ADVANCED BACKCROSS QTL ANALYSIS IN TOMATO - I - IDENTIFICATION OF QTLS FOR TRAITS OF AGRONOMIC IMPORTANCE FROM LYCOPERSICON HIRSUTUM

Advanced backcross QTL (AB-QTL) analysis is a new strategy for studyin g the effect of unadapted alleles on the agronomic performance of elit e cultivated lines. In this paper we report results from the applicati on of the AB-QTL strategy to cultivated tomato using the wild species Lycopersicon hirsutum LA1777 as the donor parent. RFLP genomic fingerp rints were determined for 315 BC2 plants and phenotypic data were coll ected for 19 agronomic traits from approximately 200 derived BC3 lines which were grown in replicated field trials in three locations worldw ide. Between I and 12 significant QTLs were identified for each of the 19 traits evaluated, with a total of 121 QTLs identified for all trai ts. For 25 of the QTLs (20%) corresponding to 12 traits (60%), the L. hirsutum allele was associated with an improvement of the trait from a horticultural perspective, despite the fact that L. hirsutum is overa ll phenotypically inferior to the elite parent. For example, L. hirsut um has fruit that remains green when ripe (lack of red pigment) yet al leles were found in this species that significantly increase red color when transferred into cultivated tomatoes. Wild alleles were also ass ociated with increases in total yield and soluble solids (up to 15%) a nd brix x red yield (up to 41%). These results support the idea that o ne cannot predict the genetic potential of exotic germplasm based on p henotype alone and that marker-based methods, such as the AB-QTL strat egy, should be applied to fully exploit exotic germplasm.