Cytological analysis of the Phalaris arundinacea (L.) x Phalaris aquatica (L.) amphidiploid

The amphidiploid of the hybrid Phalaris arundinacea (L.) x Phalaris aquatica (L.), 2n = 8x = 56 chromosomes, is a high perennial grass with scarce seed production. Using free pollination progeny, we studied the mitosis in root meristems, the meiosis in pollen mother cells, the meiotic index, pollen viability and seed set production. The average of somatic chromosomes was 48,94 2,20, with a range of variation between 41 and 55 chromosomes. In meiosis, the bivalent average was 22,01 2,93, with a wide variation range, frequent univalents and occasional multivalents. Only four cells had 2n = 5 6; moreover, only one had 28 II. Both cellular divisions allowed to verify high aneuploidy. Asymmetric divisions, laggards and chromosomes bridges were observed in anaphase I. The Meiotic Index varied from 35 to 65% and stainable pollen had very high variation among individuals. Cytological instability, aneuploid gametes and loss of chromosomes contribute to explain the low fertility of the amphidiploid. Polyploid nature and the genome relationships are discussed.