Resistance Determination and Histopathological Observation of Induced Pinus densiflora Families from Japan to Bursaphelenchus xylophilus

The resistance of 27 wilt-resistant Pinus densiflora families induced from Japan to 3 isolates of Bursaphelenchus xylophilus was determinated. The result indicated that all 27 Pinus densiflora families had resistance to the 3 isolates,and there were significant differences from each other. It was found by bark inoculation that 13 families(No.1,4,5,6,7,8,13,14,15,17,20,23 and 25) were more resistant than others. The histopathological observation of No.5 family sampled at 4,8,12,24,36,48,72,96,120 h after inoculation showed that B.xylophilus migrated much slower in the induced pine seedlings than in the control. Pathological changes in parenchyma radial cell and the parenchymatous cells around resinosis cells occured later in wilt-resistant pine seedlings than in the control.In addition,the pathological changes occured more gently in the induced pine seedlings than in the control.