A. RUPA*, B. RUPESH KUMAR REDDY, R. NARASIMHULU AND M. PRADEEP

Department of Genetics and Plant Breeding, ANGRAU-S.V. Agricultural College,Tirupati-517 502.

ABSTRACT

Mendel’s law of segregation assumes equal transmission of alleles from parent to offspring. However, real-world genetic studies frequently reveal deviations from this expected pattern, a phenomenon known as segregation distortion (SD). This refers to the unequal inheritance of alleles during the formation of gametes or the development of zygotes. Such distortion is commonly observed in segregating populations, including F₂ generations, backcrosses, and recombinant inbred lines (RILs). Initially, researchers attributed these deviations are due to technical errors in genotyping or experimental design. However, it is now widely accepted that segregation distortion is often a result of underlying biological mechanisms. These include gametic selection, zygotic selection, meiotic drive, chromosomal rearrangements, and genetic incompatibility. In plant breeding, segregation distortion pose both challenges and opportunities. It may disrupt the accuracy of marker-assisted selection (MAS), QTL mapping, and genetic linkage analysis, potentially leading to the misidentification of desirable traits. However, if properly identified and analyzed, distorted markers can help uncover important genomic regions involved in reproductive barriers or trait inheritance. Advanced statistical methods such as chi-square analysis, likelihood ratio tests and bayesian models as well as specialized mapping tools can assist in detecting and interpreting segregation distortion. Understanding these patterns enables plant breeders to refine selection strategies and accelerate the development of improved crop cultivars.

KEYWORDS: Gametic selection, genomic regions, meiotic drive, marker-assisted selection (MAS), segregation distortion, zygotic selection.