STERILITY IN POTATOES

Abstract

Microspore tetrads were rarely formed in three male-sterile potato varieties studied. Dyads and triads were much more common. The failure of the second meiotic divisions appeared to be the main reason for the lack of tetrads. Many of the microspores aborted without enlarging, some did grow, however, and round off. In presumably mature anthers from open flowers, microspores were very variable in size and in the appearance of the nucleus and cytoplasm. Anther pores usually failed to open. The pollen-fertile varieties formed microspores that were almost entirely in tetrads. Mature anthers had roomy locules, open anther pores, and large numbers of uniform, sound-appearing pollen grains. They contained also some empty grains. About one-half the grains from one pollen-fertile line were empty. Abscission of buds and flowers is an important factor contributing to sterility or at least unfruitfulness in many potato varieties, including the three male-sterile ones reported in this paper. Following pollination with sound pollen, a few seeds have been obtained, though with some difficulty, from each of the male-sterile lines. Premature flower abscission rather than female sterility appears to be the main bar to seed production when sound pollen is applied.