While working with tomato species crosses at Cheyenne, Wyoming several years ago, I did some work with L. hirsutum that I have not yet published. The L. hirsutum plants used were unfruitful in the field and greenhouse, but eventually set some seeded fruits in plants 2 years old in the greenhouse. The plants failed to set seeded fruits from flowers treated with L. esculentum pollen, but their pollen functioned perfectly in the reciprocal cross. The F1 hybrids were self-sterile and cross-sterile with L. hirsutum. They set seedless fruits from flowers treated with L. esculentum pollen, but their pollen functioned perfectly in the reciprocal cross. These results are similar to those obtained by other investigators.
In addition to the diploid material, numerous amphidiploids were obtained from F1 hybrids treated with colchicine. About half of the amphidiploids exhibited leaf necrosis progressing from the base of the plant upward. The others were apparently normal; they were large, and vigorous and retained their green color very well. They were more fruitful than the diploid F1 hybrids and set seedless fruits following self- and cross-pollinations.
Meiosis in diploid and amphidiploid hybrids was comparable with meiosis in diploids and autotetraploids of the parental species.
These studies suggested that L. hirsutum is basically cross-fertile with L. esculentum at the diploid level. Unfruitfulness of diploid hybrids may be like unfruitfulness encountered in many collections of L. hirsutum and may not indicate cross-sterility with L. esculentum. It would be interesting to determine whether all or part of this unfruitfulness results from self-sterility observed in the green-fruited species of Lycopersicon by Rick and his students.