Meiotic nuclear restitution mechanisms in a triploid lily

Chromosome number and pollen stainability were evaluated in Lilium L. species (L. formosanum, L. miryophillum, L. regale), and in cultivars coming from Asiatic (Elite, Pollyanna, Vivaldi) and Oriental hybrid group (Cascade, Casablanca, Galdei). All the genotypes are diploid (2n=2x=24) except cv. Elite which results triploid (2n=3x=36). The pollen stainability ranged from 90 to 98% among diploids and from 80 to 90% in the triploid which exhibited pollen grains of different size, as well. A detailed analysis of microsporogenesis was carried out in the triploid cultivar. The chromosome associations at diakinesis were either trivalents or bivalents and univalents. Anaphases I and II exhibited lagging chromosomes and unequal distribution of chromosomes at the two poles. Single and double bridges plus acentric fragments formed possibly due to a paracentric inversion. Meiotic nuclear restitution mechanisms occurred following the failure of the reductional wall or, alternatively, of the equational wall. The analysis of sporads evidenced tetrads as well as dyads, triads and rare monads and poliads.