Correlation relationship of resistance against pinewood nematode between clonal grafts and progeny seedlings from pinewood nematode resistant individuals of Japanese black pine（Pinus thunbergii）

Abstract

For 6 years from 1999 through 2004, we performed inoculation testing on 11 Japanese black pine pedigrees selected in a breeding project for their resistance to pinewood nematode. In the previous study, there was no correlation between the survival rates of the clonal grafts（trees in a seed orchard）and half-sib family seedlings produced in the seed orchard. However, in this study, the correlation coefficient was 0.840（P = 0.001）. We were able to confirm that there was a strong positive correlation between the two. The pollen constitution ratio and the climatic conditions differed among inoculation years, and these differences influenced the survival rates of clonal grafts and family seedlings. We considered that these influences were reduced by increasing the number of inoculation years. Therefore, we suggest that the survival rates of half-sib family seedlings produced in the seed orchard might be estimated from the survival rates of the clonal grafts.