The Autoptoids 331 



111 japan, production of tiiploids as a method for improving 

 watermelon production has been successfully explored. The opinions 

 of American horticulturists on this subject vary with the experiences 

 gained from testing the Japanese varieties. Success is reported in per- 

 sonal conmiunications from Professor E. C. Stevenson, Purdue Uni- 

 versity, Lafayette, Indiana, and Professor W. S. Barham, North Caro- 

 lina State College, Raleigh, N. C. Undoubtedly other unpublished 

 reports in America and elsewhere concur in many of the general 

 observations published by Kihara and his associates relative to yield 

 adxantages, disease resistance, and improved quality. 



Seed production and wide-scale commercial growing will increase 

 as l)etter adapted varieties are made available. Some problems pecul- 

 iar to cultivating triploids and to seed production need attention in 

 the American system. If watermelons of better quality can be ol)- 

 tained. fruits produced without seeds, or almost so, and if triploid 

 varieties are placed in the hands of commercial groovers who can pro- 

 duce melons more profitably than by present methods, the problems of 

 seed production and triploid cultivation will eventually be solved. The 

 time required for this transition in America is difficult to calculate; 

 however, the records of acceptance of h)bridi/ation in mai/e set a 

 standard that might well obtain in watermelon seed production and 

 commercial growing of this fruit. 



The application of colchicine to the problems of watermelons 

 represents a most specific and outstanding i)ractical advantage gained 

 from the use of this drug. 



1^.2-2: Triploid sugar beets. Early in the colchicine era poly- 

 ploidy breeding was directed at the improvement of sugar beets. Raw 

 tetraploids did not prove to be as good as the parental diploids. This 

 was to be expected for reasons outlined in the section on jirinciples 

 of polyploidy breeding.^- e^- ^^^' n-*- '--• "-• ^'""^ 



A significant rejjort was made that triploid plants yielded more 

 sugar than diploids because the larger roots maintained the same 

 percentage while the diploid tended to reduce the percentage of sugar 

 per hundred grams as the larger-sized beets developed. An additional 

 set of chromosomes raising the number from 18 to 27 did not \noxe 

 detrimental to volume of sucrose per acre of plants. 1 his represented 

 an imiKjriant advancement in sugar beet breeding'- (Fig. 13.8). 



11 triploids were superior — and this has been shown in several 

 cases — then special procedures were required to produce triploid 

 seed. Tetraploid seed parents are made, and then pollinations are 

 carried out with the dij^loid. Studies by Jajjanese workers show prac- 

 tical plans for making triploids.-"-' 



The increase in sucrose per unit area of cultivated triploids justi- 

 fied the additional work to make triploids which produce more su- 



