Ontogeny of the Ascoma of Glomerella cingulata

Abstract

The ascogonium of Glomerella cingulata forms as a loop or coil from an assimilative hypha and becomes septate, each cell being uninucleate. Branches from the parent hypha envelop the ascogonium, become septate, branch further and produce the nonascogenous portions of the centrum as well as the ascomal wall. The ascogonium wraps around itself in various ways, elongates, and spreads into a flattened layer above the wall at the base of the young ascoma. Ascogenous hyphae, croziers, and asci arise from the ascogonium. Paraphyses form as vertical rows of expanded cells among the ascogenous hyphae. This tissue appears as an area of pseudoparenchyma in sectional view but the rows of cells are separable and, therefore, are equivalent to more typically filamentous paraphyses. The paraphyses are digested as the asci develop and are no longer evident when asci are mature. A small cavity forms just beyond the tips of the paraphyses when the neck and neck canal begin formation. The neck canal is lined with periphyses. Development of the centrum of G. cingulata is shown to be sordariaceous and especially similar to that in Triangularia backusii and Plectosphaerella cucumerina.