In vitro induction of tetraploids in the ornamental plant Melastoma candidum D. Don using colchicine treatment
摘要
Artificially inducing tetraploids can aid in breeding new acarpous varieties and distant hybridization. This study first achieved polyploid induction in Melastoma, a popular ornamental shrub in southern China and northern Vietnam. Colchicine was used as a mutagenic agent for chromosome number doubling of germinating seed explants. By in vitro method, survival rate and tetraploid rate were affected by pre-culture, chemical concentration, and exposure duration. Explants treated with 0.2% concentration for 4 or more d showed 100% polyploid induction based on radicle morphology. However, considering induction success and mortality, the best option was 0.2% concentration for 2 d, resulting in a 71.9% polyploidization rate and 71.7% survival rate. Plantlets were then inoculated on Murashige and Skoog medium supplemented with 0.5 mg L−1 6-benzylaminopurine and 0.1 mg L−1 α-naphthaleneacetic acid for shoot induction and ½ Murashige and Skoog medium supplemented with 0.5 g L−1 α-naphthaleneacetic acid for further rooting. Twelve mature tetraploid plantlets were confirmed by flow cytometry. Phenotypic analysis revealed smaller, rounder, and thicker leaves with more abundant and longer epidermal hairs in polyploid and mixoploid plants compared to diploids. Also, stomata of polyploid were larger and sparser than those of the diploid wild type. These findings provided an effective methodology for artificial polyploidy germplasm resource acquisition within Melastomataceae, which lay an important foundation for breeding fruitless cultivars.