Inbreeding refers to the mating of closely related individuals through common ancestry. It is known to reduce fitness-related traits in various species, including plants, animals, and humans. Inbred (consanguineous) families exhibit a higher frequency of major abnormalities than outcrossed populations. The phenomenon of reduced fitness and vigor in inbred individuals is termed inbreeding depression. This occurs due to increased homozygosity, which impacts fitness in two distinct genetic ways viz., heightened homozygosity for partially recessive harmful mutations, and increased homozygosity at loci where heterozygotes have a fitness advantage (overdominance).¹
In hermaphroditic organisms, inbreeding depression is evaluated by examining survival or reproduction following a single generation of self-fertilization. In outcrossing species, fitness traits are compared between outcrossed individuals and those inbred to varying degrees, as determined by inbreeding coefficients. These approaches reveal the effects of inbreeding on fitness across diverse reproductive strategies. Inbreeding depression can be assessed through direct experiments or indirectly by analyzing genetic markers. Understanding the genetic basis of heterosis and inbreeding depression provides valuable insights for breeders to develop cultivars with improved agronomic traits.¹
In rice, inbreeding depression was studied through the analysis of three panicle traits, revealing that dominance, segregation distortion, and epistasis collectively constitute the genetic basis of inbreeding depression. This research offered a new perspective on understanding heterosis.² Similarly, the reduced vigor observed in diploid and tetraploid maize was primarily attributed to homozygosity for mildly deleterious recessive alleles, which were quantitatively assessed.³
Understanding the genetics of inbreeding depression is essential for optimizing breeding programs aimed at preserving genetic diversity and preventing the loss of crop vigour. By uncovering the mechanisms underlying reduced fitness, such as the expression of deleterious recessive alleles or the loss of heterozygosity, breeders can design strategies to minimize these effects. Additionally, it helps breeders strike a balance between maximizing yield potential and maintaining a broad genetic base, ensuring the long-term sustainability of agricultural systems in the face of challenges such as climate change, pests, and diseases.
REFERENCES:
1 CHARLESWORTH, D. AND WILLIS, J.H., 2009, The genetics of inbreeding depression. Nat. Rev. Genet., 10(11): 783-796.
2 XU, X., XU, Y., CHE, J., HAN, X., WANG, Z., WANG, X., ZHANG, Q., LI, X., ZHANG, Q., XIAO, J. AND LI, X., 2024, The genetic basis and process of inbreeding depression in an elite hybrid rice. Sci China Life Sci., 67: 1-12.
3 YAO, H., SRIVASTAVA, S., SWYERS, N., HAN, F., DOERGE, R.W. AND BIRCHLER, J.A., 2020, Inbreeding depression in genotypically matched diploid and tetraploid maize. Front. Genet., 11: 564928.
%20(2).png)
0 Comments