Characterization of the effect of introgressed segments of chromosome 7 and 10 from Lycopersion chmielewskii on tomato soluble solids, pH, and yield.

Three chromosomal segments from the wild tomato L. chmielewskii have been introgressed into the L. esculentum genome. Using molecular markers they have been mapped to the middle and terminal regions of chromosome 7 (7M, 7T respectively), and to the terminal region of chromosome 10 (10T). This study was conducted to further clarify the physiological influence of the introgressed segments of chromosome 7 and 10 on tomato soluble solids (SS), and other fruit and yield parameters. The effect of the 10T segment was evaluated using five lines that differ for the presence of this segment. As previously reported this segment increased fruit pH with no significant effect on SS. Sixty-four BC2F5 backcross inbred lines (BILs) were developed from a cross using LA1501 (an L. esculentum line that contains the 7M and 7T fragments from L. chmielewskii) as the donor parent, and VF145B-7879 (a processing cultivar) as the recurrent parent. BILs were classified in four groups (+ +, inbreds without either of the L. chmielewskii segments; 7M +, lines with only the 7M segment; + 7T, inbreds with only the 7T segment, and 7M7T, inbreds with both segments) based on RFLP information, and then compared to each other for all the parameters under study. Inbreds homoyzgous for the 7M fragment displayed greater SS (26%) and higher pH (0.10) than the control group (+ +). The 7L fragment did not influence either SS or pH, but was observed to significantly increase fruit yield by 12% when compared to the recurrent parent. A gene or genes that increase yield without affecting SS or pH may have potential in the development of commerical cultivars.