Studies on the variability and pathogenicity of Rigidoporus lignosus

Abstract

White root disease in Hevea, caused by the fungus Rididoporus lignosus (Fomes lignosus) occurs widely in Sri Lanka, In recent years, the severity of the disease has increased alarmingly. One of the factors that could be attributed to the increased incidence of the disease is the virulence of the pathogen. This paper report the results of laboratory experiments on the effects of pH, temperature, light and dark, and relative humidity on a number of isolates, obtained from sites located in different rubber growing areas. The fungus is able to grow over a wide range of temperature with maximum growth being recorded at 30ºC. All the isolates grew better when kept in continuous darkness except one isolate which grew equally well under both light and dark conditions. There was wide variability in the pH requirements for the growth of the fungus. The virulence of the different isolates was examined using healthy rubber roots under laboratory conditions and rubber seedlings in pot culture. The results show that there are differences in virulences and pathogenicity.