Resynthesis of Brassica napus through hybridization between B. juncea and B. carinata

Abstract

First report for the resynthesis of Brassica napus by recombining A and C genome from B. juncea and B. carinata , respectively. Also documents B genome introgressions in resynthesized B. napus. Resynthesis of Brassica napus (AACC) was achieved by hybridizing Brassica juncea (AABB) with Brassica carinata (BBCC). This was facilitated by spontaneous chromosome doubling in the F1 hybrid (ABBC) to yield octaploid (AABBBBCC), elimination of extra B genome chromosomes in the resulting octaploid and in subsequent selfed generations, aided with directed selection for fertile plants having B. napus morphology. Twenty-five plants with varying degrees of resemblance to natural B. napus were identified from 17 A5 progenies and assayed for cytogenetic stability and genetic diversity. Majority of these plants, except six (2n = 38) were hyperploids (2n = 40-56). The six plants with 2n = 38 were designated as derived B. napus types. These showed an expected meiotic configuration of 19II at metaphase-I, with 19-19 distribution at anaphase-I. Genotyping based on A and C genome specific primers confirmed genetic identity of six derived (2n = 38) B. napus plants with natural types whereas genotyping with B genome specific primers indicated introgression of B genome segments. This was also confirmed by genomic in situ hybridization (GISH). Strong signals of B genome probe were detected, proving hitherto unreported genetic exchanges between B and A/C chromosomes. These introgressions possibly occurred en route five generations of selfing. Derived plants yielded fertile hybrids in crosses with natural B. napus var. GSC 6. The selfed derived plants as evaluated in A6 plant to progeny rows were morphologically similar to natural B. napus, and meiotically stable. Agronomic assessment of these progenies revealed variation for key morpho-physiological traits. Of special interest were the progenies with plants having oil content exceeding 47% as against about 39-41% in existing cultivars.

Cytogenetic and Molecular Characterization of B-Genome Introgression Lines ofBrassica napusL.

“…Comparative mapping of different Brassicaceae lineages has illustrated the presence of conserved genome blocks in B. napus (Parkin et al 2005; Schranz et al 2006). Molecular characterization of B. napus , resynthesized through B. juncea × B. carinata hybridizations, had also revealed introgressed B-genome segments (Chatterjee et al 2016) from all the B-chromosomes but more so from B6. More recently, Gupta et al (2016) have reported a sizeable number of C-genome chromosome substitution lines in the progenies of derived B. juncea , suggesting that the substituting C-genome chromosomes were likely to have replaced the B-genome chromosomes.…”

Potential of rutabaga (Brassica napus var. napobrassica) gene pool for use in the breeding of B. napus canola

“…() used B. rapa and B. oleracea to broaden the genetic base of B. napus by crossing a hexaploid (AACCCC) line, generated from B. napus (AACC) and B. oleracea (CC), to B. rapa (AA); the B. napus lines derived from this interspecific cross were found to be genetically distinct from B. napus cultivars, especially for the A genome. Genetically distinct B. napus lines have also been developed from B. juncea × B. carinata (Chatterjee et al., ), B. napus × B. rapa (Attri & Rahman, ) and B. carinata × B. rapa (Zou et al., ) interspecific crosses. However, the approach of broadening the genetic base of B. napus canola through interspecific hybridization is generally associated with several challenges, such as the difficulty of producing the interspecific hybrid plants, sterility in the progeny, and introduction of several undesired traits from the allied species (for review, see Rahman, ).…”

Reconstituting the genome of a young allopolyploid crop, Brassica napus, with its related species

“…To utilize the variation among the different basic genomes and different subgenomes to broaden the genetic diversity of B. napus , many studies have introgressed genomic regions from a single related species and even other genera, such as B. rapa (Qian et al ., ), B. oleracea (Li et al ., ; Quazi, ), Brassica juncea (Roy, ), B. carinata (Navabi et al ., , ), Brassica maurorum (Chrungu et al ., ), Sinapis arvensis (Hu et al ., ) and Isatis indigotica (Kang et al ., ). In addition, substantial efforts have been extended to resynthesize B. napus by combining the genomes from two or more species, such as crossing B. rapa with B. oleracea (Becker et al ., ; Hansen and Earle, ; Nagaharu, ), B. juncea with B. carinata (Chatterjee et al ., ), and B. carinata with B. rapa (Li et al ., , ; Xiao et al ., ).…”