Yield loss of Oryza glaberrima caused by grain shattering under rainfed upland conditions

The general perception of Oryza glaberrima as low yielding is a potential drawback to intraspecific breeding of this species. Yields of 21 O. glaberrima accessions were evaluated alongside four O. sativa check varieties under two conditions in which panicles were both covered by paper sacks to avoid grain shattering (potential yield plot) and also not covered (control plot) in a rainfed upland field of Benin in 2010 and 2011. Average potential yields of O. glaberrima with panicles covered were 2.42 and 3.65 t ha-1 in 2010 and 2011, respectively, while those of O. sativa were respectively 2.99 and 3.49 t ha-1. Although there was no significant difference between potential yield and control yield in O. sativa, 19 O. glaberrima accessions showed significant yield reduction by grain shattering — the average percentages of lost yield by shattering were 57.88% in 2010 and 66.76% in 2011. These results suggest that low yield of O. glaberrima is due to grain shattering and that its potential yield would not be inferior to O. sativa if the grain shattering problems were overcome. Two O. glaberrima accessions, TOG 12303 and TOG 9300, possessing strong resistance to grain shattering comparable to O. sativa checks, were identified.Keywords: Panicles, paper sacks, potential yield, yield reduction

Physiological responses of cowpea simultaneously exposed to water deficit stress and varying light intensities at vegetative and reproductive growth stages

A combination of stresses as it occurs on the field poses more challenges to crop production than individual stress. Crops’ response to single stress also differs from that of combined stresses. The morpho-physiological responses of two cowpea varieties (IT89KD-288 and IT99K573-1-1) to a combination of stresses (water deficit stress and high light intensity) were investigated at different growth stages. Three levels of light intensities (L3: 259 Lux- 36%, L2: 394 Lux-55% and L1: 710.2 Lux-100%) were imposed using one, two and zero layer(s) of the net, respectively, while, water deficit stress at four levels (W1: no water stress; 0-5 bars, W2: moderate water stress; 5-15 bars, W3: moderately-severe; 15-40 bars and W4: severe water stress; 40 -70 bars) was imposed differently at vegetative and reproductive growth stages. Data were collected on the cowpea yield, Leaf Temperature (LT), Chlorophyll (C), Photosynthesis (P), Stomatal Conductance (SC) and Canopy Transpiration Rate (CTR). Exposure to W4 under L1 considerably reduced cowpea yield by 80% compared to those grown under L3 and full watering. Reduced light intensity enhanced cowpea grain yield irrespective of water deficit stress and IT89KD-288 was superior to IT99K573-1-1. Reduction in light intensity also increased the SC from 55.18 in L1 to 76.88 in 36 % L3. Full light intensity without water stress (100% light intensity), increased C content, while severe water stress reduced the C content and CTR. Photosynthesis was, however, reduced under low light intensity compared to 100% light intensity. It was also observed that water deficit stress imposed at the reproductive stage did not affect P, CTR and SC unlike that of the vegetative stage. In conclusion, reduced light intensity enhanced cowpea tolerance to water deficit and increased yield. Cowpea response was dependent on growth stage, variety and severity of stress

Hepatitis C virus cell-cell transmission and resistance to direct-acting antiviral agents

Hepatitis C virus (HCV) is transmitted between hepatocytes via classical cell entry but also uses direct cell-cell transfer to infect neighboring hepatocytes. Viral cell-cell transmission has been shown to play an important role in viral persistence allowing evasion from neutralizing antibodies. In contrast, the role of HCV cell-cell transmission for antiviral resistance is unknown. Aiming to address this question we investigated the phenotype of HCV strains exhibiting resistance to direct-acting antivirals (DAAs) in state-of-the-art model systems for cell-cell transmission and spread. Using HCV genotype 2 as a model virus, we show that cell-cell transmission is the main route of viral spread of DAA-resistant HCV. Cell-cell transmission of DAA-resistant viruses results in viral persistence and thus hampers viral eradication. We also show that blocking cell-cell transmission using host-targeting entry inhibitors (HTEIs) was highly effective in inhibiting viral dissemination of resistant genotype 2 viruses. Combining HTEIs with DAAs prevented antiviral resistance and led to rapid elimination of the virus in cell culture model. In conclusion, our work provides evidence that cell-cell transmission plays an important role in dissemination and maintenance of resistant variants in cell culture models. Blocking virus cell-cell transmission prevents emergence of drug resistance in persistent viral infection including resistance to HCV DAAs

Étude de la variabilité agromorphologique de la collection nationale de mils locaux du Sénégal

Objectif : Le mil est la première culture vivrière au Sénégal. Il joue un rôle capital dans la vie des populations rurales qui en dépendent pour leur survie (STAT/FAO/SENEGAL, 2010). Il est cultivé sur plus 60% des terres arables. Les variétés locales étaient les plus utilisées mais depuis quelques années leur survie est menacée par l'introduction des variétés améliorées.Methodology et application des résultats : Pour éviter l'érosion génétique, des missions de collecte ont été organisées en 1994 et 2006 dans les principales zones de culture du mil. Le matériel collecté est caractérisé pour faciliter leur utilisation dans les programmes de création variétale. L'objectif du présent travail est caractériser le germoplasme national mil du Sénégal pour les rendre utilisables par les sélectionneurs pour la création de nouvelles variétés hautement productives pour l'augmentation de la production céréalière et l'atteinte de la sécurité alimentaire. Pour caractériser les accessions, 12 variables sélectionnées à partir du Descripteur du mil IPGRI/ICRISAT, 1993 ont été utilisées. Un dispositif expérimental en blocs complets randomisés avec 3 répétitions a été choisi et les sites d'essais étaient Bambey, Nioro et Darou pendant les hivernages 2011 et 2012. Les analyses descriptives ou qualitatives ; statistiques simples (ANOVA) ; de la diversité (phénologique ; génétique avec la méthode de la classification ascendante (CAH), avec les composantes principales (ACP) et l'analyse factorielle discriminante (AFD)) ont été réalisées avec les logiciels Genstat Discovery4 et R. Les analyses descriptives ont montré l'existence d'une grande variabilité entre les accessions pour les caractères qualitatifs comme l'architecture de l'épi et la couleur des grains. Les analyses statistiques simples (ANOVA) ont montré qu'il existe une différence hautement significative entre les entrées et les sites. Cependant, les interactions étaient non significatives à l'exception de la floraison, de l'indice de récolte et des rendements en grains et en matière sèche. Les analyses de la diversité phénologique a permis de classer les variétés en trois groupes selon le cycle végétatif (G1 des variétés extra-précoces, G2 des cycles courts et G3 des cycles longs). La classification ascendante hiérarchique (CAH) suivant la méthode de Ward a permis d'identifier la valeur des axes et les compositions des 3 groupes y découlant (le groupe G1 compte 106 accessions, le G2 compte 129 accessions et le G3 compte 8 accessions) et de tracer le dendrogramme de filiations. L'analyse de la diversité génétique par les composantes principales (ACP) a permis de déterminer la position des accessions par rapport aux axes expliquant les variabilités inter-accessions. L'analyse de la diversité génétique par la méthode factorielle discriminante a permis de déterminer la structuration de la diversité agromorphologique et la représentation graphique des accessions suivant un plan factoriel. Les groupes ainsi formés seront convertis en des entités hétérotiques constituées de pools de gènes différents où les sélectionneurs et autres scientifiques vont puiser pour créer des variétés hautement productives et résistantes aux stress bio et abiotiques afin de nourrir les populations et de lutter contre la faim et la malnutrition

Implications of farmer perceived production constraints and varietal preferences to pearl millet breeding in Senegal

Pearl millet ( Pennisetum glaucum L.) plays a critical role in smallholder food security in sub-Saharan Africa. The production of pearl millet has, however, stagnated or even declined due to several factors. The objective of this study was to assess farmer perceptions on production constraints and varietal preferences in Senegal. A survey was conducted involving 150 randomly selected farmers from 15 villages, in five representative rural communities of Senegal. A semi-structured questionnaire was used, supplemented by focus group discussions. Results revealed that parasitic Striga weed was the most constraining factor to pearl millet production across the rural communes. This was followed by low soil fertility and insect pests in that order. Other constraints included lack of machinery for sowing, plant diseases, drought, seed-eating birds, limited access to land for pearl millet cultivation and limited seed availability. Among the traits for varietal preference, farmers unanimously considered grain yield as the most important trait. Other important traits mentioned were adaptation to drought, adaptation to low soil fertility and earliness. These production constraints and varietal preference should be integrated in the profile of the national pearl millet breeding programmes in order to improve the productivity and adoption of bred-cultivars.Le mil est une importante culture c\ue9r\ue9ali\ue8re et joue un r\uf4le essentiel dans la s\ue9curit\ue9 alimentaire de la plupart des producteurs de l\u2019Afrique subsaharienne. Cependant, la production est oscillante et faible en raison de plusieurs facteurs. Une \ue9tude a \ue9t\ue9 conduite pour \ue9valuer la perception des producteurs sur les contraintes limitant la production du mil et leurs pr\ue9f\ue9rences vari\ue9tales au S\ue9n\ue9gal. Une enqu\ueate avec150 producteurs s\ue9lectionn\ue9s al\ue9atoirement a \ue9t\ue9 men\ue9e dans 15 villages situ\ue9s dans cinq communaut\ue9s rurales du S\ue9n\ue9gal. Une \ue9valuation rurale participative et des enqu\ueates ont \ue9t\ue9 men\ue9es. Les r\ue9sultats ont montr\ue9 que le Striga est le facteur majeur qui limite la production de mil au niveau des diff\ue9rentes communaut\ue9s rurales. Les autres contraintes rencontr\ue9es dans les communes rurales \ue9taient le manque de machines pour le semis, les maladies, la s\ue9cheresse, les oiseaux granivores, l\u2019acc\ue8s limit\ue9 \ue0 la terre et la faible disponibilit\ue9 des semences de vari\ue9t\ue9s am\ue9lior\ue9es. Les producteurs ont unanimement consid\ue9r\ue9 le rendement en grains comme le trait le plus important dans le choix d\u2019une nouvelle vari\ue9t\ue9. Les autres traits jug\ue9s important sont l\u2019adaptation \ue0 la s\ue9cheresse l\u2019adaptation \ue0 la faible fertilit\ue9 des sols et la pr\ue9cocit\ue9. Ces contraintes de production et pr\ue9f\ue9rences vari\ue9tales doivent \ueatre incluses parmi les objectifs du programme national de s\ue9lection de mil pour am\ue9liorer la productivit\ue9 et le taux l\u2019adoption des nouvelles vari\ue9t\ue9s

DNA immunization as a technology platform for monoclonal antibody induction

To combat the threat of many emerging infectious diseases, DNA immunization offers a unique and powerful approach to the production of high-quality monoclonal antibodies (mAbs) against various pathogens. Compared with traditional protein-based immunization approaches, DNA immunization is efficient for testing novel immunogen designs, does not require the production or purification of proteins from a pathogen or the use of recombinant protein technology and is effective at generating mAbs against conformation-sensitive targets. Although significant progress in the use of DNA immunization to generate mAbs has been made over the last two decades, the literature does not contain an updated summary of this experience. The current review provides a comprehensive analysis of the literature, including our own work, describing the use of DNA immunization to produce highly functional mAbs, in particular, those against emerging infectious diseases. Critical factors such as immunogen design, delivery approach, immunization schedule, use of immune modulators and the role of final boost immunization are discussed in detail

A novel monoclonal anti-CD81 antibody produced by genetic immunization efficiently inhibits Hepatitis C virus cell-cell transmission

BACKGROUND AND AIMS: Hepatitis C virus (HCV) infection is a challenge to prevent and treat because of the rapid development of drug resistance and escape. Viral entry is required for initiation, spread, and maintenance of infection, making it an attractive target for antiviral strategies. METHODS: Using genetic immunization, we produced four monoclonal antibodies (mAbs) against the HCV host entry factor CD81. The effects of antibodies on inhibition of HCV infection and dissemination were analyzed in HCV permissive human liver cell lines. RESULTS: The anti-CD81 mAbs efficiently inhibited infection by HCV of different genotypes as well as a HCV escape variant selected during liver transplantation and re-infecting the liver graft. Kinetic studies indicated that anti-CD81 mAbs target a post-binding step during HCV entry. In addition to inhibiting cell-free HCV infection, one antibody was also able to block neutralizing antibody-resistant HCV cell-cell transmission and viral dissemination without displaying any detectable toxicity. CONCLUSION: A novel anti-CD81 mAb generated by genetic immunization efficiently blocks HCV spread and dissemination. This antibody will be useful to further unravel the role of virus-host interactions during HCV entry and cell-cell transmission. Furthermore, this antibody may be of interest for the development of antivirals for prevention and treatment of HCV infection

Genotype 1 hepatitis C virus envelope features that determine antiviral response assessed through optimal covariance networks

The poor response to the combined antiviral therapy of pegylated alfa-interferon and ribavarin for hepatitis C virus (HCV) infection may be linked to mutations in the viral envelope gene E1E2 (env), which can result in escape from the immune response and higher efficacy of viral entry. Mutations that result in failure of therapy most likely require compensatory mutations to achieve sufficient change in envelope structure and function. Compensatory mutations were investigated by determining positions in the E1E2 gene where amino acids (aa) covaried across groups of individuals. We assessed networks of covarying positions in E1E2 sequences that differentiated sustained virological response (SVR) from non-response (NR) in 43 genotype 1a (17 SVR), and 49 genotype 1b (25 SVR) chronically HCV-infected individuals. Binary integer programming over covariance networks was used to extract aa combinations that differed between response groups. Genotype 1a E1E2 sequences exhibited higher degrees of covariance and clustered into 3 main groups while 1b sequences exhibited no clustering. Between 5 and 9 aa pairs were required to separate SVR from NR in each genotype. aa in hypervariable region 1 were 6 times more likely than chance to occur in the optimal networks. The pair 531-626 (EI) appeared frequently in the optimal networks and was present in 6 of 9 NR in one of the 1a clusters. The most frequent pairs representing SVR were 431-481 (EE), 500-522 (QA) in 1a, and 407-434 (AQ) in 1b. Optimal networks based on covarying aa pairs in HCV envelope can indicate features that are associated with failure or success to antiviral therapy