Cell wall α-1, 3-glucans from a biocontrol isolate of Rhizoctonia elicits plant defense responses and induces protection against Rhizoctonia solani AG-3 and Fusarium solani f. sp. Eumartii.

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

Alemania, Berlin, 20-23rd August 2008.

Congreso; International Symposium on Rhizoctonia; 2008

TU Berlin Servicegesellschaft mbH

Plants are continually exposed to a vast number of pathogens and its recognition is mediated by signal molecules called elicitors. Most elicitors from fungal cell walls have been described as ß-glucans. In a previous work we isolated and characterized a cell wall α-1,3-glucan from non-pathogenic binucleate Rhizoctonia (BNR), which have elicitor activity. In this work we showed that the α-1, 3-glucan not only induced ß-1,3-glucanase activity, but also chitinase activity in potato sprouts. We also observed an increase of pathogenesis-related proteins (PRs), for example: PR-2 (ß-1,3-glucanase), PR-3 (chitinase) and PR-5 (thaumatin-like protein). Histological studies showed an increase in cell wall deposition of callose and lignin, which contribute to cell wall reinforcement. In addition, the a-1,3-glucan induced protection of potato against two fungal diseases, Rhizoctonia canker and Dry rot. Protection assays showed that pre-treatment of potato sprouts and potato tubers with the glucan results in a 40% of protection against Rhizoctonia canker and 60% protection against dry rot. On the other hand, we prepared an antibody against the a-1,3-glucan to localize it by transmission electron microscopy. The results showed the presence of the a-1,3-glucan in intercellular spaces and along the cell walls, mainly on the inner layers. This result and the presence of the a-1,3-glucan in liquid culture, where BNR was grown, confirmed that the a-glucan had been secreted. In addition, α-glucanase activity in potato sprouts was detected using cell wall glucans from the pathogenic isolate R. solani AG-3 as substrates; whereas, when cell wall glucans from BNR isolate were used, no α-glucanase activity was detected. The present study is the first report of an α-glucan elicitor from Rhizoctonia, that may be important as a biocontrol agent. In addition, our results suggest that the presence of α-1,3-glucans could be associated with plant–fungi interactions. Supported by: CONICET, CIP, UNMDP.