Effects of inbreeding depression on seed production in Scots pine (<i>Pinus sylvestris</i>)

Mullin, T. J.; Persson, Torgny; Abrahamsson, Sara; Gull, Bengt Andersson

doi:10.1139/cjfr-2019-0049

Cited by 12 publications

(9 citation statements)

References 20 publications

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“…Recently, in 2013 and 2014, a new series of crosses was conducted in Sweden with Pinus sylvestris creating 9 different inbreeding levels. As a preliminary result, 48 % of the variance in the percentage of filled seeds was explained by inbreeding level (Mullin et al 2019).…”

Section: Inbreeding Depressionmentioning

confidence: 86%

Towards new seed orchard designs in Germany – A review

Liesebach¹,

Liepe²,

Bäucker³

2021

Silvae Genetica

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New first and 1.5 generation seed orchards are to be created in Germany based on recently assembled breeding populations of Acer pseudoplatanus, Larix sp., Picea abies, Pinus sylvestris, Pseudotsuga menziesii, and Quercus sp. To justify the high expenses in time and cost for orchard establishment and maintenance, planning should make use of consolidated knowledge and experience of both the national and international scientific community. Here, we briefly describe advances in genetic gains achieved through tree breeding, and resume population genetic aspects and design considerations to draw conclusions for clonal composition and spatial design of the new orchards. We conclude that to avoid outbreeding depression separate orchards are required for each breeding zone. The zones are species-specific and defined by ecological and climatic aspects. A minimum of 60-80 clones per orchard is recommended for native tree species with high proportions of natural regeneration in forest practice. This would allow future selective thinning based on estimated breeding values from progeny testing. It would also permit the transfer of seed orchard progenies into a naturally regenerating forest stands without the risk of a genetic bottleneck. Lower clone numbers are appropriate for non-native species and hybrids. It is important to strictly avoid inbreeding depression, achieved by using only one clone per progeny or population, from which the plus trees were selected. Further, the spatial layout should promote random mating by optimizing the neighbourhood of each clone. With all of these considerations taken into account, we expect superior quality traits and at least 10-15 % more volume from the new seed orchards.

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Section: Inbreeding Depressionmentioning

confidence: 86%

Towards new seed orchard designs in Germany – A review

Liesebach¹,

Liepe²,

Bäucker³

2021

Silvae Genetica

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“…We also found low levels of inbreeding ( Figure 6B ). Inbreeding has generally been regarded as something to avoid in seed orchards, lesser relatedness between parents would lead to more successful fruiting, with inbreeding depression expressed only later in the established plantation ( Mullin et al., 2019 ). It is generally recommended to manage the breeding population with separate sublines so that individual, unrelated seed orchard parents can be selected from each subline ( McKeand and Bridgwater, 1998 ).…”

Section: Discussionmentioning

confidence: 99%

Mating pattern and pollen dispersal in an advanced generation seed orchard of Cunninghamia lanceolata (Lamb.) Hook

Zhao²,

Wang³

et al. 2022

Front. Plant Sci.

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Seed orchards represent the link between forest breeding and conifer production forests, and their mating patterns determine the genetic quality of seed orchard crops to a large extent. We genotyped the parental clones and their open pollination offspring in the third-generation seed orchard of Chinese fir using microsatellite markers and observed the synchronization of florescence in the seed orchard to understand the genetic diversity and mating structure of the seed orchard population. Genetic coancestry among parental clones was detected in the third generation seed orchard of Chinese fir, and the genetic diversity of the open-pollinated offspring was slightly higher than that of the parental clones. The external pollen contamination rate ranged from 10.1% to 33.7%, 80% of the offspring were produced by 44% of the parental clones in the orchard, and no evidence of selfing was found. We found that 68.1% of the effective pollination occurred within 50 m, and 19.9% of the effective pollination occurred in the nearest neighbors. We also found that successful mating requires about 30% of florescence overlap between males and females, and there was a significant positive correlation between male reproductive energy and male parental contribution. Our results provide a valuable reference for the management and design of advanced generation seed orchards.

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“…Inbreeding depression expected from mating amongst close relatives and high selfing rates was not found, despite high amounts of empty seeds. This can be an artefact explained by postzygotic abortion of inbred embryos that results in empty seeds as reported for several conifers [43,45,50], but these empty seeds cannot be genetically studied. Further, we estimated that at least 70% of viable seeds were formed by immigrant pollen.…”

Section: Discussionmentioning

confidence: 99%

“…Factors that may increase the formation of empty seeds are, amongst others, lack of or insufficient pollination and unsuitable environmental conditions during seed maturation. Nonetheless, inbreeding is the main cause of empty seeds and attributed to increased homozygosity and resulting expression of deleterious recessive alleles, as shown for different spruce species [10,[39][40][41][42] and other conifers [43][44][45]. The higher proportion of empty seeds is thus likely caused by selfing and inbreeding but cannot be confirmed by genetic analyses because postzygotic abortion leaves no material to study.…”

Section: Germination and Relatednessmentioning

confidence: 99%

Mating System in a Native Norway Spruce (Picea abies [L.] KARST.) Stand-Relatedness and Effective Pollen Population Size Show an Association with the Germination Percentage of Single Tree Progenies

et al. 2020

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Norway spruce differs little in neutral genetic markers among populations and provenances often reported, but in terms of putative adaptive traits and their candidate genes, some clear differences have been observed. This has previously been shown for crown morphotypes. Stands with mostly narrow crown shapes are adapted to high elevation conditions, but these stands are scattered, and the forest area is often occupied by planted stands with predominantly broad crowned morphotypes. This raises questions on whether this differentiation can remain despite gene flow, and on the level of gene flow between natural and planted stands growing in close neighbourhood. The locally adapted stands are a valuable seed source, the progeny of which is expected to have high genetic quality and germination ability. The presented case study is useful for spruce plantation by demonstrating evaluation of these expectations. Immigrant pollen and seeds from planted trees could be maladaptive and may alter the genetic composition of the progeny. This motivated us to study single tree progenies in a locally adapted stand with narrow crowned trees in a partial mast year at nuclear genomic simple sequence repeat (SSR) markers. Spruce is a typical open-pollinated conifer tree species with very low selfing rates, which were also observed in our study (s = 0.3–2.1%) and could be explained by efficient cross-pollination and postzygotic early embryo abortion, common in conifers. The estimated high amount of immigrant pollen found in the pooled seed lot (70.2–91.5%) is likely to influence the genetic composition of the seedlings. Notably, for individual mother trees located in the centre of the stand, up to 50% of the pollen was characterised as local. Seeds from these trees are therefore considered to retain most of the adaptive variance of the stand. Germination percentage varied greatly between half-sib families (3.6–61.9%) and was negatively correlated with relatedness and positively with effective pollen population size of the respective families. As pollen mostly originated from outside the stand and no family structures in the stand itself were found, germination differences can likely be explained by diversity differences in the individual pollen cloud.

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Effects of inbreeding depression on seed production in Scots pine (Pinus sylvestris)

Cited by 12 publications

References 20 publications

Towards new seed orchard designs in Germany – A review

Towards new seed orchard designs in Germany – A review

Mating pattern and pollen dispersal in an advanced generation seed orchard of Cunninghamia lanceolata (Lamb.) Hook

Mating System in a Native Norway Spruce (Picea abies [L.] KARST.) Stand-Relatedness and Effective Pollen Population Size Show an Association with the Germination Percentage of Single Tree Progenies

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