In this study, we investigated the genetic control of dwarfism in naturally occurring dwarf mutant lines of grapevines. Through trait–segregation and marker–trait association analyses, we identified a major locus on Chromosome 14 tightly associated with the dwarf trait. Subsequently, we conducted a bulked RNA-seq analysis, fine mapped the dwarf trait and identified VviBR6OX1 , a cytochrome P450 enzyme involved in brassinostero...