Cytology of unreduced microspore formation in dihaploids of the potato

In two Solanum tuberosum dihaploids and one S. tuberosum-dihaploid S. phureja hybrid, the mechanism of unreduced microspore formation has been studied. Cytological observations on microsporogenesis suggested that the formation of unreduced microspore may be caused by; (i) fused spindles at M II, (ii) parallel spindles at M II, (iii) premature cytokinesis at prophase II, (iv) non-disjunction at A I and (v) nuclear fusion at T TI. It has been found that dyads with two unreduced microspores and ttriads with one unreduced and two reduced microspores are formed, depelding on the type of mechanism involved.