| According to the results of disease investigation in field and detached Ginkgo leaves inoculation with Phytophthora nicotianae in lab, relative humidity 90%～100% and temperature 28～30℃ were the best cond i t i ons for the deve I opment of G i nkgo b I i ght. When the different age detached Ginkgo leaves were inoculated with P. nicotianae, the results show that the elder leaves were, the lower disease incidence occurred and the slower spreading speed of disease development had, and vice versa. When detached leaves of different Ginkgo varieties were wounded inoculated with P. nicotianae, Ha i yanghuang was resistant, and the disease incidence of Chaotian No. 1 and Dafoshou No. 2 were lower, while the disease incidence of Dafoshou No. 1 was highest. When we inoculated fungi on unwounded leaves, Dafoshou No. 1 and Gui G86-1 were susceptible, wh i I e the d i seaes i ndex of Chaot i an No. 1, Ha i yanghuang and Dafoshou No. 2 were I ower. The fungi static effects of leaves' extracts from different Ginkgo varieties in order were Chaot i an No. 1 (7. 78%) >Dafoshou No. 1 (5. 84%) > Gui G86-1 (4. 67%) >Dafoshou No. 2 (3. 50%) 2>Ha \ yanghuang (-1.17%). The d i sease i nc i dence of some var i et i es were I ower , but the i r leaves' tissues extracts had lower fungi static effects. Maybe it was because the extraction methods were not perfect, we didn't get the fungi static material.There were two peaks i n the act i v i t i es of perox i dase (POO). po I ypheno I ox i dase (PPOD) and phenyI a I anine arnnonia-1yase(PAL) in inoculated different age leaves. The activities peaks of the enzymes in elder leaves were higher than those in younger ones. It can be concluded that the elder Ginkgo leaf has stronger resistance to the blight.The activity rise variation in wounded-inocuIated leaves were stronger than those in wounded-not-inocuIated leaves and health leaves. According to the results of the enzymes determination after different age and varieties Ginkgo leaves were inoculated with P. nicotianae, the rise ranges of the enzymes activities in wounded inoculated leaves were higher than those in unwounded-inoculated ones. Moreover, the enzymes activities in the former were from hundreds to thousands of times higher than those in health ones. So that we suggested that inoculation should induce the enzymes activities become higher. There were obvious peaks of POD, PPOD, PAL activities when leaves of different Ginkgo varieties were inoculated . Furthermore,these peaks were related to the disease progress. Among the five varieties , the rise ranges of POD and PPOD activities in Dafoshou No. 2 were highest;WhiIe those of PAL activities in Chaotian No.1 and GuiG86-1 were highest.The structure of different age and var ieties Ginkgo leaves were mostly the same, but the wax on the leaf's surface was thicker when the leaf's age became elder .The inclusions also changed with the leaf's age variation. The crystal cluster and amyloplasts changed from less to more, and the crystalline material changed from noth i ng to someth i ng. These var i at i on maybe one reason of the res i stance hav i ng become stronger. There were no distinctive differentiation at the structure of leaf surface and the inclusion among different Ginkgo varieties. |
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