RECOMBINANT INBRED LINES FOR GENETIC-MAPPING IN TOMATO

A cross between the cultivated tomato Lycopersicon esculentum and a re lated wild species L. cheesmanii yielded 97 recombinant inbred lines ( RILs) which were used to construct a genetic map consisting of 132 mol ecular markers. Significant deviation from the expected 1:1 ratio betw een the two homozygous classes was found in 73% of the markers. In 98% of the deviating markers, L. esculentum alleles were present in great er frequency than the L. cheesmanii alleles. For most of the markers w ith skewed segregation, the direction of the deviation was maintained from F-2 to F-7 generations. The average heterozygosity in the populat ion was 15%. This value is significantly greater than the 1.5% heteroz ygosity expected for RILs in the F-7 generation. On average, recombina tion between linked markers was twice as high in the RILs than in the F-2 population used to derive them. The utility of RILs for the mappin g of qualitative and quantitative traits is discussed.