MOLECULAR ANALYSIS OF COLLETOTRICHUM SPECIES ASSOCIATED TO OLIVE IN CALABRIA.

A new molecular approach based on the use of genus-specificprimers targeting the internal transcribed spacer (ITS) regions ofrDNA, was developed and used to study the diversity of Colletotrichumspecies associated with the olive canopy in the Gioia Tauroplain (Calabria, southern Italy). Representative symptomatic andsymptomless samples of leaves, flowers and fruits were collectedduring 2012 and analyzed by extracting total DNA and amplifyingthe target region with the genus-specific primers. Amplicons werecloned and sequenced in order to use the ITS as a barcode gene.No Colletotrichum species were detected in the first sampling period(May 28, 2012), whereas around 15% of the analyzed samplesincluding leaves, dead floral parts and symptomless fruits proved tobe colonized in the second (June 29, 2012) and third sampling (October17, 2012). A significantly higher colonization rate was foundin the fourth sampling (December 12, 2012) with Colletotrichumspecies detected in 74% of the analyzed samples, including manyasymptomatic fruits and leaves. On the whole C. clavatum, C. acutatumsensu stricto and C. gloeosporioides sensu stricto were the mostcommon species accounting for 54, 22 and 21% of the sequencedclones, respectively. Few sequences belonged to C. karstii and toa Colletotrichum sp., closely related to C. coccodes. Most sampleswere colonized by two or three different species. The new methodproved very effective for discriminating multiple Colletotrichumspecies colonizing olive tissues and could be also applied to detectColletotrichum spp. in other plant species.