| 論文英文摘要 |
Brown blight disease mainly damages tea leaves and young branches, resulting in a decline in tea quality and yield. Tea farmers mainly rely on chemical control, however, in the past ten years, they have reported that the registered fungicides are not effective. To understand whether the population of the pathogen associated with brown blight of tea in Taiwan has emerged resistance to methyl benzimidazole carbamate (MBC) fungicides, 37 isolates of Colletotrichum camelliae, three isolates of C. fructicola, and one isolate of C. aenigma from eight major tea-producing counties and cities in Taiwan were tested for mycelial growth on potato dextrose agar containing 1000 ppm (mg a.i./L), 100 ppm, 10 ppm, and 1 ppm of benomyl and thiophanate-methyl. While C. camelliae isolates highly and lowly sensitive to the fungicides were found in each county/city (except that C. camelliae from Pingtung County were all resistant), the isolates of C. fructicola and C. aenigma were all highly sensitive. All 41 isolates tested showed similar trend of sensitivity or resistance to the two fungicides, and the sensitivity of the resistant isolates to thiophanate-methyl was lower. For 15 isolates of C. camelliae from different counties and cities, a segment of β-tubulin that is known to have the most frequent fungicide resistance mutations was sequenced. The sensitive and resistant isolates differed only at the 860th nucleotide, which caused the 198th amino acid changed from glutamic acid (GAG) to alanine (GCG). The phenomenon conforms to the mechanism of the emergence of high fungicide resistance in the literature. The fungicide sensitivity of Colletotrichum spp. associated with brown blight of tea was related to the modes of management in the field. The resistant isolates were all from conventional tea plantations, and the isolates from the plantations organically managed or with less fungicide application showed high sensitivity. This study indicated that C. camelliae isolates resistant to MBC fungicides have been widely present in many tea-growing areas across Taiwan. It is recommended that rotation or mixed use of fungicides with different modes of action, together with integrated pest management measures should be implemented to effectively control the disease. |