Genomic organization and structure of cytochrome P450 CYP736 genes in grapevines. There are three cytochrome P450 genes, CYP736A, CYP736B and CYP736C, flanked on the left with a RE-LTR gene on grape chromosome 7. Numbers on the top indicate order of exons, and the arrow indicates direction of transcription. Exon size and distance between genes and exons were drawn to approximate scale. The DNA coding sequence identity of each CYP736 gene derived from a large genomic contig CU459237.1 (4,713,370 bp) was compared with the target CYP736B gene cloned from PD- resistant 9621-67 grape selection and is shown below each gene member. The directions of PCR primers are shown in arrows at specific locations.