*3.2. Pattern of Distribution of Runs of Homozygosity in Populations of Russian Local Sheep Breeds*

The ROH segments were identified in all studied breeds on all autosomes. In all studied breeds, the highest genome coverage by ROH was found on Oar1 (10.58–12.31% in coarse wool, 9.49–12.24% in semi-fine wool, and 9.69–11.68% in fine wool group), Oar2 (8.88–12.17% in coarse wool, 10.53–12.52% in semi-fine wool, and 10.16–12.83% in fine wool group), and Oar3 (8.33–9.74% in coarse wool, 5.42–10.09% in semi-fine wool, and 8.98–10.55% in fine wool group). The Oar 26 was characterized by the lowest coverage by ROH (≤2.40% in all breeds).

Mean ROH lengths varied significantly in different sheep breeds (Table 2). Mean ROH lengths ranged from 86.44 Mb in the Mongolian breed to 282.15 Mb in the Romanov breed within the group of coarse wool breeds. The Russian longhaired breed had the maximum mean ROH length (257.15 Mb), and the Altai Mountain breed showed the minimum value (86.77 Mb) within the group with semi-fine wool. Mean ROH lengths ranged from 92.82 Mb in the Baikal fine-fleeced breed to 174.53 Mb in the Volgograd breed.

The greatest mean ROH number was found in the Romanov breed (123.14) while the lowest one was detected in the Buubei\_2 breed (56.58) within the group of coarse wool breeds. The mean ROH number varied from 37.64 in the Altai Mountain breed to 84.31 in the Russian longhaired breed within the group of semi-fine wool breeds. The maximum ROH number was estimated in the Volgograd breed (77.38), and the minimum was found in the Baikal fine-fleeced breed (52.53).

Among all studied breeds the maximum individual ROH length was found in the Kuchugur breed (872.75 Mb), and the minimum was identified in the Lezgin breed (48.78 Mb). Considering the individual ROH numbers, the greatest number was displayed in the Romanov breed (146) and the lowest number was detected in the Altai Mountain breed (26) (Table 2, Figure 2).

#### *3.3. Ranging the Runs of Homozygosity by the Length Classes in Russian Local Sheep Breeds*

A genetic pattern of predominance of the shortest ROH segments (1–2 Mb) was found in all studied sheep populations (Figure 3). Thus, the frequencies of the 1–2 Mb ROH segments were higher 80% (with maximums in 91% in the Lezgin and 93.59% in the Mongolian breeds (Figure 3A) within the coarse wool breeds, higher 66.82% (with maximums in 77.79% in the Baikal fine-fleeced and 78.39% in the Groznensk breeds (Figure 3B) within fine wool breeds, and higher 50.70% within semi-fine wool breeds with maximums in 68.69% in the Altai Mountain and 68.90% in the Tsigai breeds (Figure 3C). The Romanov (71.96%) and Kuchugur (67.73%) breeds had lower frequencies of the shortest ROH segments in comparison with other coarse wool populations.

**Figure 2.** Genomic coverage in ROH (X-axis) and ROH number per individual (Y-axis) in Russian sheep breeds: (**A**) Genomic coverage in ROH (X-axis) and ROH number per individual (Y-axis) within the group of coarse wool breeds; (**B**) Genomic coverage in ROH (X-axis) and ROH number per individual (Y-axis) within the group of semi-fine wool breeds; (**C**) Genomic coverage in ROH (X-axis) and ROH number per individual (Y-axis) within the group of fine wool breeds. For a description of the sheep breeds, see Table 1.

**Figure 3.** ROH distribution in length classes in Russian sheep populations: (**A**) Mean number of ROH by class within the group of coarse wool breeds; (**B**) Mean number of ROH by class within the group of semi-fine wool breeds; (**C**) Mean number of ROH by class within the group of fine wool breeds.

The 2–4 Mb ROH segments were more distributed in semi-fine wool (from 19.73% in the Altai Mountain to 29.76% in the Russian longhaired breeds) and in fine wool breeds (from 16.64% in the Groznensk to 22.25% in the Volgograd breeds) than in coarse wool breeds (from 5.30% in the Mongolian breed to 21.46% in the Kuchugur breeds). A similar pattern was found in the 4–8 Mb ROH length class (7.66–13.60% in semi-fine wool group and 2.54–10.59% in fine wool group versus 0.62–7.20% in coarse wool group).

The classes of the longer ROH segments (8–16 Mb and >16 Mb) were less frequent in all studied breeds. The highest share of 8–16 Mb ROH segments was found in semi-fine wool breeds (2.55% in the Tsigai to 4.86% in the Russian longhaired breeds) while the maximums in coarse wool and fine wool breeds did not exceed 3.95% and 2.24%, respectively. The frequencies of the longest ROH segments (>16 Mb) varied from 0.12% in the Tuva to 2.10% in the Kuchugur breeds in coarse wool group, from 0.38% in the Altai Mountain to 1.13% in the Kuibyshev breeds in semi-fine wool group, and from 0.05% in the Groznensk to 1.36% in the Stavropol breeds in the fine-wool group.
