Homoeologous Chromosome Pairing and Restricted Segregation in the Fern Ceratopteris

Abstract

The segregation of a marker characterized by pale green gametophytes was monitored within an inbreeding study of the polyploid fern Ceratopteris . Although all of the sporophytes showing segregation were derived from the self-fertilization of haploid garnetophytes, a low overall frequency of 2.5% pale gametophytes was observed in the F:rF,; generations. A model based upon a duplicated locus and homoeologous chromosome pairing can explain the segregational behavior within the study. The overall level of homoeologous pairing was determined to be 10'%. Occasionally. green garnetophytes that were presumably heterozygous for the marker contained pale sectors. This behavior may involve mitotic crossing-over between homoeologous chromosomes.

Insights into the evolutionary history and widespread occurrence of antheridiogen systems in ferns

“…As sensitivity towards AGs limits the ability to form bisexual gametophytes, polyploids might be more likely to abandon the use of AGs. That way, each polyploid gametophyte can self‐fertilize and take advantage of their inherent genetic diversity (Hickok, 1978). However, the ratio of responsive diploids and polyploids is nearly identical (Fig.…”

“…In theory, some fern species may gain very little but lose a lot by responding to AGs. For example, neopolyploid species ( sensu Vida, 1976; herein after referred to as polyploid), having more than two sets of chromosomes and therefore the potential to ‘buffer’ against the deleterious effects of gametophytic selfing, may reproduce by self‐fertilization and still retain genetic variation (Klekowski & Baker, 1966; Hickok, 1978). So, polyploids should tend to self‐fertilize more than diploids (Masuyama, 1979; Soltis & Soltis, 2000; Sessa et al ., 2016).…”

Mapping X-Disease Phytoplasma Resistance in Prunus virginiana

“…Cytological determination of the inheritance pattern (the chromosome pairing behavior) for tetraploid chokecherry is difficult due to its small chromosome size. Allotetraploids have similar inheritance as diploids and are easier to achieve accurate genetic mapping vs. autotetraploids; however, many tetraploid species have intermediate inheritance in which some chromosomes have diverged enough to preferentially pair, while others are similar enough to have levels of random pairing during meiosis (Hickok, 1978a , b ; Stift et al, 2008 ; Koning-Boucoiran et al, 2012 ).…”

Inbreeding and homozygosity in the fern, Ceratopteris pteridoides (Hooker) Hieronymus (Parkeriaceae)

“…Individual sporophytes whose gametophytes exhibit differential genetic load may be considered heterozygous and therefore, to have originated by cross-fertilization between two genetically dissimilar gametophytes (intergametophytic mating). Alternatively, they may be homozygous and express interlocus heterozygosity in duplicated loci via homoeologous chromosome pairing; a phenomenon documented in C. thalictroides by Hickok & Klekowski (1974) and Hickok (1978). Sporophytes lacking genetic variability are considered to be homozygous and to have resulted from inbreeding (Klekowksi, 1979).…”