Pathogenicity of Fusarium isolates to Striga hermonthica in Burkina Faso

Striga hermonthica (Del.) Benth. is an important constraint to cereal crop production in Burkina Faso, of which sorghum (Sorghum bicolor L. Moench) is the most important component. Native Fusarium species to use as bio-control agents to S. hermonthica has been investigated. Fifty one Fusarium isolates obtained from diseased plants of S. hermonthica were evaluated for their pathogenicity against Striga under controlled environmental conditions. Of 51 Fusarium isolates, 14 were pathogenic to S. hermonthica but their virulence differed. These 14 isolates were evaluated for their effects on Striga seed germination in the laboratory and their ability to kill emerged Striga plants growing in greenhouse pots. Spores of Fusarium sp. isolates 150a-M, 125b-Za, 6-Fa, Fusarium equiseti isolates 5-Kou, 31-Kom, 32-Or, 13-Ba and Fusarium oxysporum isolate 34-Fo reduced Striga germination by 78 to 96% compared to the untreated control. The study showed that at the rate of 33 mg mL(-1), metabolites of Fusarium sp. isolates 125b-Za, 6-Fa, F. equiseti 5-Kou and F. oxysporum 34-Fo prevented Striga seed germination. In addition to these four isolates, Fusarium sp. isolates 141b-O, 150a-M and F. equiseti isolate 32-Or were effective at 67 mg mL(-1). Percentage of Striga mortality ranged from 17-37% between 14 and 28 days after inoculation with spores of F. oxysporum 34-Fo and F. equiseti 5-Kou. Striga dry biomass was reduced by 84 and 78% for the respective isolates compared to the untreated control with Striga. Sorghum yield was improved by 84 and 99% with Fusarium sp. 6-Fa and F. oxysporum 34-Fo, respectively, compared to the control without Striga. The use of Fusarium spores and metabolites against Striga offers different possibilities of bio-herbicides formulation that can be combined with other controls methods in the integrated Striga management. Further studies will be carried out under field conditions to assess the efficacy and safety of these Fusarium isolates to environment and humans and evaluate low cost strategies for transfer to subsistence farmers.