A series of crosses between the tomato cultivar 'New Yorker,' L. pennellii (accession LA 716) and their F1 (New Yorker x LA 716) was made to try obtain crosses with L. pennellii cytoplasm. The crosses attempted were LA 716 x New Yorker and LA 716 x [New Yorker x LA 716]. Successful crosses of this type between L. pennellii and L. esculentum have not been reported previously. No fruit set was obtained from more than 50 pollinations of LA 716 x New Yorker. Two fruit were obtained from over 200 crosses of LA 716 x [New Yorker x LA 716]. These fruit grew to approximately half the size of self pollinated fruit on LA 716, and abscised about 40 days after pollination without any sign of fruit softening. These fruit were surface sterilized, and the seeds removed and cultured on Linsmaier-Skoog media containing 2% sucrose and no hormones. The seeds turned from white to tan, then germinated two weeks after removal from the fruit. Twenty seedlings were obtained from 23 seeds. The seedlings were transferred from the media to sterile vermiculite, then to Cornell mix. The hybrid nature of plants were evidenced by general plant morphology, elongate shape of the leaflets, and the presence of a much larger root system and earlier flowering date than LA 716. The presence of L. esculentum peroxidase and/or esterase isozyme bands was also noted in leaf extracts of many of these plants. Pollen production and seed set varied considerably among these plants ranging from plants which had >90% stainable pollen to those with less than 10% stainable pollen, and from plants which readily set seed to others from which seed could not be obtained. These LA 716 x Fl plants are being maintained through cuttings, and several have been crossed reciprocally with New Yorker. The cross with New Yorker as the female parent is easily obtained (100% success) mature seed is produced without recourse to embryo or ovule culture. The reciprocal cross is easier to obtain (4 fruit with seed per 55 crosses) than the LA 716 x Fl cross, but ovule culture was still required to obtain seedlings. We have also used the Neal and Topoleski HLH medium instead of L.S. medium with success. We have not yet cultured a sufficient number of ovules or embryos to state which medium works better. We are continuing the backcross program to study the effects of L. pennellii vs. L. esculentum cytoplasms with an L. esculentum nuclear genome on several traits, including male fertility.
Literature cited:
Linamaier, E.M. and F. Skoog. 1965. Physiol. Plant. 18:100-127.
Neal, C.A. and L.D. Topoleski. 1984. J. Amer. Soc. Hort. Sci. 108:434-438.