QTL Mapping of Yield-Related Traits using Recombinant Inbred Lines Derived from a Four-Way Cross of Two F1 Hybrids of Tomato

Production of tomato (Solanum lycopersicum) for the fresh fruit market and for processing in Japan is characterized by consumer demand for high fruit quality. However, recent unusual weather conditions such as high temperature, are making it very difficult for Japanese producers to obtain a steady yield of fruit of high quality. Therefore, improvements in the yield as well as the quality are very important themes in tomato production and breeding in Japan. To analyze the genetic factors that contribute to the yield of tomato, Bayesian QTL mapping was performed using recombinant inbred lines (RILs) derived from a cross of two F₁ hybrids of tomato. One parent was the Japanese F₁ cultivar ‘Momotaro 8’ (Takii & Company, Ltd., Japan), which is characterized by high sugar content, and the other was the high-yield Dutch F₁ cultivar ‘Geronimo’ (De Ruiter Seeds, the Netherlands). This cross corresponds to a four-way cross, as the four parental lines of the two F₁ cultivars were considered to be the founders. We generated about 200 RILs (in generations later than F₆) from a repeated cycles of selfing with single-seed descent of F₁ population consisting of 240 individuals derived from the cross. Genotyping data using more than 180 genome-wide simple sequence repeat (SSR) markers were subjected to the construction of linkage map. We report the results of QTL analysis for yield-related traits in F₆-F₉ RILs evaluated in hydroponic cultures.