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Induction of Defense Reactions in Sugar Beet and Wheat by Treatment with Cell Wall Protein Fractions from the Mycoparasite Pythium oligandrum

To detect molecules with elicitor properties from Pythium oligandrum, cell wall protein fractions (CWPs) were extracted from 10 P. oligandrum isolates and examined for elicitor activity in sugar beet and wheat. P. oligandrum isolates were divided into two groups based on the number of major proteins in CWP: isolates with two major proteins (D-type) and isolates with one major protein (S-type). Sugar beet seedlings treated with both types of CWP through their roots showed enhanced activities of phenylalanine ammonia lyase and chitinase, and D-type-treated seedlings also showed significantly higher cell wall-bound phenolic compounds, mainly ferulic acid, compared with the distilled-water-treatment control. Damping-off severity was significantly reduced on seedlings treated with both types of CWP compared with the control, following challenge with Rhizoctonia solani AG2-2. Both types of CWP significantly reduced the number of infected spikelets developed from the injected spikelet compared with the control, following challenge with Fusarium graminearum. Neither type of CWP resulted in any reduction in pathogen growth rate in plate tests. These results demonstrate that CWPs of P. oligandrum have elicitor properties in sugar beet and wheat.