Molecular analyses of ambrosia beetles and its symbiotic fungi associated with mass mortalities of oak

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To clarify the differences in morphological and molecular characteristics of a pathogenic fungus, Raffaelea quercivora, 21 isolates of the fungus were collected from areas where the mass mortality of oak trees has occurred. Additional 5 fungal isolates that were type species of R.quercivora were also used for comparison of the characters described among these isolates. The size of conidial spores was 1.8-3.1×3.3-8.1 μm for in the type species and 1.4-5.4×3.0-10.3 μm for the 21 isolates. The fungal isolates used for the morphological characterizations were further applied for DNA analyses focusing on both an internal transcribed spacer (ITS) region and a D1/D2 region in the 28s region of ribosomal DNA. The 21 isolates collected from the damage sites were quite similar in morphological and molecular traits with those of the type species suggesting that the isolates were identical to R.quercivora. We added 114 fungal isolates that supposed to be R.quercivora obtained from wilting or dead … More trees at damage sites of the mass mortality of oak trees in Japan. They were applied for random fragment length polymorphism (RFLP) analyses with three enzymes. Seventy-eight of 114 were successful for the RFLP analyses in all the enzymes, and the RFLP pattern was identical to that of the type species. These results indicate that R.quercivora is a pathogen of the mass mortality of oak trees and prevalent over damaged areas in Japan.We inoculated R.quercivora to the seedling of 4 Fagaceae species to determine the major factors associated with the susceptibility of the species to the fungus. After fungal inoculation, we measured the axial length of the discoloration and the areas of discolored and non-conducting sapwood on stem cross-sections. There were significant differences in the susceptibility among the tree species that was a strong correlation between the expansion of transverse discolored areas and the range of non-conductive sapwood areas formed.We measured morphological traits of ambrosia beetles, Platypus quercivorus that have mycangia retaining R.quercivora collected from Wakayama prefecture. The mating test of P.quercivorus was conducted for populations between Wakayama prefecture and Kyoto prefecture. Although the cross mating derived from the different populations were successful, the reproduction rate in the cross mating was lower than that within the same population. We further examined the effect of both the body size of adult beetles and the formation of galleries on reproduction successes by the cross mating between the populations obtained the two prefecture as above. Less