Rick, C. M.
Frankel's finding of graft transmission of cytoplasmic male sterility from sterile stocks to genetically fertile scions in petunia suggested an attempt to make the same transmission to fertile tomato scions. Grafts were accordingly tried with scions of var. Pearson, Red Cherry, and 2 lines of L. pimpinellifolium as scions, and the same line of male-sterile petunia used by Frankel as stock. In most instances cleft grafts were made, but approach grafts gave best results with Pearson. The scion lines had been inbred for several generations and had been entirely fertile throughout their pedigrees. The donor plants of scions were retained and selfed for control progeny tests. Male sterility of each petunia stock was varified in flowers that appeared before grafting. Many leaves, which were retained on each petunia stock, grew large and leathery before the end of the experiment. Plants were kept in a screened greenhouse throughout the test.
Unexpected success was experienced with the grafts, except for those with Red Cherry. Three to five good unions were obtained of each of the other combinations. Growth of one of the Pearson scions was supported entirely by the petunia stock; with the others contact with the tomato root system was kept at a minimum by repeated shaving of the tomato stem below the graft. Scion growth was slow in all cases and the plants were prone to wilt on warm sunny days. Flowering and fruiting did not seem to be restricted except for reduced fruit size of Pearson scions, but viable seeds were produced by the latter. One of the pimpinellifolium scions, pruned to a single stem, produced 11 successive inflorescences.
The pollen produced by all flowers of the scions was normal in both quantity and quality. These observations of undisturbed fertility of scions are in keeping with the results of Frankel's petunia experiment. No difficulties were experienced in obtaining fruits and seeds from selfpollination of scion flowers, and small progenies of 10-15 plants apiece from these as well as from donor controls were grown. Contrary to the petunia experience, all plants in the scion progenies had normal pollen production and yielded fruits on self-pollination.