| Summary: | 碩士 === 國立臺灣大學 === 植物病理與微生物學研究所 === 104 === Peach (Prunus persica (L.) Batsch) is native in China, planted worldwide now. In Taiwan, peaches are mainly planted in Taichung, Taoyuan, Hsinchu and Nantou. Production is divided into three types: Low altitude crisp peaches, low altitude and high altitude juicy peaches. In recent years, for mitigating the pressure from alpine reclamation, agricultural scientists developed the technology for planting peaches in low altitude or plain area. “Premier” is one of the most important cultivar of the low altitude juicy peaches. Thus we choose this cultivar for this study. Aphids, bacterial leaf spot, leaf curl and gummosis are major diseases of peach. Peach gummosis is one of the most destructive diseases. According to the statistics, peaches will lose more than 40% yield if infected with this disease. After investigation in oneTaichung and one Taipei orchard, we found that gummosis occurs seriously in poor-managed orchards, with a lot of wounds and weak growth. This study isolated the pathogens of peach gummosis from stem lesions, blisters and gums in these two orchards by tissue block isolation method and dilution isolation method. The healthy peach stems showed gummosis after inoculating by mycelium discs and spore suspensions at wounds.The infected seedlings showed reduced tree height and wrose health. And we could reisolate the pathogens from diseased peach stem for fulfilling the Koch’s postulates. This study identified 2 different peach gummosis isolates from Taichung and Taipei, respectively. The best mycelial growth temperature of these two isolates is about 25o. The isolate from Taichung is identified as Botryosphaeria dothidea, while the isolate from Taipei preliminarily identified as Diplodia seriata, Sphaeropsis sapinea or Botryosphaeria obtusa. The different conidia morphology and DNA sequence show that the two isolates are different pathogens. By testing some fungicides reported in recent paper for chemical control, we showed that benomyl, carbendazim, difenoconazole, prochloraz, procymidone, propiconazole, tebuconazole, and thiophanate-methyl were able to inhibit the mycelial growth of peach gummosis isolates; while benomyl, carbendazim, difenoconazole, prochloraz, procymidone, propic-onazole and tebuconazole were able to inhibit the conidia germination of the pathogen. In pot test, azoxystrobin, carbendazim and prochloraz had shown good control effect. In field test, spraying azoxystrobin and prochloraz on stem exhibited good control effect. With big peach trees in orchard, we inject the fungiciedes in the basal stem. Results showed that difenoconazole and tebuconazole can reduced the gummosis. There is no formal chemical control fungiciedes recommended for controlling the peach gummosis in Taiwan. Therefore, this research is aimed to screen some adequate fungiciedes and develop better applying techniques for controling this serious disease.
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