allopolyploidy
Cifuentesa M, Eberb F, Lucasb M-O, Lodeb M, Chèvreb A-M & Jenczewskia E 2010 Repeated polyploidy drove different levels of crossover suppression between homoeologous chromosomes in Brassica napus allohaploids. Plant Cell 22:2265-2276.
- polyploid species usually have multiple origins
- one intriguing, yet largely underexplored, question is whether different mechanisms suppressing crossovers between homoeologs may coexist within the same polyphyletic species
- we first analyzed the meiotic behavior of 363 allohaploids produced from 29 accessions
- two main clear-cut meiotic phenotypes were observed
- only two plastid haplotypes were found
- these correlated with the dichotomy of meiotic phenotypes
- segregation of two alleles at PrBn could adequately explain a large part of the variation in meiotic behavior found among B. napus allohaploids
- little is known about natural variation in recombination rates within species
- the existence of natural variability for CO regulation is particularly relevant in polyploid species
- considering that most have multiple origins and that genetic systems restricting CO to homologs are required
- recurrent polyploidy is known to be the rule rather than an exception
- most nascent polyploid species should be considered as a set of genetically variable lineages produced from distinct diploid progenitors that can subsequently produce novel genotypes through hybridization and recombination
- these new polyploid species are not completely isolated from their diploid progenitors
- the variability present in the diploids can continue to be incorporated into the polyploids
- this may subsequently lead to different genetic/epigenetic changes, which can further expand the range of phenotypes
- little is known about the consequences of recurrent polyploidy on the establishment of polyploid species
