Breeding and combining ability of heterostylous genotypes for hybrid seed production in Lycopersicon esculentum Mill

Summary

A subjective rating scale was used to select tomato inbreds with inserted stigmas (inserted) for crossing with inbreds possessing exserted stigmas (exserted) in a combining a bility study. Six inserted parents were inbred to F₅ or F₆, but were not stable for stigma position in most cases. The exserted x inserted hybrids were all slightly exserted and it appeared stigma exsertion was incompletely dominant to stigma insertion. No reciprocal cross differences were detected for stigma position indicating the absence of cytoplasmic inheritance. There was no clear relationship between hybrid stigma positions and the level of insertion of the inserted parents. Stigma insertion was more consistently detrimental to fruit set than was stigma exsertion. Hybrids were either heterotic or dominant for yield.

The inability to attain hybrids with standard stigma positions by crossing exserted x inserted genotypes could limit fruit-set under some environmental conditions. Furthermore, difficulty in breeding stable inserted lines and the incomplete dominance of exserted over inserted genotypes limits the feasibility of using heterostyly alone for producing reliable hybrids.