a STUDY OF ISOLATES OF RIG1DIPORUS L1GNOSUS THE CAUSATIVE AGENT OF WHITE ROOT ' DISEASE OF RUBBER

. Rigidiporus lignosus (Klotz.) Imazaki cause the white root disease of rubber (Hevea brasiliensis). Five isolates of the fungus, Tl, 01, SI, Fl arid H2, obtained from different rubber growing districts of Sri Lanka, were examined for their growth patterns in different solid media. The secretion of cell-wall degrading enzymes was also studied in the isolates Tl', SI. and H2. when grown in different "media with different sources of carbon. \ ; J; *' The isolate Tl, which; is known to be. the most.virulent, grew fast and densely on nutrient rich-'solid.media.-such as potato dextrose"agar (PDA) and malt extract agar (MEA), but its growth ' was poor on Czapek Dox agar, Knop-Glucose agar and the medium for wood, rotting fungi The other four isolates; also grew best on PDA-and MEA, but the growth was less, than'that in Tlv The-growth, of SL, 01,'El and. H2 on the other media however, was. more-, than that ofisolate Tl,..;."All-isolates except Tl formed branched, strand-like aggregations when growing on solid media. • Statistical analysis of- the growth studies indicated, that a significant difference existed among the. isolates and also between the isolates arid the media. The isolate Tl. secreted polygalacturonase, pectin lyase, B-glucosi-dase and cellobiase. The isolates SI and H2 secreted only pectin lyase, B-glucosidase and cellobiase. In t l, the secretion of all the enzyme3 occurred'earlier: and the*'amount, of enzyme secreted was 1 Address for all correspondence