Computer Simulation of a Sporophytic Self-Incompatibility Breeding System

Imrie, B. C.; Kirkman, Colleen J; Ross, Mark

doi:10.1071/bi9720343

Cited by 45 publications

(42 citation statements)

References 5 publications

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“…In sporophytic incompatible species, the dominance structure among the alleles caused the more dominant alleles to be less frequent at equilibrium. This distribution of allele frequencies was also found in other studies which modelled sporophytic incompatibility (Imrie et a!., 1972;Sampson, 1974;Charlesworth, 1988). These less frequent alleles may be easily lost with a decrease in population size due to genetic drift, which will decrease the number of available mates.…”

Section: Discussionsupporting

confidence: 61%

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Mate availability in small populations of plant species with homomorphic sporophytic self-incompatibility

1992

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Plants of a self-incompatible species, which occur in small populations, may have reduced fitness due to the limited availability of compatible mates. Self-incompatibility decreases inbreeding by allowing successful mating to occur only with individuals which differ by at least one-allele at the S-locus. A computer simulation model was developed to test the effect of small population size upon the diversity and the relative frequency of the S-alleles which determine the number of available mates. In a large population at equilibrium, the greater the number of S-alleles the greater the frequency of available mates for all individuals in the population. In small populations (less than 50 individuals), they are unable to maintain a high diversity of S-alleles and therefore there is a decrease in the frequency of available mates. In addition, in small populations there is an increase in the variance of available mates. The number of mates in these populations depends on the genotype of a particular individual. Two patterns would be expected in a small population of incompatible species: (1) a lower seed set per individual due to limited mates, and (2) an increase in variation of seed set among individuals due to the variance in available mates. Lower seed set would lead to a decrease in fitness of particular genotypes and could increase the possibility of local extinction of the species.

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Section: Discussionsupporting

confidence: 61%

“…Seed banks consist of a mixture of seeds produced by many generations, so it may serve as a pool of genetic diversity (Levin, 1978b). A previous computer simulation model of sporophytic incompatibility (Imrie et at., 1972) examined the effects of both migration and seed banks in the preservation of S-allelic diversity. Tmrie et at.…”

Section: Discussionmentioning

confidence: 99%

Mate availability in small populations of plant species with homomorphic sporophytic self-incompatibility

1992

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“…Unequal S-allele frequencies have also been reported in Brassicaceae (Ockendon, 1974(Ockendon, , 1982Stevens & Kay, 1989). Imrie et al (1972) studied by computer simulation the equilibrium allele frequencies in a sporophytic self-incompatibility system with three or six S-alleles and found that, as expected, equilibrium frequencies were dependent on the level of dominance, with alleles increasing in frequency as their degree of dominance decreased. This dominance dependency may be explained in terms of the number of successful matings, i.e.…”

Section: S-alleles Of /Pomoea Trif/da 279mentioning

confidence: 99%

Number, frequency & dominance relationships of S-alleles in diploid Ipomoea trifida

et al. 1994

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Self-incompatibility genotypes of 224 plants of Ipomoea trifida from six populations in Central America have been determined by genetic analysis of segregants in F1 families derived from crosspollinations with the most recessive homozygote. A total of 49 different S-alleles was identified in these populations. From analyses of S-allelic interactions in heterozygous plants which were generated from cross-pollinations between plants possessing different S-alleles, a linear dominance hierarchy with six levels has been established among 28 S-alleles in both pollen and stigma.Codominance of alleles occurred more frequently in the stigma (9.2 per cent) than in the pollen (4.9 per cent). Nonlinear dominance relationships were rarely observed. Unequal frequencies of Salleles have been found in all populations examined, the most common S-allele being, as expected, the most recessive. This suggests that recessive S-alleles are widely distributed throughout Central America. The diversity of the multiple S-alleles observed in the present study also suggests that the southern area of Mexico to Guatemala is a centre of genetic variation in diploid I. trijIda.

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“…These are firstly the "recessive effect" (Sampson, 1974; also described by Bateman, 1952;Imrie et al, 1972), which tends to increase the frequency of recessive alleles, and secondly the "small number effect" (Sampson, 1974), which favours alleles at uncommon dominance levels (i.e., dominance levels represented by relatively few alleles). The underlying cause of these two effects is that recessive alleles, and alleles at uncommon dominance levels, tend to be involved in relatively few incompatible cross-pollinations.…”

Section: Introductionmentioning

confidence: 99%

The number, dominance relationships and frequencies of self-incompatibility alleles in a natural population of Sinapis arvensis L. in South Wales

Stevens

Kay

1989

Heredity

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The incompatibility genotypes of a further 25 plants from the South Wales population of Sinapis arvensis studied by Ford and Kay (1985) have been determined, and an additional 21 S-alleles have been found. This brings the overall number of plants analysed from the population to 35, and the total number of S-alleles found also to 35. It is estimated that there are 52 S-alleles in the population.Dominance interactions between S-alleles have been established in a total of 42 different heterozygotes (pooling data obtained during the present study with that of Ford and Kay (bc. cit.)). Co-dominance of alleles in both pollen and stigma occurred in 18 (42.8 per cent), dominance of one allele in the pollen occurred in 21(50 per cent), dominance of one allele in the stigma occurred in two (4.8 per cent), and dominance of one allele in both pollen and stigma occurred in one (2.4 per cent). There is a minimum of three levels in the pollen dominance hierarchy, and two in the stigma dominance hierarchy; dominance interactions between S-alleles in the stigma may be non-linear. There is some indication that pollen dominant alleles tend to be found in lower frequencies than pollen recessive alleles.Preliminary data show that at least some S-alleles in S. arvensis have a very wide geographical distribution.

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Computer Simulation of a Sporophytic Self-Incompatibility Breeding System

Cited by 45 publications

References 5 publications

Mate availability in small populations of plant species with homomorphic sporophytic self-incompatibility

Mate availability in small populations of plant species with homomorphic sporophytic self-incompatibility

Number, frequency & dominance relationships of S-alleles in diploid Ipomoea trifida

The number, dominance relationships and frequencies of self-incompatibility alleles in a natural population of Sinapis arvensis L. in South Wales

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