Submitted to: Molecular Genetics and Genomics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/8/2007
Publication Date: 8/1/2007
Citation: Kumar, S., Gill, B.S., Faris, J.D. 2007. Identification and Characterization of Segregation Distortion Loci Along Chromosome 5B in Tetraploid Wheat. Molecular Genetics and Genomics. 278:187-196. Interpretive Summary: Competition among gametes for preferential fertilization can cause segregation ratios of progeny that differ from the expected ratios. The wheat group 5 chromosomes (5A, 5B, and 5D) are known to possess factors that cause segregation distortion. Using molecular markers, we evaluated segregation distortion and recombination frequency along chromosome 5B in wheat. To determine if the segregation distortion factors specifically functioned in the male or the female, we evaluated populations that allowed for competition only in male gametes or only in female gametes. We identified three separate segregation distortion factors, and all affected the transmission of male gametes. Distortion of one of the factors through the male was dependant on the presence of corresponding genes in the female. The other two factors were a result of competition among male gametes for preferential fertilization. This work provides important knowledge for breeders and geneticists to develop populations in the appropriate manner so as to not be confounded by complications that may result due to the segregation distortion factors.
Technical Abstract: Segregation distortion genes are widespread in plants and animals and function by their effect on competition among gametes for preferential fertilization. In this study, we evaluated the segregation distortion of molecular markers in multiple reciprocal backcross populations derived from unique cytogenetic stocks involving the durum cultivar Langdon (LDN) and wild emmer accessions that allowed us to study the effects of chromosome 5B in isolation. No segregation distortion of female gametes was observed, but three populations developed to analyze segregation of male gametes had genomic regions containing markers with skewed segregation ratios. One region of distortion was due to preferential transmission of LDN alleles over wild emmer alleles through male gametes. Another region required the presence of LDN 5B chromosomes in the female for preferential fertilization by male gametes harboring LDN alleles indicating that the corresponding genes in the female gametes can govern genes affecting segregation distortion of male gametes. A third region of distortion was the result of preferential transmission of wild emmer alleles over LDN alleles through male gametes. These results indicate the existence of different distorter/meiotic drive elements among different genotypes and show that distortion factors along wheat chromosome 5B differ in chromosomal location as well as underlying mechanisms.