Abstract
We investigated the seed productivity and the resistance of open pollinated resistant families (ORF) which comprise the clonal seed orchard in Okayama (established in 1985, 1.0ha). Seed productivity in seed orchard had increased from 1991 to 1995 and it amounted to about 4.5kg in 1995. However it decreased to about 0.5kg in 1996. The seed production of these showed clones annual correlation between each year. As in this seed orchard the seed production by a few clones was very large, about 50% of all production, therefore, was produced by the clones ranked from top to the fifth. Artifical inoculation test of the pine wood nematode had been conducted with ORF, in the nursery and greenhouse. As a result the extent of damage changed year by year depending on the year and testing condition. The average of survival rate of all families was from 20 to 95%. Moreover there was a difference between the ORF. By comparison of ORF with the seedlings from unselected trees, it was found that there was a clear difference in the degree of resistance between them when the inoculation test was carried out under the condition that the disease did not easily proceed. Under the easy-to-suffer condition, however, many seedlings of both groups died and no distinct difference was observed. From these results rankings of seed productivity of the mother stocks and degree of resistance of their families were given, respectivity.
