ISHS Acta Horticulturae 706: IV International Symposium on Brassicas and XIV Crucifer Genetics Workshop
RESISTANCE TO A BRASSICA JUNCEA-ATTACKING ISOLATE OF LEPTOSPHAERIA MACULANS IN B. NAPUS-B. JUNCEA LINES |
| Authors: | H. Winter, K. Sterenberg, M.D. Sacristan |
| Keywords: | oilseed rape, blackleg, Phoma lingam, aggressive isolates, pathogenicity group, genomic in situ hybridisation (GISH), fluorescent in situ hybridisation (FISH) |
| Abstract:
Blackleg caused by Leptosphaeria maculans (Phoma lingam) is the most significant disease affecting oilseed rape (Brassica napus) worldwide. Due to the narrow genetic background of current oilseed rape cultivars and limitations for GM crops in many parts of the world the importance of interspecific resistance transfer for plant breeding is expected to increase in the next years. Although wild crucifers are very promising resistance sources and blackleg resistances from these species have been successfully transferred into B. napus, resistance from the Brassica B genome still remains valuable. A test with double inoculation, performed in the greenhouse, was found to be the method of choice for accurate evaluation of plant resistance levels, both at the seedling and adult plant stages. Genomic in situ hybridisation (GISH) is a powerful tool for the detection of alien chromosomes in interspecific hybrids, but for the visualisation of alien introgressions limitations in Brassica and related genera have to be considered. In this study GISH was applied to dihaploid (DH) backcross progenies from interspecific hybrids between B. napus (genome AACC, 2n=38) and B. juncea (AABB, 2n=36) exhibiting resistance to blackleg. Putative recombination lines (2n=38) with oilseed rape karyotype (no B genome GISH signals) were identified. Plants showed adult plant resistance to two aggressive isolates (PG 4), W4 from Germany and M1 from Australia. The latter was known to overcome the Brassica B genome resistance. Adult plant resistance to isolate W4 was found to be inherited by a single dominant gene. In the case of M1 adult plant resistance was detected in several B. napus-B. juncea DH lines, although the parents in the original cross, B. napus ‘Liropa’ and B. juncea, were both susceptible. Crossing experiments revealed that the monogenic inheritance of adult plant resistance to M1 is modified by an additional epistatic gene. | |
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