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Stabilization of Resistance to Leptosphaeria maculans in Brassica napus--B. juncea Recombinant Lines and Its Introgression into Spring-Type Brassica napus

August 2008 , Volume 92 , Number  8
Pages  1,208 - 1,214

A.-M. Chèvre, INRA, UMR118, F-35000 Rennes, France; H. Brun, INRA, UMR1099, F-35000 Rennes, France; F. Eber, J.-C. Letanneur, and P. Vallee, INRA, UMR118, F-35000 Rennes, France; M. Ermel and I. Glais, INRA, UMR1099, F-35000 Rennes, France; Hua Li, School of Plant Biology, The University of Western Australia, Crawley, W.A. 6009, Australia; K. Sivasithamparam, School of Earth and Geographical Sciences, The University of Western Australia, Crawley, W.A. 6009, Australia; and M. J. Barbetti, School of Plant Biology, The University of Western Australia, Crawley, W.A. 6009, Australia and Department of Agriculture and Food Western Australia, Baron-Hay Court, South Perth, W.A. 6151, Australia



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Accepted for publication 21 April 2008.
ABSTRACT

The value of Katanning Early Maturing (KEM) breeding lines from Western Australia, derived from Brassica napus × B. juncea crosses, was assessed as a source of germplasm for resistance to blackleg disease (caused by Leptosphaeria maculans) in spring-type oilseed rape cultivars. The stability of blackleg resistance in these KEM lines was related to key cytological characteristics to determine why there are poor levels of introgression of this resistance into progeny. Promising recombinant KEM lines were crossed with the spring-type B. napus cv. Dunkeld, which has useful polygenic resistance to blackleg, and screened for resistance. The lines were analyzed cytologically for pairing of bivalents in each generation to aid in the selection of stable recombinant lines. KEM recombinant lines showing regular meiotic behavior and a high level of blackleg resistance were obtained for the first time. We also showed that the stable introgression of the B. juncea resistance from the KEM lines into a ‘Dunkeld’ background was possible. Inoculation of selfing and backcross populations with isolates of L. maculans having different AvrLm genes indicated that the B. juncea resistance gene, Rlm6, had been introgressed into a B. napus spring-type cultivar carrying polygenic resistance. The combination of both resistances would enhance the overall effectiveness of resistance against L. maculans. This is clearly needed in Australia and France where cultivars relying upon single dominant gene-based resistance for their effectiveness have proved not durable.


Additional keywords:blackleg, breeding, canola, oilseed rape, phoma

© 2008 The American Phytopathological Society