Potential Biological Control of Damping-off Pathogens in Emerging Sugar Beet by Pythium oligandrum Drechsler

Seed treatment with ascospores of Chaetomium globosum reduced damping-off of sugar-beet caused by seed-borne Phoma betae and soil-borne Pythium ultimum or Rhizoctonia solani in growth chamber experiments. Seed treatment with a fluorescent Pseudomonas sp. controlled Ph. betae and P. ultimum but not R. solani. Coating cotton seeds with ascospores controlled P. ultimum and R. solani damping-off. In some experiments, biological seed treatments were equally or more effective than seed treatment with captan. However, greater variability in disease control occurred with the antagonists than with captan. Fifty percent of freshly harvested ascospores of C. globosum germinated in 8 h on water agar. When ascospores were stored under air-dried conditions for 3 days to 2.5 years, germination increased to > 90%. Under same storage conditions, survival of Pseudomonas sp. was detected after 4 months. Antagonistic activities observed in vitro were hyphal coiling of C. globosum on R. solani, and mycostasis was induced by C. globosum or Pseudomonas sp. on agar and soil. The presumed cause of mycostasis is the diffusible antifungal metabolites which may also be involved in the biological control of damping-off.

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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

Phytopathology ◽

10.1094/phyto.2003.93.10.1228 ◽

2003 ◽

Vol 93 (10) ◽

pp. 1228-1232 ◽

Cited By ~ 57

Author(s):

Shigehito Takenaka ◽

Zenta Nishio ◽

Yumi Nakamura

Keyword(s):

Cell Wall ◽

Sugar Beet ◽

Phenylalanine Ammonia Lyase ◽

Protein S ◽

Cell Wall Protein ◽

Protein Fractions ◽

Major Protein ◽

Damping Off ◽

Pythium Oligandrum ◽

Treatment Control

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.

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