Landscape genomics of thermotolerance: Environmental and genetic determinants of the slick hair phenotype in Montana Tropical cattle

The slick hair phenotype in cattle is a thermotolerance trait of increasing relevance in the context of climate change. This study evaluated 3233 Montana Tropical cattle to investigate environmental and spatial factors associated with genetic variation in the genomic region linked to the slick hair trait and to identify candidate genes potentially involved in thermotolerance. A panel of 120 SNPs spanning 5.5 Mb of the slick hair region on BTA20 was analyzed using logistic regression against six environmental variables: temperature, humidity, altitude, precipitation, NDVI, and solar radiation. Spatial genetic structure was assessed through Mantel tests, spatial autocorrelation, genetic landscape modeling, and Monmonier's algorithm. Eight SNPs were significantly associated with at least four environmental variables, with radiation and humidity showing the strongest effects. Gene annotation revealed five key genes—PRLR, RAD1, BRIX1, TTC23L, and DNAJC21—and functional annotation indicated roles in immune function, DNA repair, and ribosome biogenesis. Spatial analyses detected fine-scale genetic structure and multiple genetic barriers, particularly in southern Brazil, suggesting the combined effects of environmental selection and region-specific breeding practices. These findings enhance understanding of environmental influences on the slick hair genomic region and provide markers for breeding strategies aimed at improving heat tolerance in tropical cattle populations.