Morphology of A New Species of Aulacostroma (Hemisphaeriales)

Abstract

SUMMARYAulacostroma parvispora (Parmulariaceae) is an epiphyllous parasite on the evergreen tree Olax wightiana var. nigrescens in tropical rain forests of Mysore State, India. Yellowish spots appearing on new leaves in April result from infection by a hyaline, intracuticular mycelium. Hyphae emerging through the cuticle expand into globose cells on the surface. From these centers restricted brown hyphae radiate outward and produce short, erect branches which form a loose black felt over the leaf spot. Hemispherical pycnidia containing hyaline microconidia and orbicular, radiately-structured shields of the young ascocarps appear beneath the surface mycelium in June. The expanding shields fuse into a smaller number of hysterioid ascocarps. Within the hyaline stroma beneath the thick, dark shield paraphyses and asci appear in August and develop into a continuous, flat hymenium in a single elongated locule. The hymenium is exposed by a longitudinal slit in the shield as the bitunicate asci begin to mature in November. The elongated, dimidiate-scutate ascocarps are laterally confluent into an almost continuous crust. They remain connected at numerous points with the intracuticular mycelium above the living host cells. Hyaline, 1-septate ascospores are present throughout the dry season of December-February and for more than a month after the host puts on a new flush of leaves in March. Cultures from forcibly discharged ascospores produce slow-growing, black colonies on agar media. Among Loculoascomycetes paraphyses have now been reported in the Phillipsiellaceae and Patellariaceae, which are appended to the Hysteriales, and in the Parmulariaceae, which is retained in the Hemisphaeriales.