Genetic analysis of the blackleg fungus Leptosphaeria maculans.

A genetic and physical map has been developed for Leptosphaeria maculans, which causes blackleg of oilseed Brassicas. The genetic map was constructed from 58 F1 progeny and comprises 154 Amplified Fragment Length Polymorphic (AFLP) markers, 3 Random Amplified Polymorphic DNA (RAPD) markers, a gene encoding a retinal-binding protein, the mating type locus and a host specificity locus. Pulsed field gel electrophoresis experiments showed that the parental isolates each had 16 chromosomes and a genome size of about 33.5 Mb. Many markers bound to every chromosome indicating that L. maculans has a high level of dispersed repetitive DNA sequences. This fungus displays chromosomal length polymorphisms, but in the cross examined, the linkage and physical maps were congruent and there was no evidence of translocations. The host specificity locus is flanked by two AFLP markers 19 and 27 cM distant and is located on a chromosome sized 1.85 Mb in the virulent parent. The mating type locus is on a chromosome sized 2.6 Mb and co-incident on an AFLP marker amplified from the virulent parent.