Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Experiments were conducted in 1979 to determine the genetic and environmental influences on early and total yield in segregating populations of several tomato crosses. Five tomato breeding parents were used that showed considerable differences in total yield and earliness. L401, an early maturing breeding parent, was crossed with L414, a late maturing breeding parent, to study inheritance of earliness. The cross of 'VF65-433', a midseason maturing cultivar, and L401 was also used to study this character. The F(,1) hybrid of both crosses produced as many ripe fruit as the early parent, L401. The late maturing parent, L414, was significantly lower in yield than both F(,1) hybrids. For the cross, L414 X L401, the plant frequency distributions for early maturity of the F(,2) and backcrosses exceeded the range of either parent in early fruit weight indicating transgressive inheritance. In general, plant distribution for mean early fruit numbers per plant was similar to those for the mean early fruit weight per plant for the cross L401 X L414. Heritability estimates as calculated by the total variances of the F(,2) and backcross generations were used to study the portion of variation in the segregating population that was due to gene action. Heritability estimates for early yield components depended on the parental combination. Estimates of heritability calculated for early fruit numbers and weight were 48.0 and 79, respectively, for the cross L401 X L414. Estimates of heritability for 'VF65-433' X L401 were negative values. Conclusions from the early maturity studies were that individual plant selections for early maturity may be feasible only for parents that differ greatly in maturity dates. In the inheritance of total yield studies, heritability, nature of gene action, and mode of inheritance was studied for fruit weight and numbers. Environmental influences masked the effects of the genes in many cases. The frequency distribution of the plants in the progenies of five crosses for fruit number characteristic produced a skewness in the backcrosses toward high fruit number in four out of five cases. Parental lines differed in combining ability for total fruit weight and fruit numbers. Heritability estimates for all crosses for total yield as measured were very low. Heritability estimates of total yield were masked by a strong environmental influence which resulted in negative values in some cases. Selection for yield in early filial generations should be by massing the best high yielding plants with good horticultural characteristics for subsequent testing and reselection.