A STATISTICAL APPROACH TO ESTIMATE THE FREQUENCY OF N, 2N AND 4N POLLEN GRAINS IN DIPLOID ALFALFA

Using pollen grain diameter, a statistical approach has been applied in order to estimate the percentage of n, 2n and 4n pollen grains produced by diploid plants of alfalfa. Pollen grain size distributions of normal diploids, normal tetraploids and jumbo pollen mutants were used as controls for n = x, 2n = 2x and 4n = 4x pollen grains, respectively. The least squares method was used to fit the observed distributions of the plants under examination with three reference distributions. Six out of 22 plants analyzed were 2n pollen grain producers and one also produced 4n pollen grains. The results obtained indicate that the method can be efficiently applied in breeding programmes aimed at the selection of alfalfa mutants producing unreduced gametes at high frequency.