Pollination dynamics in a Platycladus orientalis seed orchard as revealed by partial pedigree reconstruction

Pollination dynamics was studied in a first-generation Platycladus orientalis (L.) Franco seed orchard with pedigree reconstruction using eight nuclear and four chloroplast SSRs. The pedigree reconstruction assigned 371 of 448 studied seeds to one of the orchard's 192 candidate male parents and showed a high level of outcrossing and pollen contamination in the orchard's seed crop. While the orchard's seed population showed greater allelic richness compared with the parental population, a few alleles present in the parental population were missing in the seed crop. Additionally, we detected no significant correlation between male reproductive energy (pollen yield) and male reproductive success; however, uneven parental contribution was also observed. Pollen management practices were recommended to ensure the maintenance of genetic diversity in the seed crops and increase in genetic gain. Key words: seed orchard, pedigree reconstruction, gametic contribution, pollen contamination, selfing rate, genetic diversity. La dynamique de la pollinisation a ete etudiee dans un verger a graines de premiere generation de Platycladus orientalis (L.) Franco a l'aide de la reconstruction de pedigree se basant sur huit marqueurs SSRs de type nucleaire et quatre de type chloroplastique. La reconstruction de pedigree a permis d'assigner 371 des 448 graines etudiees a l'un des 192 parents males candidats du verger, tout en indiquant un niveau eleve d'exogamie et de contamination pollinique parmi la recolte de graines du verger. Alors que la population de graines du verger avait une richesse allelique plus elevee comparativement a la population parentale, certains des alleles presents dans la population parentale etaient absents des graines recoltees. De plus, une correlation significative a ete detectee entre l'energie des males consacree a la reproduction (production de pollen) et leur succes reproducteur; toutefois, des contributions parentales inegales ont aussi ete observees. Des pratiques de gestion du pollen sont recommandees afin d'assurer le maintien de la diversite genetique des recoltes de graines et d'augmenter le gain genetique. [Traduit par la Redaction] Mots-cles: verger a graines, reconstruction de pedigree, contribution gametique, contamination pollinique, taux d'autofecondation, diversite genetique.
Introduction Platycladus orientalis (L.) Franco, the only member of the family Cupressaceae, is native to northwestern China, Korea, and the Russian far east (Cheng and Fu 1978). As a pioneer [...]