日 植 病 報61: 425-433 (1995) Ann. Phytopathol. Soc. Jpn. 61: 425-433 (1995) Brown Root Rot of Trees Caused by Phellinus noxius in Windbreaks on Ishigaki Island, Japan -Incidence of Disease , Pathogen and Artificial Inoculation- Yasuhisa ABE*, Takao KOBAYASHI**, Masatoshi ONUKI***, Tsutomu HATTORI•õ and Masaichi TSURUMACHI*** Abstract Extensive wilts of trees have recently occurred in the windbreaks at Okinawa Branch of the Tropical Agricultural Research Center in Ishigaki Island, Okinawa, Japan. Dead or declined trees were observed at 43 points, the total number of dead and declined trees was over 200 and total length of damaged windbreaks was 515m, in about 11% of the total length of windbreaks. Roots of dead and declined trees were collected and many fungus cultures were isolated from them. Most isolates had the following common cultural characteristics: no clamp connections on septa, staghorn-like hyphae and arthroconidia. Two cultures isolated from tissue of diseased trees were artificially inoculated into saplings of Podocarpus macrophyllus. Nine saplings were killed out of 19 inoculated saplings within 13 months and the fungus was reisolated from the dead saplings. As the isolates were considered to be a hymenomycetous fungus, fungal fruiting bodies were collected from windbreaks and from nearby and cultures were isolated from the collected fruiting bodies. One of cultures isolated from the collected fruiting bodies coincided in cultural characteristics with the isolates from dead and declined trees. The fruiting body from which this culture was isolated, was identified as Phellinus noxius (Corner) Cunningham. Taxonomic study revealed that Ph. sublamaenis (Lloyd) Ryvarden, published as a prior name for Ph. noxius, is a synonym of Ph. lamaensis. The fungus reported as Ph. lamaensis by Yasuda from Bonin Island of Japan in 1916, was identified as Ph. noxius. (Received January 1995; Accepted May 15, 1995) Key words: brown root rot, Phellinus noxius, Phellinus sublamaensis, root and butt rot, windbreak, wood decay. orientalis. In addition, Hibiscus rosa-sinensis is planted in INTRODUCTION the outermost part of windbreaks as ornamental trees. There is also a plantation of Pinus luchuensis in the In Okinawa Prefecture, plantations of windbreaks windbreaks. have been encouraged for protection of cultivated land, Wilt of one tree was first found in the windbreaks at especially for sugar cane cultivation. The windbreaks at the Okinawa Branch of TARC in 1983 or 1984 and the the Okinawa Branch of the Tropical Agriculture Re- number of dead and declined trees increased year by search Center (TARC)*1 in Ishigaki Island were estab- year. Surveys were made to find the cause of the wilts in lished as a model of plantations in 1975. Main tree 1988. A preliminary survey suggested that the wilts were species included Casuarina equisetifolia, Calophyllum caused by a fungus not reported previously from Japan, inophyllum, Podocarpus macrophyllus, Garcinia subel- characterized by a quick decline of trees and the forma- liptica, Delonix regia and Erythrina variegata var. tion of dark-brown mycelial mats on the surface of the ＊Shikoku Research Center , Forestry and Forest Products Research Institute (FFPRI), 915, Asakura-Tei, Kochi 780, Japan 森林総合研究所四国支所 ＊＊Forest Development Technological Institute , 7, Rokuban-cho, Chiyoda-ku, Tokyo 102, Japan (Formerly at FFPRI, Ibaraki)林 業 科 学 技 術 振 興 所 ＊＊＊Kyushu National Agricultural Experiment Station , 2421, Suya, Nishigoushi, Kikuchi-gun, Kumamoto 861-11, Japan (Formerly at Okinawa Branch of Tropical Agriculture Research Center)九 州 農 業 試 験 場 †FFPRI ,1, Matsunosato, Kukizaki, Inashiki-gun, Ibaraki 305, Japan森 林 総 合 研 究 所 *1The institute was reorganized into Japan International Research Center for Agricultural Sciences (JIRCAS)in October 1993. Okinawa Branch also changed its name to Okinawa Sub-tropical Station of JIRCAS. 426 日本植物病理学会報 第61巻 第5号 平成7年10月 roots of dead trees. The roots of diseased or dead trees U.S.A (BPI), were also examined for a comparative were dug up and cultures isolated from them. Some of study with the collected fruiting bodies. the diseased roots were sent to Forestry and Forest Inoculation. Five-years old saplings of P. macro- Products Research Institute (FFPRI) and isolation of phyllus, 1 to 1.2m high and about 1.5cm in diameter at fungi also made there. The pathogen was finally identifi- the base, were used for an inoculation study. Each ed by a comparative study on cultures and specimens, sapling was planted in an unglazed pot one month before and its pathogenicity was confirmed by artificial inocula- inoculation. Two cultures isolated from tissue of dis- tion. Cultural characteristics and wood-decaying ability eased trees (WD-190, 191) were used for inoculations. of the causal fungus were also studied. Cultures were grown in sawdust medium (70g of beech The objective of this study were 1) to investigate the sawdust, 20g of rice bran, 120g of water) in plastic incidence of the disease of windbreaks at the Okinawa bottles at 30℃ for 30 days. Approximately 50g of fungal Branch of TARC, 2) to determine the pathogen of the mycelia with sawdust medium was used as inoculum, disease, and 3) to evaluate the pathogenicity and other which was placed on lateral roots and covered with soil characteristics of the pathogen. A part of this study has in each pot. Small lateral roots were cut and inoculum been reported preliminarily elsewhere2,12). was placed on them in injuring treatment. Controls were inoculated only with sawdust medium. Inoculation was MATERIALS AND METHODS performed on 26 July, 1989. Inoculated saplings were placed in the half-shade in the yard of FFPRI and were Field survey. Field surveys were made in observed till the end of 1990. Isolation was made from November to December in 1988. Species and number of roots and stems of dead saplings by taking small pieces dead and declined trees were recorded and their loca- of tissue. The pieces were treated with 70% ethanol, tions were plotted on a map. Forest gaps produced by 0.1% HgCl2 and sterilized water, then placed on PDA dead and declined of trees were recorded by measuring slants and incubated at 25℃ for several days. the maximum distance between wilting trees at opposite Cultural characteristics and wood-decay abil- sides of each affected site. As the damages of the ities. Cultures isolated from tissue of diseased trees windbreaks were suspected to be caused by a wood-de- were grown on PDA plates and their cultural character- caying fungus, fungal fruiting bodies on dead trees or istics were studied and assigned to the key patterns by decayed stumps were collected from the windbreaks of Nobles15) and Stalpers21). The effect of temperature on Okinawa Branch and adjacent area. mycelial growth was studied for two isolates (WD-190, Isolation and identification. For isolation of 191) using 9-cm diameter petri dishes containing 20ml cultures, small pieces of tissue were cut out from sap PDA. The agar was placed centrally with 5-mm diam. wood and inner bark in roots of diseased or dead trees. plug cut from the colony of the test fungus on PDA Isolation was performed by two methods. In one method, plate. Inoculated plates were incubated at temperatures cut pieces of tissue were rinsed in running tap water for from 4℃ to 40℃ at intervals of 3℃ with five replicates two hours, placed on potato-dextrose agar (PDA) medi- for each temperature. Colony size was measured along um in petri dishes and incubated at 15•Ž for two weeks. two diameters at right angles every 2 days and growth In the other method, pieces of tissue were soaked in 70% of mycelium radius was calculated. ethanol for a few seconds, treated with 0.1% HgCl2 for Wood blocks of Calophyllum vexans, Casuarina glauca, a few minutes, rinsed in sterilized water, then placed on Fagus crenata, P. macrophyllus, and Quercus acutissima, PDA slants and incubated at 25•Ž for a few days. 15×15×20mm in size, were used for wood-decay test. Hyphae growing from these pieces were transferred to Wood blocks were numbered and dried in a circulating- PDA medium in petri dishes, incubated at 25•Ž for air drying oven at 60℃ for 48hr, then cooled in a several days to a few weeks and hyphal characteristics desiccator and weighed. Sawdust medium was prepared were examined with a microscope. by mixing 70g of beech sawdust and 20g of rice bran Cultures were also isolated from fungal fruiting and 120g of water in a plastic bottle of 850-ml content. bodies collected on dead trees and decayed stumps. Five wood blocks were buried flush with the surface of Small pieces of tissue were taken from inner part of sawdust medium in each bottle and the bottles were fruiting bodies, placed on PDA slants with or without 5 autoclaved at 120℃ for 1hr. Two isolates from tissue of ppm benomyl and incubated at 25•Ž. Cultural character- diseased trees (WD-190, 191) and one isolate of Coriolus istics were compared between the isolates obtained from versicolor (L.: Fr.) Quel. (WD-876=Rinshi 1030 in JIS Z diseased or dead roots and those from fungal fruiting 2119) were inoculated into each bottle, which was in- bodies. cubated at 30℃ for 6 months. Wood blocks of Fa. Collected fruiting bodies of fungi were examined with crenata and Q. acutissima inoculated with the same a microscope and morphological characteristics were isolates were incubated at 25℃ for 6 months. After recorded. Specimens of Fomes noxius and related incubation, wood blocks were taken out from bottles, species from the herbaria of the National Science dried as described above and dry weight was measured. Museum in Tokyo (TNS), the Singapore Botanic Gar- Percentage of weight loss was determined as the aver- dens (SING) and the National Fungus Collections in age of 5 wood blocks.