Summary of doctoral thesis: Study on rhizosphere microbial communities of medicinal plant Curcuma longa L. to enhance turmeric yield and quality

The purpose of this thesis was to exploit beneficial aspects of microbial rhizosphere communities, especially effective bacteria and fungi of turmeric plant C. longa. The results were expected to support fundamental documents for proposing a suitable integrated nutrient management for turmeric plant in Vietnam.
Nội dung trích xuất từ tài liệu:
Summary of doctoral thesis: Study on rhizosphere microbial communities of medicinal plant Curcuma longa L. to enhance turmeric yield and quality MINISTRY OF EDUCATION VIETNAM ACADEMY AND TRAINING OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY ---------------------------- Hoang Kim Chi STUDY ON RHIZOSPHERE MICROBIAL COMMUNITIES OF MEDICINAL PLANT Curcuma longa L. TO ENHANCE TURMERIC YIELD AND QUALITY Major: Microbiology Code: 9 42 01 07 SUMMARY OF DOCTORAL THESIS Hanoi - 2020 The thesis was accomplished at: Graduate University of Science and Technology, Vietnam Academy of Science and Technology. First supervisor: Prof. Dr. Le Mai Huong Second supervisor: Dr. Tran Thi Nhu Hang First reviewer: Second reviewer: Third reviewer: The thesis defence will be held on …………….……………….. at Graduate University of Science and Technology, Vietnam Academy of Science and Technology. The thesis will be documented at: - Library of Graduate University of Science and Technology - National Library of Vietnam INTRODUCTION 1. Relevance of the research topic Curcuminoids are main bioactive ingredients of turmeric Curcuma longa L.. As a result of the recent growing demand for these compounds for pharmaceutical industrial application, the development of high quality turmeric production has become an urgent issue. To solve the problem, amendments in agricultural practices, post-harvesting processing techniques, and biotechnological methods have been highlighted. From another perspective, reducing chemical fertilizer while remaining crop yield is a trend of modern environmental friendly agronomy these years. Developing microbial inoculations from effective microorganisms for particular agricultural plants has thus been considered a practical focus. On the other hand, several rhizosphere soil microorganisms have been reported to play important roles in promoting biosynthesis of secondary metabolites, including curcuminoids. The entitled “Study on rhizosphere microbial communities of medicinal plant Curcuma longa L. to enhance turmeric yield and quality” was conducted to apply microbiology in sustainable development of agricultural productivity in Vietnam and worldwide. 2. Thesis objectives The purpose of this thesis was to exploit beneficial aspects of microbial rhizosphere communities, especially effective bacteria and fungi of turmeric plant C. longa. The results were expected to 1 support fundamental documents for proposing a suitable integrated nutrient management for turmeric plant in Vietnam. 3. Thesis contents Major contents of the research include: (i) Study on the relationship between varied nitrogen fertilizing managements and turmeric productivity; (ii) Isolation and biological assessments of rhizobacteria and fungi from turmeric plant; (iii) Study on genetic diversity of turmeric rhizosphere microbiomes in relation to high productivity nitrogen fertilizing managements; (iv) Preparation of biofertilizer from selected turmeric rhizosphere microbial candidates and case study in turmeric plant. CHAPTER 1. OVERVIEW 1.1. Turmeric Curcuma longa L. and curcuminoids component Turmeric (Curcuma longa L.) is a medicinal plant of family Zingiberaceae that distributes widely in South- and Southeast Asia, most abundantly in India and Thailand, and followed by Bangladesh, Indonesia, Myanmar and Vietnam [38] [39]. Chemical composition The rhizome of turmeric C. longa was determined to compose of 6,3-7% protein, 5,1-7,5% fat, 3,5-5% minerals, 69,4% carbohydrate and 9,5-13,1% water [43]. Major bioactive components of turmeric rhizome comprise curcuminoids [including curcumin, demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC)], aromatic turmerone (ar-turmerone), α-turmerone and β-turmerone. Commercialized curcumin mix was known to composed of 77% pure (Cur), 17% DMC and 3% BDMC [44]. According to Naama et al. 2 (2013), curcumin and DMC are less stable than BDMC [45]. In terms of antioxidant and tumor inhibiting active intensities, curcumin was considered the most potent, followed by DMC and BDMC, respectively [46] [44]. Biological and pharmaceutical activities of curcuminoids from turmeric The biological and pharmaceutical activities of turmeric and curcuminoids in particular have been well studied. As estimation until 2011, more than 7000 published articles have shed light on various aspects of curcumin including its antioxidant, hypoglycemic, anti-inflammatory and anti-cancer activities. Also, this natural compound exerts its beneficial effects by modulating different signaling molecules including transcription factors, chemokines, cytokines, tumor suppressor genes, adhesion molecules, microRNAs, etc. [47]. 1.2. Turmeric rhizosphere associated microorganisms Rhizosphere is defined as the area around a plant root that is inhabited by a unique population of microorganisms influenced by the chemicals released from plant roots [70, 71, 72]. The special conditions shape rhizosphere a desirable niche for microbial communities and one of the most biodiverse and dynamic habitat on the earth. Rhizosphere microorganisms have received attention since the intimate plant-microbe relationship being mentioned and evidenced. About 2–5% of rhizosphere microorganisms have been known to positively affect plant growth, and plants in turn are able to control these beneficial microorganisms [73, 74]. Accordingly, the rhizosphere microbiome plays an important role in improving soil fertility, plant metabolisms and ultimately enhancing plant ...