| Summary: | Chianina, Marchigiana, Maremmana, Podolica and Romagnola are the main Italian beef cattle breeds, and the quality of their products is largely recognized worldwide. This paper aims to determine the genetic variability and population differentiation by heterozygosity and fixation indices using SNPs data. The dataset was composed of 3,581 animals (Chianina, n = 909; Marchigiana, n = 879; Maremmana, n = 334; Podolica, n = 555; Romagnola, n = 904). The blood samples were collected in ANABIC performance testing station from 1985 to 2019. All the animals were genotyped with the GeneSeek GGP-LDv4 33k SNP chip containing 30,111 SNPs. The genotype quality control for each breed was conducted separately, and SNPs with call rate smaller than 0.95 and minor allele frequency larger than 5% were used for further analysis. Heterozygosity and FIS index were estimated in PLINK v1.9, and FST index was estimated using the hierstat package of R 4.0.1 software. The genetic analysis highlighted low values of heterozygosity in the improved beef breeds compared to the heritage breeds; moreover, the low values of FIS indicated a positive effect of controlled genetic inbreeding in the studied breeds. The FST; analysis confirmed the historical origin of Marchigiana breed and the values are consistent with their common breeding programmes. In this study, the importance of monitoring genetic variability of Italian beef cattle breeds was emphasized in order to maintain breed identity and genetic diversity in the selection process.
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