Occurrence of plaster disease in Phellodendron chinense and physiological response under different stand conditions

Objective  To study the correlation between stand factors, physiological indexes of resistance and occurrence degree of plaster disease in Phellodendron chinense.

Method  Incidence and disease index of plaster disease were investigated by field survey. Moisture content was represented by bark swelling degree. Protein contents were determined by the Coomassie brilliant blue (G250) method. Enzyme activities were determined by measuring the inhibition of photochemical reduction of nitroblue tetrazolium. MDA content was measured by thiobarbituric acid colorimetric assay.

Result  The disease index was higher for P. chinense with older tree age. The disease incidence was higher in shady slope compared with sunny slope. The P. chinense forest with single-species composition was more susceptible to disease. After affected with plaster disease, the moisture content of P. chinense bark largely reduced. The relative bark swelling degree had highly significant negative correlation with disease incidence and disease index. The defense enzyme activities of healthy P. chinense bark in three sample plots were higher than those of diseased bark. Superoxide dismutase (SOD) activity fluctuated greatly, and peroxidase (POD) and phenylalaninammo nialyase (PAL) activities showed significant downward trends for diseased P. chinense. The activities of three enzymes had significant or highly significant negative correlation with disease index. The soluble protein and MDA contents of diseased P. chinense bark significantly increased in the most serious period of disease occurrence.

Conclusion  Tree age, terrain, species composition had significant influence on occurrence of plaster disease in P. chinense. The bark water content, defensive enzyme activities and MDA content are significantly affected by this disease.