Alternatives to hypochlorous acid and fungicides are needed for treatment of fruit and fruit-handling facilities. Chlorine dioxide was evaluated and found effective against common postharvest decay fungi and against filamentous fungi occurring on fruit packinghouse surfaces. In vitro tests with conidial or sporangiospore suspensions of Botrytis cinerea, Penicillium expansum, Mucor piriformis, and Cryptosporiopsis perennans demonstrated >99% spore mortality within 1 min when the fungi were exposed to aqueous chlorine dioxide at 3 or 5 ,ug * ml-'. Longer exposure times were necessary to achieve similar spore mortalities with 1 ,ug * ml-'. Of the fungi tested, B. cinerea and P. expansum were the least sensitive to Cl02. In comparison with the number recovered from untreated control areas, the number of filamentous fungi recovered was significantly lower in swipe tests from hard surfaces such as belts and pads in a commercial apple and pear packinghouse after treatment of surfaces with a 14.0to 18.0-,ig *mVl-' Cl02 foam formulation. Chlorine dioxide has desirable properties as a sanitizing agent for postharvest decay management when residues of postharvest fungicides are not desired or allowed.
Character states during sporulation have been used to segregate and describe many small-spored species of Alternaria, but some are not supported by published phylogenetic analyses. The conidiation response of Alternaria gaisen was characterized by selective subtractive hybridization of cDNA produced from cultures of A. gaisen grown either in total darkness or in total darkness followed by scarification and 24 h exposure to light. Transcripts or their translation products were identified using BLAST. Multiple transcripts with similarity to ORF-1 of the AM-toxin gene were obtained from the light library. L152 is a full reading frame EST in the light library whose ORF translation has similarity to the conserved domain aegerolysin (pfam06355). A set of 11 ex-type or representative isolates including A. alternata, A. gaisen, A. yaliinficiens, A. arborescens, A. tenuissima and A. brassicicola were resolved by UPGMA analysis of a partial genomic sequence (415-425 base pairs) of L152, but were not resolved by a similar analysis of ITS sequences. Furthermore, the resolved lineages of the L152 dataset were reflective of the diversity previously hypothesized by morphological evaluations of sporulation patterns. Although the ITS rDNA sequence region is generally accepted as the most likely candidate for fungal barcoding, the analysis of L152 sequences presented here resolved closely related species or species groups where other loci, including ITS, have not. Based on these results, the sequences of putative aegerolysin homologs were variable, parsimonyinformative and warrant additional analyses with a broader isolate set including related genera and species.
The ex-type strain of Alternaria cerasidanica was isolated in 2001 from an immature, asymptomatic drupe of Prunus avium collected at a commercial cherry orchard near Sklskør, Denmark. Cultural morphology, sporulation pattern and cluster analyses of combined RAPD, RAMS (microsatellite), and AFLP fingerprints of A. cerasidanica and 167 strains of Alternaria spp. support the placement of A. cerasidanica within the A. infectoria species-group sensu Simmons and its segregation from other members of this group. A. cerasidanica is currently monotypic and known only from preharvest sweet cherry fruit in Denmark.
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