Brcd1 Is Associated with Plant Height through the Gibberellin Pathway in Brassica rapa L.

In crops such as Brassica rapa, the agronomic trait plant height affects the leaf light absorption rate, benefits substance accumulation, and increases production by increasing the biological yield of the population. The mechanism of plant height was adequately studied in Brassica napus and Arabidopsis, while Brassica rapa had been rarely reported. Herein, we studied a B. rapa dwarf mutant Brcd1(YS). Compared with its wild-type, Yellow sarson, Brcd1(YS) showed shorter hypocotyls and slow growth, with inhibited root elongation and reduced numbers of lateral roots. Chlorophyll content determination and pollen viability detection indicated that the mutant's chlorophyll content was higher than that of the wild-type; however, its pollen was inactive. Cytological identification showed that the number of cells in Brcd1(YS) leaves was significantly reduced and were arranged irregularly compared with those of the wild-type. Bulked Segregant RNA sequencing combined with conventional linkage mapped the dwarf mutation Brcd1(YS) to Chromosome A06, at position 21,621,766 to 24,683,923 bp. Application of exogenous gibberellic acid (GA) partially rescued the dwarf phenotype of Brcd1(YS). GA-related genes BraA06g034110.3C and BraA06g033010.3C were identified as the most promising candidate genes. These results make a valuable contribution to our understanding of the mechanism of plant height determination in B. rapa, paving the way for further breeding of dwarf B. rapa.