Quantitative trait loci controlling flowering time and related traits in a Solanum lycopersicum × S. pimpinellifolium cross

Flowering time is an important factor determining early yield in tomato. However, the quantitative trait loci (QTLs) controlling flowering time and their relation to other QTLs for morphological and physiological traits have not been well studied. The aim of this study was to map the chromosomal regions controlling days to flowering (DTF) concurrently with other traits, such as the number of leaves preceding the first inflorescence (LN), length of the largest leaf (LL), number of lateral shoots (LS), fresh weight (FRW) and plant height (PH). This was undertaken using an inbred backcross population derived from a cross between the commercial cultivar Solanum lycopersicum cv. 'M570018' and its close wild relative S. pimpinellifolium (PI124039). S. pimpinellifolium flowers earlier than the cultivated tomato. Plants were grown in spring and summer. Composite interval mapping detected 16 QTLs for the six traits evaluated. These QTLs explained 10-42% of the individual phenotypic variation. QTLs detected in spring generally did not differ from those detected in summer. In chromosome 1, the DTF QTL was co-located with the QTLs for LL, LS and FRW, while in chromosome 3 it was co-located with the QTLs for LN, FRW (summer) and PH. One DTF QTL that was detected in chromosome 3 and conferred by the S. pimpinellifolium allele hastens flowering. The co-location of the DTF QTL with the LN QTL suggested that the DTF QTL in chromosome 3 controls the period from the vegetative to reproductive phase. Co-locations of DTF QTLs with the other traits might be pleiotropic effects of a single gene or cluster of genes via physiological relationships among traits because they were found to be highly significantly correlated.