Development of Male-Sterile Elite Lines using Marker-Assisted Backcrossing (MABC) in Tomato

Abstract

Recurrent backcrossing is a traditional breeding method that is commonly employed to transfer alleles at one or more loci from a donor to an elite variety. In order to develop male-sterile elite tomato lines, marker-assisted foreground and background selections were performed during backcross breeding. Compared to conventional backcrossing, marker-assisted backcrossing (MABC) is extremely useful for recovery of a recurrent parent's genetic background. For foreground selection, the tomato mutant anthocyanin absent (aa) presents a green hypocotyl during the seedling stage. Lines carrying the Aa genotype were selected from BC1F1 and BC2F1 populations using indel markers derived from the unique aa mutation of T2-517. This trait has been utilized in marker-assisted selection of male sterile 10 (ms10) at the seedling stage because their corresponding loci are closely linked on chromosome 2. For background selection, a total of 48 single nucleotide polymorphism (SNP) markers obtained from resequencing data between the MR10-3211 and T2-517 lines evenly distributed in the tomato genome were finally selected. BC1F1 and BC2F1 plants carrying the heterozygous (Aa) genotype were subjected to background selection using a set of 48 SNP markers. Multiple genotype analysis was done using a high-throughput genotyping system. As a result, one plant, 87.5% similar to the recurrent parent genome in the BC1F1 generation, and three plants with a 95.5% recovery rate of the recurrent parent genome in the BC2F1 generation, were selected. These selected plants were fixed in the BC 2 F 2 and BC 2 F 3 generations for the male sterile tomato elite line. We therefore demonstrate the utility of the MABC method for the recovery of recurrent parent genomes in tomato breeding strategies.