Genetic variability among landraces of sesame in Ethiopia

Sesame ( Sesamum indicum d 46.4% for landraces and cultivars, respectively, indicates that both landraces and cultivars are line mixtures and segregants of past outcrossing results. A Neighbour-Joining dendrogram based on Modified Rogers' Distances (MRD) and a principal coordinate analysis based on a simple dissimilarity matrix, points towards some grouping based on geographical origin. The established SSR markers will be very useful for further diversity analyses among a large landrace collection of Ethiopian sesame and in the establishment of a core collection. Moreover, existence of great genetic variability between the landraces is a good starting point of sesame crop improvement programs in Ethiopia.La S\ue9same ( Sesamum indicum L.) est une culture \ue0 huile anciennement d\ue9nom\ue9e "Reine de graines ol\ue9agineuses"lus petite que la divergence g\ue9n\ue9tique parmi les populations. Un croisement h\ue9t\ue9rog\ue8ne \ue9lev\ue9 de 45 et 46.4 % pour les races locales et les cultivars, respectivement, indique que les races locales et les cultivars sont des lign\ue9es mixtes et s\ue9gr\ue9gants des r\ue9sultats des croisements h\ue9t\ue9rog\ue8nes pass\ue9s. Un dendogramme d\ue9velopp\ue9 sur base des Distances modifi\ue9es de Rogers (DMR) et l'analyse de principales coordonn\ue9es bas\ue9e sur une simple dissemblance matricielle montrent quelques groupements sur base de l'origine g\ue9ographique. Les marqueurs (SSR) \ue9tablis seront tr\ue8s utiles pour d'autres analyses de diversit\ue9 au sein d' une large collection de races locales de s\ue9sames ethiopiennes et dans l'\ue9tablissement d'une collection de base. En plus, l'existence d'une grande variabilit\ue9 g\ue9n\ue9tique entre les races locales est un bon point de d\ue9part pour des programmes d'am\ue9lioration de la cultutre de s\ue9same en Ethiopie

Patterns of molecular and phenotypic diversity in pearl millet [Pennisetum glaucum (L.) R. Br.] from West and Central Africa and their relation to geographical and environmental parameters

<p>Abstract</p> <p>Background</p> <p>The distribution area of pearl millet in West and Central Africa (WCA) harbours a wide range of climatic and environmental conditions as well as diverse farmer preferences and pearl millet utilization habits which have the potential to lead to local adaptation and thereby to population structure. The objectives of our research were to (i) assess the geographical distribution of genetic diversity in pearl millet inbreds derived from landraces, (ii) assess the population structure of pearl millet from WCA, and (iii) identify those geographical parameters and environmental factors from the location at which landraces were sampled, as well as those phenotypic traits that may have affected or led to this population structure. Our study was based on a set of 145 inbred lines derived from 122 different pearl millet landraces from WCA.</p> <p>Results</p> <p>Five sub-groups were detected within the entire germplasm set by STRUCTURE. We observed that the phenotypic traits flowering time, relative response to photoperiod, and panicle length were significantly associated with population structure but not the environmental factors which are expected to influence these traits in natural populations such as latitude, temperature, or precipitation.</p> <p>Conclusions</p> <p>Our results suggested that for pearl millet natural selection is compared to artificial selection less important in shaping populations.</p

Association analysis of photoperiodic flowering time genes in west and central African sorghum [Sorghum bicolor (L.) Moench]

Abstract Background: Photoperiod-sensitive flowering is a key adaptive trait for sorghum (Sorghum bicolor) in West and Central Africa. In this study we performed an association analysis to investigate the effect of polymorphisms within the genes putatively related to variation in flowering time on photoperiod-sensitive flowering in sorghum. For this purpose a genetically characterized panel of 219 sorghum accessions from West and Central Africa was evaluated for their photoperiod response index (PRI) based on two sowing dates under field conditions. Results: Sorghum accessions used in our study were genotyped for single nucleotide polymorphisms (SNPs) in six genes putatively involved in the photoperiodic control of flowering time. Applying a mixed model approach and previously-determined population structure parameters to these candidate genes, we found significant associations between several SNPs with PRI for the genes CRYPTOCHROME 1 (CRY1-b1) and GIGANTEA (GI)

Genetic variability among landraces of sesame in Ethiopia

Sesame ( Sesamum indicum d 46.4% for landraces and cultivars, respectively, indicates that both landraces and cultivars are line mixtures and segregants of past outcrossing results. A Neighbour-Joining dendrogram based on Modified Rogers&apos; Distances (MRD) and a principal coordinate analysis based on a simple dissimilarity matrix, points towards some grouping based on geographical origin. The established SSR markers will be very useful for further diversity analyses among a large landrace collection of Ethiopian sesame and in the establishment of a core collection. Moreover, existence of great genetic variability between the landraces is a good starting point of sesame crop improvement programs in Ethiopia.La Sésame ( Sesamum indicum L.) est une culture à huile anciennement dénomée "Reine de graines oléagineuses"lus petite que la divergence génétique parmi les populations. Un croisement hétérogène élevé de 45 et 46.4 % pour les races locales et les cultivars, respectivement, indique que les races locales et les cultivars sont des lignées mixtes et ségrégants des résultats des croisements hétérogènes passés. Un dendogramme développé sur base des Distances modifiées de Rogers (DMR) et l&apos;analyse de principales coordonnées basée sur une simple dissemblance matricielle montrent quelques groupements sur base de l&apos;origine géographique. Les marqueurs (SSR) établis seront très utiles pour d&apos;autres analyses de diversité au sein d&apos; une large collection de races locales de sésames ethiopiennes et dans l&apos;établissement d&apos;une collection de base. En plus, l&apos;existence d&apos;une grande variabilité génétique entre les races locales est un bon point de départ pour des programmes d&apos;amélioration de la cultutre de sésame en Ethiopie

Association of single nucleotide polymorphic sites in candidate genes with aggressiveness and deoxynivalenol production in Fusarium graminearum causing wheat head blight

BACKGROUND: Fusarium graminearum sensu stricto (s.s.) is an ubiquitous pathogen of cereals. The economic impact of Fusarium head blight (FHB) is characterized by crop losses and mycotoxin contamination. Our objective was to associate SNP diversity within candidate genes with phenotypic traits. A total of 77 F. graminearum s.s. isolates was tested for severity of fungal infection (= aggressiveness) and deoxynivalenol (DON) production in an inoculated field experiment at two locations in each of two years. For seven genes known to control fungal growth (MetAP1, Erf2) or DON production (TRI1, TRI5, TRI6 TRI10 and TRI14) single nucleotides polymorphic sites (SNPs) were determined and evaluated for the extent of linkage disequilibrium (LD). Associations of SNPs with both phenotypic traits were tested using linear mixed models. RESULTS: Decay of LD was in most instances fast. Two neighboring SNPs in MetAP1 and one SNP in Erf2 were significantly (P < 0.05) associated with aggressiveness explaining proportions of genotypic variance (p(G)) of 25.6%, 0.5%, and 13.1%, respectively. One SNP in TRI1 was significantly associated with DON production (p(G )= 4.4). CONCLUSIONS: We argue that using the published sequence information of Fusarium graminearum as a template to amplify comparative sequence parts of candidate genes is an effective method to detect quantitative trait loci. Our findings underline the potential of candidate gene association mapping approaches to identify functional SNPs underlying aggressiveness and DON production for F. graminearum s.s populations

Investigation of pollen competition between wild and cultivated sorghums (Sorghum bicolor (L.) Moench) using simple sequence repeats markers

In self-compatible plant species stigmata receive a mixture of self and outcrossed pollen and competition between them is expected to play a major role in determining the pollen-mediated gene flow. The use of male sterile bait plants in field trials to demonstrate the rate of gene flow is questionable due to lack of pollination competition. However, little direct evidence has been published. A field experiment of male sterile and male fertile sorghum pollen recipient bait plants was conducted to evaluate pollen competition between wild and cultivated sorghums and the effects of pollen competition on gene flow assessment. Pollen competition between wild and cultivated sorghums was estimated from two-component pollen mixtures of wild and cultivated sorghum (1:1 ratio) applied to wild, cultivated and male-sterile maternal bait plants. Paternity was determined in the progeny using two diagnostic Simple Sequence Repeat markers. The study found that self pollen has higher seed-siring success. Maternal genotype influences the siring ability of the pollen donor components which significantly deviated from the 1:1 pollen loads. The study showed that published estimates of gene flow derived from studies using male-sterile bait plants seriously overestimate gene flow and that pollen competition may be a significant factor influencing outcrossing rates. The results suggest that the predominant direction of gene flow is from cultivated to wild sorghum, potentially leading to introgression of crop genes into wild sorghum. Pollen competition should be taken into account in gene flow estimation, since presence of self-pollen can account for over half of seed produced irrespective of maternal genotype. (Résumé d'auteur