Sclerotinia trillii, sp. nov., causing a new sclerotinia disease on Trillium in Japan

Abstract

Sclerotinia trillii n. sp., which attacks Trillium tschonoskii and T. smallii in Hokkaido and northern Honshu, Japan, is described. The characters identifying this species with the genus Sclerotinia are large tuberoid sclerotia, produced both on infected plants and in culture, which consisted of only mycelium (true sclerotia) and flesh apothecia produced on them. This species is distinguished from S. sclerotiorum, S. minor, S. trifoliorum, and S. nivalis by relatively large sclerotia, cultural colony appearance, and red-brown to yellow-brown, relatively large apothecium, in addition to its parasitic nature on Trillium. Sclerotinia trilliiis a psychrophilic having an optimum temperature for mycelial growth at 15-20~ Key Words sclerotinia disease; taxonomy; Trillium.A sclerotinia disease was first observed at Tomakomai, Hokkaido, in June, 1996, on Trillium tschonoskii Maxim., with the symptoms of grayish brown rot on leaves, peduncle and stem (Figs. 1, 2). Occasionally, periphery of the rotted part changed red purple. The same disease was observed in June, 1997, on Trillium smalliiMaxim, in Hirosaki, Aomori Pref. Sclerotinia disease on Trillium has not hitherto been reported in Japan. In the USA, somewhat similar diseases caused by Ciborinia trillii Batra et Korf and Sclerotinia sclerotiorum (Lib.) de Bary have been reported (Batra and Korf, 1959;Holcomb, 1990). The present study revealed that the pathogenic fungus is an undescribed species of Sclerotinia. It is described here as S. trillii sp. nov. Material and MethodsIsolation Sclerotia collected from Trillium tschonoskii and T. smallii were directly placed on clear agar containing 100 ppm streptomycin-sulfate in 9-cm Petri dishes. The plate was incubated at 1 5~ under lighting for 12 h per day (12 LD, daylight type fluorescent lamp: 15 W). After 4 d, 3 x 3 mm agar disks were cut from developing mycelia and transferred to fresh PeA plates (potato 200 g, sucrose 20 g, agar powder 20 g, distilled water 1000 ml) for immediate use or to PeA slants for storage. The slants were first incubated for 1 mo at 15~ under 12 LD, then transferred to a refrigerator (7~ Trillium plants: small agar pieces with developing mycelia (5 • 5 mm) were applied to the stem and peduncle of potted T. tschonoskii plants and wrapped with Parafilm. The pots were then placed in a moist chamber in the shade. On control plants, PSA pieces without mycelia were likewise applied.Fruits of non-host plants: fruits of cowpea (Phaseolus vulgaris L.) and eggplant (Solanum melongena L.) were inoculated with the trillium fungus (No. 2843), or with S. sclerotiorum for comparison. Small agar pieces with mycelia were applied on surface-sterilized fruit surface (wiped with 70% ethanol), wrapped with plastic tape, and the pieces were placed in deep dishes. The dishes were incubated at 1 5~ under 12 LD for 20 d. Cultural characteristics To see the colony appearance, the fungi was grown at 15~ under 12 LD on fresh PeA. In addition, wheat grain medium (wheat grain 12 g, distilled water 25 ml) (Drayton, 1934), and ...