| Effect of aneuploids on the yield of tetraploid rye
S. ELLERSTROM Swedish Seed Association, Svalof, Sweden In a recent paper by Hagberg and Ellerstrom (Hereditas 45, 1959), among other things, the frequency of aneuploids and their effect on the yield of tetraploid rye was discussed. It was concluded that it is very difficult to obtain a good estimation of the relation of the aneuploids in the population to yield. This is due to the fact that the aneuploid plants can not be distinguished phenotypically but have to be identified by determining their chromosome number. Using cytological methods for distinguishing euploids and aneuploids in a rye field, however, means a removal of organs from the plants, which most probably will disturb the equilibrium of the population. Thus a direct estimation of the effect of aneuploids on the yield of tetraploid rye seems practically impossible. However, an indirect approach to the problem may yield results of some interest. Considering the fact that a correlation exists between seed size and frequency of aneuploid, especially hypotetraploid seeds, it was possible, by sieving, to put together three seed lots with the following percentages of aneuploid seeds: 30, 19 and 5%. The original seed lot of tetraploid Steel-rye, which was divided in the three fractions, contained 9% aneuploids. The three seed size fractions together with the original seed lot were tested in field trials during two years. The following table gives the data for the seed yield in 1958 and 1959 of the three seed size fractions (I containing 30, II 19 and III 5% aneuploids) relative to the original seed lot (35):
A statistical analysis of these data shows that there is an indication of a significant difference in seed yield between the fraction with the highest aneuploid frequency and the one with the lowest (t=6.05, 0.05>P>0.01). The three seed size fractions differ, however, not only in frequency of aneuploids, but also in seed size, which may have an effect on seed yield too. To obtain an estimation of the effect of seed size on seed yield a seed lot of the variety Steel-rye, the diploid progenitor to the tetraploid variety used, was divided into three seed size fractions with the same relative seed size differences as between the tetraploid fraction. These diploid fractions (I, II and III corresponding to the 4x fractions) were tested in a field trial together with the original seed lot (13). The relative figures for seed yield are given below:
There are no significant differences between the seed size fractions. Moreover, the mean square for the error in this trial is of the same magnitude as in the tetraploid trials, which strenghtens the indication of significance in the latter case. Thus, it may be concluded that, at least in the material investigated, aneuploid plants have an effect on the seed yield of the tetraploid rye population. As a complement to the results briefly reported here, an investigation, based on a thorough examination of single plants from the different tetraploid seed fraction populations in under way. |