Cytoplasmic Inheritance in The Genus Streptocarpus Lindley

Oehlkers, Friedrich

doi:10.1016/s0065-2660(08)60418-6

Cited by 32 publications

(12 citation statements)

References 18 publications

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“…Similar results were obtained in Streptocarpus, e.g. in the F1 of S. wendlandii x S. rexii (Oehlkers, 1964, and earlier) -This Streptocarpus cross is particularly interesting because the reciprocal cross was male fertile but had a high degree of female sterility, which was increased by backcrossing. Many other examples could be given, also from intraspecific crosses (Edwardson, 1970).…”

Section: Differential Fertility Effectssupporting

confidence: 81%

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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Section: Differential Fertility Effectssupporting

confidence: 81%

Behaviour of a sex-differential fertility gene in hermaphrodite populations

Ross¹

1977

Heredity

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“…Plants with one major phyllomorph were classed as unifoliate and those with more than one as rosulate. Previous studies had suggested that the rosulate character was determined by a dominant allele at either of two loci: one promoting the rosulate character early in development, the other acting later (Oehlkers, 1938(Oehlkers, , 1942(Oehlkers, , 1964. If this were the case, the F1 plants should have been heterozygous at both Hilliard and Burtt [1971] and Jong [1978]).…”

Section: Two Loci Determine the Differences In Form In Clade II Strepmentioning

confidence: 99%

“…In crosses between rosulate and unifoliate species, inheritance of the rosulate character was suggested to involve dominant alleles at two loci (Oehlkers, 1938(Oehlkers, , 1942(Oehlkers, , 1964. In some acaulescent species, application of gibberellic acid (GA) resulted in either the formation of extra phyllomorphs or induction of a vegetative shoot (Rosenblum and Basile, 1984).…”

Section: Introductionmentioning

confidence: 99%

The Role ofKNOXGenes in the Evolution of Morphological Novelty in Streptocarpus

et al. 2005

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The genus Streptocarpus comprises species with diverse body plans. Caulescent species produce leaves from a conventional shoot apical meristem (SAM), whereas acaulescent species lack a conventional SAM and produce only a single leaf (the unifoliate form) or clusters of leaves from the base of more mature leaves (the rosulate form). These distinct morphologies reflect fundamental differences in the role of the SAM and the process of leaf specification. A subfamily of KNOTTED-like homeobox (KNOX) genes are known to be important in regulating meristem function and leaf development in model species with conventional morphologies. To test the involvement of KNOX genes in Streptocarpus evolution, two parologous KNOX genes (SSTM1 and SSTM2) were isolated from species with different growth forms. Their phylogenetic analysis suggested a gene duplication before the subgeneric split of Streptocarpus and resolved species relationships, supporting multiple evolutionary origins of the rosulate and unifoliate morphologies. In S. saxorum, a caulescent species with a conventional SAM, KNOX proteins were expressed in the SAM and transiently downregulated in incipient leaf primordia. The ability of acaulescent species to initiate leaves from existing leaves was found to correlate with SSTM1 expression and KNOX protein accumulation in leaves and to reflect genetic differences at two loci. Neither locus corresponded to SSTM1, suggesting that cis-acting differences in SSTM1 regulation were not responsible for evolution of the rosulate and unifoliate forms. However, the involvement of KNOX proteins in leaf formation in rosulate species suggests that they have played an indirect role in the development of morphological diversity in Streptocarpus.

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“…Differentiation between races and between species, which is based at least in part on changes in the plasmon, is not uncommon in higher plants and has been reported in a number of genera. Oehlkers (1964) has shown that speciation in Streptocarpus has been accompanied by changes in the plasmon, while Michaelis (1964) found that Epilobium hirsutum was differentiated into a number of distinct plasmon types which could be associated with different geographical regions. The recognition of these plasmon differences is derived from a study of the developmental patterns observed between reciprocal F1's and back-crosses involving widely dispersed races or species.…”

Section: The Role Of Extra-nuclear Variability In Population Differenmentioning

confidence: 99%