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Sweet Potatoes flowering induced by grafting scion on ornamental

M. P. Zobel and G. C. Hanna

Most varieties of sweet potatoes- ering scion on easy-flowering ; 3, lpomeu bututas-normally do not pro- nonflowering scion on easy-flowering root duce under California conditions. with the foliage growth of the The ability to induce and seed kept trimmed off; 4, easy-flowering scion production would greatly facilitate the on easy-flbwering root; 5, nonflowering Rooted -30-compared to a dwarfed scion of the same variev growing on morning development of varieties with superior scion on nonflowering root; and 6, rooted glory root-103. Left portion of picture Is a close- quality, higher yield, and disease resist- cuttings. As in the 1951-52 tests, the re- up showins the heavy production of buds and ance. sults were inconclusive, but the results mowers of 103. In 1950, some new strains of sweet po- did indicate that the blooming of the easy- tatoes were obtained from the U.S.D.A. flowering portion of thegrafted plant did was resumed. These buds continued to and from the Texas Agricultural Experi- not stimulate flower production in the appear, develop, and produce normal ment Station. Among these, two easy- nonflowering portion. flowers. In some cases the were flowering strains were included which It was thought that the slight stimula- dwarfed-plant 103-but in others the proved to be of little value in the breed- tion of flower production in the nonflow- growth of the scion was normal. The re- ing program. Some of the others pro- ering noted in 1951-52 could be due to sponse of the sweet scions was duced a few flowers, while still others the limited storage of carbohydrates in the same regardless onto which orna- failed to flower. Since certain of the the of the easy-flowering stock. This mental they were grafted. The grafts latter possessed some of the desired char- might result in a build-up of materials made on the easy-flowering sweet potato acteristics, a number of methods were within the aerial portion of the plant and roots on the other hand grew normally tried to induce flowering. These treat- thus induce bud formation. Following but flower production was no better than ments included , sugar sprays, this reasoning, grafts were made in 1952- where they were on their own roots- 53 on some closely related species com- hormone applications, controlled length rooted cuttings or grafted. The accom- of day, and growing in various volumes monly found in many home flower gar- dens. They were selected because they panying table shows the relative degree of soil. None of these produced con?’ of flower production of the various com- sistent results. Some plants produced have no storage roots. These species are: binations. Frequently the sweet potato buds but these abscissed before they de- Morning Glory-Zpomeu purpureu-va- riety Heavenly Blue, Cardinal-climber- grafted on a sweet potato root produced veloped into flowers. Most of them failed buds but the buds abscissed shortly after to respond to the treatments. In the win- Quamoclit sloteri-Moonflower -Culo- nyction uculeutum-and Cypress-vine- formation. This occurred also when the ter of 1951-1952, grafts were made with plants were rooted cuttings, but not when the nonbloomers using the easy-flowering Quumoclit pennutu. The method of graft- ing was the cleft graft. After insertion of the sweet otato scion was grafted on a varieties both as rootstocks and scions. morning g ory root. The results were encouraging but highly the scion, the union was tightly wrapped P variable and inconclusive as only a slight with a strip of rubber made from a cut stimulation of flower production oc- rubber band. No other treatment was Continuing Studies given. A total of 125 such grafts were curred. The reasons for the increased flower tried of which 95% were successful. production when a sweet potato scion Grafts were successful on all except Cy- Tests in 1952-1953 press-vine which has a stem smaller than was grafted on an ornamental rootstock are not completely understood because that of the sweet potato; however, even During the winter of 1952-1953, a not all plants produced flowers in equal more extensive set of grafts were made these grafts took and grew for a short abundance. In fact in a very few cases to explore further this method of flower time before dying. the plants failed to develop buds into induction. The following treatments were On many of the plants flower buds be- gan to appear about one month after flowers or to even produce buds. This in- tried: 1, easy-flowering sweet potato dividualism of the sweet potato plant in scion on nonflowering root; 2, nonflow- grafting or soon after growth of the scion its blooming habit has been recognized for some time but not understood. Re- Degree of Flowering as Affected by the Root on Which the Plant Was Grown search is continuing to determine the fac- Vorietv or used as scion tors that induce flowering; meanwhile the plant breeder can utilize this technique of 11-2~15-5-6-2~ 11-2~ 15941 Sunnyside 15999 Odis 15-54 1-2 159994 15999 B5999-7 grafting sweet potatoes on ornamentals as a tool in his unending search for better Roold cu??ing None None Few None None None None None None varieties. Grafiod on own root None .... Few ...... Rootstork 11748 None None Few .... Moderate ...... M. P. Zobel is Assistant Specialist in Vege- (wry flowering) table Crops, University of California, Davis. Morning Glory None Many Many Many Mony Moderate Many Many Many G. C. Hanna is Olenculturist, University of California, Davis. Cordinal-climber Moderate Many Many Few ...... Moodower Moderate Nono Mony Moderate ...... The above progress report is based on Re- search Pro ject No. 11 75.

CALIFORNIA , JULY, 195% 13