Objective: This study investigates runs of homozygosity (ROH) in 11 Tibetan sheep populations using resequencing technology.Its aim is assess the inbreeding status and the timing of inbreeding events in Tibetan sheep.Additionally, by integrating analyses of gene flow and genetic diversity, the study seeks to deepen our understanding of the genomic diversity of Tibetan sheep.The ultimate goal is to provide a theoretical foundation for conserving of genetic diversity and the optimizing genetic breeding strategies for Tibetan sheep. Methods: High-quality sequencing data were obtained from 220 Tibetan sheep representing 11 different breeds across the provinces of Gansu, Qinghai, and the Tibet Autonomous Region.The size and distribution of genomic runs of homozygosity (ROH) fragments in these 11 Tibetan sheep populations were analyzed.Results: Among the 11 Tibetan sheep populations, 85% of the ROH detected ranged from 0.5 Mb to 1 Mb in length.Only five populations (KC, GJ, QK, WT, and GBB) exhibited ROH segments longer than 3 Mb, although these were relatively rare.Chromosome length affects the number and length of ROH in the genome.Tibetan sheep have longer chromosomes 1, 2, and 3, which contribute to a higher occurrence of ROH.The FROH values for TS, GJ, and QK populations were relatively high, while the ZSJ population had the lowest.Although some Tibetan sheep populations harbor individuals with severe inbreeding (FROH > 0.2), overall inbreeding levels are relatively low, with most inbreeding events occurring in earlier generations.The expected heterozygosity (He) of the Tibetan sheep genome is higher than the observed heterozygosity (Ho), indirectly confirming the occurrence of inbreeding within Tibetan sheep populations.In several Tibetan sheep populations, there is evidence of gene flow, with the most extensive gene flow observed between HB and WT. Conclusion:In summary, the current breeding strategy for Tibetan sheep has room for improvement; therefore, breeding management and and genetic diversity conservation should be prioritized in future breeding programs.
Sun et al. (Thu,) studied this question.