we consistently detected the known SNP (S4_62316425) in TAN1 gene, a regulator of tannin accumulation in sorghum grain to be significantly associated with grain mold resistance. Identification of loci associated with new mechanisms of resistance provides fresh insight into genetic control of the trait, while the highly resistant accessions can serve as sources of resistance genes for breeding. Overall, our association data suggest the critical role of loci harboring seed protein genes and implicate grain chemical and physical properties in sorghum grain mold resistance.

Physio-morphological, biochemical, and anatomical traits of drought-tolerant and susceptible sorghum cultivars under pre- and post-anthesis drought.

Understanding the physiological mechanisms that control drought tolerance in crop plants is vital for effective breeding. In this study, we characterized drought stress responses in four sorghum cultivars exhibiting differential levels of drought tolerance at pre- and post-anthesis. Greenhouse-grown plants were subjected to two types of drought treatment, water stress (WS) and desiccant-induced water stress (DA), timed to occur at pre- and post-anthesis. Multiple physiological measurements were then made revealing varying responses among the experimental cultivars. The pre- and post-flowering drought-tolerant cultivar P898012 showed a significantly higher net photosynthetic rate, higher transpiration rate, and greater stomatal conductance compared to the drought-susceptible cultivars at both pre- and post-anthesis. A significantly greater stomatal size was also detected in P898012, while the highest stomatal density was found in the drought-susceptible cultivar P721Q. Meanwhile, the two post-flowering drought-tolerant cultivars P898082 and B35 had a higher starch content and exhibited greater osmotic potential under post-anthesis water stress. Compared to WS and well-watered control plants, a greater increase in root biomass was observed in P898012 under DA at pre-anthesis. This finding suggests that plants invested more assimilates into the roots under severe DA at pre-anthesis. Overall, our results show good conformity between drought tolerance in sorghum and key physiological mechanisms of stomatal conductance, root growth patterns, and starch accumulation, all of which act as coping mechanisms during critical drought-sensitive growth stages.

A comprehensive phenotypic and genomic characterization of Ethiopian sorghum germplasm defines core collection and reveals rich genetic potential in adaptive traits.

Understanding population genetic structure and diversity of a crop is essential in designing selection strategies in plant breeding. About 2010 Ethiopian sorghum accessions were phenotyped for different traits at multiple locations. A subset of the collection, 1628 accessions, predominantly landraces, some improved varieties, and inbred lines were genotyped by sequencing. Phenotypic data revealed association of important traits with different sorghum growing agro-climatic regions, high genetic diversity and the presence of rare natural variation in the Ethiopian sorghum germplasm. Subsequent genotypic analysis determined optimum number of sub-populations, distinct cluster groups and ancestries of each sorghum accessions. To improve utilization of germplasm, a core subset of 387 lines were selected following posteriori grouping of genotypes based on cluster groups obtained through GBS analysis followed by stratified random sampling using quantitative traits. In order to evaluate how well this new sorghum and millet innovation lab (SMIL) collection from Ethiopia is represented within the largest world sorghum collection at United States Department of Agriculture - National Plant Germplasm System (USDA-NPGS) and the sorghum association panel (SAP), comparisons were conducted based on SNP data. The SMIL collection displayed high genetic diversity with some redundancy with the USDA-NPGS germplasm but SAP showed clear distinction. Furthermore, genome-environment association analysis identified candidate genes associated with adaptation to abiotic factors, that will be important for exploitation of adaptive potential to different environments. In summary, our results described the diversity and relationship of sorghum collections, representativeness of developed core and provide novel insights into candidate genes associated to abiotic stress tolerance.

What factors are associated with maternal undernutrition in eastern zone of Tigray, Ethiopia? Evidence for nutritional well-being of lactating mothers.

BACKGROUND: Maternal undernutrition is a pervasive health problem among Ethiopian mothers. This study aims at identifying the level of maternal undernutrition and its associated factors in Kilte Awaleo-Health and Demographic Surveillance Site (KA-HDSS), Tigray region, Ethiopia. METHODS: Nutritional status of 2260 lactating mothers was evaluated using the mid-upper-arm circumference (MUAC). Data from the vital events and verbal autopsy databases were linked to the survey and baseline recensus data to investigate the association of adult mortality from chronic causes of death (CoD) on maternal undernutrition. We employed a generalized log-binomial model to estimate the independent effects of the fitted covariates. RESULTS: The overall prevalence of maternal undernutrition based on MUAC < 23 cm was 38% (95% CI: 36.1, 40.1%). Recent occurrence of household morbidity (adjusted prevalence ratio (adjPR) = 1.49; 95%CI: 1.22, 1.81) was associated with increased risk of maternal undernutrition. In addition, there was a 28% higher risk (adjPR = 1.28; 95%CI: 0.98, 1.67) of maternal undernutrition for those mothers who lived in households with history of adult mortality from chronic diseases. Especially, its association with severe maternal undernutrition was strong (adjusted OR = 3.27; 95%CI: 1.48, 7.22). In contrast, good maternal health-seeking practice (adjPR = 0.86; 95%CI: 0.77, 0.96) and production of diverse food crops (adjPR = 0.72; 95%CI: 0.64, 0.81) were associated with a lower risk of maternal undernutrition. Relative to mothers with low scores of housing and environmental factors index (HAEFI), those with medium and higher scores of HAEFI had 0.81 (adjPR = 0.81; 95%CI: 0.69, 0.95) and 0.82 (adjPR = 0.82; 95%CI: 0.72, 0.95) times lower risk of maternal undernutrition, respectively. CONCLUSIONS: Efforts to ameliorate maternal undernutrition need to consider the influence of the rising epidemiology of adult mortality from chronic diseases. Our data clearly indicate the need for channeling the integrated intervention power of nutrition-sensitive development programs with that of nutrition-specific sectoral services.

Biomass and Bioenergy Potential of Brown Midrib Sweet Sorghum Germplasm.

Public appetite for fossil fuels continues to drive energy prices and foment the build-up of intractable environmental problems. Ethanol (ETOH) production from lignocellulosic biomass grown in marginal lands offers a sustainable alternative without diverting arable land from food and feed production. The quantity and quality of lignocellulosic biomass can be enhanced by the abundant genetic diversity for biomass production as well as stem sugar and lignin composition in sorghum (Sorghum bicolor L. Moench). The objective of this study was to assess yield and quality of lignocellulosic biomass enhancement for ethanol production potential in a population of sorghum derived from two cultivars with contrasting biomass yield and compositional traits. We tested 236 recombinant inbred lines (RIL) of sorghum in a randomized complete block design (RCBD) with two replications for lignocellulosic biomass performance and determined hemicellulose, cellulose and lignin concentrations through detergent fiber analysis (DFA). The stover compositional values were used to estimate theoretical ethanol yield (ETOH on a mass basis) and production (ETOH on an area basis). Results showed that RIL carrying the brown midrib mutation had significantly higher theoretical glucose recovery (released glucose from cellulose, > 200 g kg-1). Those carrying both mutations, had high theoretical ethanol yield (>400 L ton-1) and high theoretical ethanol production (>14,500 L ha-1). Lignin concentration was determined as most reliable predictor (R2 = 0.67) for glucose recovery. Lignin and stem sugar concentrations (R2 = 0.46 and 0.35, respectively) were good predictors for ethanol yield. Stover yield traits (R2 = 0.89) were most important determinants for ethanol production. Our findings suggest that careful breeding of sorghum for genetic enhancement of biomass quantity and quality could double lignocellulosic ethanol yields.

Nutrition-specific and sensitive drivers of poor child nutrition in Kilte Awlaelo-Health and Demographic Surveillance Site, Tigray, Northern Ethiopia: implications for public health nutrition in resource-poor settings.

Background: Child undernutrition is a prevalent health problem and poses various short and long-term consequences. Objective: This study seeks to investigate the burden of child undernutrition and its drivers in Kilte Awlaelo-Health and Demographic Surveillance Site, Tigray, northern Ethiopia. Methods: In 2015, cross-sectional data were collected from 1,525 children aged 6-23 months. Maternal and child nutritional status was assessed using the mid upper arm circumference. Child's dietary diversity score was calculated using 24-hours dietary recall method. Log-binomial regression and partial proportional odds model were fitted to examine the drivers of poor child nutrition and child dietary diversity (CDD), respectively. Results: The burden of undernutrition and inadequate CDD was 13.7% (95% CI: 12.1-15.5%) and 81.3% (95%CI: 79.2-83.1%), respectively. Maternal undernutrition (adjusted prevalence ratio, adjPR = 1.47; 95%CI: 1.14-1.89), low CDD (adjPR = 1.90; 95%CI: 1.22-2.97), and morbidity (adjPR = 1.83; 95%CI: 1.15-2.92) were the nutrition-specific drivers of child undernutrition. The nutrition-sensitive drivers were poverty (compared to the poorest, adjPR poor = 0.65 [95%CI:0.45-0.93], adjPR medium = 0.64 [95%CI: 0.44-0.93], adjPR wealthy = 0.46 [95%CI: 0.30-0.70], and adjPR wealthiest = 0.53 [95%CI: 0.34-0.82]), larger family size (adjPR = 1.10; 95%CI: 1.02-1.18), household head's employment insecurity (adjPR = 2.10; 95%CI: 1.43-3.09), and residing in highlands (adjPR = 1.93; 95%CI: 1.36-2.75). The data show that higher CDD was positively associated with wealth (OR wealthy = 3.06 [95%CI: 1.88-4.99], OR wealthiest = 2.57 [95%CI: 1.53-4.31]), but it was inversely associated with lack of diverse food crops production in highlands (OR = 0.23; 95%CI: 0.10-0.57]). Conclusions: Our findings suggest that the burden of poor child nutrition is very high in the study area. Multi-sectoral collaboration and cross-disciplinary interventions between agriculture, nutrition and health sectors are recommended to address child undernutrition in resource poor and food insecure rural communities of similar settings.

A Large-Scale Genome-Wide Association Analyses of Ethiopian Sorghum Landrace Collection Reveal Loci Associated With Important Traits.

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.

Mating Design and Genetic Structure of a Multi-Parent Advanced Generation Intercross (MAGIC) Population of Sorghum (Sorghum bicolor (L.) Moench).

Multi-parent advanced generation intercross (MAGIC) populations are powerful next-generation mapping resources. We describe here the mating design and structure of the first MAGIC population in sorghum, and test its utility for mapping. The population was developed by intercrossing 19 diverse founder lines through a series of paired crosses with a genetic male sterile (MS) source, followed by 10 generations of random mating. At the final stage of random mating, 1000 random fertile plants in the population were identified and subjected to six generations of selfing to produce 1000 immortal MAGIC inbred lines. The development of this sorghum MAGIC population took over 15 yr. Genotyping-by-sequencing (GBS) of a subset of 200 MAGIC lines identified 79,728 SNPs, spanning high gene-rich regions. Proportion of SNPs per chromosome ranged from 6 to 15%. Structure analyses produced no evidence of population stratification, portraying the desirability of this population for genome-wide association studies (GWAS). The 19 founders formed three clusters, each with considerable genetic diversity. Further analysis showed that 73% of founder alleles segregated in the MAGIC population. Linkage disequilibrium (LD) patterns depicted the MAGIC population to be highly recombined, with LD decaying to r2 [Formula: see text] 0.2 at 40 kb and down to r2 [Formula: see text] 0.1 at 220 kb. GWAS detected two known plant height genes, DWARF1 (chromosome 9) and DWARF3 (chromosome 7), and a potentially new plant height quantitative trait locus (QTL) (QTL-6) on chromosome 6. The MAGIC population was found to be rich in allelic content with high fragmentation of its genome, making it fit for both gene mapping and effective marker-assisted breeding.

Social determinants of adult mortality from non-communicable diseases in northern Ethiopia, 2009-2015: Evidence from health and demographic surveillance site.

INTRODUCTION: In developing countries, mortality and disability from non-communicable diseases (NCDs) is rising considerably. The effect of social determinants of NCDs-attributed mortality, from the context of developing countries, is poorly understood. This study examines the burden and socio-economic determinants of adult mortality attributed to NCDs in eastern Tigray, Ethiopia. METHODS: We followed 45,982 adults implementing a community based dynamic cohort design recording mortality events from September 2009 to April 2015. A physician review based Verbal autopsy was used to identify the most probable causes of death. Multivariable Cox proportional hazards regression was performed to identify social determinants of NCD mortality. RESULTS: Across the 193,758.7 person-years, we recorded 1,091 adult deaths. Compared to communicable diseases, NCDs accounted for a slightly higher proportion of adult deaths; 33% vs 34.5% respectively. The incidence density rate (IDR) of NCD attributed mortality was 194.1 deaths (IDR = 194.1; 95% CI = 175.4, 214.7) per 100,000 person-years. One hundred fifty-seven (41.8%), 68 (18.1%) and 34 (9%) of the 376 NCD deaths were due to cardiovascular disease, cancer and renal failure, respectively. In the multivariable analysis, age per 5-year increase (HR = 1.35; 95% CI: 1.30, 1.41), and extended family and non-family household members (HR = 2.86; 95% CI: 2.05, 3.98) compared to household heads were associated with a significantly increased hazard of NCD mortality. Although the difference was not statistically significant, compared to poor adults, those who were wealthy had a 15% (HR = 0.85; 95% CI: 0.65, 1.11) lower hazard of mortality from NCDs. On the other hand, literate adults (HR = 0.35; 95% CI: 0.13, 0.9) had a significantly decreased hazard of NCD attributed mortality compared to those adults who were unable to read and write. The effect of literacy was modified by age and its effect reduced by 18% for every 5-year increase of age among literate adults. CONCLUSION: In summary, the study indicates that double mortality burden from both NCDs and communicable diseases was evident in northern rural Ethiopia. Public health intervention measures that prioritise disadvantaged NCD patients such as those who are unable to read and write, the elders, the extended family and non-family household co-residents could significantly reduce NCD mortality among the adult population.

Mutation in sorghum LOW GERMINATION STIMULANT 1 alters strigolactones and causes Striga resistance.

Striga is a major biotic constraint to sorghum production in semiarid tropical Africa and Asia. Genetic resistance to this parasitic weed is the most economically feasible control measure. Mutant alleles at the LGS1 (LOW GERMINATION STIMULANT 1) locus drastically reduce Striga germination stimulant activity. We provide evidence that the responsible gene at LGS1 codes for an enzyme annotated as a sulfotransferase and show that functional loss of this gene results in a change of the dominant strigolactone (SL) in root exudates from 5-deoxystrigol, a highly active Striga germination stimulant, to orobanchol, an SL with opposite stereochemistry. Orobanchol, although not previously reported in sorghum, functions in the multiple SL roles required for normal growth and environmental responsiveness but does not stimulate germination of Striga This work describes the identification of a gene regulating Striga resistance and the underlying protective chemistry resulting from mutation.

Cellular Response to the high protein digestibility/high-Lysine (hdhl) sorghum mutation.

A high protein digestibility/high-lysine mutant P721Q (hdhl) with a multi-folded protein body morphology has been developed, with a 22kDa α-kafirin single point mutation having also been recently identified. Relatively little is known regarding the resulting cellular response in hdhl endosperm. The aim is to elucidate these biochemical changes. Two-dimentional gel electrophoresis showed an apparent increase of non-kafirin and a decrease in kafirins content in hdhl endosperm. Mass spectrometry data yielded the identity of differentially expressed non-kafirin proteins in hdhl, wild-type lines such as cytoskeleton and chaperones proteins, and also others involved in amino acids and carbohydrates biochemical synthesis pathways. Western blot analysis showed that chaperone proteins were more highly expressed in the hdhl than the wild-type sorghum and confirmed the non-kafirin proteins proteomic results. Two-dimentional gel electrophoresis showed that the γ-kafirin subunits content had decreased, and the 22kDa α-kafirin subunit was increased in hdhl without any apparent molecular mass change. The observed differential expression most likely led to proteins interactions between γ- and α-kafirin subunits in particular, which resulted in a kafirins packing differently to form the protein body's multi-folded morphology, while also improving its digestibility.

Molecular tagging and validation of microsatellite markers linked to the low germination stimulant gene (lgs) for Striga resistance in sorghum [Sorghum bicolor (L.) Moench].

Striga is a devastating parasitic weed in Africa and parts of Asia. Low Striga germination stimulant activity, a well-known resistance mechanism in sorghum, is controlled by a single recessive gene (lgs). Molecular markers linked to the lgs gene can accelerate development of Striga-resistant cultivars. Using a high density linkage map constructed with 367 markers (DArT and SSRs) and an in vitro assay for germination stimulant activity towards Striga asiatica in 354 recombinant inbred lines derived from SRN39 (low stimulant) × Shanqui Red (high stimulant), we precisely tagged and mapped the lgs gene on SBI-05 between two tightly linked microsatellite markers SB3344 and SB3352 at a distance of 0.5 and 1.5 cM, respectively. The fine-mapped lgs region was delimited to a 5.8 cM interval with the closest three markers SB3344, SB3346 and SB3343 positioned at 0.5, 0.7 and 0.9 cM, respectively. We validated tightly linked markers in a set of 23 diverse sorghum accessions, most of which were known to be Striga resistant, by genotyping and phenotyping for germination stimulant activity towards both S. asiatica and S. hermonthica. The markers co-segregated with Striga germination stimulant activity in 21 of the 23 tested lines. The lgs locus similarly affected germination stimulant activity for both Striga species. The identified markers would be useful in marker-assisted selection for introgressing this trait into susceptible sorghum cultivars. Examination of the sorghum genome sequence and comparative analysis with the rice genome suggests some candidate genes in the fine-mapped region (400 kb) that may affect strigolactone biosynthesis or exudation. This work should form a foundation for map-based cloning of the lgs gene and aid in elucidation of an exact mechanism for resistance based on low Striga germination stimulant activity.

African Green Revolution needn't be a mirage.

Africa missed out on the scientific breakthroughs that revolutionized agriculture in Asia. However, with locally developed and locally relevant technologies, a built-up human and institutional capacity, and supportive national policy and leadership, an African Green Revolution can be a reality.

A genomewide analysis of the cinnamyl alcohol dehydrogenase family in sorghum [Sorghum bicolor (L.) Moench] identifies SbCAD2 as the brown midrib6 gene.

The content and composition of the plant cell wall polymer lignin affect plant fitness, carbon sequestration potential, and agro-industrial processing. These characteristics, are heavily influenced by the supply of hydroxycinnamyl alcohol precursors synthesized by the enzyme cinnamyl alcohol dehydrogenase (CAD). In angiosperms, CAD is encoded by a multigene family consisting of members thought to have distinct roles in different stages of plant development. Due to the high sequence similarity among CAD genes, it has been challenging to identify and study the role of the individual genes without a genome sequence. Analysis of the recently released sorghum genome revealed the existence of 14 CAD-like genes at seven genomic locations. Comparisons with maize and rice revealed subtle differences in gene number, arrangement, and expression patterns. Sorghum CAD2 is the predominant CAD involved in lignification based on the phylogenetic relationship with CADs from other species and genetic evidence showing that a set of three allelic brown midrib (bmr) lignin mutants contained mutations in this gene. The impact of the mutations on the structure of the protein was assessed using molecular modeling based on X-ray crystallography data of the closely related Arabidopsis CAD5. The modeling revealed unique changes in structure consistent with the observed phenotypes of the mutants.

Resistance to Striga hermonthica in a maize inbred line derived from Zea diploperennis.

Breeding for resistance to Striga in maize (Zea mays), with paucity of donor source and known mechanisms of resistance, has been challenging. Here, post-attachment development of S. hermonthica was monitored on two maize inbreds selected for field resistance and susceptibility reactions to Striga at the International Institute of Tropical Agriculture. Haustorial invasion of the parasite into roots of these inbreds was examined histologically. Morphological differences were observed between roots of the susceptible and the resistant inbreds. The resistant maize had fewer Striga attachments, delayed parasitic development and higher mortality of attached parasites compared with the susceptible inbred. Striga on the susceptible inbred usually penetrated the xylem and showed substantial internal haustorial development. Haustorial ingress on the resistant inbred was often stopped at the endodermis. Parasites able to reach resistant host xylem vessels showed diminished haustorial development relative to those invading susceptible roots. These results suggest that the resistant inbred expresses a developmental barrier and incompatible response against Striga parasitism.