Fusarium oxysporum Strains as Potential Striga Mycoherbicides: Molecular Characterization and Evidence for a new forma specialis

摘要

Fusarium oxysporum isolates (Foxy 2 and PSM197) are potential, highly host specific mycoherbicides for thecontrol of the parasitic weeds Striga hermonthica and S. asiatica. Their target weeds, Striga spp., are major biotic constraintsin cereal and legume production in semi-arid tropical Africa, where they adversely affect livelihood of millions ofsubsistence farmers. The aim of this study was to characterize and sequence the Striga mycoherbicides Foxy 2 & PSM197in order to more clearly distinguish them from other morphologically similar pathogenic Fusarium oxysporum strains. Thefungal isolates were cultivated on PDA medium and characterized based on the analysis of partial DNA sequence of theinternal transcribed spacer (ITS) regions of the nuclear ribosomal RNA gene. Both isolates were identical in their ITSsequence.The unique and identical ITS-sequence of the two isolates obtained, compared to the sequences of Fusariumoxysporum forma speciales deposited in GenBank along with the host specificity to Striga demonstrated in previous studies,provides strong evidence to propose these pathogens of Striga as a new forma specialis (f. sp. strigae). The possibilityto clearly distinguish between the new forma specialis and all pathogenic Fusarium oxysporum strains sequenced so farwill facilitate and encourage the acceptance and introduction of Striga-mycoherbicides for practical field application byregulatory authorities and farmers.