Rigidoporus lignosus . [Descriptions of Fungi and Bacteria

Abstract

Abstract A description is provided for Rigidoporus lignosus . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Hevea and over 40 other tropical genera icluding cacao, coconut, coffee, tea and bamboo. DISEASE: White root rot. Common on rubber where it destroys the tap root so that diseased trees are easily blown over. The foliage turns yellow and this is accompanied by die-back in Asia, but these symptoms are absent in West Africa (45, 1166). Also parasitic on other perennial crops. GEOGRAPHICAL DISTRIBUTION: Africa (Cameroon, Congo, Ethiopia, Fernando Po I., 'French Equatorial Africa', Ghana, Ivory Coast, Kenya, Mauritius, Nigeria, Sierra Leone, Uganda), Asia (Brunei, Burma, Ceylon, India, Indo- China, Indonesia, Japan, Malaysia, Philippines, Thailand); Australasia & Oceania (New Guinea, New Hebrides); North America (Mexico); Central America & West Indies (Costa Rica, Dominica); South America (Argentina, Brazil, Guyana). (CMI Map 176, ed. 2, 1966). TRANSMISSION: Rigidoporus lignosus is a rhizomorphic root-infecting fungus with an ectotrophic growth habit. The rhizomorph requires a food base, generally the tree stump on which it originated, until it encounters other dead wood or living or moribund tree roots which it can invade. Epiphytic growth of rhizomorphs may extend 5-15 feet ahead of actual penetration of live rubber roots (Napper, 1938) and descend the full length of the tap root to a depth of 181 feet (45, 1161d). Air-borne spores may also infect tree stumps immediately after felling (45, 201) and thus provide foci for the spread of rhizomorphs, as was earlier postulated by Petch (1921). This source of infection, however, is regarded as less important than root-infection (46, 1089).