Fine mapping of a major locus representing the lack of prickles in eggplant revealed the availability of a 0.5-kb insertion/deletion for marker-assisted selection

Abstract

As prickles cause labour inefficiency during cultivation and scratches on the skin of fruits during transportation, they are considered undesirable traits of eggplant (Solanum melongena L.). Because the molecular basis of prickle emergence has not been entirely revealed in plants, we mapped an eggplant semi-dominant Prickle (Pl) gene locus, which causes the absence of prickles, on chromosome 6 of a linkage map of the F₂ population derived from crossing the no-prickly cultivar 'Togenashi-senryo-nigo' and the prickly line LS1934. By performing synteny mapping with tomato, the genomic region corresponding to the eggplant Pl locus was identified. Through bacterial artificial chromosome (BAC) screening, positive BAC clones and the contig sequence that harbour the Pl locus in the prickly eggplant genome were revealed. The BAC contig length was 133 kb, and it contained 16 predicted genes. Among them, a characteristic 0.5-kb insertion/deletion was detected. As the 0.5-kb insertion was commonly identified with the prickly phenotype worldwide, a primer pair that amplifies the insertion/deletion could be used for marker-assisted selection of the no-prickly phenotype. Such findings contribute to map-based-cloning of the Pl gene and the understanding of gene function, ultimately providing new insights into the regulatory molecular mechanisms underlying prickle emergence in plants.

Keywords: eggplant; fine mapping; marker-assisted selection; prickle.

Fig. 1.

The prickly phenotype on leaf veins (upper) and calyxes (lower) of LS1934 (a1, a2), F₁ plant (b1, b2) and ‘Togenashi-senryo-nigo’ (c1, c2), respectively. White bars mean scales of 10 mm.

Fig. 2.

Genetic and physical maps of Pl locus. a: The Pl locus was firstly located between markers SOL6046 and emd16C09 on chromosome 6 using the T2LF2 population. b: Pl locus was further mapped between markers SmTgn22 and emd16C09, with the T2LF2 population. c: Phenotype and genotype of the T2LF3 progenies with the SmTgn1_series and SmTgn2_series markers mapped on the BAC contig. Phenotype and genotype data of the 11 T2LF3 progenies showed that the Pl locus was mapped between markers SmTgn2_31k and SmTgn2_163k. Names of the SmTgn2_series primers are abbreviated (SmTgn_**k is showed as **k).

Fig. 3.

Predicted genes on the eggplant BAC contig, “pl_contig_133313” and a position of 0.5-kb insertion detected in the AE-P03 genome. Pairs of arrows show a primer position of pl_indel_0.5k.

Fig. 4.

Difference of the fragment size among T2LF2 parents and F₁ plant, amplified with the primer pairs of pl_indel_0.5k which can amplify the 0.5-kb insertion/deletion site.

Fig. 5.

Pie charts of the number of accessions for each phenotype (no-prickly/prickly) and the marker genotype with the pl_indel_0.5k (‘Togenashi-senryo-nigo’-type; 0.2-kb/LS1934-type; 0.8-kb) in the worldwide eggplant collection.