Effect of Juglone on Active Oxygen Species and Antioxidant Enzymes in Susceptible and Partially Resistant Banana Cultivars to Black Leaf Streak Disease

The black leaf streak disease (BLSD), caused by Mycosphaerella fijiensis, is the most destructive disease of bananas and plantains around the world. Breeding for resistance is the most promising strategy to fight this disease especially in small farmer plantations. Mycosphaerella fijiensis produces many phytotoxins such as juglone, which can be used, jointly with field and inoculations under controlled conditions, for screening banana cultivars for BLSD-resistance. This non-host specific phytotoxin has been shown to act on chloroplasts and disturbs the proton electrochemical gradient across the plasmalemma membrane. Moreover, an involvement of the oxidative burst during the interaction has been suggested. The present study was carried out using two cultivars that differed for either their juglone-responses or their resistance to BLSD (cv. Grande Naine susceptible to BLSD and juglone and cv. Fougamou partially resistant to BLSD and highly tolerant to juglone). The production of active oxygen species (AOS) and the enhancement of the enzymatic and/or non-enzymatic AOS-scavenging systems were investigated after treatment of the two cultivars with juglone. The time-course of AOS-production and AOS-scavenging was shown to be the key difference between these two tested cultivars after treatment with juglone. Thus, an early release of AOS (O₂⁻ radical and H₂O₂) and a quick stimulation of a preferment anti-oxidant system (superoxide dismutases, catalases, and peroxidases) was observed for cv. Fougamou as compared to cv. Grande Naine for which a late and weak generation of AOS accompanied by a late stimulation of the anti-oxidant systems were detected.     

Survey of viruses infecting open‐field pepper crops in Côte d'Ivoire and diversity of Pepper veinal mottle virus and Cucumber mosaic virus

The prevalence of viruses in pepper crops grown in open fields in the different agro‐ecological zones (AEZs) of Côte d'Ivoire was surveyed. Pepper veinal mottle virus (PVMV; genus Potyvirus) and Cucumber mosaic virus (CMV; genus Cucumovirus) were the most frequent viruses among those surveyed, while tobamoviruses (genus Tobamovirus) were detected at low frequency. PVMV showed a high heterogeneity across AEZs, which may be related to climatic, ecological or agronomical conditions, whereas CMV was more homogeneously distributed. The molecular diversity of CMV and PVMV were analysed from partial genome sequences. Despite the low number of CMV isolates characterized, two molecular groups were revealed, one corresponding to subgroup IA and the other to reassortants between subgroups IA and IB. RNAs 1 and 3 of the reassortants clustered with the IB subgroup of CMV isolates, whereas their RNA 2 clustered with the IA subgroup. Importantly, RNA 1 of CMV isolates of the IB subgroup has been shown to be responsible for adaptation to pepper resistance. The diversity of PVMV in the VPg‐ and coat protein‐coding regions revealed multiple clades. The central part of the VPg showed a high level of amino acid diversity and evidence of positive selection, which may be a signature of adaptation to plant recessive resistance. As a consequence, for efficient deployment of resistant pepper cultivars, it would be desirable to examine the occurrence of virulent isolates in the CMV or PVMV populations in Côte d'Ivoire and to follow their evolution as the resistance becomes more widely deployed.     

Differences in the crude protein fractions of lucerne leaves and stems under different stand structures

Protein degradability in forage legumes is of global importance because utilization efficiency of forage has economic and environmental consequences. However, there are no published studies on the effect of legume stand structure on differences in crude protein (CP) fractions. The main objective of the present research was therefore to investigate differences in CP fractions in leaves and stems of lucerne (Medicago sativa L.) during the growing season. Stand traits were measured over 2 years, and forage was sampled at the early bud and early flower stages in the first, second and third cuts. Stems had significantly higher concentrations (in g kg^?1 CP) of non‐protein (fraction A: 430 g kg^?1 CP) and indigestible nitrogen (fraction C: 92 g kg^?1 CP) than leaves and had lower relative content of true protein (fraction B: 478 g kg^?1 CP). In the total forage (stems and leaves combined), about 80% of the variation in CP fractions was explained by year, cut and maturity. Year was the most important factor, particularly for the B fractions. Cut was the second‐most important factor; its main effect was that the relative abundance of fraction A declined from 394 g kg^?1 CP in the first cut to 293 in g kg^?1 CP the third cut. Maturity increased the amounts of indigestible fraction C and protein fractions B₁ and B₃. This was associated with the leaf weight ratio, which had an inverse relationship with maximal stem length and dry matter yield. Variation partitioning showed that 75% of CP fraction variability associated with cut, maturity and year could be explained by the evaluated stand traits. This research has highlighted the need to consider plant morphological traits when legume CP fractions are evaluated.     

Exploration of beer proteome using OFFGEL prefractionation in combination with two-dimensional gel electrophoresis with narrow pH range gradients

Two-dimensional gel electrophoresis in combination with mass spectrometry has already been applied successfully to study beer proteome. Due to the abundance of protein Z in beer samples, prefractionation techniques might help to improve beer proteome coverage. Proteins from four lager beers of different origins were separated by two-dimensional electrophoresis (2-DE) followed by tandem mass spectrometric analysis. Initially 52 proteins mostly from Hordeum vulgare (22 proteins) and Saccharomyces species (25 proteins) were identified. Preparative isoelectric focusing by OFFGEL Fractionator was applied prior to 2-DE to improve its resolution power. As a result of this combined approach, a total of 70 beer proteins from Hordeum vulgare (30 proteins), from Saccharomyces species (31 proteins), and from other sources (9 proteins) were identified. Of these, 37 proteins have not been previously reported in beer samples.     

Seroprevalence of Neospora caninum antibodies and its consequences for reproductive parameters in dairy cows from Dakar–Senegal,West Africa

The aim of this study was to determine the seroprevalence of Neospora caninum antibodies and its effects on reproductive parameters in cows in intensive dairy herds in Dakar. Randomised blood samples were taken for serology from 196 cows in four herds with a history of sporadic abortion. All of the sera were assayed for antibodies against N. caninum, Candida guillermondii, Coxiella burnetii, and Chlamydophila sp. The associations between serostatus and reproductive parameters (abortion, number of inseminations to conception, and calving to conception interval) were assessed over a period of 5 years (2004–2008). The seroprevalence of N. caninum antibodies in dairy cattle was 17.9%. The local Gobra breed and crossbreeds had higher levels of N. caninum antibodies than exotic breeds (p < 0.05). For the most recent pregnancies, seropositive cows required more inseminations to establish conception than seronegative cows (p < 0.05). The results indicate that dairy cattle from Dakar are exposed to N. caninum. Neosporosis should, therefore, be systematically considered as a cause when the calving to conception interval is prolonged.     

Assessing sub-Saharan Erythrina for efficacy: traditional uses, biological activities and phytochemistry

The genus Erythrina comprises more than 100 species, widely distributed in tropical and subtropical areas. In Africa, 31 wild species and 14 cultivated species have been described. In sub-Saharan Africa, Erythrina species are used to treat frequent parasitic and microbial diseases, inflammation, cancer, wounds. The rationale of these traditional uses in African traditional medicine was established by screening several species for biological activities. Promising activities were found against bacteria, parasites (Plasmodium), human and phytopathogenic fungi, some of which were multidrug resistant (MDR) micro organisms. Some species also exhibited antioxidant, anti-inflammatory activities and enzymes inhibitory properties. Most of the species chemically investigated were reported to contain flavanones, prenylated isoflavones, isoflavanones and pterocarpans. Some phytochemicals (vogelin B, vogelin C, isowightcone, abyssinin II, derrone) were the active principles as antibacterials, antifungals, antiplasmodials and inhibitors of enzyme borne diseases (PTP1B, HIV protease, DGAT). This review highlights the important role of Erythrina species as sources of lead compounds or new class of phytotherapeutic agents for fighting against major public health (MDR infections, cancer, diabetes, obesity) in sub-Saharan Africa.     

Response of lowland rice to agronomic management under different hydrological regimes in an inland valley of Ivory Coast

A large proportion of the rice in West Africa is produced in rainfed lowland ecosystems, mainly in inland valleys. The hydrological conditions (duration and intensity of flooding) vary with the toposequence position between the fringe and the centre of the valley. Production methods tend to evolve from the currently predominant unbunded plots without external input use, to input-intensive production in bunded plots. Agronomic management interventions co-evolve and may include varietal choice, herbicide use, and mineral N fertilizer application. The response of rice and the associated weeds to such interventions is likely to vary with the prevailing hydrological regime. A 2-year field experiment was conducted in northern Ivory Coast to determine the impact of water regime (plot position in the valley, presence of bunds) and input use (mineral N fertilizer and herbicide) on the productivity (yield and N use efficiency) of traditional and modern rainfed lowland rice cultivars and the biomass and composition of the associated weeds. Installing field bunds reduced seasonal variations in ponded water depth and resulted in a mean increase in rice grain yield of 30–40% (p < 0.005). This increase was associated with a 25% lower cumulative weed biomass and a several-fold increase in the agronomic use efficiency of applied mineral N in bunded than unbunded plots. Under low input management, traditional varieties tended to out-yield modern varieties in unbunded plots. Improved crop management such as herbicide and fertilizer application, and the construction of field bunds was more effective to increase the yield and N use efficiency in the flooded valley centre than in the drought-prone valley fringes. There is a need for site-specific targeting of modern cultivars, land development and improved production methods in the inland valleys of the West African savanna zone.