Optimization of Production Methods for Black Soldier Fly Larvae (Hermetia illucens L.) in Burkina Faso.

Larvae of Hermetia illucens are a valuable source of protein for animal feed that can be produced by exposing animal and agro-industrial wastes to naturally occurring flies. The objective of this study was to improve techniques for obtaining H. illucens larvae to feed livestock in Burkina Faso. An experiment was conducted to determine the most favourable substrates and seasons for larval production. The substrates used were poultry manure, local beer waste, local beer waste mixed with poultry manure, cottonseed cake, and industrial brewery waste mixed with poultry manure. The production of larvae was carried out in four different seasons. The effect of the container's oviposition area (0.07 m2, 0.09 m2, and 0.11 m2) and the type of container (terracotta, plastic, and iron) on larval production was also assessed. The produced larval biomass was high during, or just after, the rainy season but very low during the cool dry and hot dry seasons. Yields were higher with local beer waste mixed with poultry manure followed by local beer waste and cottonseed cake. The average mass of H. illucens larvae increased slightly with the oviposition area for the same amount of substrate. Iron and terracotta containers provided better results than plastic containers. The suitability of this production method for H. illucens larvae production is discussed.

The impact of the rice production system (irrigated vs lowland) on root-associated microbiome from farmer's fields in western Burkina Faso.

Due to their potential applications for food safety, there is a growing interest in rice root-associated microbial communities, but some systems remain understudied. Here, we compare the assemblage of root-associated microbiota in rice sampled in 19 small farmer's fields from irrigated and rainfed lowlands in Burkina Faso, using an amplicon metabarcoding approach of the 16S rRNA gene (prokaryotes, three plant samples per field) and ITS (fungi, one sample per field). In addition to the expected structure by root compartments (root vs rhizosphere) and geographical zones, we showed that the rice production system is a major driver of microbiome structure. In irrigated systems, we found a higher diversity of prokaryotic communities from the rhizosphere and more complex co-occurrence networks, compared to rainfed lowlands, while fungal communities exhibited an opposite pattern (higher richness in rainfed lowlands). Core taxa were different between the two systems, and indicator species were identified: mostly within Bacillaceae in rainfed lowlands, and within Burkholderiaceae and Moraxellaceae in irrigated areas. Finally, a higher abundance in rainfed lowlands was found for mycorrhizal fungi (both compartments) and rhizobia (rhizosphere only). Our results highlight deep microbiome differences induced by contrasted rice production systems that should consequently be considered for microbial engineering applications.

Sustainable Use of Macrotermes spp. to Improve Traditional Poultry Farming through an Efficient Trapping System in Burkina Faso.

This study aimed to promote the use of termites as feed in traditional poultry farming by developing sustainable and inexpensive termite trapping techniques. Various tests were carried out in Burkina Faso to improve the traditional technique of trapping termites of the genus Macrotermes using a reversed container filled with organic matters. We studied the effect of containers' types, substrates, habitats, harvesting times, duration of trap deposition, and season on the quantity of termites trapped. Calabashes and terra cotta pots trapped more termites than iron boxes, but calabashes were quickly destroyed by termites. The quantity of termites harvested increased proportionally with the volume of the pot and was higher in a cultivated habitat than in a forest, despite the higher number of termite mounds in the forest. The quantity of termites harvested was lowest in the cold-dry season and highest during the rainy season, however, sizeable amounts of termites were collected throughout the year. Among six substrates and mixtures of substrates tested, maize cobs trapped the highest number of termites and cow dung the lowest. The best time of harvest varied among seasons and, if substrates are abundant, it is more efficient to empty the containers on a daily basis.

Spatiotemporal Survey of Multiple Rice Diseases in Irrigated Areas Compared to Rainfed Lowlands in the Western Burkina Faso.

Multiple constraints affect rice yields in West Africa. Among these constraints are viral, bacterial, and fungal pathogens. We aimed to describe the spatiotemporal patterns of occurrence and incidence of multiple rice diseases in farmers' fields in contrasting rice growing systems in the western Burkina Faso. For this purpose, we selected a set of three pairs of sites, each comprising an irrigated area and a neighboring rainfed lowland, and studied them over four consecutive years. We first performed interviews with the rice farmers to better characterize the management practices at the different sites. This study revealed that the transplanting of rice and the possibility of growing rice twice a year are restricted to irrigated areas, while other practices, such as the use of registered rice cultivars, fertilization, and pesticides, are not specific but differ between the two rice growing systems. Then, we performed symptom observations at these study sites to monitor the following four diseases: yellow mottle disease, Bacterial Leaf Streak (BLS), rice leaf blast, and brown spot. The infection rates were found to be higher in irrigated areas than in rainfed lowlands, both when analyzing all observed symptoms together (any of the four diseases) and when specifically considering each of the two diseases: BLS and rice leaf blast. Brown spot was particularly prevalent in all six study sites, while yellow mottle disease was particularly structured geographically. Various diseases were frequently found together in the same field (co-occurrence) or even on the same plant (coinfection), especially in irrigated areas.

Host range and species diversity of Tephritidae of three plant formations in Western Burkina Faso.

In Western Burkina Faso, the host range of fruit flies was evaluated in three plant formations between May 2017 and April 2019. Samples of 61 potential hosts were collected and incubated for fruit fly emergence. Twenty-seven hosts including cultivated and wild fruit were identified. Among cultivated fruit species, mango, and guava were the most infested while high infestation incidences were observed in the fruit of the indigenous plants Vitellaria paradoxa, Annona senegalensis, Sarcocephalus latifolius, and Saba senegalensis. Low infestation rates were observed in Anacardium occidentale, Citrus species, Opilia celtidifolia, and Cissus populnea. The highest infestation index (1648.57 flies kg-1) was observed from V. paradoxa. Eleven new host fruit infested with many fruit fly species are reported in Burkina Faso. A total of 18 fruit fly species were reared; Bactrocera dorsalis (42.94%), Ceratitis cosyra (29.93%), and Ceratitis silvestrii (22.33%) dominated those that emerged. Four fruit fly species have been detected for the first time in Burkina Faso. The main suitable fruit hosts are abundant and available from May through August during the rainy season and become rare and have low infestation from November to April during the dry season. This is the first study of its kind in the region. This study shows that the three plant formations had an impact on population dynamics of the three tephritid species of economic importance in Western Burkina Faso. This information should be integrated into the development of a fruit fly pests management strategy.

Impact of Cultivated Hosts on the Recombination of Cucumber Mosaic Virus.

Cucumber mosaic virus (CMV) is one of the most successful viruses known, infecting over 1,200 species of plants. Like other single-stranded RNA viruses, CMV is known to have a high potential for population diversity due to error-prone replication and short generation times. Recombination is also a mechanism that allows viruses to adapt to new hosts. Host genes have been identified that impact the recombination of RNA viruses by using single-cell yeast systems. To determine the impact that the natural plant host has on virus recombination, we used a high-recombination-frequency strain of CMV, LS-CMV, which belongs to subgroup II, in three different cultivated hosts: Capsicum annuum cv. Marengo (pepper), Nicotiana tabacum cv. Xanthi nc (tobacco), and Cucurbita pepo cv. Black Beauty (zucchini). The recombination frequency was calculated by using an RNA 3 reporter carrying restriction enzyme sites created by introducing silent mutations. Our results show that the recombination frequency of LS-CMV is correlated with the infected host. The recombination events in pepper were 1.8-fold higher than those in tobacco and 5-fold higher than those in zucchini. Furthermore, we observed the generation of defective RNAs in inoculated pepper plants, but not in tobacco or zucchini. These results indicate that the host is involved in both intra- and intermolecular recombination events and that hosts like pepper could foster more rapid evolution of the virus. In addition, we report for the first time the production of defective RNAs in a CMV subgroup II isolate.IMPORTANCE Recombination is an important mechanism used by viruses for their diversification and to adapt to diverse hosts. Understanding the host role in the mechanisms of evolution is important for virus disease management and controlling the emergence of new strains. This study shows the impact that cultivated hosts are playing in the evolution of CMV. Furthermore, our results and previous studies show how some specific hosts could be an ideal environment for the emergence of new viral strains.

Assessment of Tomato (Solanum lycopersicum L.) Producers' Exposure Level to Pesticides, in Kouka and Toussiana (Burkina Faso).

To assess producers' exposure level to pesticides in vegetable production in Burkina Faso, a study was carried out in 2016 and 2017 among 30 tomato producers in the municipalities of Kouka and Toussiana. Eighteen (18) commercial formulations were identified, with more than 50% of pesticides destined for cotton production. Eleven active substances have been identified and the most frequently used are λ-cyhalothrin (35%), acetamiprid (22%) and profenofos (13%). The most commonly used chemical families are pyrethroids (28%) and organophosphates (18%). The study revealed a low level of training for producers, a high use of pesticides according to the Frequency Treatment Indicator, and a very low level of protection used by producers. The Health Risk Index shows that active substances such as methomyl, λ-cyhalothrin and profenofos present very high risk to operators' health. Based on the UK-POEM model, the predictive exposure levels obtained varied from 0.0105 mg/kg body weight/day to 1.7855 mg/kg body weight/day, which is several times higher than the Acceptable Operator Exposure Level. However, the study also shows that exposure can be greatly reduced if the required Personal Protective Equipment is worn. Producers' awareness and training on integrated pest management are necessary to reduce the risks linked to the pesticides use in Burkina Faso.

Effects of temperature and pH on mycelium growth of Phoma sorghina (Sacc.) Boerema Dorenbosch and Van Kesteren in vitro.

Abstract: The effects of temperatures 22, 28, 32, 36 and 40 degrees C and those of pH 5, 6.5 and 6 were evaluated on 11 isolates of P. sorghina on malt agar medium. The optimal mycelium growth of the most isolates is noted at 28 degrees C. At 32 degrees C, we have recorded a significant reduction of mycelium growth of all the isolates tested when compared with the control at 22 degrees C. At this same temperature, P. sorghina isolates can be group on sensitive isolates, on moderately isolates and on resistant isolates to temperature. The mycelium growth of all the isolates is inhibited at 36 degrees C. On the other hand, the temperature of 40 degrees C kills the mycelium of all the isolates of P. sorghina. The results of our work also show that, least variation of pH (6.5-6) significantly reduced the mycelium growth of P. sorghina isolates at 22 and 28 degrees C. At pH 5 most of the isolates tested are well adapted and the mycelium growth is more important when compare with that at pH 6.

Importance of seed-borne fungi of sorghum and pearl millet in Burkina Faso and their control using plant extracts.

Seed-borne fungi of sorghum and pearl millet in Burkina Faso were surveyed. A total of 188 seed samples from various locations, collected in 1989 (42) and 2002 (146), were tested, using the blotter, dry inspection and washing methods. Infection experiments were carried out with the major fungi recorded on each crop by the blotter test. Six essential oils of plants were investigated for their inhibitory activity against eight pathogenic fungi. Thirty four and 27 fungal species were found in seed samples of sorghum and pearl millet, respectively. Phoma sp. and Fusarium moniliforme infected 95 to 100% of the seed samples of both sorghum and pearl millet. Sphacelotheca sorghi and Tolyposporium ehrenbergii were encountered in respectively, 75 and 33% of seed samples of sorghum. T. penicillariae, Sclerospora graminicola and Claviceps fusiformis were present in 88, 41 and 32% of seed samples of pearl millet, respectively. Seeds inoculated with Acremonium strictum, Curvularia oryzae, F. equiseti, F. moniliforme and F. subglutinans and sown in sterilized soil, showed considerable mortality of the seedlings. Three essential oils inhibited in vitro the mycelial growth of all the fungi used by 85 to 100% and reduced significantly sorghum and pearl millet seed infection rates of Phoma sp., Fusarium sp., Curvularia sp., Colletotrichum graminicola and Exserohilum sp. Presence of many pathogenic fungi in considerable number of seed samples indicates the need of field surveys for these and other pathogens. Development of plant extracts for the control of seed-borne pathogens and public awareness on seed-borne diseases management measures for maintaining quality seed should be increased.