Brown Root Rot Caused by Phellinus Noxius in Subtropical Areas of Japan

102 年森林健康之管理與經營國際研討會 2013 International Symposium on Forest Health Management Brown root rot caused by Phellinus noxius in subtropical areas of Japan Norio Sahashi Department of Forest Microbiology, Forestry and Forest Products Research Institute (FFPRI) ABSTRACT The fungus Phellinus noxius has a broad host range and causes brown root rot in a variety of tree species of various ages, irrespective of their original health. The fungus is widely distributed in tropical countries of Southeast Asia, Oceania, Central America and Caribbean, and Africa. Since 1988 when brown root rot was first found on Ishigaki Island, Okinawa Prefecture, the disease has been reported on several islands in the Ryukyu (Nansei) Islands and the Ogasawara Islands, and it has been causing serious problems to shade, windbreak, ornamental, and landscape trees in the subtropical region of southern Japan. Here, I report on the current status of P. noxius-caused brown root rot in subtropical areas of Japan, including symptoms, distribution and host tree species of the disease, and pathogenicity and/or virulence of the pathogen based on our surveys and previously published reports from Japan. In the Ryukyu Islands, brown root rot has been confirmed in 53 tree species from 32 plant families at different sites on 10 of the 12 islands surveyed. Among the 53 tree species, 34 were first recorded in Japan as host plants of P. noxius. In the Ogasawara Islands, we confirmed brown root rot in 33 tree species from 20 plant families．Among them, 20 tree species were first recorded in Japan as host plants, including endemic species of the Ogasawara Islands. The disease occurs mainly in shade, windbreak, and ornamental or landscape trees at scenic areas, parks, roadsides, agricultural land such as sugar cane fields and around residences or other places associated with human activities. Key Words: brown root rot, Phellinus noxius, The Ryukyu Islands, The Ogasawara Islands, Subtropical areas of Japan Corresponding E-mail：[email protected] 102 年森林健康之管理與經營國際研討會 2013 International Symposium on Forest Health Management Introduction Phellinus noxius (Corner) G. Cunn. is widespread in tropical countries of Southeast Asia, Oceania, Central America and Caribbean, and Africa, where it causes brown root rot in a variety of trees of all ages and health conditions (Singh et al. 1980; Bolland 1984; Hodges and Tenorio 1984; Neil 1986, 1988; Nandris et al. 1987a; Arentz and Simpson 1989; Bolland et al. 1989; Dennis 1992; CABI/EPPO 1997; Quanten 1997; Chang and Yang 1998; Larsen and Cobb-Poulle 1990; Ann et al. 2002; Brooks 2002; Albrecht and Venette 2008). The fungus has a very wide host range (Bolland 1984; Hodges and Tenorio 1984), with more than 200 woody plant species representing 59 families currently reported as host plants worldwide (Ann et al. 2002). In Japan, brown root rot was first found in windbreak trees on Ishigaki Island, Okinawa Prefecture, in 1988 (Abe et al. 1995; Fig. 1). Since then, the disease has been reported on several islands in both the Ryukyu and the Ogasawara Islands, causing serious problems to shade, windbreak, and ornamental or landscape trees in subtropical regions of southern Japan (Kobayashi and Kawabe 1991; Kobayashi et al. 1991; Kawabe et al. 1993; Hattori et al. 1996; Kobayashi and Kameyama 2002; Sahashi et al. 2007, 2012, 2013; Shimada et al. 2013; Kawabe 2010). Here, I report on the current status of P. noxius-caused brown root rot in subtropical areas, the Ryukyu Islands and the Ogasawara Islands, Japan, as well as general information about the disease, based on our surveys and previously published reports. Characteristics of the pathogen Phellinus noxius, a causal pathogen of brown root rot, is easily isolated from root tissues of newly dead or declining trees at a relatively high frequency after incubation of flame-sterilized pieces of affected tissues (Sahashi et al. 2007, 2012, Fig 2a). On potato sucrose agar (PSA), the fungus first produces a white colony, which turns brown, with irregular dark brown lines or patches (Fig. 2b). Arthrospores and 102 年森林健康之管理與經營國際研討會 2013 International Symposium on Forest Health Management Fig. 1. Geographic distribution of brown root rot caused by Phellinus noxius in the Ryukyu Islands. Red circles indicate sites where the disease has been confirmed in our 13 field surveys. Each number on left side map is corresponding to each island indicated by the same number on right side. The precise locations of each island are indicated in left side map. Fig. 2. Cultural characteristics of Phellinus noxius. (a) Colonies growing up from small pieces of decayed wood. (b) Colony morphology on potato sucrose agar (PSA) with irregular dark brown patches. (c) Arthroconidia produced on PSA. (d) Staghorn-like hyphae produced on PSA. 102 年森林健康之管理與經營國際研討會 2013 International Symposium on Forest Health Management staghorn-like hyphae (Fig. 2c, d) are commonly observed in culture. The pathogen can grow at temperatures between 12-13 to 37 ºC, with the optimal temperature near 30 ºC (Abe et al. 1995; Ann et al.1999). Fruiting bodies of P. noxius are rarely observed on diseased trees in the field (Sahashi, 2007, 2012). Similar observations have been reported from Taiwan (Chang and Yang 1998; Ann et al. 1999, 2002; Chang, T. T. 2002), which is very close to Okinawa, and from West Africa (Nandris et al. 1987a). Disease symptoms Brown root rot has been observed on a variety of tree species of various ages and health conditions in Japan (Table 1). Infected trees usually exhibit reduced growth, discoloration and wilting of the foliage, defoliation, and dieback of branches, after which whole plant eventually dies (Figs. 3, 4). These symptoms are similar to decline symptoms caused by other root rot pathogens. However, these aboveground symptoms and the rate of their development may vary considerably depending on tree species, age, and possibly environmental conditions (Fig. 3). Generally, young trees show rapid tree death, while older trees exhibit more gradual decline. In contrast to foliage symptoms, belowground (root) symptoms are quite unique, and differ from those caused by other root rot pathogens, such as Rigidoporus microporus (Sw.) Overeem (syn. R. lignosus (Klotzsch) Imaz.) and Armillaria spp. (Bolland 1984; Nandris et al. 1987a, b; Intini, 1991; Mohd Farid et al. 2009). A thick mycelial sheath or crust with first a cinnamon, then a dark-brown to blackish color appears on the surface of the affected stem base (Fig. 5a, b). The encrustation may extend up to 2 m above the ground level in tropical countries (Hodges and Tenorio 1984; Singh et al. 1980), but does not grow that high in Japan except for several cases in the Ogasawara Islands. Diseased roots are also covered with a brown to black mycelial crust (Fig. 5d, f, h), with soil particles and small stones usually adhered tightly to or embedded in the mycelial crust. Infected wood becomes brown at first (Fig. 5e), but in the late stage it forms a soft textured white rot, with conspicuous brown lines irregularly distributed in the decaying tissue, yielding a honeycomb appearance (Fig. 5c, g, i, j). A thin white to brown mycelial mat is usually present between the bark and wood (Fig. 5 k). 4 102 年森林健康之管理與經營國際研討會 2013 International Symposium on Forest Health Management Table 1. Host records of brown root rot caused by Phellinus noxius in the Ryukyu Islands, Japan Reported as Location Plant families Plant species References2) new hosts （Island)1) 1 Anacardiaceae Rhus succedanea a3) 1 9 2 Apocynaceae Cerbera manghas 6 10 3 Aquifoliaceae Ilex rotunda a 3 9 4 Araliaceae Aralia elata a 1 9 5 Berberidaceae Nandina domestica a 3 9 6 Bombacaceae Chorisia speciosa a 8 1,3,5,10 7 Boraginaceae Argusia argentea a 8 10 8 Ehretia dichotoma a 9 10 9 Buxaceae Buxus bodinieri a 6 10 10 Casuarinaceae Casuarina equisetiforia a 1,2,3,4,6,7,8,9,10 1,2,3,4,5,7,8,9,10 11 Celastraceae Maytenus diversifolia a 7 10 12 Clusiaceae Calophyllum inophyllum a 6,8,9 1,3,7,10 13 Garcinia subelliptica a 9 3,7,10 14 Ebenaceae Diospyros ferrea var. 9 10 buxifolia 15 Elaeocarpaceae Elaeocarpus sylvestris a 1,7 9, 10 var.ellipticus 16 Euphorbiaceae Bischofia javanica 2 10 17 Glochidion obovatum a 1 9 18 Jatropha pandurifolia a 8 4 19 Macaranga tanarius 8,10 10 20 Hamamelidaceae Distylium racemosum a 6 10 21 Hernandiaceae Hernadia nymphaeifolia 4 9 22 Lauraceae Cinnamomum a 6,7 10 doederleinii 23 Cinnamomum japonicum a 1,2,3,4,5,7,8 9, 10 5 102 年森林健康之管理與經營國際研討會 2013 International Symposium on Forest Health Management Reported as Location Plant families Plant species References2) new hosts （Island)1) 24 Litsea japonica a 1,2,3,5 9,10 25 Machilus thunbergii a 1,7 9, 10 26 Leguminosae Acacia confusa a 8,9 1,3,7,10 30 Bauhinia acuminata a 8 4 31 Bauhinia racemosa a 9 3,7 27 Bauhinia variegata 6 10 32 Delonix regia 9 3,6,7 28 Erythrina variegata 8,9 3,7,10 29 Leucaena leucocephala 9,8,10 1,10 33 Lythraceae Lagerstroemia subcostata a 1 9 34 Malvaceae Hibiscus rosa-sinensis 5,9 1,9 35 Hibiscus tiliaceus 2,6 10 36 Meliaceae Melia azedarach var. 10 10 subtripinnata 37 Moraceae Ficus microcarpa 4,10 9, 10 38 Ficus virgata a 4 9 39 Morus australis a 1 9 40 Myrsinaceae Ardisia sieboldii a 3 9 41 Myrtaceae Eugenia uniflora a 9 10 42 Eucalyptus sp. 6 4 43 Oleaceae Ligustrum japonicum a 1 9 44 Palmae Areca catechu a 8 4 45 Pittosporaceae Pittosporum tobira a 1 10 46 Podocarpaceae Podocarpus macrophyllus a 1,9 3,7,9,10 47 Rosaceae Prunus cerasoides var.

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