Biochemical Resistant Mechanism Of Poplar To Leaf Rust Melampsora Larici-Populina Kleb.

Poplar is an important ecological and commercial forest tree species. Leaf rust is a major leaf disease, which is caused by Melampsora larici-populina Kleb. Research of domestic and foreign experts showed that the application of disease resistant species could be used to control the poplar leaf rust. The interaction between different poplar species and different Melampsora larici-populina Kleb. races was studied firstly in this paper. The relationship in this interaction between outbreak of reactive oxygen, dynamic changes of related enzyme activity and lignin content in the tissue structure in poplar leaf tissues and the host disease resistance was studied. Then PCD mechanism of the host after inoculated with Melampsora larici-populina Kleb. was discussed to provide scientific basis for the molecular mechanism of poplar leaf rust and poplar disease resistance varities screening .The conclusions showed that:1,There were significantly differences on the variation amplitude of ROS in the different poplar varieties (species) after inoculated with Melampsora larici-populina Kleb.The production rate of O₂^- and the content of H2O2 respectively rapidly increased in 0.5 d and 1 d, furthermore ROS of each varity was the highest in it's pathogene process compared with the CK. The change of ROS in susceptible species often appeared one peak and 2 to 3 peaks in the resistant ones. Moreover, the higher resistance to rust, the sooner occuring of second peak,and the higher of ROS value. ROS was fluctuatedly changed throughout the infection process,and the rate of ROS fluctuation rate immune and resistance in the susceptible varieties was higher than susceptible.2,The activity of POD, SOD and CAT had a dynamic change all the time after poplar inoculated with Melampsora larici-populina Kleb., and they were cooperative controled by each other. The activity of SOD was negatively correlated with the poplar resistance. The POD activity did not change significantly in early period after inoculation, but it had negative correlation with disease resistance later. The CAT activity was highly increased in 0.5 d ,then decreased in 1 d,moreover appeared one peak in 3 d to 5 d.The higher resistance to rust the lower CAT activity.3,The PAL activity increased rapidly and had stronger strength in the host of immune and resistance species after inoculated with Melampsora larici-populina Kleb. There were significant differences in the ration of PAL activity in each combination to the corresponding controls. The chitinase activity was positively correlated with poplar resistance basically. There were 2³ times of peaks in the resistant poplar varieties. In the ratio with the corresponding controlls, there was significantly difference between immune and others species, but little differences in others.4,In the pathogene process between poplar and Melampsora larici-populina Kleb.,there was very little accumulation of lignin in 1 d to 2 d in the leave tissue of incompatible combinations and comparatively obvious accumulation in 3 d. But lignin almost had no accumulation in the compatible one and healthy control, while more accumulation in highly resistant poplar varieties. There was no correlation between the accumucation of lignin and poplar rust resistance.5,Using DAPI stain after slicing the poplar leaves ,there was a strong blue light in mucli under the fluorescence microscope. The nucleolus were round or nearly round in the healthy leaves of different poplar varieties. There was HR phenomena and significantly change of PCD in P. szechuanica after inoculated with Melampsora larici-populina Kleb. The nuclei began to change in 0.5d after inoculation, then cracked in 5 d, disappeared in 7 d at last. However we found HR phenomenon after the inoculation of Populus purdomii,but it did not belong to PCD process.