Genetic Diversification and Selection Strategies for Improving Sorghum Grain Yield Under Phosphorous-Deficient Conditions in West Africa

Sorghum, a major crop for income generation and food security in West and Central Africa, is predominantly grown in low-input farming systems with serious soil phosphorus (P) deficiencies. This study (a) estimates genetic parameters needed to design selection protocols that optimize genetic gains for yield under low-phosphorus conditions and (b) examines the utility of introgressed backcross nested association mapping (BCNAM) populations for diversifying Malian breeding materials. A total of 1083 BC1F5 progenies derived from an elite hybrid restorer “Lata-3” and 13 diverse donor accessions were evaluated for yield and agronomic traits under contrasting soil P conditions in Mali in 2013. A subset of 298 progenies were further tested under low-P (LP) and high-P (HP) conditions in 2014 and 2015. Significant genetic variation for grain yield was observed under LP and HP conditions. Selection for grain yield under LP conditions was feasible and more efficient than the indirect selection under HP in all three years of testing. Several of the BCNAM populations exhibited yields under LP conditions that were superior to the elite restorer line used as a recurrent parent. The BCNAM approach appears promising for diversifying the male parent pool with introgression of diverse materials using both adapted Malian breed and unadapted landrace material from distant geographic origins as donors

Transforming a traditional commons-based seed system through collaborative networks of farmer seed-cooperatives and public breeding programs: the case of sorghum in Mali

Malian farmers’ traditional system for managing seed of sorghum, an indigenous crop of vital importance for food security and survival, can be conceptualized as a commons. Although this system maintains a wide range of varieties and helps ensure access to seed, its ability to create and widely disseminate new varieties to meet evolving opportunities and challenges is limited. A network of farmer groups, public breeding programs, and development organizations collaborating in decentralized creation and dissemination of sorghum varieties in Mali is examined regarding (1) how the network developed and what activities it conducts; (2) the resulting varietal diversity, varietal performance and organizational models; and (3) the elements of the traditional seed system that were maintained, strengthened or transformed. A single-case study approach was used that relies on published literature, official catalogues of released varieties and a database of farmer seed-cooperative requests for foundation seed. The functioning of the network and its varietal-, seed-, and organizational- outcomes are documented and the elements of the traditional sorghum seed system that are maintained or strengthened are analyzed. The evolution of the network’s reliance on commoning as a social process and its strengthening of core Seed Commons features are discussed with a view to the network’s contributions to targeted development outcomes and potential replicability. The case demonstrates how creating a framework for collaboration, enabling actors and organizations to take on collective responsibility while maintaining distributed decision-making at local level, opens opportunities for transforming farming- and food-systems towards sustainability and resilience

Antibody responses to <i>P. falciparum</i> blood stage antigens and incidence of clinical malaria in children living in endemic area in Burkina Faso

Abstract Background High parasite-specific antibody levels are generally associated with low susceptibility to Plasmodium falciparum malaria. This has been supported by several studies in which clinical malaria cases of P. falciparum malaria were reported to be associated with low antibody avidities. This study was conducted to evaluate the role of age, malaria transmission intensity and incidence of clinical malaria in the induction of protective humoral immune response against P. falciparum malaria in children living in Burkina Faso. Methods We combined levels of IgG and IgG subclasses responses to P. falciparum antigens: Merozoite Surface Protein 3 (MSP3), Merozoite Surface Protein 2a (MSP2a), Merozoite Surface Protein 2b (MSP2b), Glutamate Rich Protein R0 (GLURP R0) and Glutamate Rich Protein R2 (GLURP R2) in plasma samples from 325 children under five (05) years with age, malaria transmission season and malaria incidence. Results We notice higher prevalence of P. falciparum infection in low transmission season compared to high malaria transmission season. While, parasite density was lower in low transmission than high transmission season. IgG against all antigens investigated increased with age. High levels of IgG and IgG subclasses to all tested antigens except for GLURP R2 were associated with the intensity of malaria transmission. IgG to MSP3, MSP2b, GLURP R2 and GLURP R0 were associated with low incidence of malaria. All IgG subclasses were associated with low incidence of P. falciparum malaria, but these associations were stronger for cytophilic IgGs. Conclusions On the basis of the data presented in this study, we conclude that the induction of humoral immune response to tested malaria antigens is related to age, transmission season level and incidence of clinical malaria

Humoral response to the Anopheles gambiae salivary protein gSG6: IgG1 and IgG4 subclasses in exposed individuals from Burkina Faso.

The ability to monitor malaria transmission and to evaluate vector control measures are two basic ingredients of any effective anti-malaria intervention. The use of serology, in addition to classical parasitological and entomological methods, could represents an important complementary/alternative tool that may allow for wider, easier and perhaps more sensitive epidemiological analyses. In the course of mosquito salivary transcriptome studies we identified a group of anopheline-specific salivary proteins (i.e. not found so far in any other blood sucking arthropod) which could be useful as indicators of exposure to bites of malaria vectors. We have previously shown that the Anopheles gambiae salivary protein gSG6 is immunogenic and elicits an IgG response that (i) is short-lived, (ii) varies with the transmission season and (iii) is stronger in the ethnic group Fulani as compared to Mossi in West Africa (in preparation). Moreover, the anti-gSG6 IgG response decreases with age suggesting the involvement of some mechanism of tolerance as a consequence of the continued exposure to the antigen. To get further insights into the nature of this anti-gSG6 IgG response we measured the levels of IgG1 and IgG4 subclasses in human sera collected in a rural malaria hyperendemic area of Burkina Faso at the beginning and at the end of the transmission season, as well as during the following dry season. Overall the results are in line with our previous observations and high levels of anti-gSG6 IgG4 were found in exposed individuals. Data appear compatible with the involvement of a mechanism of desensitization and suggest that in high transmission/exposure areas this tolerance may take place early, most likely in 3 to 6 years old children

Human IgG response to the Anopheles gambiae salivary protein gSG6: an indicator of exposure to anopheline mosquito bites.

The ability to estimate the risk of malaria infection is crucial for the development and evaluation of control programmes and currently relies on both entomological and parasitological methods. The availability of rapid and sensitive tools to measure the exposure to Anopheles mosquito bites would be extremely valuable in this context. Human antibody response to Anopheles saliva may represent such an indicator (Remoue F et al, 2006, Trans R Soc Trop Med Hyg). However, mosquito saliva is a complex cocktail of bioactive factors and cross-reactivity with other antigens (i.e. salivary proteins from blood-feeders other than anophelines) may be misleading. In the attempt to identify immunogenic and anopheline-specific proteins to be used as serological indicators of exposure to malaria vectors we focused our attention on the Anopheles gambiae gSG6. This is a small, female salivary gland-specific protein involved in blood feeding (Lombardo F et al, 2009, Insect Biochem Mol Biol). So far, gSG6 has been found only in anopheline species (An. gambiae complex, An. stephensi, An. funestus and An. freeborni) whereas it is absent in culicine mosquitoes and in other blood feeding arthropods. Previous studies suggested that gSG6 is immunogenic (Poinsignon A et al, 2008, PLoS One) and, therefore, we expressed the protein in recombinant form and measured the humoral immune response to gSG6 in human sera collected during three consecutive years in rural malaria hyperendemic areas of Burkina Faso. gSG6 was confirmed to be immunogenic and to elicit an IgG response that varies according to malaria transmission intensity. Interestingly, a significant decrease in the IgG levels was observed during the dry season, suggesting that this response is short-lived. Moreover, anti-gSG6 IgG levels differed significantly in the two sympatric ethnic groups, Mossi and Fulani, already known for their differential response to several P. falciparum antigens (Modiano D et al, 1996, Proc Natl Acad Sci USA). Finally, the IgG response varied with age, being higher in children and progressively decreasing in older people. This decline suggests the possible involvement of a mechanism of tolerance developed as consequence of a continued exposure to the antigen. The high level of anti-gSG6 IgG4 found in the sera of exposed individuals appears compatible with the implication of a desensitization mechanism. Overall, our study provides a solid indication that individual recombinant salivary proteins may represent useful tools for epidemiological studies, evaluation of vector-control campaigns and perhaps for the development of risk maps. (*equal contribution)

Humoral response to mosquito salivary proteins as serological indicator of exposure to disease vectors: IgG response to the Anopheles gambiae gSG6 and malaria.

Saliva of hematophagous arthropods, injected into the vertebrate during blood feeding, triggers the production of anti-saliva IgG and IgE antibodies. This host immune response to vector saliva (from ticks, sand flies, triatomines, tsetse and mosquitoes) may be used as a marker of exposure to vector bites and indicator of disease risk. Indeed, the potential to estimate vector density through serological assays may represent a very valuable tool for epidemiological studies. Human humoral response to Anopheles saliva has been correlated with the exposure to anopheline vectors and with malaria transmission (Remoue F et al., 2006; Waitayakul A et al., 2006; Orlandi-Pradines E et al., 2007). However, saliva is a complex mixture and cross-reactivity with antigens from other mosquitoes and/or other blood-feeding arthropods may be misleading. Moreover, obtaining large amounts of mosquito saliva or salivary extracts is tedious and not easily reproducible. In this respect recent studies on the salivary transcriptomes of blood feeding vectors provided some interesting perspectives. In fact, comparative analysis clarified that the mosquito salivary repertoire includes both salivary proteins that are widely shared among Culicidae family members and proteins that are genus-specific, i.e. found only in Anopheles, but not in Aedes or Culex species, and viceversa. This finding implies that anopheline-specific proteins, if immunogenic, may be ideal serological indicators of exposure to Anopheles bites and, similarly, that Aedes-specific proteins could be used as markers of exposure to Aedes-mosquitoes. The An. gambiae salivary protein gSG6 is a small protein specifically expressed in adult female glands where it plays some important role in blood feeding (Lanfrancotti A et al., 2002; Lombardo F et al., 2009). So far gSG6 has been found only in species of the An. gambiae complex and in a few additional anophelines (An. stephensi, An. funestus and An. freeborni), whereas it is absent in culicine mosquitoes and in other blood feeding arthropods. Preliminary indications suggested that gSG6 is immunogenic (Poinsignon et al., 2008) encouraging a deeper evaluation of its possible use as epidemiological marker of exposure to Anopheles vectors. To test this hypothesis we measured the humoral immune response to the An. gambiae salivary protein gSG6 in human sera collected during three consecutive years in rural malaria hyperendemic areas of Burkina Faso. We confirmed that gSG6 is immunogenic and found that it elicits, in the exposed population, an IgG response that varies according to the level of malaria transmission. Interestingly, this anti-gSG6 IgG response: (a) is short-lived, since a drop in the IgG levels was observed during the dry low transmission season; (b) is significantly different in the two sympatric ethnic groups, Mossi and Fulani, previously shown to differentially respond to several P. falciparum antigens (Modiano D et al., 1996; Torcia MG et al., 2008); (c) starts very early, reaching a maximum in one-two years old children, and then decreases according to age. This is to our knowledge the first study employing a mosquito recombinant salivary protein for a large scale malaria epidemiological analysis. We believe that our study provides a solid indication that antibody response to anopheline-specific salivary antigens may be a reliable marker of exposure to malaria vectors suggesting that, similarly, culicine-specific salivary antigens may be exploited as markers of exposure to Aedes and Culex vectors. In conclusion salivary antigens from mosquito disease vectors may represent valuable complementary tools for epidemiological studies in settings where the assessment of classical entomological parameters would be difficult or impossible

Genetic Diversity and Population Structure of the Invasive Oriental Fruit Fly, Bactrocera dorsalis (Diptera: Tephritidae) in Burkina Faso

Bactrocera dorsalis Hendel is a highly invasive horticultural pest that is of major economic importance worldwide. In Burkina Faso, it is one of the main insect pests that affects the production and exportation of mangos. Understanding the biology and the genetic dynamics of this insect pest provides crucial information for the development of effective control measures. The aim of this study was to understand the distribution, diversity, and genetic structure of B. dorsalis in Burkina Faso. Male flies were collected transversally in Burkina Faso and analyzed by PCR using 10 microsatellite markers. The results showed an abundance of B. dorsalis varying from 87 to 2986 flies per trap per day at the different sampling sites. The genetic diversity was high at all sites, with an average Shannon’s Information Index (I) of 0.72 per site. The gene flow was high between study populations and ranged from 10.62 to 27.53 migrants. Bayesian admixture analysis showed no evidence of structure, while Discriminant Analysis of Principal Components identified three weakly separated clusters in the population of B. dorsalis in Burkina Faso. The results of this study could be used to optimize the effectiveness of current control interventions and to guide the implementation of new, innovative, and sustainable strategies