Chromosomal regions associated with segregation distortion in maize.

Segregation distortion skews the genotypic frequencies from their Mendelian expectations. Our objectives in this study were to assess the frequency of occurrence of segregation distortion in maize, identify chromosomal regions consistently associated with segregation distortion, and examine the effects of gametophytic factors on linkage mapping. We constructed a simple sequence repeat (SSR) linkage map for a LH200/LH216 F(2)Syn3 (i.e., random-mated three times) population, and compared the segregation distortion in this map with the segregation distortion in three published linkage maps. Among 1,820 codominant markers across the four mapping populations, 301 (17%) showed segregation distortion ( P < 0.05). The frequency of markers showing segregation distortion ranged from 19% in the Tx303/CO159 mapping population to 36% in the B73/Mo17 mapping population. A positive relationship was found between the number of meioses and the frequency of segregation distortion detected in a population. On a given chromosome, nearly all of the markers showing segregation distortion favored the allele from the same parent. A total of 18 chromosomal regions on the ten maize chromosomes were associated with segregation distortion. The consistent location of these chromosomal regions in four populations suggested the presence of segregation distortion regions (SDRs). Three known gametophytic factors are possible genetic causes of these SDRs. As shown in previous research, segregation distortion does not affect the estimate of map distance when only one gametophytic factor is present in an SDR.