Molecular mapping of quantitative trait loci in tomato

A major objective in modern biology is deciphering the genetic and molecular bases of natural phenotypic variation. Over the past three decades the tomato clade (Solanum sect. Lycopersicon) has been a model system not only for the identification and positional cloning of quantitative trait loci (QTL), but also for the development of new molecular breeding strategies aimed at a more efficient exploration and exploitation of the rich biodiversity stored in wild germplasm for hundreds of biologically and agronomically relevant quantitative traits. The numerous QTL mapping studies conducted so far have resulted in the detection of several thousands of QTL. Despite this wealth of genetic information, the molecular bases have been revealed for only a handful of major QTL. The release of the tomato genome sequences (Tomato Genome Consortium 2012), along with the rapid development of cost-effective next generation sequencing (NGS) technologies, new mapping resources, and the ever-growing 'omic' platforms, are holding the promise to reverse this trend. This deluge of genomic resources are undoubtedly re-shaping QTL analyses also in this crop, allowing a re-examination of the variation and inheritance of complex traits at the intraspecific level, increasing the spectrum of potentially valuable alleles available for breeding. In this framework, precision phenotyping, advanced bioinformatics tools, as well as public phenotype "warehousing" databases are foreseen as the necessary tools to boost our understanding of the genetic and molecular architecture of quantitative traits, and to guarantee sustainable crop improvements in the face of an ever-growing human population and changing climates.