Backcrossing is a plant breeding method most commonly used to incorporate one or a few genes into an adapted orelite variety. To facilitate MAB (marker-assisted backcrossing) in a practice breeding program, we developed a SNP databaseand a program for providing selected markers for background selection from genome-wide SNPs of seven tomato accessionsdownloaded from NCBI-SRA. We identified 410,074 SNPs among 21 parental combinations with data from seven transcriptomesand developed a SNP database. To select the optimized number of markers for background selection, we divided 12 chromosomesaccording to physical length and genetic length. Initially, each chromosome was equally divided into five blocks according tophysical length, and three SNPs were positioned per block. Additionally, we applied the genetic distance from tomato-EXPEN2000 map because the frequency of recombination can vary greatly among chromosomal regions. When considering geneticdistance, each chromosome was divided into fifteen blocks unequally and one SNP was positioned per block. The program forbackground selection was designed to be simple and easy to use, and it is available at http://tgsol.seeders.co.kr/index.php/tg/mab.When the user selects the parental combination, the program provides selected markers with primer information. The value ofthis program for tomato breeding will further increase if more accession numbers are added to the database.
