Interaction of Laterispora brevirama and the mycoparasites Sporidesmium sclerotivorum and Teratosperma oligocladum

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Abstract
Laterispora brevirama, a fungus found in association with the Sclerotinia mycoparasites Sporidesmium sclerotivorum and Teratosperma oligocladum, was markedly similar in morphology to the other two fungi yet differed in its parasitic activity. Laterispora brevirama colonized and proliferated on sclerotia of Sclerotinia minor which had been infected first by Sporidesmium sclerotivorum or T. oligocladum but did not do so in the absence of these specific mycoparasites. Macroconidia of L. brevirama germinated in soil in response to sclerotia infected by Sporidesmium sclerotivorum, and to hyphae of Sporidesmium sclerotivorum. Aqueous extracts of hyphal mats of Sporidesmium sclerotivorum stimulated maximal germination of macroconidia in vitro, although other nutrients also supported germination to a lesser extent. In culture and in its parasitic phase in soil, L. brevirama formed specialized contact cells on the hyphae of Sporidesmium sclerotivorum and T. oligocladum, but never appeared to invade hyphae. Laterispora brevirama added to soil at 1000 macroconidia/g, along with Sporidesmium sclerotivorum at the same concentration, did not influence the rate of infection and destruction of sclerotia of Sclerotinia minor by Sporidesmium sclerotivorum. The resulting numbers of new macroconidia of Sporidesmium sclerotivorum formed in the soil from energy derived from the infected sclerotia, however, were reduced by the presence of L. brevirama. Laterispora brevirama is either a direct parasite of Sporidesmium sclerotivorum and T. oligocladum or is a secondary parasite of Sclerotinia spp. that is active only in association with either of the two primary mycoparasites.