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Measurements of the cross sections are conducted for coherent photoproduction of the neutral pion and eta meson on the d, gamma deutron to pi0 eta deutron, at the incident energy in the range of the reaction threshold to 1.15 GeV. A rapidly increasing trend below 1 GeV is observed in the total cross section. The data are effectively reproduced by theoretical calculations incorporating the meson-deutron final-state interactions. However, the measured deutron angular distribution d sigma/d Omegad in the center-of-mass frame (gamma d) is rather flat, and it differs significantly from the strong backward-peaking behavior expected in the kinematics of d formation after pi0 eta photoproduction on an initial bound nucleon. In addition, the d sigma/dMeta d differential cross section exhibits a prominent enhancement near the eta d threshold, while d sigma/dMpi d exhibits an enhancement near the known pi d resonance with I=1 and JP=2+. From these observations, we have concluded that two reaction sequences occur; gamma d to pi0 D01 to pi0 eta d and eta D12 to pi0 eta d, where DIJ denotes a state with a baryon number of 2, an isospin of I, and a spin of J. The enhancement corresponding to D01 is expected to be a theoretically predicted eta NN bound state with I=0 and JP=1- or a virtual state of eta d. It is found that attraction between eta d is certainly very strong.

クロマツのマツ材線虫病抵抗性クローン (川内ク-290号) の実生苗38個体に対して, マツノザイセンチュウ (島原個体群) を用いて接種検定を行い, 抵抗性個体を15個体選抜した。これら15個体を採穂個体として3年間連続して挿し木を行い, 得られた挿し木苗に島原個体群を接種した結果, 各年における健全率は61～71%と年変動が少なく安定した抵抗性を示した。次に, 12の抵抗性クローンの実生苗18個体を対象に, 島原個体群より強い病原性をもつ線虫2系統 (Ka-4と唐津3) を用いて接種検定を行い, 抵抗性個体群の選抜を行った。選抜された9個体から挿し木を行い, 得られた苗木に強病原性線虫 (唐津3) を接種した結果, 健全率は97.7%ときわめて高かった。このように, マツ材線虫病抵抗性種苗生産において, 強病原性線虫の接種検定により抵抗性をもつ採穂個体群を選抜し, それらから挿し木を行う方法は有効であると考えられた。

The reproductive success of pollen derived from selected and non-selected sources and its impact on the performance of orchard crops were evaluated, using five pairs of microsatellite markers, in a Japanese black pine (Pinus thunbergii Parl.) clonal seed orchard consisting of 16 nematode-resistant clones. The paternity of each open-pollinated seed was determined by comparing the genotypes of seeds from six clones (24 trees) with genotypes of the 16 orchard clones and two trees (N1, N2) representing other genotypes that had been inadvertently included in the orchard. Out of 384 seeds examined, the paternity of 316 seeds (82.3%) was assigned to the clones within the seed orchard. On average, the male reproductive success of orchard clones varied from 0.0% to 10.5%, and was significantly related to the male-flowering fecundity of each clone. It was not related to the synchrony of flowering phenology between mates. The expected proportions of seeds produced by clonal trees as a result of pollination by orchard clones, and by contaminating pollen originating from internal and external sources were estimated at 86.8%, 3.3% and 9.9%, respectively. Nematode-resistant seedlings of Japanese black pine were produced from surviving 2-yr seedlings that had previously been inoculated with pinewood nematode (Bursaphelenchus xylophilus). Without pollen contamination, the survival rate of seedlings produced by mating between resistant clones is expected to be 62.4%. However, in this orchard the figure was reduced to 57.5%, due to pollen contamination from both internal and external sources.

Overall male reproductive success was investigated in a Japanese black pine (Pinus thunbergii Parl.) clonal seed orchard consisting of 16 nematode-resistant clones, using random amplified polymorphic DNA (RAPD) markers. We genotyped all 16 of the orchard clones at selected RAPD loci by analyzing diploid needles and 10 haploid megagametophytes from each of them. In addition, the male parent of open-pollinated seedlings was identified by comparing their phenotypes with the genotypes of the orchard clones. In this way the male parents of 559 seedlings of 648 seedlings of progenies from 14 parental (orchard) clones were determined. The level of external pollen contamination in the seed orchard was estimated to be 2.2% for the total population. The effective mean selfing rate observed was 1.5%. Male reproductive success among clones varied widely, from 0.8 to 24.4%, for the total population. Our data suggest that the significant deviation in male reproductive success of individual clones from panmictic ratios may be a problem for the genetic quality in seed orchard crops. To improve the parental balance of seed orchard crops, the use of artificial management techniques such as gibberellin A4/7 treatment, supplemental mass pollination, and rearrangement of clonal ramets is recommended in seed orchards.