Colchicine Treated Coleus 



To teach a class of students how to use colchicine in plant breeding, a com- 

 mon ornamental coleus plant, Coleus blumei Benth., grown in the green- 

 house, was treated with this material in 1953. The original plant had leaves 

 with a green border next to a red area and with maroon color at the leaf 

 center. The apical growing points were removed from two plants 8 inches 

 tall and then they were immersed in one half of one percent colchicine 

 solution for about 20 hours. The idea was to see what the effect of doubling 

 the chromosomes might have on the color of the leaves, if any. From these 

 two plants, 42 lateral shoots were removed and rooted. Among the 42 

 rooted cuttings there were 7 color variations, all distinctly different from 

 the original plant and from each other. 



These seven selected plants were grown for a year and increased by di- 

 vision to 20 plants of each clone. During this time, they retained the differ- 

 ences originally noted. Chromosome counts were made from root tips from 

 plants of each clone by a graduate student, Dr. D. L. Craig. It was found 

 that the original plant had 43 chromosomes. Of the 7 variants, 2 had 48 

 chromosomes, 3 had 72 chromosomes, one had 96 chromosomes and an- 

 other approximately 96. Thus what resulted from the colchicine-treated 

 plants was two new color patterns with no increase in chromosome number, 

 three new ones which had half the chromosomes doubled producing trip- 

 loids, and two which had all chromosomes doubled and were tetraploids. 

 Those which had the doubled number 

 of chromosomes were weak plants 

 with narrow irregular leaves and 

 rather poor root systems. The ones 

 with 72 chromosomes were much 

 stronger even than the original plants. 

 Of the ones which had the same 

 chromosome number as the original, 

 one was weak and died. 



These results have indicated a be- 

 havior of plants following colchicine 

 treatment different from what is or- 

 dinarily expected. They tend to con- 

 firm the findings of the South Dakota 

 Experiment Station with Sorghum 

 where somatic segregation was found 

 to have resulted from colchicine treat- 

 ment. Seemingly colchicine offers 

 some possibilities in breeding other 

 than the doubling of chromosomes 



which some some have assumed to Colchicum in a border planting. The 

 be its direct effect. bulbs of this plant furnish colchicine. 



