Cytogenetic studies on meiotic chromosome behaviors in sterile Oriental x Trumpet lily.

In order to determine the reasons for pollen sterility in lily hybrids, four diploid sterile Oriental x Trumpet (OT) lily cultivars ('Nymph', 'Gluhwein', 'Yelloween', and 'Shocking') were used to investigate the meiotic chromosome behaviors in pollen mother cells (PMCs), using genomic in situ hybridization and conventional cytological methods. At metaphase I, chromosome associations were quite variable, not only among different genotypes but also in different PMCs of the same genotype. In addition to bivalents, a certain amount of univalent, trivalents, and quadrivalents were observed in all of the investigated genotypes. In addition, ring octavalents and ring hexavalents were observed in 'Nymph'. Even dodecavalents were observed in 'Nymph'. These abnormal chromosome associations at metaphase I implied the occurrence of chromosome interchanges (translocation) in these intersectional hybrids. At anaphase-telophase, a large number of laggard chromosomes and different kinds of chromosome bridge configurations were observed. At the tetrad stage, micronuclei and polyads were also found in many PMCs. All of these abnormal chromosome behaviors in PMCs were responsible for the pollen sterility in lily hybrids.