Dempsey, W. H.
For this study, the consistency of tomato concentrates was predicted by measuring the viscosity of the unconcentrated juice according to the method described in TGC 4:10. The inheritance data were accumulated by using the variety Pearson as the low viscosity parent and San Marzano as the high parent to produce F1, F2, BC to Pearson, and BC to San Marzano generations. Samples of 40 ounces of fruit were analyzed from each of 703 plants distributed among these six generations.
Frequency distributions of the six arrays showed that there was no transgressive variation and probably no dominance involved. Normal curves for the data transformed by logarithms and the position of generation means indicated that gene action for the consistency character was multiplicative.
Of three known genes that differentiate the parents (Lc, sp, and o), highly significant associations were found between sp and low consistency and o and high consistency. Therefore, at least two genes determine this character and these are located near sp in linkage group IV and near o in group I. This minimum estimate was further substantiated when a factorial analysis of the data gave good fits to genetic schemes involving 2 to 4 multiplicative genes.
Attempts to correlate consistency with soluble solids or total solids failed. However, high correlation coefficients were found between high consistency and total alcohol-insoluble solids (AIS). Since the AIS are made up of pectin and other lyophilic colloids, this correlation is not surprising.
Attempts to discover a character that could be measured in the field that would predict consistency (such as "dryness", "thickness of flesh", etc.) also failed. Apparently consistency measurements or AIS determinations are the most valid means of screening breeding materials.
It was interesting that several selections were obtained in the F2 that were as large fruited as Pearson and yet had the consistency of San Marzano.