Abstract:
Plant yield is the integrated outcome of processes
taking place above and below ground. To explore
genetic, environmental and developmental aspects of fruit
yield in tomato, we phenotyped an introgression line (IL)
population derived from a cross between the cultivated
tomato (Solanum lycopersicum) and a wild species (Solanum
pennellii). Both homozygous and heterozygous ILs
were grown in irrigated and non-irrigated fields and evaluated
for six yield components. Thirteen lines displayed
transgressive segregation that increased agronomic yield
consistently over 2 years and defined at least 11 independent
yield-improving QTL. To determine if these QTL
were expressed in the shoots or the roots of the plants, we
conducted field trials of reciprocally grafted ILs; out of 13
lines with an effect on yield, 10 QTL were active in the
shoot and only IL8-3 showed a consistent root effect. To
further examine this unusual case, we evaluated the metabolic
profiles of fruits from both the homo- and heterozygous
lines for IL8-3 and compared these to those
obtained from the fruit of their equivalent genotypes in the
root effect population. We observed that several of these
metabolic QTL, like the yield QTL, were root determined;
however, further studies will be required to delineate the
exact mechanism mediating this effect in this specific line.
The results presented here suggest that genetic variation for
root traits, in comparison to that present in the shoot,
represents only a minor component in the determination of
tomato fruit yield.
