Stability in and Correlation between Factors Influencing Genetic Quality of Seed Lots in Seed Orchard of Pinus tabuliformis Carr. over a 12-Year Span

Coniferous seed orchards require a long period from initial seed harvest to stable seed production. Differential reproductive success and asynchrony are among the main factors for orchard crops year-to-year variation in terms of parental gametic contribution and ultimately the genetic gain. It is fundamental in both making predictions about the genetic composition of the seed crop and decisions about orchard roguing and improved seed orchard establishment. In this paper, a primary Chinese pine seed orchard with 49 clones is investigated for stability, variation and correlation analysis of factors which influence genetic quality of the seed lots from initial seed harvest to the stable seed production over a 12 years span. Results indicated that the reproductive synchrony index of pollen shedding has shown to be higher than that of the strobili receptivity, and both can be drastically influenced by the ambient climate factors. Reproductive synchrony index of the clones has certain relative stability and it could be used as an indication of the seed orchard status during maturity stage; clones in the studied orchard have shown extreme differences in terms of the gametic and genetic contribution to the seed crop at the orchard's early production phase specifically when they severe as either female or male parents. Those differences are closely related to clonal sex tendency at the time of orchard's initial reproduction. Clonal gamete contribution as male and female parent often has a negative correlation. Clone utilization as pollen, seed or both pollen and seed donors should consider the role it would play in the seed crop; due to numerous factors influencing on the mating system in seed orchards, clonal genetic contribution as male parent is uncertain, and it has major influence on the genetic composition in the seed orchard during the initial reproductive and seed production phase

What are the consequences of growth selection on wood density in the French maritime pine breeding programme?

Volume and stem straightness were the main selection criteria for the first two generations of the French maritime pine (Pinus pinaster Ait.) breeding programme. In this article, we investigate the consequences of this selection on wood quality. Wood density, as a predictor of wood quality, is studied both in the breeding populations and in commercial varieties. Phenotypic and genetic correlations between wood density and growth traits are investigated in successive breeding populations with three genetic field experiments of respectively 30, 29 and 12 years old. Correlation estimates were either slightly negative or non-significantly different from zero depending on the test considered. Consequently, a low impact of growth selection on wood quality should be expected in improved seed sources. However, we observed a significant wood density decrease in two improved varieties as compared to unimproved seed sources at age 15. In addition to this first effect on wood density, growth improvement is also expected to reduce the rotation age and thus increase the proportion of juvenile wood, which is known as having a lower density than mature wood. This change was studied and quantified using a growth model. Finally, a wood density decrease reaching up to 6% was predicted in the improved varieties compared to unimproved material, when both the observed decrease in wood density and the predicted increase in juvenile wood proportion were taken into account. Implications for the breeding programme were considered