465 PB 324 QTL MAPPING AND MARKER-ASSISTED SELECTIONUSING INDEPENDENTLY GENERATED INBRED BACKCROSS TOMATO POPULATIONS

Abstract

The inbred backcross (IBC) breeding method is being used to introgress genes controlling high fruit soluble solids from a wild tomato species (Lycopersicon cheesmanii f. minor) into a California processing tomato cultivar (Lycopersicon esculentum cv. UC204B). One IBC tomato population (i.e. P1: 106 lines) is being used to map quantitative trail loci (QTL) for soluble solids and other traits. A genetically related but independently generated IBC population (i.e. P2: 96 lines) is being used to lest the efficiency of QTL-linked RPLPs for indirect marker-assisted selection (MAS) to improve soluble solids. P1 was analyzed for fruit quality traits in a replicated field design over 2 years. Twelve P1 lines were significantly greater than UC204B for soluble solids and also had acceptable fruit weights and horticultural traits. All twelve lines have been publicly released for further breeding efforts. In P1. we have identified RPLP markers that have significant correlations to QTL. Some of these markers map to regions previously reported by other researchers to contain QTL for the same traits. We will use 70-80 markers spaced approximately 10-20 cM apart across the genome to screen PI and map QTL. The RPLP analyses are currently in progress. P2 was replicated for one year using the same field design as P1. and analyzed for the same traits. P2 will be screened with QTL-linked RFLPs identified in P1 to test the consistency of QTL locations between independently derived populations. P2 lines selected using RFLP data will be compared to P2 lines identified by classical selection indices. This will indicate if MAS for QTL is effective in a population (P2) genetically independent from the mapping population (P1).