RESUMO
The pathogenicity of the pine wood nematode (PWN), Bursaphelenchus xylophilus together with the bacteria isolated from black pine (Pinus thunbergii) bark inoculated to axenic black pine seedlings, significantly exceeded that of the axenic PWNs alone, demonstrating that the bacteria play an important role in pine wilt disease. Inoculation of seedlings with bacteria-free culture filtrates of the seven isolates from the dead seedlings from the above experiment showed that all isolate filtrates killed the seedlings within 8 days. Identification of the bacteria using 16S rDNA sequencing showed that the isolates belonged to strains By253Ydz-fq, S209, 210-50 and 210-50 in Bacillus and the DN1.1 strain of Stenotrophomonas maltophilia, respectively. Completing Koch's postulates using the seven bacterial isolates to inoculate pine seedlings showed that all the seedlings that received aseptic PWNs mixed with the seven bacterial isolates died within 18 days post inoculation, while those inoculated with 'wild' PWNs died 16 days post inoculation. No disease symptoms developed on seedlings that received sterile water or aseptic PWNs. The horizontal transfer of the pathogenic bacteria may explain differences in bacterial species carried by PWN in different geographic areas.
RESUMO
Fifty strains of bacteria were isolated from six isolates of the nematode Bursaphelenchus mucronatus (Bm) from China and Russia and identified using the BioMerieux Vitek 32 system. In bioassay, 3 bacterial strains showed the high levels of phytotoxin production while 19, 16, and 12 strains showed moderately, low and no phytotoxin production, respectively. Inoculation of 2-month-old Pinus thunbergii seedling with each of the six Bm isolates showed that the mean number of days from inoculation to death of 80% of the seedlings was significantly related to the ratio of the total number of bacterial strains for a nematode isolate to the number of pathogenic bacterial strains of the nematode isolate. The results of inoculation of 3-year-old P. thunbergii seedlings showed that inoculation with either axenic Bm (ABm) or axenic B. xylophilus (ABx) and the pathogenic bacterial strain together were essential for inducing pine wilt. These findings demonstrate that wilt symptoms caused by Bm conform to our earlier hypothesis (Zhao et al., 2003) that pine wilt disease, induced by certain Bx or Bm isolates, is caused by a complex of both the nematodes and their associated pathogenic bacteria. The results also account for the variation in pathogenicity of Bm populations from different parts of the world.
RESUMO
The Paulownia bagworm, Clania variegata Snell. (Lepidoptera: Psychidae), is one of the most significant forest defoliators in China. In gas chromatographic (GC)-electroantennographic detection analyses of pheromone gland extracts of female C. variegata on three GC columns (DB-5, DB-23, DB-210), two compounds (A and B) elicited strong responses from male antennae. The more abundant component B was isolated by high-performance liquid chromatography and identified as 1-ethyl-2-methylpropyl 3,13-dimethylpentadecanoate by transesterification, GC-mass spectrometry (MS), and comparison of its spectral and GC retention characteristics with those of synthetic compounds. In field trapping experiments in China, racemic and (1S)-1-ethyl-2-methylpropyl 3,13-dimethylpentadecanoate [but not the (1R)-stereoisomer] attracted male C. variegata. The absolute configuration of B (a molecule with three chiral centers) and the structure of component A remain to be determined.
