| 10. In relation to the values of fertility and plant height obtained from
euploid standard plants the average values of the offspring of those plants
came to 5% resp. 2% lower. The difference between the highest possible values
of the euploid plants and the average values of the offspring was found
to be larger when the proportion of euploid plants in the offspring is smaller.
11. The incomplete fertility and the variability in plant height of octoploid wheat-rye amphidiploids is caused in the main by an unusual proportion of aneuploids in the offspring of these amphidiploids. [II] Studies on aneuploidy and fertility resp. plant height of the octoploid wheat rye amphidiploid "Trc 220" gave the following results : 1. With increasing aneuploidy fertility of cytologically examined aneuploids was not only reduced when chromosomes were lost but also when the chromosome number surpassed the euploid level. In the range of the chromosome numbers 56 to 49 fertility was diminished on an average of 11.4% when chromosome was lost (euploid plants = 100%). Fertility of aneuploids with chromosome numbers between 49 and 45 to the contrary varied only unimportantly. The smallest seed setting came to about 14% of euploid seed setting. Aneuploids with less than 45 chomosomes were on an average more fertile than euploid plants and reached partly about 25% better seed setting. Because of this otherwise behaviour and in cosideration to the more or less strong resemblance to wheat aneuploids with chromosome numbers between 44 and 40 were comprehended in a special group and called "backregulated amphidiploids". 2. Plant height was also dependent on chromosome number. In the range of the chromosome numbers 56 to 49 reduction came to an average of 6.4% when one chromosome was lost whilst plant height of aneuploids with chromosome numbers between 49 and 45 varied unimportantly. Backregulated amphidiploids with 44 to 40 chromosomes reached 85% of the euploid plant height. 3. In relation to reduction of fertility and plant height in two different years and under different conditions of cultivation nearly the same results were obtained. An influence of possible cross-fertilization under open flowering conditions could not be observed. |
| <-- Back | | | --> Next |