Evaluation and selection of sources of cytoplasmic male sterility in broccoli

Abstract

Broccoli is an important Brassica vegetable that shows obvious heterosis. The main method for hybrid broccoli production is to use cytoplasmic male sterility (CMS) and pollination by bees. Therefore, the evaluation and selection of high quality sources of CMS is important for broccoli breeding. We aimed to evaluate the effects of different CMS sources on the morphology and size of floral organs, the attractiveness to pollinators and yield of hybrid seeds. Using broccoli CMS lines generated from different CMS sources with the same maintainer lines, we studied morphophysiological characteristics of flowers, such as flower shape and size, nectar production and sugar content, as well as the number of bee visits and seed yield. The degree of bud abortion, floral organs shape, degree of flower opening, nectar production, bee visits, and hybrid yield differed in CMS lines with same recurrent parent. When the CMS source was same and the recurrent parents were different, the degrees of bud abortion were different among the CMS lines, while the flowering characteristics were similar. Generally, larger floral organs and higher volumes of nectar were associated with higher frequency of bee visits and higher seed yield. Based on the morphological characteristics and size of floral organs, nectar secretion, bee-attracting ability and hybrid yield, we selected four CMS sources suitable for future use in broccoli breeding. Our results will provide an important reference for breeding high-quality CMS lines in broccoli and provide valuable CMS sources for breeding other cruciferous crops.