| The objective of this study is to characterize 14 eggplant isolates of Verticillium dahliae Kleb. from different cropping areas in China. Four independent experiments, covering the morphological characterization, pathogenicity test, mechanism of virulence, and PCR-based ISSR fingerprinting analysis, were carried out. The results of each part were respectively described as follows:1. To characterize the morphology of V. dahliae isolates from affected eggplants, 5 isolates of Verticillium were involved in this study. The results indicated that all of the collected fungi are belonging to the single species of V. dahliae Kleb., and the optimal temperature for single clone development was 25℃; however, restrained under 30℃, and no surviving beyond 33℃.The further inoculation on different hosts, e.g. eggplant, tomato, pepper, and cotton using double-layer-plate method, displayed that the 5 isolates differed in pathogenicity to each host. According to the morphological characteristics, 14 single spore isolates were therefore classified into three morphotypes: HS (Hypha-Sclerotia), Sc (Sclerotia), and SS (Sparse Sclerotia); moreover, there were significant differences in mean size of conidia and sclerotia (p<000001) among 14 isolates. Interestingly, there are also significant differences in the size of sclerotia between southern and northern China.2. To identify the differentiation of pathogenicity among the eggplant isolates of V. dahlia, all of the 14 isolates were inoculated to eggplant by simultaneously using conidial suspension and crude toxin. Significant differences among isolates were consensus in both inoculations. Therefore, the isolates were divided into three pathotypes, e.g. strongly, moderately and weakly pathogenic, depending on the integrating performance on G24, 85m, and Sm90017. Further correlation analysis revealed that closely associations were detected among numbers of morphological characters, including between morphotype and both aerial hypha and microsclerotia, between microsclerotia length and width, between conidia length and width, between Defoliating/Non-Defoliating (D/ND) and sclerotia and morphotype, and between aerial hypha and conidial length. Unexpectedly, there was no significant correlation between pathogenicity and D/ND type, morphological characteristics, and geographical origin, even all three isolates involved in Defoliating type demonstrated strong pathogenicity.3 To insight into impacts of crude toxin to activities of enzyme and photosynthetic characters, both susceptible and resistant eggplants were inoculated with crude toxin isolated from Verticillium dahliae Kleb.. The result showed that theperoxidase(POD) and superoxide dismutase(SOD) activities of resistant eggplant were higher than that of susceptible one. However, polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) activities were relatively stable. Meanwhile, the Net photosynthetic rate(Pn), Stomata conductance(G5), Transpiration rate(Tr) and Intercellular CO2 concentration (C,)of resistant eggplant were less than that of susceptible. While both eggplants displayed descending trend in Pn, Gs, and Tr after inoculation for 72 hours.4. To distinguish the eggplant isolates of Verticillium dahliae at molecular level, the ISSR-based fingerprinting analysis was carried out using genomic DNA from 12 isolates collected from different areas. The results showed that the optimal ISSR reaction system comprised 20ng template DNA, 0.25 u mol/L ISSR primer, 2.5 mmol/L MgCl2, 250 \x mol/L dNTP, 1U Taq DNA-polymerase, and 1 X PCR buffer in a total volume of 20μL reaction mixture, with the procedure of one cycle denaturing at 94℃ for 5 min;40 cycles each involved denaturing at 94℃ for 30s, annealing at 48℃ for 45s;extending at 72℃ for 2 min; a final extension at 72℃ for 6 min after the last cycle; and then remaining at 4℃. The abundant amplification products implied that ISSR (inter simple sequence repeat) was ubiquity in genome of Verticillium dahilae isolates from eggplant. The fingerprint...
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