Sorghum is the most cultivated cereal in Burkina Faso. However, sorghum is produced extensively without respect for good agricultural and storage practices and the resulting grains are permanently infected by mold species. These mold species cause seeds rot, seedling damping-off and others diseases in field. They also secrete mycotoxins harmful to human health. The main method recommended for their control is seed treatment with chemicals. However, handling pesticides presents high risks of toxicity and ecotoxicity. The search for an alternative method made it possible to identify the essential oil of Cymbopogon citratus which has antifungal properties. This essential oil was then formulated by adsorption on clay in order to facilitate its use in the field. The objective of this study was to test the efficacy of the formulation made with two types of clay against Phoma sorghina and Fusarium moniliforme, the main species of molds encountered, and to evaluate the effect of the formulation on seed germination and seedling growth. Sorghum grains from two varieties were thus coated with the formulations. The grains thus coated were first analyzed to assess the presence of the target molds and then sown in pots containing sterilized fine sand to assess the germination and growth of the seedlings. The formulations significantly reduced grain infection rates from both fungi by more than 70%. The formulation with Sitiéna clay significantly improved germination, plant vigor and root length of both varieties. Field trials are necessary to confirm the efficacy of this formulation and initiate the popularization procedure.

The use of synthetic pesticides may present a danger to humans and the environment, to the point that the research of an alternative to these chemicals is necessary. The present study, aimed finding new natural molecules that may replace synthetic chemicals, looked at the effect of the ethanolic extract of B.grandiflora bark on eight seed-borne phytopathogenic fungi. The results of this study showed that C. lunata and C. dematium are the most sensitive to the ethanolic extract. This attests the presence of fungicidal or fungistatic substances in B. grandiflora bark. These results show that the ethanolic extract contains active molecules which, once fractionated, could constitute an alternative in the fight against phytopathogenic fungi. These preliminary results open up the possibility of using the bark of B. grandiflora for the production of a natural fungicide. Bioguided fractionation and phytotoxicity tests will identify the most active and non-toxic fractions which could be use in seed protection.

Aspergillus and Fusarium species are the major seed-borne fungi occurring on onion in Burkina Faso according to a previous study. In order to work out effective, available and healthy method of seed treatment against these fungi, this study aimed to evaluate the antifungal activity of three local botanical species. Mycelial growth of Aspergillus niger, Fusarium moniliforme, Fusarium oxysporum and Fusarium solani was evaluated in vitro on media prepared with aqueous extracts of Cymbopogon citratus, Eclipta alba and Portulaca oleracea. The health and germination quality of seeds previously treated with the best aqueous extracts were then evaluated. The aqueous extract of C. citratus significantly inhibited the mycelial growth of all Fusarium species at rates ranged from 42,8 to 92,0% but stimulated the growth of A. niger. Those of P. oleracea inhibited the mycelial growth of all tested fungi at rates ranged from 3,2 to 42,4% while those of E. alba stimulated the mycelial growth of all tested fungi. Seed treatment with the extracts of C. citratus and P. oleracea allowed reducing their infection rates by fungi of over 50%. However, the emergence and growth of seedlings were respectively reduced by P. oleracea and C. citratus compared to those of untreated seeds. Our study concludes that both aqueous extracts have proven antifungal properties. The appropriated shape and dose of use, that does not affect the seedling emergence and growth, should be sought.