First report of Inonotus rickii causing canker and decay on Hevea brasiliensis in China

Hevea brasiliensis (rubber tree) is an important commercial tree in China, with more than 386,000 ha planted on Hainan island. In 2008, twelve trees with cankers and signs of decay were found in a 40 ha rubber tree plantation in Hainan. Sap flow occurred from cankered areas. Inside the trunk the decayed wood area was yellow-brown and clearly edged by a darker border. Semi-spherical or cushion shaped structures, velvety and yellow-brownish, with a reddish brown zonate inner part were present. These masses, soft when young, later on became dry and released a large quantity of dark brown, thick-walled and irregularly-shaped chlamydospores (10– 26 x 8–14 µm). Pileate to ungulate fruiting bodies occasionally occurred on the trunks (up to 6 cm long, 5 cm wide and 5 cm thick at base). They contained 3–4 pores per mm with a monomitic hyphal structure and distinct hyphoid setae; ellipsoid, yellowish and thick-walled basidiospores, 7–8 x 5–6 µm; and abundant, dark brown chlamydospores as already described. These characteristics are consistent with Inonotus rickii (Bernicchia, 2005).

DNA was directly extracted from the fruiting body, and the nuclear ribosomal internal transcribed spacer (ITS) region was amplified using primers ITS4 and ITS5. The DNA sequence was deposited in GenBank (Accession No. FJ667753). Blast analysis showed a 98% similarity to existing sequences of I. rickii from Argentina (AY072025, AY072027). Restriction fragment length polymorphism (RFLP) endonuclease digestion patterns (AluI, HaeIII, RsaI and MboI) of ITS region matched those of three Italian isolates of I. rickii (ISPaVe/PF 55-57, held at CRA-PAV). Dried fruiting bodies of I. rickii from Hainan were deposited in the herbarium of the Institute of Applied Ecology, Chinese Academy of Sciences (IFP 10359). I. rickii was originally reported from Cuba. It occurs in tropical and subtropical countries and more recently has been reported from the Mediterranean areacausing severe disease, progressive decline and sometimes death of tree species such as Celtis australis (Ramos et al., 2008), and Albizia julibrissin and Acer negundo (Annesi et al., 2003; Mazza et al., 2008). To our knowledge this is the first record of I. rickii both on Hevea brasiliensis and in China.