A recessive high-density pod mutant resource of Brassica napus

In Brassica napus, pod number and pod density are critical factors to determine seed yield. Although the pod density is an essential yield trait, the regulation of yield formation in oil crops, as well as the genetic and molecular mechanisms, are poorly understood. In this study, we characterized a rapeseed high-density pod mutant (dpt247) from composite hybridization. To shed some light on the nature of this mutation, it was investigated morphologically, anatomically, physiologically, genetically and transcriptomically. The mutant plant showed noticeable phenotypic differences in comparison with the control plant, including reduced plant height and primary branch length, decreased number of primary branches, significantly increased number of pod on the main inflorescence, and more compact pod distribution. Besides, the mutant had higher levels of indole-3-acetic acid (IAA) and zeatin riboside (ZR) in the shoot apical meristem (SAM). The dense pod trait was controlled by two major recessive genes identified in the segregating genetic populations of GRE501 and dpt247. RNA sequencing indicated genes participated in auxin, cytokinin and WUS/CLV signalling pathway in dpt247 were more active in the mutant. These results provide important information for understanding the regulation of yield formation and high yield breeding in rapeseed.