The Frequency of Lethal Alleles in Forest Tree Populations

Namkoong, Gene; Bishir, John

doi:10.2307/2409197

Cited by 17 publications

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“…A large proportion of selfed zygotes, however, are killed by recessive lethal genes before the seed stage during embryo development (Namkoong & Bishir, 1987). Koski (1971) found that on controlled selfing of Scots pine, on average, 85 per cent of the ovules produce no live seed which conesponds to 9.4 recessive lethal equivalents per diploid genome.…”

Section: Introductionmentioning

confidence: 99%

“…Koski (1971) found that on controlled selfing of Scots pine, on average, 85 per cent of the ovules produce no live seed which conesponds to 9.4 recessive lethal equivalents per diploid genome. The degree of inbreeding depression is not constant but varies between genotypes (Koski, 1971(Koski, , 1973 and there are some suggestions that it may also vary between conifer populations (Namkoong & Bishir, 1987;K. Kärkkäinen et at., unpublished data).…”

Section: Introductionmentioning

confidence: 99%

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The degree of early inbreeding depression determines the selfing rate at the seed stage: model and results from Pinus sylvestris (Scots pine)

Kärkkäinen

Savolainen

1993

Heredity

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Early inbreeding depression, i.e. embryonic recessive lethals, eliminates a large proportion of selfed progeny during embryo development. A model of early inbreeding depression suggested that in most conifers the variation between genotypes in the number of lethals rather than the variation in the actual rate of self-fertilization accounts for the variation between selfing rates at the seed stage. Polyembryony, the formation of several embryos per ovule in conifers, diminished the fitness cost of embryonic lethals and allowed embryo competition. We studied variation in the outcrossing rate at the seed stage in an experimental population of Scots pine. Despite extensive variation, pollen production of the trees, which is expected to predict the probability of self-fertilization, did not account for the low selfing rate variation at the seed stage. The genotypes having lowest numbers of embryonic lethals had the highest selfing rates at the seed stage. Early inbreeding depression maintains a very low selfing rate at the seed stage and masks the correlation between the rate of selffertilization and the selfing rate at the seed stage. This is typical of most conifers and can also be common among perennial angiosperm species.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The degree of early inbreeding depression determines the selfing rate at the seed stage: model and results from Pinus sylvestris (Scots pine)

Kärkkäinen

Savolainen

1993

Heredity

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“…The resulting high genetic load is expressed only under extreme inbreeding. The suggestion by Namkoong and Bishir (1987) that many of the genes that depress embryo viability in conifers may represent unique mutants, which will be eliminated by selection, is consistent with this idea. Ledig (1986) has also summarized the patterns of distribution of genetic variation in various pine species.…”

Section: Genetic Variation In Other Species Of Pinesmentioning

confidence: 70%

“…These deleterious alleles are referred to collectively as a population's genetic load, and expressed genetic load can significantly depress the population's overall levels offertility and viability. Genetic load in conifers is often high; for example, depression in embryo viability following inbreeding is commonly reported (Namkoong and Bishir 1987). Ledig (1986) reported that embryonic lethal equivalents (recessive lethals that if dispersed among different embryos would cause, on average, one selective death) range from 0.3 to 9.4 per zygote and average 5.2 in eight species of Pinus; the usual range is 1 to 4 in other plants, humans, and fruit flies.…”

Section: Genetic Variation In Other Species Of Pinesmentioning

confidence: 99%

Proceedings-symposium on whitebark pine ecosystems: Ecology and management of a high-mountain resource; 1989 March 29-31; Bozeman, MT

Schmidt¹,

McDonald²

1990

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“…Simple recurrent selection for a single, large breeding population was preferred at that time, today population subdivision strategies are more commonly used [3,15,24]. Recently, selfing as a breeding tool has been revived because of the growing interest in small elite breeding populations [27] and the possibility of purging deleterious alleles [10,16]. Successful use of the inbreeding and cross breeding method in trees will depend on its effectiveness in purging deleterious alleles and in producing heterosis.…”

Section: Introductionmentioning

confidence: 99%

Inbreeding in Pinus radiata. IV: the effect of inbreeding on wood density

Matheson

Abarquez

2002

Ann. For. Sci.

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-The effects of inbreeding on basic wood density in a 17-year-old radiata pine trial were studied using five populations, each inbred to one of five inbreeding levels: outcross (OC, F = 0), half-sib (HS, F = 0.125), full-sib (FS, F = 0.25), selfing (S 1 , F = 0.5) and two-generations of selfing (S 2 , F = 0.75). These five populations were derived from a founder population of eight clones. Although inbreeding resulted in slightly depressed wood density (inbreeding depression was 1.47%, 2.50%, 1.65%, 0.02%, respectively at F = 0.125, 0.25, 0.50 and 0.75), the effects were not significant. However, the variation of wood density among trees was increased by inbreeding, by 3.70%, 3.40%, 15.74%, and 29.01% respectively for populations at F = 0.125, 0.25, 0.5, and 0.75. In all five populations, the basic wood density increased linearly from 400 kg m -3 at age 4 (the earliest age for most samples) to about 525 kg m -3 at age 12 and stabilized with some fluctuation thereafter. There were significant differences among pedigrees in response to inbreeding for wood density. The pedigrees can be divided into three classes according to their response patterns to inbreeding: no decline of wood density under any inbreeding level; a linear decline from F = 0 to F = 0.75; and an initial decline at mild inbreeding levels contrasted with an increase in selfed generations. The lack of significant inbreeding depression of wood density at the population level combined with increased variation in wood density in the inbred populations suggests that it will be possible to quickly develop inbred lines with high wood density. The combination of low inbreeding depression for growth with a lack of inbreeding depression for wood density makes radiata pine a species ideally suited for the use of inbreeding as a breeding tool. radiata pine / inbreeding depression / wood density / purging Résumé -Consanguinité chez Pinus radiata. IV : l'effet de la consanguinité sur la densité du bois. Les effets de la consanguinité sur la densité basale du bois sont étudiés dans une expérience de pins radiata âgés de 17 ans. Cinq types de croisements (et donc niveaux de consanguinité) sont considérés : intercroisement (OC, F = 0), croisement demi-frère (HS, F = 0,125), plein frère (FS, F = 0,25), auto-fécondation (S1, F = 0,5) et deux générations d'auto-fécondation (S2, F = 0,75). Ces 5 populations sont dérivées d'une population fondatrice de 8 clones. Bien que la consanguinité produise une densité du bois légèrement plus basse (la dépression de consanguinité atteignant 1,47 %, 2,50 %, 1,65 % et 0,02 % respectivement avec un F = 0,125, 0,25, 0,50 et 0,75), les effets ne sont pas significatifs. Cependant, la variation de la densité du bois entre arbres augmente avec le niveau de consanguinité de 3,70 %, 3,40 %, 15,74 % et 29,01 % respectivement pour les populations avec un F = 0,125, 0,25, 0,50 et 0,75. Dans les 5 populations, la densité du bois augmente linéairement de 400 kg m -3 à l'âge de 4 ans (le plus jeune âge pour la plupart des échantillons) à...

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The Frequency of Lethal Alleles in Forest Tree Populations

Cited by 17 publications

References 0 publications

The degree of early inbreeding depression determines the selfing rate at the seed stage: model and results from Pinus sylvestris (Scots pine)

The degree of early inbreeding depression determines the selfing rate at the seed stage: model and results from Pinus sylvestris (Scots pine)

Proceedings-symposium on whitebark pine ecosystems: Ecology and management of a high-mountain resource; 1989 March 29-31; Bozeman, MT

Inbreeding in Pinus radiata. IV: the effect of inbreeding on wood density

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