Polyploidization, or genome doubling, has a significant impact on plant speciation and adaptation, and it is commonly used in agriculture to improve crop traits. In this study, we investigated the induction of polyploidy in three wild Allium species native to Korea: A. senescens and A. spirale Willd. and A. taquetii, using colchicine treatments tailored to meet specific experimental requirements. By avoiding tissue culture methods, we developed a more accessible, cost-effective, and scalable approach to polyploidization. Our research demonstrated that polyploid Allium plants exhibit distinct phenotypic changes, such as reduced growth rates and increased stomatal size. Flow cytometry and chromosome counting confirmed the successful induction of polyploidy, with clear peaks indicating double DNA content and stable chromosome numbers in polyploid plants. The presence of B chromosomes in A. spirale Willd. following polyploidization suggest interesting genetic dynamics. Despite the initial growth lags, polyploid plants may offer enhanced photosynthetic efficiency and resilience under optimal conditions. This study highlights the potential of polyploidization to improve ornamental traits in Allium species, thereby contributing to the diversification and sustainability of ornamental plant offerings. Future research should focus on the long-term performance and ecological adaptability of polyploid Allium species to fully harness their horticultural potential.

The present study was performed to investigate the effects of the colchicine concentrations on chromosome doubling for producing of tetraploid plants of Codonopsis lanceolata, and its effect on plant morphology. A total of 180 individuals germinated from 16 treatment groups, were exposed to various concentrations (0.05-1.0% w/v) of colchicine for different soaking duration (3-24 hour). The highest numbers of tetraploid plants (3) were observed from the lowest concentration of colchicine (0.05%), and one (1) tetraploid plant was obtained from the 0.5% concentration group with a 6 hour treatment. However, no tetraploid individual was observed in any other treatment groups. The plant height of the diploid (18.1 ㎝) was slightly shorter than that of the tetraploid (13.4 ㎝). The fresh weight of the main root in the diploid (0.5 g) was four-fold higher than the tetraploid (2.2 g). The colchicine-treated plant regeneration rate in C. lanceolata was decreased when the plants were subjected to high concentration of colchicine. In particular, the highest number of tetraploid plants (5 and 3) was obtained from the lower concentration (0.05% and 0.1%) of colchicine for 6-hour treatment, which were a higher rate (29.4% and 30%) of regenerated tetraploid plants than other regenerated plants. As in the seed treatment result, the plant height of the diploid was significantly higher (10.4 ㎝) than tetraploid. The higher morphological changes were observed comparatively from tetraploid plants than the diploid.

To produce high quality watermelon, three tetraploid watermelon breeding lines (‘SA03-1’, ‘SA06-1’ and ‘SB01-1’) were developed by treatment with different chromosome doubling reagents. To identify the optimal tetraploid inductive conditions, the three watermelon breeding lines were selected by counting the number of doubled chloroplasts in guard cells. Tetraploid induction rates differed depending on the genotypes and treatment with doubling reagents. However, the highest induction rate occurred with 1.0% colchicine (82.2%). These putative tetraploid lines were re-confirmed for ploidy using flow cytometric analysis and chromosome counting. The internode length of the tetraploid breeding lines was different when the leaf size was larger in all three tetraploid lines compared to their diploids. The fruit weight of the tetraploid fruits for ‘SA03-1’ and ‘SB01-1’ was lower than for their diploid, and the rind thickness and total sugar content (°Brix) of tetraploid SB01-1 were significantly different from those of its diploid. Tetraploid lines were sterile, yielded a lower number of seeds per fruit for ‘SA03-1’ (21), ‘SA06-1’ (62), and ‘SB01-1’ (34.7), and the seeds were larger and thicker than those of their diploids. These tetraploid breeding results will be useful for breeding new seedless watermelon cultivars.