Interchanges in popcorn (Zea mays L.) involving the nucleolus organizer chromosome
Maria Suely Pagliarini, Gléia Laverde Ricci, Neide da Silva, and Carlos Alberto Scapim
The analysis of microsporogenesis in endogamous plants of popcorn (S5 to S7) showed several and distinct interchanges which involve the nucleolus organizer (chromosome 6). The detection of cells with interchanges was facilitated by the presence of two nucleoli of different sizes in contrast to normal ones with a single big nucleolus. Interchange points do not always seem to be at the same place. Whereas in several situations the interchange point clearly involved more than two chromosome pairs, a simple terminal translocation seemed to occur in others. During diplotene, a cross-shaped configuration connected with the nucleoli was observed in some meiocytes. Some heteromorphic bivalents were found during diakinesis, after which meiosis progressed normally to the end and gave rise to apparently normal tetrads with one normal nucleolus in each microspore. Tests of pollen viability in fixed pollen grains showed 100% stainability in normal and in affected plants. This is the first report on chromosome interchanges in popcorn.