Advanced backcross QTL analysis: a method for the systematic use of exotic germplasm in the improvement of crop quality

Most traits of agronomic interest, including those related to quality, are polygenically inherited. Exotic germplasm represents a valuable and unique source of genetic variation, but it has rarely been used for the genetic improvement of quantitative traits. We have efficiently screened for new and beneficial quantitative trait loci (QTL) able to improve the agronomic performance of elite varieties. We refer to this method as Advanced Backcross QTL (AB-QTL) analysis. The strategy has been tested in tomato over the past 5 years (using 5 different wild species donors) and in rice for 2 years (one wild species donor). In each case, QTL from the wild species have been identified which are able of substantially increasing quality or productivity of the cultivated species. We have created lines, in the genetic background of an elite processing tomato cultivar, which contain wild QTL alleles for several quality attributes important for the tomato processing industry including soluble solids content, fruit colour, viscosity and firmness. These lines have been subjected to replicated field trials in five locations world-wide. A number of these lines significantly outperformed the elite variety by 22%, 33% and 48% for soluble solids, fruit colour and yield, respectively.