Identification and characterization of white onion ( Allium cepa L.) genotypes for high total soluble solid content through molecular markers

Onion ( Allium cepa L.) is one of the most important bulbous vegetable used in global kitchen. Although it has various important traits but among them the high total soluble solid content (HTSS) of white onion is highly preferred by the industries for processing purpose. Looking into the broader use of the white onion; we utilized a total of 23 polymorphic simple sequence repeats (SSRs) and intron length polymorphic markers (ILPs) to characterize thirty five white onion genotypes for HTSS. Further, we also correlated these DNA fingerprint data with the TSS for identification of HTSS and LTSS lines. The total average numbers of alleles for SSR and ILP locus, heterozygosity (He) and polymorphism information content were found to be 2.4, 0.35 and 0.29 respectively. The UPGMA dendrogram revealed two distinct clusters of genotypes. Based on the TSS and DNA genotype data, our study revealed that Bhima-shweta (LTSS-12.09%, sub-cluster IAa) & WHT-12L-HT-15-Reject-M-7(HTSS- 18.02%, cluster II) are more diverse than the others. Other white onion lines including WHTB-7G-GT-15-SC-M-7 small bulb (HTSS 18.80%), WHT-2B-GT-18-SC-M-7 (HTSS 18.51%), WHTS-4D-GT-18-MC-M-7 (HTSS 18.49%), WHTB-3C-GT-18-MC-M-7 (HTSS 18.27%) and WHTS-11K-Pickle-SC-M-7 (HTSS 17.68%) were identified as superior HTSS lines. These identified diverse HTSS and LTSS lines could be useful for the mapping of HTSS coding genes for the acceleration of molecular breeding of onion through the marker assisted selection (MAS) which could be used by the industries for the larger scale processing of the white onion products required by the global community.