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    Resistance to quinone-outside inhibitor (Qoi) fungicides in colletotrichum species isolated from anthracnose disease occurring in Thailand
    (2020-01-01) ;
    Imamoto, Kazuumi
    ;
    Ishii, Hideo
    Colletotrichum species are plant pathogens causing anthracnose diseases in many crops that result in significant reduction of quality and quantity of the crop products. Management of these diseases has become increasingly difficult recently due to the development of fungicide resistance in pathogens. Thus, monitoring for fungicide sensitivity in the pathogen is important to manage these diseases. The isolates of Colletotrichum species were isolated from anthracnose disease on various crops collected during 2016-2017 in central and southern Thailand. They were tested for their mycelium growth sensitivity to azoxystrobin, a quinone-outside inhibitor (QoI) fungicide and their internal transcribed spacer (ITS) and 5.8S regions of rDNA were analyzed. The results showed that eleven out of twenty four isolates of Colletotrichum species were resistant to azoxystrobin. They were able to grow on PDA amended with 100 mg/l azoxystrobin in the presence of salicylhydroxamic acid (SHAM) at 100 mg/l. Moreover, two isolates of azoxystrobin-resistant Colletotrichum spp. produced much larger lesions than azoxystrobin-sensitive isolates on mango fruits after treatment with 100 mg/l azoxystrobin. This is the first report on the occurrence of azoxystrobin resistance in Colletotrichum species present in Thailand and will contribute to the management of these important diseases in the future.
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    In vitro assessment of crude extract from Gomphrena weed (Gomphrena celosioides Mart.) for control of plant pathogenic fungi causing chili diseases
    (2023-03-01)
    Apithanasakulngeon, P.
    ;
    Somnuek, S.
    ;
    ;
    Jaenaksorn, T.
    The phytochemical screening of both the flowers and other aerial parts of the Gomphrena weed extract (Gomphrena celosioides Mart.) presented alkaloids, flavonoids, saponins, phenolics/tannins, and terpenoids. The extracts from both parts at 80, 160, and 240 mg/ml were significantly inhibited the mycelial growth of C. gloeosporioides and Fusarium sp. compared to inoculated control by paper disc diffusion. The extract from both parts of the Gomphrena weed at the highest concentration (160 mg/ml) significantly showed the greatest inhibitory effect on mycelial growth of Sclerotium sp. (100 percent), followed by C. gloeosporioides (82.5 percent), Cercospora sp. (41.16 percent), and Fusarium sp. (24.41 percent) when tested using the poisoned food technique. The spore germination test revealed both parts of the weed extract yielded concentrations which were completely inhibited (100 percent) on the spore germination of C. capsici, C. gloeosporioides, and Fusarium sp.