Abstract

To genetically improve a complex trait we can dissect it into simpler component traits that follow a physiological model. We investigated this approach in tomato for total plant biomass, which was decomposed into fraction of intercepted light (Fint), calculated from leaf area index (LAI), and light use efficiency (LUE). We identified quantitative trait loci (QTLs) in hybrids created out of a multi-parent population of recombinant inbred lines (RILs) and detected 9 QTLs for LUE and 10 QTLs for Fint or LAI. Total biomass correlated equally with LUE (r = 0.72) and Fint (r = 0.69). QTLs for total biomass colocalized with 4 QTLs for LUE and with 7 QTLs for Fint or LAI. LUE and Fint were uncorrelated and had largely independent QTLs. Therefore, high-total-biomass hybrids can be produced by combining QTL alleles positively contributing to total biomass for the component traits LUE and Fint. All RIL hybrids with higher yield than the elite parent hybrids showed higher total biomass than the elite parent hybrids due to both a higher LUE and a higher Fint (7 RIL hybrids) or a higher LUE alone (3 RIL hybrids). Most QTL alleles that contributed positively to total biomass via LUE and Fint stemmed from the elite parents, but some were identified in wild parent germplasm as well. A dissection approach for genetic improvement of a complex trait was proven to be a useful tool for breeding.