Meiotic chromosome organization and segregation in F1 intergeneric hybrid between Chrysanthemum horaimontanum and Nipponanthemum nipponicum by GISH identification

Abstract

The maternal Chrysanthemum horaimontanum (2n=18) and the paternal Nipponanthemum nipponicum (2n=18) were artificially crossed and produced F1 hybrid plants. GISH was applied on meiotic chromosomes in pollen mother cells (PMCs) of the F1 hybrid to study chromosome organization and segregation of the two parents. Uni- Bi- and multivalents were observed during diakinasis showed only single terminal chiasmata. Multi-valents were observed during meiosis-I and showed nonhomologous pairing occurred between homoeologous chromosomes among the same haploid chromosome set and between chromosomes of the two parents. The most common meiotic abnormalities were those related to the irregular segregation of univalent chromosomes, characterized by laggards, fragments and multiple bridges in anaphase-telophase I and telophase II. In general, these chromosomes gave rise to micronuclei during telophase that remained until the second meiosis. GISH displayed that all chromosomal bridges were related to N. nipponicum genome. Tetrads showed different sizes of nuclei and elimination of one of the parental genome from others. One of the very interesting phenomenon of parental genome separation and spatial organization that was detected for the first time in the pollen grains of the intergeneric F1 hybrid between C. horaimontanum and that of N. nipponicum the two genomes were differentially stained and fluoresced as distinct domains of two different colors following GISH.