Development of Allium cepa potential intron polymorphism markers for molecular breeding of Alliums

Abstract

Allium cepa is a widely grown crop for its spice and culinary properties. For molecular breeding of Allium cepa, mining and utilization of various sequence-based markers have been widely reported. Unfortunately, none has reported its molecular breeding using potential intron polymorphism (PIP) markers. Due to advantage of intron positioning prediction and practical utility, the PIP markers used for screening the possible polymorphism and cross-transferability in the Alliums. Screening results showed that among 500 Allium cepa potential intron polymorphism (AcPIP) markers, 275 are cross-transferable and polymorphic. Among the 275 AcPIP, 111 polymorphic markers were physically mapped on to 1st to 8th chromosomes of the Allium cepa. Out of the 275 AcPIP containing functionally significant markers, 118 were mapped in onion with Arabidopsis proteome. A set of 10 Alliums were utilized to interpret the polymorphic possibilities of the 500 AcPIP markers. In totality, 55 % AcPIP markers were polymorphic and cross-transferable among the Alliums. The polymorphic information content (PIC) of AcPIP markers ranged from 0.03 to 0.47 and heterozygosity index (H) varied between 0.16 and 0.80. The constructed phylogenetic tree based on the AcPIP markers of 10 Alliums revealed different clusters due to differences in their taxonomic positions. Out of 275 AcPIP markers, 10 AcPIP markers genotyping based Jaccard dissimilarity-based NJ tree of 96 individuals of Allium cepa showed two distinct groups (high total soluble solid; HTSS and low total soluble solid; LTSS). NJ tree and dissimilarity matrix reveal that group I genotypes are distinct, and dissimilar from group II and III genotypes hence it seems that group II and III genotype evolve from group I genotypes. Further we identified nine diverse Allium cepa subsample among which, genotype number 74 has HTSS and could be used for identification and introgression of HTSS coding genes in elite cultivars. Further DNA fingerprint of Alliums with 20 AcPIP markers suggested geographical reach of the released onion varieties. Hence results suggest that 275 AcPIP markers may be useful for accelerating the breeding programme of the Alliums and other species.