Characterization of Penicillium Species Isolated from Dioscorea polystachya in Hokkaido, Japan.

Chinese yam (Dioscorea polystachya) has been cultivated as a food crop in Japan. The blue mold disease of Chinese yam during the storage and treatment of forced sprouting is one of the hindrances in attaining productivity that can lead to food security in tropical countries and steady farming that will eventually lead to farmers' profitability. In this study, three species of the genus Penicillium related to the blue mold of yam were isolated from two locations in Hokkaido, Japan. From the morphology and phylogeny, these were Penicillium albocoremium, P. polonicum, and P. sclerotigenum. Pathogenicity was confirmed in all Penicillium-like isolates, and sensitivity against benomyl was evaluated based on MIC. The first two species were newly recorded as the causal fungi of the blue mold of yam in Japan, and the pathogenicity of P. albocoremium is first confirmed in yam seed tuber. Moreover, some isolates showed possible resistance to benomyl.

Cross-resistance to the new fungicide mefentrifluconazole in DMI-resistant fungal pathogens.

In the European Union (EU), regulation of sterol demethylation inhibiting (DMI) fungicides is tightened due to their suspected endocrine disrupting properties. However, the new DMI fungicide mefentrifluconazole was reported to have high fungicidal activity with minimal adverse side effects. In addition, some evidence suggests inconsistent cross resistance between mefentrifluconazole and other azoles. In this study, mefentrifluconazole and other triazoles were examined for activity to select pathogens sensitive or resistant to DMIs using mycelial growth tests on fungicide-treated culture medium or spray trials using cucumber plants. Cross-resistance was confirmed for all of the fungal species tested but activity levels varied. The sensitivity of Monilinia fructicola from peach to mefentrifluconazole was higher compared to other DMIs. In contrast, the inhibitory activity of mefentrifluconazole was equal or slightly inferior compared to difenoconazole, tebuconazole, propiconazole in Colletotrichum spp., Alternaria alternaria sp. complex and Cercospora beticola isolated from peach and sugar beet, respectively. Similar tendencies (i.e. equal or slightly inferior activity and cross-resistance) were observed for cucumber powdery mildew (Podosphaera xanthii) resistant to triflumizole, myclobutanil, and difenoconazole. Despite cross-resistance to other DMIs, mefentrifluconazole is a promising fungicide for fungal disease control on peach and other crops, with a reportedly more favorable toxicity profile.