TETRAD ANALYSIS OF ACID-PHOSPHATASE, SOLUBLE-PROTEIN PATTERNS, AND MATING-TYPE IN LEPTOSPHAERIA-MACULANS

We investigated the utility of mating type, soluble protein profiles obtained after isoelectric focusing, and acid phosphatase (ACP) patterns as genetic markers for the blackleg fungus, Leptosphaeria maculans. Fertile matings were obtained in vitro by pairing single-ascospore isolates. A method for dissecting asci and recovering the eight component ascospores was developed that allowed tetrad analysis. Protein electrophoresis revealed limited polymorphism among the 73 single-ascospore field isolates. Only one isolate (H5) displayed a different soluble protein profile (SPP), termed SPP-, characterized by one missing band and one additional band. We found three ACP patterns in our collection. Protein profiles and ACP patterns were mitotically and meiotically stable. A 4:4 segregation ratio in asci was obtained for mating type, SPP, and ACP patterns, suggesting that each marker was controlled by a single gene. Mating type and ACP genes seemed to be independent. The reliability of the crossing protocol and the Mendelian segregation of the markers following in vitro meiosis mean that this fungus is now amenable to genetic analysis of pathogenicity.