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| Induced Resistance and the Physiological and Biochemical Mechanism of Plant Against Nematodes Infections |
| , , , , , ,De-liang Peng |
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Abstract Plant parasitic nematode can parasitize various plant species and cause the yield loss of plants, which has been a serious problem in agricultural system around the world. Effectively integrated pest management (IPM) practices are needed to control these nematodes. One of these IPM strategies is the use of resistance inducers or triggers. Resistance of plant induced by special triggers can enhance defense ability of plant against different nematodes. This paper reviewed the criterions and types of induced resistance, main triggers and their physiological and biochemical mechanism in inducing plant to defense against nematodes. To determine whether plant resistance was induced by triggers, the inducing time, virulence factors and gene type of host should be taken into consideration. In recent years, research on induced resistance was focused on the microscopic observation of the interaction of nematode and host, especially on the feeding site of nematode. Reactive oxygen species (ROS) are formed as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling and homeostasis. During times of environmental stress, ROS levels can increase dramatically and be generated by exogenous sources such as microorganisms and chemicals. Effects of ROS on cell metabolism are well documented in a variety of species. These include not only roles in programmed cell death but also positive effects such as the induction of host defense genes. When a plant recognizes an attacking pathogen, one of the first induced reactions is to rapidly produce superoxide (O2-) or hydrogen peroxide (H2O2) to strengthen the cell wall. This prevents the spread of the pathogen to other parts of the plant, essentially forming a net around the pathogen to restrict movement and reproduction. Thereafter, the obseravtion of ROS has been another research area in the interaction of nematode and plants. Serveral compounds have been found to trigger resistance of various plants to defense against different pathogens. Chemicals such as acibenzolar s-methyl (ASM) and β-aminobutyric acid (BABA) have been verified to be effective in increasing the resistance of tomato (Lycopersicon esculentum) and decrease the number of root knots and eggs of Meloidogyne javanica. Potassium silicate can decrease the number of M. incognita, but increase the activity of peroxidase. Exogenous hormones such as abscisic acid (ABA), jamonic acid (JA) and ethylene (ET) have been found to be effective in decreasing infection and propagation of root-knot nematode (RKN). Some beneficial microorganisms such as Pseudomonas fluorescens and P. aeruginosa are found to effectively reduce the infection of Heterodera schachtii and M. javanica. Bacillus sphaericus can induce potato (Solanum tuberosum L.) to defense against the Globodera pallida. Arbuscular mycorrhizal fungi (AMF) can reduce the infection of M. incognita and increase the transcriptional expression level of defense-related genes and protein-synthesisrelated genes. Plant extracts from Foeniculum vulgare or Ocimum basilicum was found to decrease the population of M. javanica and M. incognita of tomato. In addition, biochar additions to soil have been shown to not only significantly improve soil tilth, nutrient retention and availability to plants, but also induce resiatance of some plants to defense against fungi, bacteria and nematodes. Research of induced resistance will be vital to formulate the integrated pest management strategy of nematodes, reduce the application of chemical nematicides and protect the ecological condition of agricultural system.
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Received: 12 June 2015
Published: 05 October 2015
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Corresponding Authors:
De-liang Peng
E-mail: pengdeliang@caas.cn;dlpeng@ippcaas.cn
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