PAG-V: S5 - IDENTIFICATION, UTILIZATION AND CLONING OF ECONOMICALLY VALUABLE QTLS

Plant & Animal Genome V Conference

Town & Country Hotel, San Diego, CA, January 12-16, 1997.

S5

IDENTIFICATION, UTILIZATION AND CLONING OF ECONOMICALLY VALUABLE QTLS

TANKSLEY, STEVEN D., Kevin Alpert, Dario Bernacchi, Jinhua Xiao, Susan McCouch
Dept Plant Breeding, 252 Emerson Hall, Cornell University, Ithaca, NY 14853

The individual loci controlling quantitative traits can be detected and localized using molecular genetic maps. A current major issue is how this capability will be used to improve crop plants. One approach is to utilize genetic maps to detect and manipulate quantitative trait loci (QTLs) in existing breeding populations. However, this strategy will not lead to the discovery of new genes, only manipulation of the same alleles that breeders have been using all along.An alternative approach is to employ molecular mapping techniques tosearch for new genes which have previously gone undetected in the wild relatives of crop species. We have developed a strategy which allows the genomes of wild species to be efficiently screened for new and beneficial genes. This method, referred to as Advanced Backcross QTL analysis (or AB analysis), has been tested in tomato over the past 4 years (using 4 different wild species donors) and in rice for 2 years (one wild species donor). In every instance, genes from the wild species have been identified which are capable of substantially increasing productivity or quality of the cultivated species. Lines nearly isogenic for these QTLs have been constructed in tomato and subjected to replicated field trials worldwide. A number of these lines significantly outperformed the elite parent by as much as 20% due to the contribution of the wild gene(s). In addition to their value as breeding material, the NILs derived from this study provide a starting point for QTL cloning. Several QTLs have now been targeted for cloning and one QTL for fruit weight has now been isolated on a yeast artificial chromosome. Candidate genes from the YAC are now in transformation.