The application of polyploidy in sustainable agriculture has already brought much appreciation among researchers. Polyploidy may occur naturally or can be induced in the laboratory using chemical or gaseous agents and results in complete chromosome nondisjunction. This comprehensive review described the potential of polyploidization on plants, especially its role in crop improvement for enhanced production and host-plant resistance development against pests and diseases. An in-depth investigation on techniques used in the induction of polyploidy, cytogenetic evaluation methods of different ploidy levels, application, and current research trends is also presented. Ongoing research has mainly aimed to bring the recurrence in polyploidy, which is usually detected by flow cytometry, chromosome counting, and cytogenetic techniques such as fluorescent in situ hybridization (FISH) and genomic in situ hybridization (GISH). Polyploidy can bring about positive consequences in the growth and yield attributes of crops, making them more tolerant to abiotic and biotic stresses. However, the unexpected change in chromosome set and lack of knowledge on the mechanism of stress alleviation is hindering the application of polyploidy on a large scale. Moreover, a lack of cost–benefit analysis and knowledge gaps on the socio-economic implication are predominant. Further research on polyploidy coupling with modern genomic technologies will help to bring real-world market prospects in the era of changing climate. This review on polyploidy provides a solid foundation to do next-generation research on crop improvement.

This study evaluated the effect of different concentrations and methods of oryzalin treatment on polyploidization in watermelon ( Citrullus lanatus ). The first method involved different concentration of oryzalin (0, 5, 10, 15, 20, and 25 mg∙L -1 ) applied to the shoot apex of watermelon seedlings. Polyploidy was not induced by concentrations of 10 mg∙L -1 or lower. In contrast, mixoploidy was observed with concentrations of 15 and 20 mg∙L -1 and 84% of the plants were tetraploid in the 25 mg∙L -1 concentration. The addition of the surfactant tween 20 in oryzalin was less effective for tetraploid induction than oryzalin alone. The second method involved soaking the seeds in different concentrations of oryzalin (0, 30, and 35 mg∙L -1 ). With this method, the 30 mg∙L -1 oryzalin concentration did not induce polyploidy and the 35 mg∙L -1 concentration only induced tetraploidy in 25% of the plants. The morphological features of the second true leaf of a tetraploid plant showed a small, thick, and wrinkled leaf unlike that of the diploid plant. In addition, the number of stomata per unit area decreased and stomata doubled in size in the tetraploid plants. Tetraploid plants (2n = 4x = 44) were confirmed by counting the number of chromosomes of the treated plants. We concluded that the shoot apex treatment with 25 mg∙L -1 oryzalin was the most effective method for inducing tetraploid watermelon.

In this study, the characteristics of ‘Tohagolred’, ‘Daewangchun’ generated by a reciprocal cross between Hibiscus sinosyriacus ‘Seobong’ and H. syriacus ‘Samchully’, and the corresponding parental lines were investigated and DNA content was measured by flow cytometry. FISH detection of 5S and 45S rDNA was conducted to analyze the parental and progeny karyotypes. The leaf margin was serrate for ‘Samchully’ and crenate for ‘Seobong’. The leaf margin of ‘Daewangchun’ was crenate, the avarage leaf length was 8.2 cm, and the average leaf width was 5.4 cm. The leaf margin of ‘Tohagolred’ was crenate, the average leaf length was 7.2 cm, and the average leaf width was 5.7 cm. The diameter of the ‘Daewangchun’ flower was 13.8 cm, which was 2 cm larger than the parents, and the red eye radius was 2.1 cm, which was approximately 1 cm larger than that of the parents. ‘Daewangchun’ appeared pink in color, similar to ‘Samchully.’ The flower diameter of ‘Tohagolred’ was 12.6 cm, which was 1 cm larger than that of the parents; the red eye length radius was 1.1 cm and approximately 1 cm smaller than that of the parents. ‘Tohagolred’ also appeared pink in color, similar to ‘Samchully.’ The DNA content was 1928.77 Mbp/1C (1.97 pg/1C) for ‘Seobong’ and 2820.34 Mbp/1C (2.88 pg/1C) for ‘Samchully’. Moreover, the DNA content of ‘Daewangchun’ and ‘Tohagolred’ was 1975.88 Mbp/1C (2.88 pg/1C) and 1914.70 Mbp/1C (1.97 pg/1C), respectively. DAPI staining showed that ‘Seobong’ was 2n = 80 and ‘Samchully’ was 2n = 126 as parents. However, Hibiscus F 1 cultivars ‘Daewangchun’ and ‘Tohagolred’ were 2n = 82. FISH analysis revealed that ‘Seobong’ had six 45S rDNA signals and two 5S rDNA signals. In contrast, ‘Samchully’ had six 45S rDNA signals and three 5S rDNA signals. Both ‘Daewangchun’ and ‘Tohagolred’ had seven 45S rDNA signals and two 5S rDNA signals. These results provide a foundation for genetic analysis and cultivation of new crops of Hibiscus spp.