Analysis of B-Genome Chromosome Introgression in Interspecific Hybrids of Brassica napus × B. carinata

Abstract

Brassica carinata, an allotetraploid with B and C genomes, has a number of traits that would be valuable to introgress into B. napus. Interspecific hybrids were created between B. carinata (BBCC) and B. napus (AACC), using an advanced backcross approach to identify and introgress traits of agronomic interest from the B. carinata genome and to study the genetic changes that occur during the introgression process. We mapped the B and C genomes of B. carinata with SSR markers and observed their introgression into B. napus through a number of backcross generations, focusing on a BC 3 and BC 3 S 1 sibling family. There was close colinearity between the C genomes of B. carinata and B. napus and we provide evidence that B. carinata C chromosomes pair and recombine normally with those of B. napus, suggesting that similar to other Brassica allotetraploids no major chromosomal rearrangements have taken place since the formation of B. carinata. There was no evidence of introgression of the B chromosomes into the A or C chromosomes of B. napus ; instead they were inherited as whole linkage groups with the occasional loss of terminal segments and several of the B-genome chromosomes were retained across generations. Several BC 3 S 1 families were analyzed using SSR markers, genomic in situ hybridization (GISH) assays, and chromosome counts to study the inheritance of the B-genome chromosome(s) and their association with morphological traits. Our work provides an analysis of the behavior of chromosomes in an interspecific cross and reinforces the challenges of introgressing novel traits into crop plants.

B chromosome in Plantago lagopus Linnaeus, 1753 shows preferential transmission and accumulation through unusual processes

“…Similarly, the inheritance of the B chromosome at the genome level has been analyzed using the SSR markers in Brassica sp. Linnaeus, 1753 (Navabi et al 2011). SSAP and SSR used in the present case have also shown the same pattern in case of mother and the progeny plant having higher chromosome number.…”

Characterization of interploid hybrids from crosses between Brassica juncea and B. oleracea and the production of yellow-seeded B. napus

“…The present observations are inconsistent with their findings, which may be due to structural differences between subgenomes originating from different species (such as B j and B c , A j and A n ). Given that homologous chromosomes can pair well even when the mating partners are of different species (Li et al 2004;Mason et al 2010;Navabi et al 2011), the occurrence of two and four additional bivalents more than was expected in the AABCC and ABCC hybrids may be due to autosyndesis in the B-genome and allosyndesis between the B and A/C genomes. This speculation is strongly supported by our results of GISH analysis.…”

“…However, yellow seeds were instead produced most abundantly in approach 3, followed by approaches 2 and then 1. Given that the frequency of allosyndetic B-genome chromosomes was significantly higher in ABCC than in AABCC plants, there may be more opportunity for recombination to take place between the B and A/C component genomes in ABCC than in AABCC plants, as also evident from the report by Navabi et al (2011), and the transfer of yellow seed color genes from the B to A genome may partly account for the more rapid occurrence of yellow seeds in approaches 2 and 3. One of the most important points to consider in generating yellow-seeded B. napus through interspecific hybridization is the genotype of the parents.…”

“…Homologies between the A, B and C genomes were initially revealed by conventional cytogenetic analyses in digenomic diploids, e.g., AC, BC and AB, digenomic triploids such as AAB, BBC and BCC, and trigenomic haploid ABC, all obtained from interspecific crosses in Brassica (U 1935; Attia and Röbbelen 1986;Attia et al 1987;Busso et al 1987;Choudhary et al 2002). In recent years, researchers have shown increasing interest in Brassica trigenomic hybrids, especially trigenomic tetraploids, for cytogenetic analysis and assessing gene introgression utilizing modern genomic in situ hybridization (GISH) and molecular marker techniques (Ge and Li 2007;Nelson et al 2009;Mason et al 2010Mason et al , 2011Navabi et al 2011). A small number of studies has been published on Brassica trigenomic hybrids, where GISH has been used to study autosyndesis within B-genome and allosyndetic pairing between B and A/C genome chromosomes, e.g., trigenomic haploids (ABC) derived from B. carinata 9 B. rapa (A r B c C c ), natural B. napus 9 B. nigra (A n B n C n ), synthetic B. napus 9 B. nigra (A r B n C o ), trigenomic tetraploids derived from B. juncea 9 B. napus (A j A n B j C n ), B. napus 9 B. carinata (A n B c C c C n ), B. juncea 9 B. carinata (A j B j B c C c ), and pentaploid hybrids (A n A r B c C c C n ) derived from hybridizations between B. carinata, B. rapa and B. napus (Li et al 2004(Li et al , 2005Ge and Li 2007;Mason et al 2010).…”

Cytogenetic and cytometric analyses in artificial intercytotypic hybrids of the emergent orchid model species Erycina pusilla

“…GISH is an effective method to determine parental genome constitution and is used widely to identify interspecific and intergeneric hybrids of various species (Ji et al 2004;Lee et al 2011;Lin et al 2005;Nakazawa et al 2011;Navabi et al 2011;Yao et al 2010). Furthermore, the use of blocking DNA can provide better differentiation of parental genome homology (Anamthawat-Jónsson et al 1990;Tang et al 2010).…”