The Cup Fungus, Ciboria Carunculoides, Pathogenic on Mulberry Fruits

Abstract

SUMMARYA developmental study has been made of a disc fungus that attacks the fruits of Morus alba. From the results obtained, the organism is transferred from Sclerotinia to Ciborio, and is assigned the binomial Ciborio, carunculoides (Siegler and Jenkins) Whetzel.This fungus possesses a sclerotial phase and an apothecial phase, but lacks conidia. Its ascospores, which are forcibly expelled, lodge on the stigmas and constitute the inoculum for initiation of infection at the time of flowering. As a result each drupelet of the aggregate fruit may become transformed into a separate Sclerotium.Sclerotia are composed both of fungus and of suscept tissues and have somewhat the appearance of grains of popcorn.Apothecia for the succeeding year are initiated in the spring about a month after discharge of ascospores. They originate from elements of a mantle that occurs immediately beneath the outer tissues normally destined to become the fleshy portion of the mulberry fruits. This mantle completely invests the young Sclerotium and consists of spermatiophores with interspersed archicarps. The spermatia are produced in such abundance as to be extruded in a column at the tip of each Sclerotium.Sclerotia fall to the ground during mid-summer, become black, and remain dormant until the following spring. Then each bears one or two apothecia. The breaking of dormancy is first indicated by increase in size of sclerotia. Increase in size is accounted for by the presence of a gelatinous covering on the sclerotial hyphae. This gelatinous envelope absorbs water, causing the sclerotia to swell, and also functions to maintain turgor during expulsion of ascospores.Ascospores possess thick gelatinous envelopes which cause them to adhere and provides moisture for germination.An Asiatic fungus, Sclerotinia Shiraiana, parasitic on mulberry appears to be distinct from C. carunculoides but properly belongs in the same genus. It is herein transferred to Ciborio Shiraiana (Henn.) Whetzel.