The Autoploids 319 



ing types from heterozygous diploids. ^"^ Comparative studies in Autir- 

 rhiniim showed that between intravarietal and intervarietal tetra- 

 ploids the problem of fertility involves something more comjilex than 

 a mere analysis of meiotic distiubances created in the tctrajiloitls.-"! 



The ecological requirements of autoploids are not as distinctive 

 from the diploids as are these requirements in amphiploids and their 

 parental diploids.''^ Hybridization does not activate processes in auto- 

 ploidy, and evolution at the tetraploid level must occur through gene 

 and chromosomal changes -which arc imdoubtedly very slow. 



From a practical standpoint, the lowered fertility at once placed 

 the tetraploid at a yield disadvantage. But these facts were well 

 known before colchicine was discovered. The problem in using tetra- 

 ploids becomes one of balancing the advantages against the disad- 

 \antages, and then measuring the net gain, in comj^arison with the 

 accepted competing diploid varieties. The use of polyploidy is not 

 a quick way to tlevelop new and improved varieties. Some projects 

 were undertaken with high hopes that revolutionary methods were 

 at hand. By now most of those concepts have been re\ised. For some, 

 polyploidy has been totally dropped as a method for improving vari- 

 eties. These are instances where the techniques should never have 

 been started; in others, the programs are stopping short of probable 

 success. Revised progiams using polyploidy are in progress in man) 

 laboratories throughout the world. 



i^.i—i: The cereals and polyploidy. In the aiuumn of 1951, large 

 quantities of seed of autotetraploid steel rye were distributed to 

 farmers in Sweden. ^•^- The first tetraploid rye was made before colchi- 

 cine was discovered and it proved to be inferior. Therefore, one 

 might suspect other polyploids in rye to be poor. Several more poly- 

 ploid varieties induced by colchicine have also proved inferior to the 

 best diploid varieties. There were variations in the different tetra- 

 ploids as well as variation among plants. Finally a superior tetra- 

 ploid was derived from a diploid variety of steel rye, and this formed 

 the beginning of this valuable series. i-'- A report on the cytogenetics 

 and practical value of tetraploid rye is a good guide for steps neces- 

 sary to develop tetraploid varieties. 



Testing the performance of tetraploid rye and diploid varieties 

 was difficult because plots coidd not be planted side by side. The 

 diploid pollen falling on tetraploid flowers greatly reduced the seed 

 yield of the tetraploid. Therefore, special tests had to be woikcd out 

 before a demonstration of practical value for the tetraploid rye was 

 possible. 



Like all autotetraj^loids. the cell size was larger than that of the 

 dijjloid. Pollen measurements were a reliable index for tetraj^loidy, 

 l)ut even less complex for practical selection was the size of seed, 



