Unexpected high frequency of the stress-susceptibility conferring RYR1 T allele in a city forest wild boar population

An opinion prevails, although supported by only a few reports that the RYR1 T (skeletal muscle ryanodine receptor) point gene mutation (C>T transition) linked to stress-sensitivity rarely occurs in the wild boar (Sus scrofa scrofa) - ancestor of the domestic swine. Consequently, the wild boar has been considered genetically resistant to stress. The present study determined the frequency of the RYR1 C>T mutation in a population of wild boars inhabiting the Gdansk city forest (Poland). Blood samples from the hunted boars were analysed for the evidence of the RYR1 T allele. Among the 29 genotyped animals, there were 19 (65%) stress-sensitive recessive homozygotes (TT), 8 (28%) stress-resistant heterozygotes (CT) and only 2 (7%) stress-resistant dominant homozygotes (CC) with both alleles intact. Thus, contrary to the reported observations, it would appear that the wild boar population of the Gdansk forest contains predominantly animals with at least one RYR1 T allele (frequency q = 0.79). The finding is a striking example of potentially detrimental, invisible, bottleneck effect in a relatively robust population of wild animals.