[Study on gene polymorphism of fumonisin-producing Fusarium verticillioides strains]

To study the gene polymorphism and genetic variation of fumonisin-producing or non-producing Fusarium verticillioides strains isolated from different geographical areas and different samples.

Two DNA probes FumrDNA and FumPKSFB were prepared, based on 5.8S, 28S rDNA, internal transcribed spacer sequences (ITS1 and ITS2) and based on the polyketide synthesase (PKS) gene fum5 involved in fumonisin biosynthesis, respectively. The polymorphism of 16 isolates and 5 typical strains from ATCC were analyzed by Southern blot and compared.

The results of FumrDNA probe hybridization indicated that the DNA hybridization patterns of SD-fm040 isolated from the sesame sample in Shandong were different from that of ATCC stains by using endonuclease EcoR I or Pst I or both, showing the great polymorphism. The hybridization patterns of the isolates from maize samples in Shandong and Zhejiang accorded with that of ATCC 52539, ATCC 38946, and ATCC 26263. ATCC 12763 (F. nygamai) and ATCC 38016 (F. subglutinans) showed the polymorphism for most of endonucleases used in this study, compared with other strains. The results of FumPKSFB probe hybridization by using endonuclease EcoR I indicated that 2 isolates of Fusarium subglutinans from Shandong and 2 isolates of Fusarium verticillioides from Henan, which are non-fumonisin strains, had no hybridization bands, according to non-fumonisin-producing strains from ATCC. 2 fumonisin-producing isolates from maize samples in Anhui had 2 bands. One band was about 15000bp, the same molecular weight as ATCC52539. The other band with about 18000bp molecular weight was particular to Anhui isolates, showing significant polymorphism comparing with other strains. Otherl0 fumonisin-producing isolates from Shandong, Zhejiang and Henan had only one band with 15000bp molecular weight, respectively, accordant with ATCC 52539.

FumrDNA probe was useful for identifying different types of Fusarium verticillioides isolates from different food samples and studying gene polymorphism of the strains, although it was not able to differentiate fumonisin-producing strains from non fumonisin-producing strains. FumPKSFB probe could absolutely identify fumonisin-producing strains and suit for studying the toxigenicity and gene polymorphism of fumonisin-producing strains isolated from different geographical areas and different food samples.