Onion bulbs production and commercialization is now a powerful tool against poverty in rural areas in Burkina Faso. However, Fusarium basal rot disease caused by a complex of soilborne fungi appears to be a serious threat to growers. The prophylactic methods proposed for its control remain difficult to apply effectively and the most used varieties of onion are susceptible to the disease. In order to work out a palliative solution to this problem, eleven onion varieties marketed in Burkina Faso were screened for their tolerance to fusarium basal rot. The varieties were produced in infested rural area on completely randomized blocs by three producers in three different sites. The harvested bulbs were then tested in the laboratory under artificial inoculation conditions with conidial suspensions of Fusarium oxysporum and F. solani, responsible for the disease. In field, the Noflaye and Gandiol+ varieties were the most tolerant to the disease with respective incidence values ​​of 0 and 1.6% while the Mercedes variety was the most sensitive with an incidence of 16,5%. In the laboratory, all the inoculated varieties developed rot at varying intensities, but the Noflaye and Gandiol+ varieties were still the least rotten. These results recommend the continuation of investigations on these two varieties with a view to their integration into an integrated control program against Fusarium basal rot disease of onion in Burkina Faso.

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.