Decreased genetic diversity in Kiso horses revealed through annual microsatellite genotyping

The Kiso horse is native to Japan and is on the verge of extinction. Here, we used microsatellites to characterize changes in their genetic diversity over time. We divided a population of Kiso horses that genotyped during 2007–2017 into three groups based on birth year: Group 1, 1980–1998 (70 horses); Group 2, 1999–2007 (61 horses); and Group 3, 2008–2017 (42 horses). We genotyped 31 microsatellites to calculate average number of alleles, observed heterozygosity, and expected heterozygosity. All indicators decreased across age groups. The results indicate that Kiso horses have been experiencing a drop in genetic diversity, and the population is expected to experience further decline unless appropriate measures are implemented.