[From a typed manuscript, undated]
Transmutation of the Gene in Hemerocallis
Hamilton P. Traub
In the course of experiments for the induction of polyploidy in plants by minimal repetitive treatments with colchicines (Traub, 1951), the idea presented itself that it might be possible to transmute the gene if a similar technic could be devised for maximal repetitive treatments of the plants while actively growing in the soil medium. It was of course realized that the immediate effect of such treatments would lead to the cessation of growth for maximal doses or death if the treatments represented lethal doses (Traub, 1951). However, when growth would be resumed after maximal dose, the effects of the maximal treatments would be revealed.
Recently, this hypothesis was tested on a number of monocotyledonous species. A new technic was devised for this purpose. A circular hole was made at the base of the pseudo-bulb or bulb by means of a cork borer. The cork borer was inserted so that the base of the hole would be about in the center of the pseudo-bulb or bulb, the base of the plug in the borer was snapped by moving the borer sideways and the finger tip was placed on the upper eid of instrument, and it with plug of tissue was removed. With a little practice, this operation could be carried out successfully in most trials. A glass tube about 6 cm. long of the same outside diameter as the hole was inserted. (Fig. 1) The tube was filled with 0.2% aqueous colchicines solution by means of a sufficiently long capillary pipette. The delivery end was lowered to the base of the hole for the operation. The glass tube was refilled at intervals over a period of time whenever the solution was absorbed by the plant. The number of refillings in these experiments extended over 60 days.
This brief report concerns the results obtained with Hemerocallis fulva clone Europa. This is a natural sterile triploid (2n=33) introduced into Europe over 200 years ago and was used by Linnaeus (1753) as the type of the genus, and which has been carried over the entire U.S. by settlers, and also into many other parts of the world so that it has now a cosmopolitan distribution. It is very stable and no mutations have been reported.
Three thrifty ramets (plants) of this clone were treated as outlined above. The immediate results were marked as shown in Figure 2, for the inflorescence which has already been formed in the plant. The flowers of the controls were fulvous, but the flowers of the treated plants were almost completely yellow.
In the following season, one of the plants produced flowers that are almost yellow contrasting markedly with the fulvous flowers of the controls (Fig. 3). The pollen grains are similar to those of the controls, the chromosome number is 2n=33, but the flower appears to be a little smaller than the controls. It would thus appear that in this case polyploidy or aneuploidy are not involved, but that there has been a transmutation of the gene as far as color of the flower is concerned, and possibly also for the gene or genes responsible for flower size. Although the experiment involved only three treated plants, it should be noted that these were ramets of a very uniform clone and thus the necessity for the usual statistical analysis is so important. The fact that one third of the treated material was changed is also significant.
Müller (1927) reported apparent transmutation of the gene in Drosophila, but recently [missing, but probably Stadler, who held this view] (1949) and others interpret this as partial destruction of the gene material. Apparently no clear-cut gene mutations have as yet been recorded. This brief report concerns an apparent case of gene mutation in angiosperms.
In the course of experiments for the induction of polyploidy in Hemerocallis and other plants, the idea presented itself that it might be possible to transmute the gene if repeated strong concentrations of colchicines were used, and not the minimal concentrations recommended by Traub (1951) for the induction of polyploidy. A new technique was worked out consisting of making a circular hole in the bulb-like or bulbous bases of various monototyledons, and inserting a glass tube, which was regularly filled with 0.2% colchicine (aqueous), over a period of time. The results when Hemerocallis fulva clone Europa was thus treated were very marked as shown in the illustration (Fig. 1) for the inflorescence developed. The color was yellow, as contrasted with a rich fulvous for the control. The inflorescence developed the following season developed flowers somewhat smaller than the control and they were more yellow than fulvous. Out of three plants treated one or 33.3% showed this mutation. All who are familiar with the clone Europa know that it is quite stable, and has been spread over the whole USA and many other parts of the world. However, so far no mutations have been reported. In this case the triploid chromosome number has not been altered but the genes for color apparently have been changed.