Previous investigations demonstrated that Fusarium oxysporum (Fo), which is not pathogenic to cucumbers, could serve as abiological control agent for managing Fusarium wilt of cucumber caused by Fo f. sp. cucumerinum (Foc) in Taiwan. However,thus far it has not been possible to separate the populations of pathogenic Fo from the nonpathogenic isolates that havebiological control potential through their morphological characteristics. Although these two populations can bedistinguished from one another using a bioassay, the work is laborious and time-consuming. In this study, a fragment of theintergenic spacer (IGS) region of ribosomal DNA from an Fo biological control agent, Fo366, was PCR-amplified withpublished general primers, FIGS11/FIGS12 and sequenced. A new primer, NPIGS-R, which was designed based on the IGSsequence, was paired with the FIGS11 primer. These primers were then evaluated for their specificity to amplify DNA fromnonpathogenic Fo isolates that have biological control potential. The results showed that the modified primer pair, FIGS11/NPIGS-R, amplified a 500-bp DNA fragment from five of seven nonpathogenic Fo isolates. These five Fo isolates delayedsymptom development of cucumber Fusarium wilt in greenhouse bioassay tests. Seventy-seven Fo isolates were obtainedfrom the soil and plant tissues and then subjected to amplification using the modified primer pair; six samples showedpositive amplification. These six isolates did not cause symptoms on cucumber seedlings when grown in peat moss infestedwith the isolates and delayed disease development when the same plants were subsequently inoculated with a virulentisolate of Foc. Therefore, the modified primer pair may prove useful for the identification of Fo isolates that arenonpathogenic to cucumber which can potentially act as biocontrol agents for Fusarium wilt of cucumber
To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.