Ploidy Analysis and Chromosome Doubling in Eggplant (Solanum melongena) and Onion (Allium cepa)

Chromosome doubling and ploidy analysis are essential techniques used today in plant breeding to quickly develop homozygous lines using doubled haploid (DH) technology. The ploidy state of the DH and haploid plants of onion (Allium cepa) and eggplant (Solanum melongena) was assessed in this study using flow cytometry, stomatal size and chlorophyll content to confirm the effectiveness of chromosomal doubling. The haploid (1N) and DH (2N) peaks were successfully separated by flow cytometric analysis employing DNA-specific fluorochromes, confirming genome duplication with 92.3% frequency in eggplant and 86.1% frequency in onion of diploid nuclei. Chromosome doubling was achieved using anther culture in eggplant and ovary culture in onion. When compared to haploids, DH plants showed significantly enhanced features. For example, the chlorophyll content of DH lines was 0.119 mg/g higher than that of haploid eggplant (0.073 mg/g) and 4.077 mg/g higher than that of haploid onions (2.171 mg/g). Improved trait with increased vegetative growth and higher stomatal sizes of 21.91 µm (eggplant) and 50.58 µm (onion) was attained in DH plants as compared to 16.69 µm and 37.90 µm in haploid plants, respectively. These findings show that screening for ploidy using flow cytometry, stomatal size, and chlorophyll content offered an effective method for speeding up the breeding of vigorous and genetically uniform lines in onions and eggplant.