Evolution of rDNA in Nicotiana allopolyploids
: a potential link between rDNA homogenization and epigenetics.
Genome constitution visualization and chromosome discrimination from different genomes in allopolyploids
are carried out by GISH practices .
as discussed below in "Polyploidy--DNA
Neopolyploids are documented recent allopolyploids
with chromosome numbers that are multiples of the lowest number presently known for their evolutionary group; whereas, paleopolyploids are assumed to be ancient allopolyploids
that have the lowest known chromosome numbers for their evolutionary group.
Discussing in turn the genomics of hybrids and of polyploids, and mechanisms for novelty in the two, they consider such topics as transcriptome profiling of Drosophila inter-specific hybrids, developments in the study of the genomics and heterosis in hybrid rice, chromosomal and gene expression changes in Brassica allopolyploids
, polyploid species-specific chromosomal polymorphisms in wheat, seed development in interploidy hybrids, and genetic and epigenetic mechanisms for polyploidy and hybridity.
Many polyploid plants including coffee (Coffea arabica), wheat (Triticum durum Desf.), cotton (Gossypium hirsutum L.), and peanut (Arachis hypogaea L.) are allopolyploids
and contain two or more distinct genomes (homoeologous chromosomes) after interspecific hybridization between related diploid species and chromosome doubling.
The genus Mangifera comprises 69 species (BOMPARD, 2009) and based on some chromosome counts and meiotic analyses these are considered ancient allopolyploids
. Chromosomal studies in Mangifera species initiated with Maheshwari (1934) who reported an uncertain number as 2n = 52-58 chromosomes for M.
PLANT SPECIATION IN THE REALM OF ALLOPOLYPLOIDS
: THE CURIOUS CASE OF THE TEMPERATE BAMBOOS.
are a sizable fraction of well-studied crop cases, such as wheat, cotton, maize, sugar cane, coffee, and tobacco.
repens represent auto or allopolyploids
. If allopolyploidy were found, then the putative parental taxa could be determined and the evolutionary origin of polyploid P.
(2001) studied the rate and time of elimination of several low-copy DNA sequences, existing at diploid level, in F1 hybrids and newly formed allopolyploids
of Aegilops and Triticum.
Lande and Schemske (1985) showed that the difference in inbreeding depression between diploids and tetraploids should hold for both autopolyploids and allopolyploids
when mutations are recessive and lethal or sublethal.