Identification and Characterization of Segregation Distortion Loci on Cotton Chromosome 18

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.

The first genetic linkage map forFraxinus pennsylvanicaand syntenic relationships with four related species

“…Segregation distortion (SD) is a general phenomenon in plants, but the percentage, degree and genetic effects may vary significantly across species (Dai et al 2016;Zhou et al 2015;Taylor and Ingvarsson 2003). In maize, it has been reported that 18 chromosome regions on 10 chromosomes were associated with SD (Lu, Romero-Severson, and Bernardo 2002) while 14 SD regions were reported for barley (Li et al 2010).…”

Maximising recombination across macadamia populations to generate linkage maps for genome anchoring

“…Markers showing distortion have been recorded in a number of crops 90,91 . Markers displaying SD can be useful in QTL mapping 92 as they are often linked to candidate genes for specific traits.…”

“…For instance, it was found that regions of SD in sweet cherry, where 8% of markers showed distortion, are linked with hotspots containing fruit and bloom time traits, as well as a self-incompatibility modifier locus 93 . In cotton, several important agronomic traits have been recorded on chromosome 18 where 34% of markers showed distortion 90 .…”

Segregation distortion: Utilizing simulated genotyping data to evaluate statistical methods

“…In an F2 population originating from a biparental cross, the expected ratio of genotypes AA:AB:BB (progeny homozygous for the allele from the first parent, heterozygotes and progeny homozygous for the allele from the second parent) in absence of segregation distortion is 1:2:1. Segregation distortion is observed across a wide range of taxa, including animals such as Drosophila [1,2] and mice [3], as well as crop species, including cotton [4], maize [5,6], potato [7], chickpea [8], barley [9] and wheat [10][11][12]. The primary explanation of the cause of segregation distortion is a selection pressure operating against one of the parental alleles at some stage of the development cycle, whether at meiosis through meiotic drive [1], through male gamete competition [4], or at the level of the zygote.…”

“…The diversity of criteria used in the literature reflect the difficulty of answering this question. Some authors settle for a simple chi-square test with the minimum significance threshold of p < 0.05 [5,10,[14][15][16], others report multiple significance thresholds [7,[17][18][19][20], whilst others use corrections for multiple testing, including false discovery rate (FDR) [11,12,21] and the even stricter Bonferroni correction [4,22]. This inconsistency has the further implication that many of the studies on segregation distortion are not comparable, which is problematic for the general advancement of our knowledge of segregation distortion.…”