| Summary: | 碩士 === 國立屏東科技大學 === 熱帶農業研究所 === 87 === Green muscardine fungi, Metarhizium spp., are entomopathogenic deuteromycetes and potentially valuable for developing into myco-insecticides. Determining the DNA fingerprinting and locating molecular markers of the different isolates of Metarhizium spp. are of vital importance to the registration of fungal products as myco-insecticides or to the identification of fungal species. There were a total of 15 isolates of Metarhizium anisopliae and a PJH isolate of Paecilomycetes javanicus collected from various places in Taiwan and other countries. The hosts from which the fungi were isolated included Lepidoptera, Coleoptera, Orthoptera, Blattaria and Homoptera. Based on the morphological characteristics, UV resistance, chemical resistance against benomyl, and entomopathogenicity, a comparison was made among the 15 isolates. The results indicated that the condiospores of the isolate HO194 were the smallest and those of the isolate 2575 were the largest. Of the 15 isolates, 14 were determined as mutants of M. anisopliae var. anisopliae on the basis of the characteristics of their conidia. The two isolates, 538 and MA-126, were significantly more resistant against UV light at 250 nm and MAUZ-1 and MA-126 were more resistant against the fungicide, benomyl. In terms of entomopathogenicity, all isolates had low virulence against Pseudaletia unipuncta. There were, however, significant differences in pathogenicity against aphids and Aedes aegypti. In addition, all of the isolates were cultured in SDB (Sabouraud Dextrose Broth) liquid media at 25C and agitated at 130 rpm for 7days before the mycelia were collected. The mycelia were then extracted with the modified SDS method. The extracted genomic DNA was analyzed by RAPD-PCR with 40 different random primers (operons). The results indicated that the closer the genetic relationship among the hosts was the higher the similarity of the DNA polymorphism; e.g., MA-1 and 35520. On the contrary, the isolates from different geographical origins had different genotypings; e.g., 683, 2575 and 3604. When comparing the UV light resistance, chemical resistance, and entomopathogenicity as well as the results of the RAPD-PCR analysis, it was determined that the isolate MA-126 was a mutant strain induced from the isolate MA-1. This determination was confirmed by the differences found in the DNA polymorphism between MA-126 and MA-1. Although MAUZ-1 and KCAL were selected from MA-126, their UV resistance, chemical resistance and entomopathogenicity were different from that of MA-126. This was also confirmed by the unique DNA polymorphism using the RAPD-PCR analysis. Therefore, the RAPD-PCR analysis could be used not only in identifying fungal isolates from different hosts basing on their genetic similarity or their geographical origins, but also in determining their physiological and biochemical differences in UV resistance, chemical resistance and entomopathogenicity.
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