The concept of male outcrossing in hermaphrodite higher plants

Horovitz, A.; Harding, James

doi:10.1038/hdy.1972.86

Cited by 56 publications

(39 citation statements)

References 17 publications

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“…Variations in degree of outcrossing between populations of a predominantly selfed species are not unusual and may be under environmental and genetic control (Imam and Allard, 1965;Heslop-Harrison, 1966;Jam, Marshall and Wu, 1970). It is also clear that in some species disparate genotypes may differ greatly in outcrossing frequency when subjected to the same pollination environments (Breese, 1959;Drayner, 1959;Harding and Tucker, 1964;Horovitz and Harding, 1972). Here we report an investigation where the primary aim was to establish whether S. vulgaris possesses a genetically variable mating system.…”

Section: Introductionmentioning

confidence: 96%

Variability of outcrossing frequency in Senecio vulgaris L.

Campbell

Abbott

1976

Heredity

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SUMMARYUsing a marker gene controlling capitulum type, 30 lines derived from each of a dune and a garden population of Senecio vulgaris L. were tested for their tendency to outcross. Compared with previous estimates of outbreeding in the species a relatively high degree of outcrossing was found in both experimental populations (an overall average of 224 per cent). It was shown that the dune population had a slightly greater mean outcrossing frequency than the garden population but, more importantly, had significantly more heritable variation (between lines) for this trait. In discussion, some reasons are advanced to account for the unexpectedly high level of outcrossing in both populations. It is suggested that the presence of significant genetic variation for outcrossing within the dune population may provide for adaptive flexibility in the native dune habitat where there is much spatial and temporal variation of the environment.

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Section: Introductionmentioning

confidence: 96%

Variability of outcrossing frequency in Senecio vulgaris L.

Campbell

Abbott

1976

Heredity

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“…As far as the multilocus estimates of t and p obtained for individual trees are concerned, it must be Table 4 Regression of pollen allele frequencies on maternal genotype and minimum variance mean over loci (1 and remembered that the t values estimate the female outcrossing rates of single trees, which need not equal the male outcrossing estimates (Horovitz & Harding, 1972;Gregorius et a!., 1987). The individual t values have been computed in two different ways, (i) keeping p constant and equal to the population estimate and (ii) allowing p to vary between families.…”

Section: Resultsmentioning

confidence: 99%

Mating system analysis in Pinus leucodermis Ant.: detection of self-fertilization in natural populations

1991

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The mating system was analysed in two natural populations of Pinus leucodermis Ant., a narrow ranged and relic species. The amount of outcrossing was estimated by assaying four enzyme loci. An efficient multilocus model was used, which allows the joint estimation of outcrossing rate and pollen allele frequencies for individual trees. The estimated multilocus outcrossing rates were 0.765 and 0.840 in the two populations. Both regression of individual pollen allele frequencies on the additive value of the maternal genotypes and outcrossing rates estimated with the unique allele method revealed that these low outcrossing rate estimates were not merely determined by mating among relatives, but reflected significant levels of self ing. They are especially significant, if compared with those observed in other conifers, which are almost complete outbreeders. The estimated selfing rate may be an upper limit because it was obtained by analysing non-germinated seeds. The presence of such a selfing level in this species could have important implications for seed production, as it seems that strong selection acts against homozygotes derived from inbreeding between germination and the adult phase.

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“…Such differential outcrossing rates have been found in experimental populations of the hermaphrodite species Lupinus nanus and Phaseolus lunatus. Both species also showed great variation in male gametophyte selection values (Harding and Tucker, 1969;Horovitz and Harding, 1972). It would be expected a priori that hermaphrodite populations should show variation for fertility, and that such variation should often affect ovules and pollen differentially.…”

Section: Introductionmentioning

confidence: 99%

Behaviour of a sex-differential fertility gene in hermaphrodite populations

Ross¹

1977

Heredity

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SUMMARYIn genera of flowering plants that contain closely related gynodioecious and near dioecious species, near dioecy has probably evolved from gynodioecy by gradual reduction of seed set on hermaphrodites, caused by the action of several genes for partial female sterility. A literature survey shows that several types of sex-function differential fertility effects are widespread in hermaphrodite plants, so that a model of such variation may be of interest both as a model of normal hermaphrodite populations, and for the above evolutionary process. Such a model is presented where there is a dominant or nondominant gene P for partial female sterility (ovule fertility values w,, w5 < 1), and where partially female-sterile hermaphrodites (" subhermaphrodites ") may be maintained by overdominance for pollen fertility (homozygote pollen fertility value w4 < 1). Subherrnaphrodites have genotypes PP or Pp, and hermaphrodites have pp. Fitness values (numbers of offspring per individual) depend upon genotype frequencies and degree of selfing, so that these values have to be distinguished from the constant fertility or selection values (the w values). Proportions of offspring left through the ovules differ among genotypes, are frequency dependent and differ from those left through the pollen. Outcrossing rates for pollen, t2, are also frequency dependent, differ among genotypes and differ from the ovule outcrossing rate, t5. For t1 t I, t, for hermaphrodites 11. Numerical results are given for equilibrium populations and include some cases of complete female sterility for comparison. These results show that frequencies of subhermaphrodites decrease with increased selfing. The heterozygous subhermaphrodite is the fittest, and the homozygous subhermaphrodite the least fit genotype. The fitness of the heterozygous subhermaphrodite decreases, and that of the hermaphrodite increases, with increased selfing. Except for males, proportions of ovule offspring decrease with increased selfing, and again with this exception and with t5 I, t2 is highest for heterozygous subhermaphrodites, and for this type is > 15, whereas t5 is least for hermaphrodites. The total ovule production of the population increases, and total pollen production decreases, with increased selfing.

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The concept of male outcrossing in hermaphrodite higher plants

Cited by 56 publications

References 17 publications

Variability of outcrossing frequency in Senecio vulgaris L.

Variability of outcrossing frequency in Senecio vulgaris L.

Mating system analysis in Pinus leucodermis Ant.: detection of self-fertilization in natural populations

Behaviour of a sex-differential fertility gene in hermaphrodite populations

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