3. Cytoplasmic male sterility.


In 1946 a study was initiated to determine the cause of variability in pollen production among male sterile lines. This is the same character studied by Rhoades (Jour. Genetics 27:71‑93. 1933). As a basis for further work, analyses of individual florets from a single plant were made. This eliminated the possible effects of genotype or environment. The results of such analyses do not give a continuous distribution of well‑developed pollen grains normally distributed about a mean. Instead, a discontinuous distribution with peaks at 58‑60, 37‑39 and 13‑15 percent is had. This suggests the probability of a Poisson distribution. Since this factor cannot be transferred through the pollen, it can be assumed that the percent of good pollen represents the class with 0 particles. Since 0 particles can be estimated by the formula em, it can be seen that the values obtained in the frequency distributions are the equivalent of .5, 1.0, and 2.0 particles as a mean number per pollen grain initiated.


The particle number in the cells of the various florets is relatively constant although sufficient variability is found to cause frequency distributions to be polymodal. If anthers within a floret are compared, results suggest less variability between anthers than between florets. Distribution at megasporogenesis also follows the Poisson.


Warren H. Gabelman