Abstract: Brown spot needle disease is one of important diseases on Pinus elliottii and P.taeda in south China.On the basis of resistance selection,the glucose-6-phosphate dehydrogenase and phenylalanine ammonia lyase activities in needles of 9 resistant clones and 4 susceptible individuals of slash pine were studied and analyzed.The results showed that there were close relations between the activity levels of glucose-6-phosphate dehydrogenase and disease resistance in two-year-old needles of slash pine.The enzyme activity levels of 9 resistant clones were mostly higher than those of 4 susceptible individuals.Phenylalanine ammonia lyase activities of the resistant clone needles,in general,were also a bit higher than those of susceptible individuals.After resistant and susceptible needles were treated by primary toxin of brown spot fungus,their glucose-6-phosphate dehydrogenase activities all increased,and the increment extents were all about 0.5-1 times,but their phenylalanine ammonia lyase activities didn't evidently change.

Key words: Brown spot needle blight, Pinus elliottii, Glucose-6-phosphate dehydrogenase, Phenylalanine ammonia lyase, Resistance machanism