BY：Sun cai yu
Anthracnose disease of pak choi [Brassica rapa L. subsp. chinensis (L.) Hanelt] is a common disease in organic farm in Taiwan. It can cause a leaf spot on several species of Brassicaceae. Colletotrichum higginsianum and C. gloeosporioides could be isolated the disease leaves. C. higginsianum could infect unwounded pak choi leaf, wounded mango leaf and tomato fruit. Comparatively, C. gloeosporioides could infect unwounded mango leaf and unwounded tomato fruit but cause leaf chlorosis on wounded pak choi leaf. It may be weak pathogen on pak choi. A standard area diagram showed the levels of 0.07, 3, 10, 25 and 50% was developed for assessing disease severity in this study. The accuracy and precision of disease assessment were improved when standard area program was used. Nine Brassica spp. crops were inoculated with C. higginsianum. Pak choi and turnip were more susceptible than leaf mustard, cabbage and radish. Among seventeen cultivars of Brassica rapa subsp. chinensis, the most susceptible cultivars were Tsai-Yu, Chief, Gai-liang-Yi-Tiao-Gen and Feng-Jhen; the most resistant cultivar was 606 chingensai. Fifteen nitrogenous compounds and eighteen carbohydrates were evaluated for their efficacy on growth of C. higginsianum. The colony color was brightest when the pathogen was cultured on the medium with ammonium phosphate as nitrogen source. The conidial germination was most improved by high methoxy pectin (HMP) as carbon source, and 3% (w/v) HMP was effective in enhancing growth of the pathogen. Among the eleven antimicrobial agents tested, streptomycin sulfate, chloramphenicol, metalaxyl , pencycuron and thiabendazole showed less adverse effect on growth of C. higginsianum but could suppress Trichoderma sp. and other fungi. Based on these results, a HMP- ammonium phosphate semiselective medium (designated as the HA semiselective medium) consisting of 30 g high methoxy pectin, 2 g monoammonium phosphate, 1 g K2HPO4, 0.5 g KCl, 0.5 g MgSO4.7H2O, 0.01 g FeSO4.7H2O, 15 g agar, 200 μg mL-1 metalaxyl, 300 μg mL-1 pencycuron, 1μg mL-1 thiabendazole, 100 μg mL-1 chloramphenicol and 200 μg mL-1 streptomycin sulfate, and pH value of medium was adjusted to pH 6.0 by KOH before autoclaving. C. higginsianum was able to be accurately detected artificially infested soil and distinguished easily other Colletotrichum spp. by using HA semiselective medium. C. higginsianum could be detected infective leaves of pak choi, peat moss, old world diamond-flower, purple cudweed and nightshade by using HA semiselective medium. Population of the pathogen increased on Cardamine parviflora, Hedyotis corymbosa, Cyperus rotundus and Amaranthus viridis, and decreased slightly on Rorippa indica. Naked conidia of the pathogen showed less survival ability in soil than it colonized in leaves of pak choi. Cow manure enhanced the proliferation of the pathogen in soil. Seed meals were significantly effective to enhance or maintain the survival of the pathogen in soil. The pathogen declined faster in infected debris buried at 5 and 10 cm depths in soil than those placed on the soil surface.
Anthracnose disease of pak choi [Brassica rapa L. subsp. chinensis (L.) Hanelt] is a common disease in organic farm in Taiwan. It can cause a leaf spot on several species of Brassicaceae. Colletotrichum higginsianum and C. gloeosporioides could be isolated the disease leaves. C. higginsianum could infect unwounded pak choi leaf, wounded mango leaf and tomato fruit. Comparatively, C. gloeosporioides could infect unwounded mango leaf and unwounded tomato fruit but cause leaf chlorosis on wounded pak choi leaf. It may be weak pathogen on pak choi. A standard area diagram showed the levels of 0.07, 3, 10, 25 and 50% was developed for assessing disease severity in this study. The accuracy and precision of disease assessment were improved when standard area program was used. Nine Brassica spp. crops were inoculated with C. higginsianum. Pak choi and turnip were more susceptible than leaf mustard, cabbage and radish. Among seventeen cultivars of Brassica rapa subsp. chinensis, the most susceptible cultivars were Tsai-Yu, Chief, Gai-liang-Yi-Tiao-Gen and Feng-Jhen; the most resistant cultivar was 606 chingensai. Fifteen nitrogenous compounds and eighteen carbohydrates were evaluated for their efficacy on growth of C. higginsianum. The colony color was brightest when the pathogen was cultured on the medium with ammonium phosphate as nitrogen source. The conidial germination was most improved by high methoxy pectin (HMP) as carbon source, and 3% (w/v) HMP was effective in enhancing growth of the pathogen. Among the eleven antimicrobial agents tested, streptomycin sulfate, chloramphenicol, metalaxyl , pencycuron and thiabendazole showed less adverse effect on growth of C. higginsianum but could suppress Trichoderma sp. and other fungi. Based on these results, a HMP- ammonium phosphate semiselective medium (designated as the HA semiselective medium) consisting of 30 g high methoxy pectin, 2 g monoammonium phosphate, 1 g K2HPO4, 0.5 g KCl, 0.5 g MgSO4.7H2O, 0.01 g FeSO4.7H2O, 15 g agar, 200 μg mL-1 metalaxyl, 300 μg mL-1 pencycuron, 1μg mL-1 thiabendazole, 100 μg mL-1 chloramphenicol and 200 μg mL-1 streptomycin sulfate, and pH value of medium was adjusted to pH 6.0 by KOH before autoclaving. C. higginsianum was able to be accurately detected artificially infested soil and distinguished easily other Colletotrichum spp. by using HA semiselective medium. C. higginsianum could be detected infective leaves of pak choi, peat moss, old world diamond-flower, purple cudweed and nightshade by using HA semiselective medium. Population of the pathogen increased on Cardamine parviflora, Hedyotis corymbosa, Cyperus rotundus and Amaranthus viridis, and decreased slightly on Rorippa indica. Naked conidia of the pathogen showed less survival ability in soil than it colonized in leaves of pak choi. Cow manure enhanced the proliferation of the pathogen in soil. Seed meals were significantly effective to enhance or maintain the survival of the pathogen in soil. The pathogen declined faster in infected debris buried at 5 and 10 cm depths in soil than those placed on the soil surface.
Yangzhou pioneer chemical CO.,LTD.
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