Meiotic investigation in Solanum tuberosum haploids.

Haploids (2n = 2x = 24) extracted from three Solanum tuberosum tetraploids (2n = 4x = 48) were investigated, in order to select fertile haploids producing 2n gametes. The haploids studied in this work were characterized by male sterility or low pollen stainability. As regards the cytological mechanisms underlying the male sterility, they are different in the various haploids. In one clone the male sterility depends on post-meiotic abnormalities and in another clone on desynapsis. In this desynaptic clone only few pollen grains, being 2n, are fertile. Two-n pollen frequency is generally low, except in two haploids. However, 2n pollen is combined with a low level of pollen stainability and, consequently, haploids were not successful as male parents in 4x - 2x crosses. On the contrary, three haploids produced 2n eggs when crossed with tetraploids. The utility of the 2n-egg producing haploids was discussed in relation to sexual polyploidization schemes