Clonal and annual variation of flower production and composition of gamete gene pool in a clonal seed orchard of Pinus densiflora

The numbers of female and male strobili were assessed for 99 clones in a Pinus densiflora Sieb. et Zucc. seed orchard for four consecutive years. The data showed that differences for the production of both female and male strobili among clones were very large and statistically significant for all years examined. The most abundant quartile of clones produced 48.1 and 37.3% of the total female and male strobili, respectively, averaged over the 4-year period. Differences in female strobilus production among clones were more variable than in male. Pearsonʹs correlations between years for flower production were positive for all combinations of years. Spearmanʹs rank correlation coefficients between years with moderate female flowers were highly significant. Both correlations between female and male flowers were moderate and positive for all 4 years. Broad-sense heritabilities for flower production on an individual ramet basis varied from 0.19 to 0.41, while those on a clone-mean basis were much higher, from 0.57 to 0.80. Maleness index showed that sexual symmetry in good and poor flower years deviated more from the ideal panmictic situation than that in intermediate years. Parental balance curves showed that orchard clones contributed more equally to the seed crop when flower production was moderate.