Genetics of the ergot fungus Claviceps purpurea

Abstract

With the purpose of improving alkaloid production in Claviceps purpurea, concerted breeding studies were conducted in order to investigate the exchange of genetic material by meiotic recombination. 1) From two homokaryotic strains differing in the amount of ergocristin produced, 52 biochemical variants were obtained including both auxotrophs and fungicide resistants, 38 of which showed virulence. 2) After host passage, sclerotia formation and ascospore production, 9 stable mutants were obtained (1 auxotrophic and 8 resistant). 3) Several cross infections between the mutant auxotrophic for lysine and different resistant mutants were established and the offspring of one cross was evaluated in detail for both segregation of the marker genes and quantitation of alkaloid production. 4) The marker genes segregated in a Mendelian pattern, as was expected for a two factor cross: 50% parental types and 50% recombination types. This shows that both marker genes are unlinked. 5) Independent of the segregation pattern of the marker genes a "segregation" of quantitative alkaloid production was found. All recombinant strains did not only exceed the level of the low producing parent but some of them showed a higher alkaloid yield than the parent with the higher production rate. The general implication of these data is twofold: under controlled conditions it is possible to perform meiotic recombination with a self-fertile parasitic fungus and it is possible to use this technique for strain improvement.