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Seed colour loci, homoeology and linkage groups of the C genome chromosomes revealed in Brassica rapa–B. oleracea monosomic alien addition lines

Heneen, Waheeb K., Geleta, Mulatu, Brismar, Kerstin, Xiong, Zhiyong, Pires, J. Chris, Hasterok, Robert, Stoute, Andrew I., Scott, Roderick J., King, Graham J., Kurup, Smita
Annals of botany 2012 v.109 no.7 pp. 1227-1242
Brassica napus var. napus, Brassica rapa, chromosome addition, chromosome mapping, chromosome number, color, cotyledons, cytogenetic analysis, flowers, fluorescence in situ hybridization, genetic markers, leaves, linkage groups, livestock feeds, loci, major genes, marker-assisted selection, microsatellite repeats, protein content, seeds
BACKGROUND AND AIMS: Brassica rapa and B. oleracea are the progenitors of oilseed rape B. napus. The addition of each chromosome of B. oleracea to the chromosome complement of B. rapa results in a series of monosomic alien addition lines (MAALs). Analysis of MAALs determines which B. oleracea chromosomes carry genes controlling specific phenotypic traits, such as seed colour. Yellow-seeded oilseed rape is a desirable breeding goal both for food and livestock feed end-uses that relate to oil, protein and fibre contents. The aims of this study included developing a missing MAAL to complement an available series, for studies on seed colour control, chromosome homoeology and assignment of linkage groups to B. oleracea chromosomes. METHODS: A new batch of B. rapa–B. oleracea aneuploids was produced to generate the missing MAAL. Seed colour and other plant morphological features relevant to differentiation of MAALs were recorded. For chromosome characterization, Snow's carmine, fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH) were used. KEY RESULTS: The final MAAL was developed. Morphological traits that differentiated the MAALs comprised cotyledon number, leaf morphology, flower colour and seed colour. Seed colour was controlled by major genes on two B. oleracea chromosomes and minor genes on five other chromosomes of this species. Homoeologous pairing was largely between chromosomes with similar centromeric positions. FISH, GISH and a parallel microsatellite marker analysis defined the chromosomes in terms of their linkage groups. CONCLUSIONS: A complete set of MAALs is now available for genetic, genomic, evolutionary and breeding perspectives. Defining chromosomes that carry specific genes, physical localization of DNA markers and access to established genetic linkage maps contribute to the integration of these approaches, manifested in the confirmed correspondence of linkage groups with specific chromosomes. Applications include marker-assisted selection and breeding for yellow seeds.