Associations were identified between the genetic polymorphism of the High Mobility Group AT-hook 2 (HMGA2) gene and growth traits in Awassi and Karakul breeds. Four polymerase chain reaction amplicons were designed to cover the coding regions of this gene. Several growth traits were analyzed every 3 mth until age 1 yr, namely body weight and length, wither and rump heights, chest and abdominal circumferences and average daily gains. The repeated measure analysis approach was used to analyze the association between HMGA2 polymorphism and growth traits. P amplicons were genotyped using single strand conformation polymorphism. Two genotypes were detected in exon 2 (TT and TA) and exon 3 also had two genotypes (AA and AB). The sequencing results showed one novel nucleic acid substitution in the TA genotype (intron1:45 A > T) and one novel deletion in the AB genotype (intron2:42 A del). Individuals with the TA genotype had significantly (p < 0.001) higher values of the majority of growth rate indices than individuals with the TT genotype, except for birth chest circumference, birth abdominal circumference, and average daily 6–9 mth gain. Individuals with the AB genotype showed significant (p < 0.05) associations with 6 mth and 12 mth weights, 6 mth wither height, rump height and abdominal circumference compared to individuals with the BB genotype. In conclusion, there was a tight association between intron1:45 A > T and better growth trait performance, supporting a link for this nucleic acid substitution with the improved growth traits. This is the first report suggesting ovine HMGA2 as a possible candidate marker for improving growth traits in Awassi and Karakul sheep.

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