FOT 1 INSERTIONS IN THE FUSARIUM-OXYSPORUM F SP. ALBEDINIS GENOME PROVIDE DIAGNOSTIC PCR TARGETS FOR DETECTION OF THE DATE PALM PATHOGEN

Populations of Fusarium oxysporum f. sp. albedinis, the causal agent o f Bayoud disease of date palm, are derivatives of a single clonal line age and exhibit very similar Fot 1 hybridization patterns. In order to develop a sensitive diagnostic tool for F. oxysporum f. sp. albedinis detection, we isolated several DNA clones containing a copy of the tr ansposable element Fat 1 from a genomic library of the date palm patho gen. Regions flanking the insertion sites were sequenced, and these se quences were used to design PCR primers that amplify the DNA regions a t several Fot 1 insertion sites. When tested on a large sample of Fusa rium isolates, including 286 F. oxysporum f. sp. albedinis isolates, 1 7 other special forms, nonpathogenic F. oxysporum isolates from palm g rove soils, and 8 other Fusarium species, the primer pair TL3-FOA28 al lowed amplification of a 400-bp fragment found only in F. oxysporum f. sp, albedinis. Sequence analysis showed that one of the Fot 1 copies was truncated, lacking 182 bp at its 3' terminus. The primer pair BIO3 -FOA1 amplified a 204-bp fragment which overlapped the Fot 1 truncated copy. and its 3' site of insertion in the F. oxysporum f. sp, albedin is genome and identified 95% of the isolates. The primer pairs BIO3-FO A1 and TL3-FOA28 used in PCR assays thus provide a useful diagnostic t ool for F. oxysporum f. sp, albedinis isolates.