Relationship between the anatomical characteristics of cortical resin canals and migration of bursaphelenchus xylophilus in stem cuttings of pinus thunbergtt seedlings

Abstract

The migration of pinewood nematode, Bursaphelenchus xylophilu, inoculated on the top of 10-cm-long stem cuttings obtained from the current shoots of two types of Pinus thunbergii seedlings - a resistant family Namikata (t)-73 and a nonselected type - were investigated. Additionally, the number of cortical resin canals and the sectional area of each resin canal in each stem cutting were examined. The mean sectional area and the total area of the cortical resin canals were significantly larger in the nonselected seedlings than in Namikata (t)-73. Three days after the inoculation, more than half of the recovered nematodes were extracted from the uppermost part, within 2 cm from the inoculation point, of the stem cuttings of Namikata (t) -73. On the other hand, in the nonselected seedlings, approximately half of the recovered nematodes passed through the stem cuttings and the number of nematodes that passed through a stem cutting increased with the total sectional area of the cortical resin canals. These results suggest that the quantitative character of a cortical resin canal affects nematode migration in pine shoots, and that the total sectional area of cortical resin canals as an index of the quantitative character may represent the individual resistance level of P. thunbergii to pine wilt disease.