Dataset Information

Genetics of distyly and homostyly in a self-compatible Primula.

ABSTRACT: The transition from outcrossing to selfing through the breakdown of distyly to homostyly has occurred repeatedly among families of flowering plants. Homostyles can originate by major gene changes at the S-locus linkage group, or by unlinked polygenic modifiers. Here, we investigate the inheritance of distyly and homostyly in Primula oreodoxa, a subalpine herb endemic to Sichuan, China. Controlled self- and cross-pollinations confirmed that P. oreodoxa unlike most heterostylous species is fully self-compatible. Segregation patterns indicated that the inheritance of distyly is governed by a single Mendelian locus with the short-styled morph carrying at least one dominant S-allele (S-) and long-styled plants homozygous recessive (ss). Crossing data were consistent with a model in which homostyly results from genetic changes at the distylous linkage group, with the homostylous allele (Sh) dominant to the long-styled allele (s), but recessive to the short-styled allele (S). Progeny tests of open-pollinated seed families revealed high rates of intermorph mating in the L-morph but considerable selfing and possibly intramorph mating in the S-morph and in homostyles. S-morph plants homozygous at the S-locus (SS) occurred in several populations but may experience viability selection. The crossing data from distylous and homostylous plants are consistent with either recombination at the S-locus governing distyly, or mutation at gene(s) controlling sex-organ height; both models predict the same patterns of segregation. Recent studies on the molecular genetics of distyly in Primula demonstrating the hemizygous nature of genes at the S-locus make it more likely that homostyles have resulted from mutation rather than recombination.

SUBMITTER: Yuan S

PROVIDER: S-EPMC6288129 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Genetics of distyly and homostyly in a self-compatible Primula.

Yuan Shuai S Barrett Spencer C H SCH Li Cehong C Li Xiaojie X Xie Kongping K Zhang Dianxiang D

Heredity 20180504 1

The transition from outcrossing to selfing through the breakdown of distyly to homostyly has occurred repeatedly among families of flowering plants. Homostyles can originate by major gene changes at the S-locus linkage group, or by unlinked polygenic modifiers. Here, we investigate the inheritance of distyly and homostyly in Primula oreodoxa, a subalpine herb endemic to Sichuan, China. Controlled self- and cross-pollinations confirmed that P. oreodoxa unlike most heterostylous species is fully s ...[more]

PMID: 29728676

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Project description:Background and aimsThe outbreeding floral polymorphism heterostyly frequently breaks down, resulting in the evolution of self-fertilization as a result of homostyle formation. Here, the loss of floral polymorphism in distylous Primula oreodoxa, a sub-alpine species restricted to western Sichuan, China, was examined by investigating the ecological correlates and genetic consequences of mating system transitions. Several key questions were addressed. (1) What are the frequencies, geographical distribution and reproductive characteristics of floral morphs in distylous and homostylous populations? (2) Does increased elevation influence pollinator service and the likelihood of inbreeding in populations? (3) How often has homostyly originated and what are the consequences of the breakdown of distyly for the amounts and distribution of genetic diversity in populations?MethodsFourteen populations throughout the range of P. oreodoxa were sampled, and morph frequencies and floral characteristics were recorded. Polymorphism at microsatellite loci and chloroplast DNA (cpDNA) variation were used to quantify population genetic structure and genetic relationships among populations. Controlled pollinations and studies of pollen tube growth and fertility were conducted to determine the compatibility status of populations and their facility for autonomous self-pollination. Finally, visitation rates of long- and short-tongued pollinators to distylous and homostylous populations at different elevations were compared to determine if increased elevation was associated with deterioration in pollinator service.Key resultsIn contrast to most heterostylous species, both distylous and homostylous morphs of P. oreodoxa are highly self-compatible, but only homostyles have the facility for autonomous self-pollination. Homostyles set significantly more fruit and seeds following open pollination than the distylous morphs. Visitation by long-tongued pollinators was significantly lower in homostylous populations, and overall rates of insect visitation decreased with elevation. Genetic diversity was significantly lower in homostylous populations, with evidence of increased inbreeding at higher elevation. Patterns of cpDNA variation were consistent with multiple transitions from distyly to homostyly and limited gene flow among populations.ConclusionsThe results of this study support the hypothesis that the multiple loss of floral polymorphism in distylous P. oreodoxa is associated with unsatisfactory pollinator service, with homostyles benefiting from reproductive assurance as a result of autonomous self-pollination.

Dataset Information

Genetics of distyly and homostyly in a self-compatible Primula.

Publications

Genetics of distyly and homostyly in a self-compatible Primula.

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