Pathogenicity and molecular character of Fusarium spp. causing leaf spot on Cymbidium and Oncidium

• Main Authors: Yi-Chi Jain, 簡苡琦
• Other Authors: 鍾文鑫
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/67326016749939835921

碩士 === 中興大學 === 植物病理學系所 === 99 === Orchid produced in Taiwan is popular in the world. Recently, the orchid has become the most important products to export to different countries. Among the orchid products, Phalaenopsis is the number one, and Cymbidium and Oncidium are second and third. Total 64 fungi and 55 fungal isolates were obtained from 21 Cymbidium plants leaves and 22 Oncidium plants leaves showed black spot, respectively. Based on morphological and molecular characteristics, the 43 isolates from Cymbidium were identified as Fusarium proliferatum and one isolate was identified as F. verticillioides. The other sides, 8 of 55 isolates from Oncidium were identified as F. proliferatum. The results demonstrated that F. proliferatum is the major species on Cymbidium and also can cause leaves spot on Oncidium, however, the F. fractiflexum published in Japan could not be found in Cymbidium or Oncidium in Taiwan. For confirming the pathogenicity, the isolates of F. proliferatum from Cymbidium and Oncidium were examined. The results showed that all isolates of F. proliferatum can cause necrosis on detatched leaves after inoculated with 5 μl of 107 conidia/ml microspore suspension by dropped method. In addition, the isolates of F. proliferatum from Cymbidium and Oncidium could cause more severe symptom on young seeding of Cymbidium and Oncidium after inoculated with 106 conidia/ml microspore suspension by sprayed method. In this study, the pathogenicity of F. proliferatum from Cymbidium and Oncidium to different hosts was exam ined. The result indicated that the isolates of F. proliferatum from Cymbidium and Oncidium can not cause necrosis spot on detached leaves of different hosts. Moreover, the isolates of F. proliferatum from Phalaenopsis, Oryza, and Dendrobidium were tested their pathogenicity to Cymbidium and Oncidium by inoculated in detached leaves. The result demonstrated that the isolates of F. proliferatum from different hosts can infect and show variably pathogenicity in Cymbidium and Oncidium. Thus, the isolates of F. proliferatum have the characteristics of wide host range and opportunism. Three DNA regions, polyketide synthase (PKs)、translation elongation factor 1 alpha (EF 1α) and intergenic spacer (IGS) of ribosome, were sequenced and analyzed the phylogenetic relationship between the isolates of F. proliferatum. The result revealed that the isolates of F. proliferatum from Cymbidium and Oncidium formed a molecular group and did not support the characters of host, location and pathogenicity based on neighbor-joining method (NJ) and maximum parsimony method (MP) analysis. However, the isolates of F. proliferatum from Phalaenopsis, Oryza, and Dendrobidium could form monophyletic group and support by high bootstrap value, respectively. Moreover, the isolates of F. proliferatum and F. fujikuroi from Oryza could be grouped a cluster by high bootstrap value. Thus, the two species f F. proliferatum and F. fujikuroi have high molecular phylogentic relationship.