Abstract
Segregation distortion is commonly detected via genetic mapping and this phenomenon has been reported in many species. However, the genetic causes of the segregation distortion regions in a majority of species are still unclear. To genetically dissect the SD on chromosome 18 in cotton, eight reciprocal backcross populations and two F2 populations were developed. Eleven segregation distortion loci (SDL) were detected in these ten populations. Comparative analyses among populations revealed that SDL18.1 and SDL18.9 were consistent with male gametic competition; whereas SDL18.4 and SDL18.11 reflected female gametic selection. Similarly, other SDL could reflect zygotic selection. The surprising finding was that SDL18.8 was detected in all populations, and the direction was skewed towards heterozygotes. Consequently, zygotic selection or heterosis could represent the underlying genetic mechanism for SDL18.8. Among developed introgression lines, SDL18.8 was introgressed as a heterozygote, further substantiating that a heterozygote state was preferred under competition. Six out of 11 SDL on chromosome 18 were dependent on the cytoplasmic environment. These results indicated that different SDL showed varying responses to the cytoplasmic environment. Overall, the results provided a novel strategy to analyze the molecular mechanisms, which could be further exploited in cotton interspecific breeding programs.
Highlights
Segregation distortion (SD) is defined as a deviation of the observed allelic frequencies at a locus from the expected Mendelian ratio in a segregating population
With the development of molecular markers, SD has been widely reported in several plant species, in interspecific crosses for genetic mapping, such as rice (Shanmugavadivel et al, 2013), wheat (Takumi et al, 2013; Adamski et al, 2014), chickpea (Ravikumar et al, 2013), Arabidopsis (Leppala et al, 2013), coffee (Gartner et al, 2013), soybean (Baumbach et al, 2012), potato (Manrique-Carpintero et al, 2016), Brassica rapa (Kitashiba et al, 2016), and Populus deltoids (Zhou et al, 2015)
SD has previously been reported in interspecific populations of cotton (Guo et al, 2007; Blenda et al, 2012; Byers et al, 2012; Liang et al, 2012; Yu et al, 2013; Diouf et al, 2014; Zhang et al, 2014; Li et al, 2016), intraspecific populations of G. barbadense (Wang et al, 2013), intraspecific populations of G. hirsutum (Lin et al, 2009; Zhang et al, 2012, 2016; Ning et al, 2014), and intraspecific populations of G. arboreum (Li et al, 2007); the genetic mechanism of SD in cotton remains unclear
Summary
Segregation distortion (SD) is defined as a deviation of the observed allelic frequencies at a locus from the expected Mendelian ratio in a segregating population This phenomenon is commonly detected via genetic mapping and has been documented in various species, including mouse (Eversley et al, 2010; Casellas et al, 2012), Drosophila (Phadnis and Orr, 2009; Larracuente and Presgraves, 2012; McDermott and Noor, 2012), Tigriopus (Pritchard et al, 2011), rice (Koide et al, 2012; Reflinur et al, 2014; Xu et al, 2014), maize (Tang et al, 2013), and cotton (Yu et al, 2011; Hulse-Kemp et al, 2015). Conspecific pollen precedence has been recognized as a potential major source for SD in closely related species of Mimulus with divergent mating systems (Fishman et al, 2008)
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