Analysis of Crossover Events and Allele Segregation Distortion in Interspecific Citrus Hybrids by Single Pollen Genotyping

ABSTRACT The recovery of the SD chromosome from a heterozygous SD male increases with brood. This is independent of the age of the female, occurs during the time the sperm are stored in the females, disappears when the segregation distortion is suppressed, and is temperature-sensitive-temperature shocks above or below 25°C applied to the mature sperm both tend to accelerate the increase in the recovery of SD. All this suggests the existence of a class of sperm affected by SD in which the sperm are able to fertilize eggs for a short time following ejaculation but become dysfunctional thereafter.

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Evolutionary dynamics of spore killers.

Genetics ◽

10.1093/genetics/135.3.923 ◽

1993 ◽

Vol 135 (3) ◽

pp. 923-930 ◽

Cited By ~ 3

Author(s):

M J Nauta ◽

R F Hoekstra

Keyword(s):

Life Cycle ◽

Segregation Distortion ◽

Population Genetic ◽

Field Data ◽

Evolutionary Dynamics ◽

Natural Populations ◽

Additional Advantage ◽

Genetic Modeling ◽

Spore Killing ◽

Ascospore Formation

Abstract Spore killing in ascomycetes is a special form of segregation distortion. When a strain with the Killer genotype is crossed to a Sensitive type, spore killing is expressed by asci with only half the number of ascospores as usual, all surviving ascospores being of the Killer type. Using population genetic modeling, this paper explores conditions for invasion of Spore killers and for polymorphism of Killers, Sensitives and Resistants (which neither kill, nor get killed), as found in natural populations. The models show that a population with only Killers and Sensitives can never be stable. The invasion of Killers and stable polymorphism only occur if Killers have some additional advantage during the process of spore killing. This may be due to the effects of local sib competition or some kind of "heterozygous" advantage in the stage of ascospore formation or in the short diploid stage of the life cycle. This form of segregation distortion appears to be essentially different from other, well-investigated forms, and more field data are needed for a better understanding of spore killing.

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Molecular Mapping of Segregation Distortion Loci in Aegilops tauschii

Genetics ◽

10.1093/genetics/149.1.319 ◽

1998 ◽

Vol 149 (1) ◽

pp. 319-327 ◽

Cited By ~ 1

Author(s):

J D Faris ◽

B Laddomada ◽

B S Gill

Keyword(s):

Segregation Distortion ◽

Molecular Mapping ◽

Aegilops Tauschii ◽

Distorted Segregation ◽

F2 Population ◽

Male Gametes ◽

Skewed Segregation ◽

Segregation Ratios ◽

Backcross Populations ◽

Intraspecific Hybrids

Abstract Distorted segregation ratios of genetic markers are often observed in progeny of inter- and intraspecific hybrids and may result from competition among gametes or from abortion of the gamete or zygote. In this study, 194 markers mapped in an Aegilops tauschii F2 population were surveyed for distorted segregation ratios. Region(s) with skewed segregation ratios were detected on chromosomes 1D, 3D, 4D, and 7D. These distorter loci are designated as QSd.ksu-1D, QSd.ksu-3D, QSd.ksu-4D, and QSd.ksu-7D. Three regions of segregation distortion identified on chromosome 5D were analyzed in two sets of reciprocal backcross populations to analyze the effect of sex and cytoplasm on segregation distortion. Extreme distortion of marker segregation ratios was observed in populations in which the F1 was used as the male parent, and ratios were skewed in favor of TA1691 alleles. There was some evidence of differential transmission caused by nucleo-cytoplasmic interactions. Our results agree with other studies stating that loci affecting gametophyte competition in male gametes are located on 5DL. The distorter loci on 5DL are designated as QSd.ksu-5D.1, QSd.ksu-5D.2, and QSd.ksu-5D.3.

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