H WINTER, A DIESTEL and MD SACRISTÁN

Institute of Applied Genetics, Freie Universität Berlin, Albrecht-Thaer-Weg 6, 14195 Berlin, Germany

Background and objectives
Wild crucifers are potential sources of resistance to important fungal diseases of oilseed rape (Brassica napus) such as blackleg caused by Leptosphaeria maculans and blackspot (Alternaria spp. e.g. A. brassicicola). In long-term backcross programmes B. juncea [1], B. elongata and Sinapis arvensis [2] were used for interspecific and intergeneric transfer of resistance to one or both pathogens into B. napus.

Materials and methods

The different backcross progenies were analysed according to resistance behavior to the pathogens using various inoculation methods. They were examined cytologically and characterized by isozyme, erucic acid and DNA patterns.

Results and conclusions
A variety of B. napus-B. juncea and B. napus-S. arvensis recombinant lines showed a high seedling and adult plant resistance to L. maculans with the normal B. napus chromosome number (2n=38) and evidence for the incorporation of genetic material of the resistant parent. Since the isozyme systems tested (SDH, EST, PGM, 6PGD, GPI, ACO and ADH) revealed to be no suitable markers for resistance detection (at least in the B. juncea derived material), studies on the correlation of the resistance traits with other features are now especially focused on the DNA level and still in progress. Further work will be concentrated on the localization of the introgressions using GISH and DNA markers.

In contrast to this, the plants of the first backcross generation of B. napus and B. elongata almost completely lost the increased level of resistance to A. brassicicola but showed the high adult plant L. maculans resistance of B. elongata.

In an extent not exceeding 5% of the plants of a line dihaploids obtained from B. napus-B. juncea backcross lines showed characteristic exceptions from the line's regular behaviour concerning morphology, flowering behaviour, chromosome numbers and isozyme patterns. These phenomena are probably caused by meiotic pairing irregularities due to the multitude of homoeologies within and among the three Brassica genomes.

References
1. Sacristán MD, Gerdemann M, 1986. Plant Breeding 97, 304-314.
2. Plümper B, 1995. PhD thesis, Freie Universität Berlin.