| Zizyphus jujuba Mill. cv. Dongzao is an endemic late-maturing jujube variety in China, and it is considered as the treasure of fruits because of the excellent quality of the fresh fruit. Jujube rust is one of the three important diseases difficult to control after occurrence and can cause a heavy loss in production and fruit quality. Present research on jujube rust has only dealt with the epidemiology and chemical control. In this study, the difference of leaf structure, change of defense enzymes, and resistant physiological indexes of different disease levels were studied in order to provide a theoretical basis for selective breeding in Z. jujuba Mill. cv. Dongzao in the aspect of generating varieties resistant to rust disease. The main results obtained are as follows:1. Rust inoculation experiment was conducted with three different-aged leaves, and the anatomic structure of leaves was observed. The results showed that the degree of rust susceptibility in leaves was in the ascending order of young leaves> fully-grown leaves> mature leaves. In other words, mature leaves had the strongest resistance to rust. The leaf morphological structure including the thickness of the cutin layer, lower epidermis, and leaf blade, the ratio of palisade tissue to spongy tissue, the porosity of leaf tissue structure, and the stoma density were correlated with jujube rust occurrence, and could be used as indicators for the control of jujube rust and for selecting rust-resistant plus trees in jujube 'Dongzao'.2. Rust inoculation experiment was conducted with Z. jujuba Mill. cv.Dongzao, Jujube Gaga, and Jujube Lingbao,and the results showed that Jujube Lingbao had the strongest ability to resist rust disease, Jujube Gaga ranked next, and Z. jujuba Mill. cv. Dongzao had the weakest resistance. Relative humidity and temperature correlated highly with the occurrence of rust disease. The weather condition could not meet the germination of rust pathogen in July and August of the year; however, we should not neglect the possibility of the occurrence of rust disease, because the slightly decrease in temperature and increase in relative humidity can induce the occurrence of rust disease.3. Scanning electron microscope showed that pathogens of Jujube rust included the stages of urediniospore and teliospore. Urediniospores are piles of dual-core spores produced by dual-core mycelium with leathery, oval-shaped or oval, dense and short thorn, and normally invade host plants from the stomata after germination. This study suggests that in the host surface teliospore may also produce a short germ tube, continue to produce dual-core mycelium which germinated to form urediniospores, then urediniospores germinate and infect host plants repeatedly. 4. According to various degrees of infection, rust degrees of leaves can be divided into degree 0 (no disease on leaf) to degree 4 (fully infected on leaf). The influences of rust induced by Phakopsora ziziphi-zulgaris(P. Henn) Diet on the activities of antioxidate enzyme and contents of relative physiological indexes were studied with leaves of Z. jujuba Mill. cv. Dongzao in this paper. The results showed that, SOD, POD, CAT, PPO, PAL, soluble sugars, soluble proteins, the rate of O2-, H2O2, MDA, phenols, and chlorophyll had different changes during the infection process. Except the PAL activity, there was significant or very significant difference among different disease levels. The results suggest that SOD, POD, CAT, O2-, H2O2, MDA, Phenols, soluble suger, soluble protain, and Chlorophyll can act as ralative indicators of rust occurrence in Z. jujuba Mill. cv. Dongzao.
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