Fuente: WIPO "tobacco agriculture" The invention provides a co-dominant SSR (simple sequence repeat) marker closely linked with a gene qCO for releasing carbon monoxide in mainstream smoke of tobacco and an application method of the co-dominant SSR marker. The serial numbers of the codominant SSR marker closely linked with the carbon monoxide release amount gene qCO in the main stream smoke of the tobacco are IDYK04177 and TMy80405, and the nucleotide sequences of PCR (Polymerase Chain Reaction) amplification products of the codominant SSR marker closely linked with the carbon monoxide release amount gene qCO in the main stream smoke of the tobacco are respectively shown as SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3 and SEQ ID No. 4. The application is the application of the codominant SSR marker closely linked with the carbon monoxide release amount gene qCO in detecting whether the carbon monoxide release amount gene qCO exists in tobacco genome DNA (Deoxyribose Nucleic Acid) or not. Compared with a method in the prior art, the codominant SSR marker has the characteristics of accuracy, high efficiency, stability, convenience, low cost and no detection opportunity limitation, so that the molecular marker can be applied to molecular marker-assisted selection of the carbon monoxide release amount gene qCO in low-harm tobacco breeding.