SWOLLEN FRUIT OF MULBERRY IN TAIWAN: THE PATHOGEN, DISEASE CYCLE AND FACTORS AFFECTING THE APOTHECIUM FORMATION

Abstract

Ciboria shiraiana引起桑(Morus australis)腫果病，僅為害果實，不侵害枝條或葉片。被害果實外表先呈灰白色，內部形成一個菌核，最後木乃尹化掉落地上，越冬菌核於翌春形成子囊盤（1~21子囊槃／菌核）產生子囊胞子感染桑花。子囊胞子在8~28℃間皆可在水瓊脂上發芽，但是發芽管在十四種供試培養基中皆不能長成菌落，終於崩解。C. shiraiana對環境條件的要求甚嚴，僅在充足的水分及12~16℃之條件下才能形成正常的子囊盤，而且形成的時機要符合桑之開花期，才能引起病害。倘若二月間之氣溫過超16℃，則會抑制子囊盤的形成並減少病害。在實驗室中atrazine及diuron等殺草劑和benomyl, PCNB及roilan等殺菌劑，皆可抑制子囊盤的形成。 Swollen fruit of mulberry (Morus australis Poir.) is caused by Ciboria shiraiana (Henn.) Whetzel. It attacks the fruit only, not leaves or twigs. Characteristically, the affected fruit developed a single scierotium inside and had a grayish white appearance at the beginning. Then, they became mummified on the tree and eventually dropped. The overwintered scierotia formed 1-21 apothecia each from which ascospores were produced for causing infection the next spring. Ascospores germinated in a temperature range of 8-28℃ on water agar. However, the germ tubes failed to grow on the 14 media tested, and finally lysed. C. shiraiana appeared to have very narrow environmental requirements. Normal apothecia were produced only at 12-16℃, with adequate moisture. For infection the formation of apothecia should match the blooming period of mulberry during Feburary in central Taiwan. A temperature above 16℃ in Feburary would inhibit apothecial formation and lessen the disease incidence. Herbicides such as atrazine and diuron, and fungicides such as benomyl, PCNB, and ronilan inhibited the formation of apothecia in the laboratory.