بررسی تغییرات آنزیم کیتیناز در برهمکنش قارچ میکوریز آربوسکولار (Glomus mosseae) و نماتد ریشهگرهی (Meloidogyne javanica) در گوجهفرنگی

Abstract

Introduction: Root knot nematode (Meloidogyne javanica) is one of the most important pathogens for different crops such as tomato. There are various methods to control, but none of them are considered as definite and efficient. One alternative that is considered in recent years in the management of root-knot nematode is using of different micro-organisms that are effective against this nematode and decreasing its population. Several studies have indicated the positive role of mycorrhizal fungi in alleviating plant disease causing agents in different ways. One method is to involve the mechanisms in the control of plant pathogens by arbuscular mycorrhizal fungi which is promoting of chitinase activity in mycorrhizal plants. In some studies alleviating nematode losses with mycorrhizal fungi inoculation have been related to host plant growth promotion resulted from mineral nutrients absorption especially phosphorous as well as increasing photosynthesis rate. It is hypothesized that these fungi could be able to stimulate host plant defense response led to decreasing pathogenicity. Study on mechanisms involving in root-knot nematode control by the mycorrhizal fungi can be used for these fungi application in nematode management. The aim of this research is to investigatt the chitinase activity changes rate in tomato inoculated host plant by mycorrhizal fungus as well as its role in the control of root-kont nematode. This method has been popular due to environmental pollution resulted from pesticides application. Several studies have indicated the positive role of mycorrhizal fungi in alleviating of plant disease causing agents in different ways. One of these involved mechanisms in the control of plant pathogens by arbuscular mycorrhizal fungi is promoting of chitinase activity in mycorrhizal plants. Materials and Methods: Mycorrhizal fungus Glomus mosseae as well as Meloidogyne javaniza nematode used in this research to study on chitinase activity changes in the interaction between mycorrhizal fungus and root-knot nematode in host tomato plant. Chitinase activity rate compared among control plants (non-mycorrhized) and mycorrhizal plants in four weeks (weekly). Next, the tomato was inoculated with mycorrhizal fungus and nematode separately, and in combination with each other. Non-inoculated plants with fungus and nematode (control) were carried out in greenhouse condition in an entirely randomized design with three replicates and enzyme activity in host plant roots were also measured during four steps every 48 hours followed by nematode inoculation. Chitinase activity rate was calculated by colorimetric and released N-acetyl glucosamine. Results and Discussion: Results of chitinase activity rate in tomato roots showed a significant difference in enzyme activity among inoculated and non-inoculated (control) host plants at different times. The mean comparison of two treatments in all of four steps also showed the significant difference among inoculated and control host plants. In other words, the enzyme activity rate was more in mycorrhizal plants rather than control plants in all the measuring times. Results of combined analysis of variance, as well as data mean comparison from chitinase activity showed the significant differences among treatments. However, differences were not significant among different times after inoculation. So, the enzyme activity rate did not show a considerable difference between control, nematode alone and mycorrhizal fungus treatments at different times. Furthermore there were no significant differences between control and nematode alone treatments across all the measuring times. In other words, root knot nematode had no significant effect on chitinase activity increasing in tomato roots. In mycorrhizal host plants inoculated with nematode, enzyme activity average was at highest amounts four days after inoculation with nematode and had a significant difference with other measured times. Conclusion: Results of this study showed that inoculation of arbuscular mycorrhizal fungus in tomato roots leads to increasing chitinase activity rate. Investigation of chitinase activity in tomato roots inoculated with mycorrhizal fungus showed the positive effect on treated plants rather than non-inoculated ones. In this study inoculation only with nematode also could not induce the increasing of chitinase acitivity but in combination with mycorrhizal fungus could promote enzyme activity considerably in initial steps of nematode invasion. This study as well as other similar investigations showed that the induction of chitinase activity by mycorrhizal fungus led to the defense of host plant against nematode invasion and the decrease of the damages.