Genetic regulation of meiotic cross-overs between related genomes in brassica napus haploids and hybrids

Abstract

Although the genetic regulationofrecombination inallopolyploid species playsa pivotal rolein evolution and plant breeding, it has received little recent attention, except in wheat (Triticum aestivum). PrBn is the main locus that determines the number of nonhomologous associations during meiosis of microspore cultured Brassica napus haploids (AC; 19 chromosomes). In this study, we examined the role played by PrBn in recombination. We generated two haploid 3 euploid populations using two B. napus haploids with differing PrBn (and interacting genes) activity. We analyzed molecular marker transmission in these two populations to compare genetic changes, which have arisen during meiosis. We found that cross-over number in these two genotypes was significantly different but that cross-overs between nonhomologous chromosomes showed roughly the same distribution pattern. We then examined genetic recombination along a pair of A chromosomes during meiosis of B. rapa 3 B. napus AAC and AACC hybrids that were produced with the same twoB. napus genotypes.Weobserved significant genotypic variation in cross-over rates between the two AAC hybrids but no difference between the two AACC hybrids. Overall, our results show that PrBn changes the rateofrecombination between nonhomologous chromosomes during meiosisofB.napus haploids and also affects homologous recombination with an effect that depends on plant karyotype. © 2009 American Society of Plant Biologists.