The role of biocontrol agents and plant resistance activators against Rhizoctonia root rot disease of bean plants
aboghalia, hoda;
Abstract
Biological control and resistance activators represent an interesting strategy to induce disease resistance against plant pathogens. In the present work two biocontrol agents (Trichoderma harzianum and arbuscular mycorrhizal "AM" fungi) and two plant resistance activators ( benzothiadiazole "BTH" and jasmonic acid "JA") were used to enhance bean plants defense against root rot disease caused by Rhizoctonia solani.
Results of “in vitro”experiments showed that T. harzianum and/or the plant resistance activators inhibited the mycelial growth of R. solani. However, JA when used individually didn’t inhibit pathogen growth. T. harzianum showed also significant inhibition of pathogen growth through production of some volatile and non-volatile metabolites especially when the resistance activators were added. T. harzianum when applied separately or in combination with the resistance activators had the ability to produce extracellular chitinolytic, cellulolytic or proteolytic enzymes that showed significant reduction on the pathogen mycelial growth.
Under greenhouse conditions, results showed that the infestation of soil with R. solani increased the percentage of disease incidence (57.6%) of root rot and reduced the growth and yield parameters of bean plants. However, the detrimental effects caused by the pathogen were less observed whether the bioagents or plant resistance activators were applied. The treatment with AM fungi however, had the highest efficiency in reducing disease incidence followed by T. harzianum.
Infection by R. solani significantly increased the activity of antioxidant enzymes (superoxide dismutase “SOD”, ascorbate peroxidase “APX” and catalase “CAT”) in bean plants. However, application of the bioagents or resistance activators showed a significant increase in the activity of these enzymes compared with the infected ones. The highest activity of SOD, APX and CAT was recorded when JA, AM fungi and T. harzianum were used respectively.
The concentration of phenolic compounds and the activity of their related enzymes (peroxidase "POX", polyphenol oxidase “PPO” and phenylalanine ammonia lyase "PAL") were increased significantly in roots and shoots of infected bean plants. AM- treated plants accumulated more phenolics and JA- treated plants showed the highest POX activity, while BTH- treated plants showed the highest PPO and PAL activities.
Results of “in vitro”experiments showed that T. harzianum and/or the plant resistance activators inhibited the mycelial growth of R. solani. However, JA when used individually didn’t inhibit pathogen growth. T. harzianum showed also significant inhibition of pathogen growth through production of some volatile and non-volatile metabolites especially when the resistance activators were added. T. harzianum when applied separately or in combination with the resistance activators had the ability to produce extracellular chitinolytic, cellulolytic or proteolytic enzymes that showed significant reduction on the pathogen mycelial growth.
Under greenhouse conditions, results showed that the infestation of soil with R. solani increased the percentage of disease incidence (57.6%) of root rot and reduced the growth and yield parameters of bean plants. However, the detrimental effects caused by the pathogen were less observed whether the bioagents or plant resistance activators were applied. The treatment with AM fungi however, had the highest efficiency in reducing disease incidence followed by T. harzianum.
Infection by R. solani significantly increased the activity of antioxidant enzymes (superoxide dismutase “SOD”, ascorbate peroxidase “APX” and catalase “CAT”) in bean plants. However, application of the bioagents or resistance activators showed a significant increase in the activity of these enzymes compared with the infected ones. The highest activity of SOD, APX and CAT was recorded when JA, AM fungi and T. harzianum were used respectively.
The concentration of phenolic compounds and the activity of their related enzymes (peroxidase "POX", polyphenol oxidase “PPO” and phenylalanine ammonia lyase "PAL") were increased significantly in roots and shoots of infected bean plants. AM- treated plants accumulated more phenolics and JA- treated plants showed the highest POX activity, while BTH- treated plants showed the highest PPO and PAL activities.
Other data
| Title | The role of biocontrol agents and plant resistance activators against Rhizoctonia root rot disease of bean plants | Authors | aboghalia, hoda | Keywords | Bean plants, Root rot, Rhizoctonia solani, Trichoderma harzianum, Arbuscular mycorrhizal fungi, Flutolanil, Benzothiadiazole, Jasmonic acid. | Issue Date | 2010 | Journal | Egypt. J. Bot |
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