Manipulation of division symmetry and developmental fate in cultures of potato microspores

The effect of media composition on microspore culture was investigated in o ne tetraploid and two diploid potatoes. The viability of microspores isolat ed from 4.5 to 5 mm buds was in the range of 33 to 52%. In media for anther culture, microspores showed no further development and lost viability with in 2 days. In M1 medium containing mineral components, sucrose, uridine, cy tidine, myo-inositol, glutamine and lactalbumin hydrolysate, 18 to 37% of m icrospores underwent mitosis within 14 days. Up to 95% of the divisions wer e symmetric and produced equal nuclei. Some symmetrically divided microspor es eventually produced structures with 3 to 10 nuclei. The proportion of th e total microspore population producing multinuclear structures reached 9% in diploid clones responsive to anther culture and 1 to 2% in recalcitrant cv. Borka. Symmetric mitoses in M1 medium were induced in the presence of g lutamine and lactalbumin hydrolysate. Nucleosides and myo-inositol had no e ffect on microspore division. In the absence of all organic components exce pt sucrose, most mitoses were asymmetric, formation of multinuclear structu res was reduced and most pollen accumulated starch indicative of gametophyt ic fate. In complete M1 medium, starch accumulation was suppressed. Suppres sion also occurred in asymmetrically divided microspores, indicating a dire ct inhibition of pollen development independent of the mode of microspore d ivision. This inhibitory effect of M1 medium might present a stress which t riggers the induction of symmetric microspore division and subsequent forma tion of multinuclear structures.