Keiya Isoda

Consecutive five-year analysis of paternal and maternal gene flow and contributions of gametic heterogeneities to overall genetic composition of dispersed seeds of Pinus densiflora (Pinaceae)

UNLABELLED PREMISE OF THE STUDY Genetic variability in monoecious woody plant populations results from the assemblage of individuals issued from asymmetrical male and female reproductive functions, produced during spatially and temporarily heterogeneous reproductive and dispersal events. Here we investigated the dispersal patterns and levels of genetic diversity and differentiation of both paternal and maternal gametes in a natural population of Pinus densiflora at the multiple-year scale as long as five consecutive years. • METHODS We analyzed the paternity and maternity for 1576 seeds and 454 candidate adult trees using nuclear DNA polymorphisms of diploid biparental embryos and haploid maternal megagametophytes at eight microsatellite loci. • KEY RESULTS Despite the low levels of genetic differentiation among gamete groups, a two-way AMOVA analysis showed that the parental origin (paternal vs. maternal gametes), the year of gamete production and their interaction had significant effects on the genetic composition of the seeds. While maternal gamete groups showed a significant FST value across the 5 years, this was not true for their paternal counterparts. Within the population, we found that the relative reproductive contributions of the paternal vs. the maternal parent differed among adult trees, the maternal contributions showing a larger year-to-year fluctuation. • CONCLUSIONS The overall genetic variability of dispersed seeds appeared to result from two sources of heterogeneity: the difference between paternal and maternal patterns of reproduction and gamete dispersal and year-to-year heterogeneity of reproduction of adult trees, especially in their maternal reproduction.

The impact of phenological and artificial factors on seed quality in a nematode-resistant pinus densiflora seed orchard

Abstract To clarify the relationship between the impact of phenological and/or artificial factors on seed quality, we measured the numbers of strobili on nematode-resistant Pinus densiflora clones grown in an immature and relatively small scale (700 m2) seed orchard. In addition, we established the clonal identities of all ramets, identified the paternal parent of the seeds, and assessed the resistance of seedlings to nematode infection. We also clarified the quantitative differences of strobili among clones; one clone produced 86.4% and 70.8% of all male strobili and female strobili, respectively. However, given that the total contamination ratio of the orchard was 82.0%, immigrant pollen had a larger impact on the success of actual crossing than phenology. Seedlings with a resistant maternal parent were resistant, even when their paternal parent was from outside the orchard. Two unselected clones were also planted in the seed orchard, one of which was not resistant and was associated with a maternal contribution of 34.7% of all seed stock. These findings suggest that, despite having a large impact on the crossing, immigrant pollen has a minor impact on seed resistance. Conversely, unselected and nonresistant clones have a marked impact on seed resistance. We concluded that artificial factors have larger impact on the seed quality than phenological factors in this orchard and the seeds will be of sufficient quality for supplying the market once nonresistant clones have been removed from the orchard.

Primer note: Development of highly polymorphic nuclear microsatellite markers for hinoki (Chamaecyparis obtusa)

Abstract We developed 32 microsatellite markers from an enriched genomic DNA library of hinoki (Chamaecyparis obtusa), one of the most important Japanese forestry conifer species. From a total of 1,056 cloned plasmids, 96 sequence-specific primer pairs were designed from 110 candidate clones. We selected 32 primers that showed successful amplification and marked polymorphism and evaluated their characteristics using DNA from 38 C. obtusa elite trees planted in the Forest Tree Breeding Center. The markers were highly polymorphic, with the number of alleles ranging from 8 to 32 (mean: 20.09), and expected heterozygosity ranging from 0.811 to 0.958 (mean: 0.901). Progress in breeding projects and studies of the ecological genetics of this species can be expected through the use of this enlarged marker pool.