Cytogenetic and Molecular Characterization of B-Genome Introgression Lines of Brassica napus L.

Brassica napus introgression lines (ILs), having B-genome segments from B. carinata, were assessed genetically for extent of introgression and phenotypically for siliqua shatter resistance. Introgression lines had 7-9 % higher DNA content, were meiotically stable and had almost normal pollen fertility/seed set. Segment introgressions were confirmed by fl-GISH, SSR analyses and SNP studies. Genotyping with 48 B-genome specific SSRs detected substitutions from B3, B4, B6 and B7 chromosomes on 39 of the 69 introgression lines whereas SNP genotyping detected a total of 23 B-segments (≥ 3Mbp) from B4, B6, B7 introgressed into 10 of the 19 (C1, C2, C3, C5, C6, C8, C9, A3, A9, A10) chromosomes in 17 introgression lines. The size of substitutions varied from 3.0 Mbp on chromosome A9 (IL59) to 42.44 Mbp on chromosome C2 (IL54), ranging from 7% to 83% of the recipient chromosome. Average siliqua strength in introgression lines was observed to be higher than that of B. napus parents (2.2 mJ to 6.0 mJ vs. 1.9 mJ to 4.0 mJ) while siliqua strength in some of the lines was almost equal to that of the donor parent B. carinata (6.0 mJ vs.7.2 mJ). These introgression lines, with large chunks of substituted B-genome, can prove to be a useful pre-breeding resource for germplasm enhancement in B. napus, especially for siliqua shatter resistance.

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