Effects of colchicine on polyploidy induction of Buddleja lindleyana seeds

Buddleja lindleyana Fort. is a garden ornamental plant with great potential for development and also a commonly used medicinal plant. To enrich its germplasm resources, the seeds of B. lindleyana were treated with colchicine solution with concentration gradients of 0.5%, 1.0%, 1.5%, 2.0% and 3.0% for 12-, 24- and 48-h respectively, and the water treatment was set as the control group. The purpose was to explore the effects of colchicine on the germination and mutagenic effect of B. lindleyana seeds at different concentrations and different times, to screen the appropriate combination of mutagenic concentration and time, to provide guidance for the construction of B. lindleyana mutation population in future research. The results were as follows: (1) Colchicine had an inhibitory effect on seed germination and seedling height of B. lindleyana seeds, and the higher the concentration, the more obvious the inhibitory effect. (2) After colchicine treatment, 30 mutant plants showed morphological variations such as leaf malformation, leaf color macular, early leaf bud germination, uneven leaf surface and leaf hyperplasia, among which 3.0% + 48-h treatment group had great potential to produce yellow-leaf plants. (3) Detection and analysis by flow cytometry revealed that among the 30 morphologically variant plants, there were 22 diploid plants, 3 tetraploid plants, and 5 chimera plants. Among them, tetraploids were mainly from colchicine concentration of 3.0% (2 plants) and 1.5% (1 plant), chimeras were mainly from colchicine concentration of 1.0% (2 plants), 1.5% (1 plant) and 3.0% (2 plants), and the seed soaking time was 48-h. (4) The length and width of guard cells and stomata were significantly different between diploid and tetraploid, and there were significant differences in leaf width and leaf shape index between tetraploid and diploid, but there were no significant differences in leaf length among diploid, tetraploid and chimera. In short, we got tetraploids and chimeras materials which were potentially useful cultivars of B. lindleyana and provided an effective identification method for polyploids of B. lindleyana. Key message The appropriate combination of mutagenesis concentration and time was screened, and tetraploid B. lindleyana plants were successfully mutagenized, which provided technical support for the breeding research of B. lindleyana polyploidy.