Studies on factors controlling plant vigor in tomato. An approach to elucidating the eco-physiological properties in horticultural crops

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It is well-known that vigorous vegetative growth hinders reproductive development but the physiological and genetic background of this phenomenon is not clear. In this study, quantitative trait analysis (QTL) analysis was performed to explore the genetic control of flowering time. Backross inbred lines developed from a cross between the commercial cultivar, Solunum lycopersicum and the wild species, S. pimpinellifolium were used as a mapping population. A phenotypic evaluation was done in spring and summer using the 114 BC1F4 families. In chromosome 1, a major DTF (days to flowering) QTL was detected near marker C2_At5g49480, which accounted for about 40% of the phenotypic variation in spring with contributing alleles from S. lycopersicum. However, in summer this QTL was responsible for only 16% of the phenotypic variation, while the DTF QTL in chromosome 3 near marker C2_At5g51110 explained more of the variance. Most of the QTLs were co-located in a single locus in chromosomes 1 and 3, while the other QTLs were sparsely mapped in chromosomes 5, 7 and 10. The DTF QTLs in chromosome 1 were co-located with QTLs for LL (leaf length), LS (number of lateral shoots) and fresh weight (FRW). This locus also corresponds to the same region to which a QTL was previously mapped for DTF, days to emergence and days to third leaf in a BC_1, population. On the other hand, in chromosome 3, the DTF QTL was found to be co-located with QTLs for LN (number of leaves before first inflorescence). Co-localization of DTF and LN QTLs indicates that the same gene/s may be control these traits. These results suggest that the DTF QTLs in chromosomes 1 and 3 probably control the rate of leaf initiation and the period from the vegetative to reproductive stage, respectively.