Identification of chromosomal regions associated with segregation distortion of SSR markers and the genes controlling the low-gossypol seed & high-gossypol plant trait of Gossypium sturtianum

Distorted segregation of DNA markers is commonly encountered, especially in inter-specific
crosses. Our main objective in this study was to identify chromosomal regions consistently
associated with segregation distortion in [(G. hirsutum x G. raimondii) x G. sturtianum] (HRS)
hybrid. Segregation distortion skews the genotypic frequencies from their Mendelian
expectations. In HRS progeny, chi square analysis (P < 0.01) showed significant skewed in all
targeted linkage groups c2-c14, c3-c17, and c6-c25. Chromosomal region was regarded as
being associated with skewed segregation, if three or more closely linked markers exhibited
significant segregation distortion in one or more population(s). The targeted introgression
regions in the tested population seem to be favourable for segregation distortion. Segregation
distortion in HRS hybrid progenies differed in male and female gametes. Furthermore, the
data indicated that the environment has strongly influenced the transfer of SSR markers
through microspores. The consistent location of these chromosomal regions in selfed and
backcross of HRS derivatives indicate probably the identification of segregation distortion
regions (SDRs) in HRS hybrid. Comparison with results regarding the segregation distortion
regions obtained in previous research by other authors and results we obtained regarding the
absence of recombinations between BNL3436 and BNL1153 markers mapped on c6-c25
chromosome and spanned by 64 cM on the G. hirsutum map, after several generations of
selfing, arise the question of the conservation of the gene order and spacing in G. sturtianum.
Results showed that three SSR markers mapped on c6-c25 linkages groups were
systematically transmitted in all selected progenies of the HRS tri-specific hybrid.
Furthermore, the high percentages of loci with significant segregation distortion observed in
this study suppose that a genetic mechanism may exist for preferential transmission of alien
chromosomes segments. High heterozygosity frequencies (+/- 80%) were observed for all
conserved G. sturtianum SSR markers, after several generations of backcrossing and selfing,
which indicate that the cytogenetic and genetic conditions for obtaining homozygotes at high
frequency are not met.