PURPOSE: A Capsicum annuum defense-associated cytochrome p450 gene(CaCYP450A) and a transgenic plant are provided to detect plant disease resistance. CONSTITUTION: A gene encoding cytochrome P450A as a plant disease-associated gene encodes a protein with an amino acid sequence of sequence number 2 or has a base sequence of sequence number 1. The isolated protein(CaCYP450A) has an amino acid sequence of sequence number 2. A method for detecting plant resistance comprises a step of confirming expression of the gene by isolating mRNA from a plant body.