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Resynthesized B. Napus (resynthesized + b._napu)

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Life Sciences	100%

Selected Abstracts

Homoeologous recombination in allopolyploids: the polyploid ratchet

NEW PHYTOLOGIST, Issue 1 2010
Robert T. Gaeta
Summary Polyploidization and recombination are two important processes driving evolution through the building and reshaping of genomes. Allopolyploids arise from hybridization and chromosome doubling among distinct, yet related species. Polyploids may display novel variation relative to their progenitors, and the sources of this variation lie not only in the acquisition of extra gene dosages, but also in the genomic changes that occur after divergent genomes unite. Genomic changes (deletions, duplications, and translocations) have been detected in both recently formed natural polyploids and resynthesized polyploids. In resynthesized Brassica napus allopolyploids, there is evidence that many genetic changes are the consequence of homoeologous recombination. Homoeologous recombination can generate novel gene combinations and phenotypes, but may also destabilize the karyotype and lead to aberrant meiotic behavior and reduced fertility. Thus, natural selection plays a role in the establishment and maintenance of fertile natural allopolyploids that have stabilized chromosome inheritance and a few advantageous chromosomal rearrangements. We discuss the evidence for genome rearrangements that result from homoeologous recombination in resynthesized B. napus and how these observations may inform phenomena such as chromosome replacement, aneuploidy, non-reciprocal translocations and gene conversion seen in other polyploids. [source]

Resynthesis of Brassica napus L. for self-incompatibility: self-incompatibility reaction, inheritance and breeding potential

PLANT BREEDING, Issue 1 2005
Article first published online: 28 JUN 200, M. H. Rahman
Self-incompatibility (SI) in Brassica has been considered as a pollination control mechanism for commercial hybrid seed production, and so far has been extensively used in vegetable types of Brassicas. Oilseed rape Brassica napus (AACC) is naturally self-compatible in contrast to its parental species that are generally self-incompatible. Introduction of S-alleles from its parental species into oilseed rape is therefore needed to use this pollination control mechanism in commercial hybrid seed production. Self-incompatible lines of B. napus, carrying SI alleles in both A and C genomes, were resynthesized from self-incompatible B. oleracea var. italica (CC) cv.,Green Duke' and self-incompatible B. rapa ssp. oleifera (AA) cv. ,Horizon', ,Colt' and ,AC Parkland'. All resynthesized B. napus lines exhibited strong dominant SI phenotype. Reciprocal cross-compatibility was found between some of these self-incompatible lines. The inheritance of S-alleles in these resynthesized B. napus was digenic confirming that each of the parental genomes contributed one S-locus in the resynthesized B. napus lines. However, the presence of two S-loci in the two genomes was found not to be essential for imparting a strong SI phenotype. Possible use of these dominant self-incompatible resynthesized B. napus lines in hybrid breeding is discussed. [source]

Effect of genome composition and cytoplasm on petal colour in resynthesized amphidiploids and sesquidiploids derived from crosses between Brassica rapa and Brassica oleracea

PLANT BREEDING, Issue 4 2002
B. Zhang
Abstract The effect of genome composition and cytoplasm on petal colour was studied in Brassica. Three accessions of yellow-petalled B. rapa (2n= 20, AA) were crossed with a white-petalled B. oleracea var. alboglabra (2n= 18, CC) and with three cream-yellow-petalled B. oleracea var. gongylodes (2n= 18, CC) to produce resynthesized B. napus (2n= 38, AACC or CCAA) and sesquidiploids (2n= 29, AAC or CAA). Petal colour was measured with a Hunter automatic colour difference meter. The results revealed that petal colour in Brassica is controlled by nuclear genes and by cytoplasmic factors. Additive and epistatic gene effects were involved in the action of nuclear genes. When crosses were made between yellow-petalled B. rapa and white-petalled B. oleracea var. alboglabra, significant additive, epistatic and cytoplasmic effects were found. White petal colour was partially epistatic over yellow petal colour. When crosses were made between yellow-petalled B. rapa and cream-yellow-petalled B. oleracea var. gongylodes, only epistatic effects were detected. Yellow petal colour was epistatic over cream-yellow. [source]

Production of yellow-seeded Brassica napus through interspecific crosses

PLANT BREEDING, Issue 6 2001
M. H. Rahman
Abstract Yellow-seeded Brassica napus was developed from interspecific crosses between yellow-seeded Brassica rapa var.,yellow sarson' (AA), black-seeded Brassica alboglabra (CC), yellow-seeded Brassica carinata (Bbcc) and black-seeded B. napus (AACC). Three different interspecific crossing approaches were undertaken. Approaches 1 and 2 were designed directly to develop yellow-seeded B. napus while approach 3 was designed to produce a yellow-seeded CC genome species. Approaches 1 and 2 differed in the steps taken after trigenomic interspecific hybrids (ABC) were generated from B. carinata×B. rapa crosses. The aim of approach 1 was to transfer the yellow seed colour genes from the A to the C genome as an intermediate step in developing yellow-seeded B. napus. For this purpose, the ABC hybrids were crossed with black-seeded B. napus and the three-way interspecific hybrids were self-pollinated for a number of generations. The F7 generation resulted in the yellowish-brown-seeded B. napus line, No. 06. Crossing this line with the B. napus line No. 01, resynthesized from a black-seeded B. alboglabra x B. rapa var.,yellow sarson' cross (containing the yellow seed colour genes in its AA genome), yielded yellow-seeded B. napus. This result indicated that the yellow seed colour genes were transferred from the A to the C genome in the yellowish-brown seed colour line No. 06. In approach 2, trigenomic diploids (AABBCC) were generated from the above-mentioned trigenomic haploids (ABC). The seed colour of the trigenomic diploid was brown, in contrast to the yellow seed colour of the parental species. Trigenomic diploids were crossed with the resynthesized B. napus line No. 01 to eliminate the B genome chromosomes, and to develop yellow-seeded B. napus with the AA genome of ,yellow sarson' and the CC genome of B. carinata with yellow seed colour genes. This interspecific cross failed to generate any yellow-seeded B. napus. Approach 3 was to develop yellow-seeded CC genome species from B. alboglabra×B. carinata crosses. It was possible to obtain a yellowish-brown seeded B. alboglabra, but crossing this B. alboglabra with B. rapa var.,yellow sarson' failed to produce yellow seed in the resynthesized B. napus. The results of approaches 2 and 3 demonstrated that yellow-seeded B. napus cannot be developed by combining the yellow seed colour genes of the CC genome of yellow-seeded B. carinata and the AA genome of ,yellow sarson'. [source]