α-carotene is one of the important components of pro-vitamin A,which is able to be converted into vitamin A in the human body.One maize (Zea mays L.) ortholog of carotenoid hydroxylases in Arabidopsis thaliana,ZmcrtRB3,was cloned and its role in carotenoid hydrolyzations was addressed.ZmcrtRB3 was mapped in a quantitative trait locus (QTL) cluster for carotenoid-related traits on chromosome 2 (bin 2.03) in a recombinant inbred line (RIL) population derived from By804 and B73.Candidate-gene association analysis identified 18 polymorphic sites in ZmcrtRB3 significantly associated with one or more carotenoid-related traits in 126 diverse yellow maize inbred lines.These results indicate that the enzyme ZmcrtRB3 plays a role in hydrolyzing both α- andβ-carotenes,while polymorphisms in ZmcrtRB3 contributed more variation in α-carotene than that inβ-carotene.Two single nucleotide polymorphisms (SNPs),SNP1343 in 5'untranslated region and SNP2172 in the second intron,consistently had effects on α-carotene content and composition with explained phenotypic variations ranging from 8.7％ to 34.8％.There was 1.7- to 3.7-fold change between the inferior and superior haplotype for α-carotene content and composition.Thus,SNP1343 and SNP2172 are potential polymorphic sites to develop functional markers for applying marker-assisted selection in the improvement of pro-vitamin A carotenoids in maize kernels.