Induction of Pathogenesis-related proteins on potato sprouts by an alpha-(1, 3)-glucan from cell wall of binucleate non-pathogenic Rhizoctonia sp. isolate.

WOLSKI, E. A.; DALEO, G. R.; A. B. ANDREU.

Anaheim, California, USA.

Congreso; APS ANNUAL MEETING; 2004

American Phytopathological Society

Binucleate Rhizoctonia (BNR) isolate is an effective biocontrol agent for protection of potato from Rhizoctonia canker. This disease is caused by Rhizoctonia solani (AG-3). Production of hydrolytic enzymes is one of the best known inducible defense responses in plants following microbial infection. In a previous work we have isolated and characterized an a-(1,3)-glucan from BNR that induce glucanase activities in potato sprouts, the primary site of R.solani infection. Here we report studies on the defense responses of potato sprouts treated with the a-(1,3)-glucan. A dose-response assay and a kinetic study of glucanase activities were performed. Maximal induction of beta ß-1,3-glucanase activity in potato sprouts was obtained with 250 micrograms of the a-(1,3)-glucan elicitor and after 6 days from inoculation. Both, BNR mycelium and the a-(1,3)-glucan induced a similar kinetic response of ß-1,3-glucanase activity in potato sprouts. On the other hand, the a-(1,3)-glucan did not induce phytoalexin accumulation. Immunological analysis of crude extracts from potato sprouts infiltrated with the a-(1,3)-glucan was performed using antibodies raised against pathogenesis-related proteins (PR).  These experiments showed that the level of PR-2 (ß-1,3-glucanase), PR-3 (Chitinase) and PR-5 (Thaumatin-like protein) were increased when the sprouts were treated with the glucan. Maximal induction were obtained after 6 days from inoculation. These results show that this a-(1,3)-glucan may contribute to protection of the host plant against Rhizoctonia canker and may be utilized as a biocontrol factor.