| The black spot was one of the important diseases on poplars and it had became an obstacle to the development of poplar plantation.The study on the black spot disease of poplar concentrated on disease pathogenesis,chemical control and so on for the moment.Lacking of understanding of the self resistance,physiological resistance and biochemical resistance of different poplars would have a negative impact on understanding and controlling the disease resistance mechanism of black spot of poplar.Therefore,this paper did a study on the resistance of different clones of black spot disease based on nine clones and the following four hybrid combinations:Erlang Mountain poplar hybrids with deltoides(ED),Chuan Yang hybrids with deltoides(SD),Populus cathayana Rehd.with deltoides(CD)and Erlang Mountain poplar hybrids with Populus cathayana Rehd.(EC).Subsequently,physiological and biochemical changes of oenzyme activity,total phenol,soluble sugar,soluble protein,malondialdehyde and chlorophyll etc were analysed.It aimed to provide a reference for the selection of tree species cultivated in poplar plantation and to enrich the content of disease controlling of poplars.(1)SD1011 had the strongest resistance to disease of the black spot and its disease indexes were thirty-eight point two and thirty-nine point seven respectively under natural and artificial inoculation conditions.ED10112 and SD102 were the ones that had the weakest disease resistance.Their disease indexes were sixty-four point eight and seventy-two point seven respectively under natural condition,sixty-six point two and sixty-three point two under artificial inoculation condition.(2)The activity of superoxide dismutase SOD in all clones increased with the aggravation of disease.It could be used as an indicator to judge the disease resistance.The activity of Peroxidase POD reflected that highly resistant poplar clones had higher activity to some extent.However,it could not fully indicate that disease resistance mechanism of Poplar was acquired physiological and biochemical resistance factor induced by the plant after the pathogen invading.(3)The contents of malondialdehyde MDA under natural condition and artificial inoculation condition were opposite.The content of MDA increased in all clones in the October,namely,in the late stage of natural condition.The contents of MDA in SD1011 and CD1017 were the least.They were zero point zero four seven and zero point zero four nine respectively.On the contrary,contents of MDA in ED10112,SD1022 and SD102 were the Most ones.Their contents were zero point zero five nine,zero point zero five nine and zero point zero five six respectively.The contents of MDA in SD1011 and CD1017 were higher than those with weaker resistance in the late stage of inoculation.The maximum difference was zero point zero one.(4)The content of soluble sugar changed obviously after affecting disease,and there were two peak values.There were significant differences in soluble sugar content between the clones with strong resistance and weak resistance under natural condition and artificial inoculation condition at the peak period of the onset of disease.(5)The content of soluble protein varied differently in different periods,and generally it showed a downward trend.The content of soluble protein decreased in the later stage of a disease than that before inoculation.(6)The total phenol content in the resistant clones increased rapidly and reached the maximum in the early stage of the onset.The total phenol content in the early onset of the disease increased rapidly.The rising amplitude of the strong resistant clones was higher than that of the less resistant clones,and the increases of SD1011 and CD1017 in the middle resistant clones were 90.9% and 86.4% respectively,and the total resistance to the clones was SD1011 and CD1017.The content of phenol is high,which is very different from the clones with poor resistance.The maximum range is eight point three two.Compared with the artificial inoculation condition,the total phenolics of the other clones increased rapidly to the maximum when the clones with strong resistance before the peak stage.(7)Chlorophyll-a,chlorophyll-b,carotenoid and total chlorophyll were related to the disease resistance of poplar.With the aggravation of the disease,the chlorophyll content of the clones with better resistance in the late onset was not obvious.In the natural condition,the ratio of the chlorophyllin-a and the chlorophyllin-b reached the peak value.Those ratios werefive point eight nine,six point one eight,nine point four nine,seven point seven three,eight point four two,ten point seven two and four point three,seven point seven and four point four three respectively.The average ratio of the chlorophyllin-a and the chlorophyllin-b in low and medium clones was relatively high.The ratio of the chlorophyllin-a and the chlorophyllin-b in poplar clone reached the maximum value at the later stage after inoculation,and the average ratio in the low sensitive clone was relatively high.In conclusion,the resistances of poplar clones to black spot are different.It is physiological and biochemical changes are closely related to disease resistance.The results in this paper are helpful to further understanding to the disease resistance mechanism of poplar plantation.This paper also provides reference for selection of poplar plantations and enrichs the contents of disease prevention and control of poplar trees. |
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