Heritability of seed weight in Maritime pine, a relevant trait in the transmission of environmental maternal effects

Quantitative seed provisioning is an important life-history trait with strong effects on offspring phenotype and fitness. As for any other trait, heritability estimates are vital for understanding its evolutionary dynamics. However, being a trait in between two generations, estimating additive genetic variation of seed provisioning requires complex quantitative genetic approaches for distinguishing between true genetic and environmental maternal effects. Here, using Maritime pine as a long-lived plant model, we quantified additive genetic variation of cone and seed weight (SW) mean and SW within-individual variation. We used a powerful approach combining both half-sib analysis and parent-offspring regression using several common garden tests established in contrasting environments to separate G, E and G x E effects. Both cone weight and SW mean showed significant genetic variation but were also influenced by the maternal environment. Most of the large variation in SW mean was attributable to additive genetic effects (h(2) = 0.55-0.74). SW showed no apparent G x E interaction, particularly when accounting for cone weight covariation, suggesting that the maternal genotypes actively control the SW mean irrespective of the amount of resources allocated to cones. Within-individual variation in SW was low (12%) relative to between-individual variation (88%), and showed no genetic variation but was largely affected by the maternal environment, with greater variation in the less favourable sites for pine growth. In summary, results were very consistent between the parental and the offspring common garden tests, and clearly indicated heritable genetic variation for SW mean but not for within-individual variation in SW.This study was financed by the Spanish National Research Grants RTA2007-100 and AGL2012-40151 (FENOPIN), both co-financed by EU-FEDER. The progeny trials and the clonal seed orchards are part of the experimental set up of the Maritime pine breeding programme developed by the Centro de Investigacion Forestal de Lourizan, Xunta de Galicia.Spanish National Research Grant RTA2007-100Spanish National Research Grant AGL2012-40151 (FENOPIN)EU-FEDERPeer reviewe

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

Genetic Variation and Realized Genetic Gain From Black Pine Tree Improvement

Summary In 1978 a 10 ha clonal seed orchard of black pine (Pinus nigra Arnold) was established in the area of Koumani in the western part of Peleponnesos, Greece. The orchard comprises 52 clones derived from intensively selected plus trees in the natural forest of black pine of Peloponnesos. In 1991 three open pollinated progeny tests were established in Peloponnesos, proximal to the villages of Raches, Vlachokerasia and Vamvakou. Seedlings from 52 families including a commercial check (CC) were planted in each one of the three locations. Assessments were made when the trees were 4, 7 and 9 years respectively, with the following results. The variation among families for growth characteristics were highly significant in all locations examined. In the combined analyses of variance over the three locations, significant differences among families were also detected, while the family x location interaction effect was not significant. This indicates that the seed produced from the seed orchard can be freely used over the environments of the three experimental plantings, which are representative of the broad area of Peloponnesos. Narrow sense heritability estimates on individual tree basis (h2) were variable depending on the characteristic, age of assessment and the location of the experimental plantings. The estimates of h2 in Vlachokerasia for height (HT) were 0.21, 0.40 and 0.43 at the ages of 4, 7 and 9 years respectively. In Raches the corresponding h2 values for HT were nearly the same in all ages (0.29, 0.28 and 0.31 at 4, 7 and 9 years respectively) and stable but little higher (0.31, 0.28 and 0.31) at the Vamvakou experimental planting. The heritability values for HT estimated over the three location, were relatively low (0.25, 0.23 and 0.19) at the ages 4, 7 and 9 years respectively. Realized genetic gains were calculated for growth characteristics at the age of 9 years, by comparing the performance of the improved (selected) materials to unimproved materials (CC). For the first stage of selection (selection made in natural stands) gain of 6.0% for HT, 8.0% for diameter breast height (DBH) and 24% for volume were estimated. When 20% of the clones, with the lower breeding values are removed from the seed orchard (genetic thinning), an additional gain of 2% for HT, 3% for DBH and 8% for volume over the unrogued seed orchard is resulted. Thus, the total genetic gain from the genetically tested, first generation seed orchard of black pine at Koumani is estimated as 8% for HT, 11% for DBH and 32% for volume. These results indicate that improvement of black pine by selection, establishment of seed orchard and progeny testing the clones, is a very promising profitable operation.</jats:p

Variation Among Individuals in Cone Production in Pinus palustris Mill. (Pinaceae)

Premise of the study: Reproductive output varies considerably among individuals within plant populations, and this is especially so in cone production of conifers. While this variation can have substantial effects on populations, little is known about its magnitude or causes. Methods: We studied variation in cone production for 2 years within a population of Pinus palustris Mill. (longleaf pine; Pinaceae). Using hurdle models, we evaluated the importance of burn treatments, tree size (dbh), canopy status (open, dominant, subordinate), and number of conspecific neighbors within 4 m (N4). Key results: Cone production of individuals—even after accounting for other variables—was strongly correlated between years. Trees in plots burned every 1, 2, or 5 years produced more cones than those burned every 7 years, or unburned. Larger trees tend to produce more cones, but the large effects of the other factors studied caused substantial scatter in the dbh-cone number relationship. Among trees in the open, dbh had little explanatory power. Subordinate trees with three neighbors produced no cones. Conclusions: Tree size alone was a weak predictor of cone production. Interactions with neighbors play an important role in generating reproductive heterogeneity, and must be accounted for when relating cone production to size. The strong between-year correlation, together with the large variance in cone production among trees without neighbors, suggests that still more of the variance may be explainable, but requires factors outside of our study

Low levels of population genetic structure in Pinus contorta

Premise of the study : Population genetic analyses provide information on the population context in which evolutionary processes operate and are important for understanding the evolution of geographically variable traits. Earlier studies showed that cone structure of lodgepole pine in the Rocky Mountains diverged among populations because of geographic variation in co-evolutionary interactions involving mammalian and avian seed predators. Analyses of population genetic variation are needed to determine whether this divergence has arisen despite extensive gene flow and whether populations to the east and west of the Rocky Mountains have evolved convergent phenotypes independently. Methods : We investigated genetic structuring across 22 stands of lodgepole pine in the central Rocky Mountains and in isolated peripheral populations that experience different seed predators and exhibit parallel divergence in cone traits using a set of nine simple sequence repeats and 235 AFLP loci. Key results : Our analyses reveal high levels of genetic diversity within and low genetic differentiation among populations. Nonetheless, geographic and genetic distances were correlated, and isolated populations to the east and west of the Rocky Mountains had higher levels of differentiation than did populations in the central part of the range. Conclusions : These data indicate not only that adaptive divergence of cone traits across a geographic mosaic of coevolution has occurred despite minimal genetic differentiation, but also that isolated populations to the east and west of the Rocky Mountains have evolved distinctive cones independently and in parallel. The population structure quantified here will inform future research aimed at detecting genetic variants associated with divergent adaptive traits