Fuente: WIPO "tobacco agriculture" The invention discloses an application of polyphenol oxidase gene NtPPO2a and/or NtPPO2b from tobacco in drought-resistant tobacco variety breeding, wherein a nucleotide sequence of the NtPPO2a is shown in SEQ ID: No. 1, and a nucleotide sequence of the NtPPO2b is shown in SEQ ID: No. 2. An amino acid sequence encoded by the NtPPO2a is shown in SEQ ID: No. 3; and an amino acid sequence encoded bythe NtPPO2b is shown in SEQ ID: No. 4. A site-directed mutation method of the polyphenol oxidase gene NtPPO2a and/or NtPPO2b from tobacco includes the steps of carrier construction, agrobacterium transformation of pORE-CRISPR/Cas9 expression carrier, genetic transformation of tobacco and the like. Real-time fluorescence quantitative PCR is used to detect and analyze the tobacco variety, when the polyphenol oxidase gene NtPPO2a and/or NtPPO2b from tobacco mutates, the drought resistance of the variety is reduced. The invention provides a basic material and a detection method for drought-resistant tobacco variety breeding.