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MINISTRY OF EDUCATION AND TRANING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM ACADEMY OF AGRICULTURE SCIENCES NGUYEN XUAN TRUONG RESEARCH ON TECHNICAL MEASURES TO DEVELOP RUBBER TREES IN THE NORTHERN MOUNTAINOUS PROVINCES Major: Crop science Code: 9620110 SUMMARY OF AGRICULTURAL DOCTORAL DISSERTATION HA NOI - 2020 The project is completed at VIETNAM ACADEMY OF AGRICULTURE SCIENCES Scientific superviors: A Dr Nguyen Van Toan Dr Le Van Duc Reviewer 1: Reviewer 2: Reviewer 3: The dissertation shall be defended in front of the Institute’s thesis evaluation council meet at: VIETNAM ACADEMY OF AGRICULTURE SCIENCES At h date month year 2020 This dissertation can be found at - National Library - The Vietnam Academy of Agriculture Sciences’ Library - The Northern Mountainous Agriculture and Forestry Science Institute’s Library LIST OF PUBLICATIONS RELATED TO THE THESIS Nguyen Xuan Truong, Nguyen Van Toan (2019), "Research results on the selection of some high-yielding rubber lines in the Northern mountainous areas", Vietnam Journal of Agricultural Science and Technology, (106), p 39-43 Nguyen Xuan Truong, Nguyen Van Toan, Le Van Duc, Bui Thi Hai Yen, Nguyen Khanh Linh and Cao Phi Bang (2018), “Effects of low temperatures on some physiological and biochemical reactions of five varieties rubber (Hevea brasiliensis)”, Scientific report on biological research and teaching in Vietnam - The 3rd National science conference Cao Phi Bang 1* , Nguyen Xuan Truong2*, Nguyen Van Toan2, Le Van Duc3, Le Manh Tu4, Nguyen Thi Hai Yen5 (2017), "Influence of potassium on some physiological and biochemical indicators of rubber trees (Hevea brasiliensis) under short-term low temperature shock”, Journal of Agriculture and Rural Development No 24, p 41-46, Periodical 2, December 2017 Nguyen Van Toan, Dao Ba Yen, Nguyen Xuan Truong, Le Thi Trang and Nguyen Thi Thu Cuc (2016), TBKT01-24: 2016/BNNPTNT: Technical procedure for rubber breeding in the Northern mountainous region, Decision No 62 / QD-TT-CCN dated March, 2016 of the Director of the Crop Division, MARD Nguyen Van Toan, Nguyen Xuan Truong, Dao Ba Yen and Nguyen Thi Thu Cuc (2015), “Research results on the completion of propagation procedure and new plantation of two rubber variety VNg 77-2 and VNg 77- for the Northern mountainous provinces”, Journal of Agriculture and Rural Development No (2015), p 34-44 Le Quoc Doanh, Nguyen Van Toan, Nguyen Xuan Truong, Do Sy An and Nguyen Huy Thuan, (2011) Decision No 1208 / QDBNN-TT on the recognition of the new agricultural plant variety, dated June 2011 of the Ministry of Agriculture and Rural Development INTRODUCTION 1.The need of this research There are two most challenging factors for developing rubber in the Northern Mountainous Region (NMR) Firstly, low temperature conditions in winters (average minimum temperature from 10-150C) Secondly, soils use for rubber plantations are mostly steep, with the slope ranges from 150 to 200 In addition, the topsoil is frequently very thin, while the total nutrients and exchangeable cation capacity of rubber soils are poor and low These limitations need to be addressed in order to sustainably develop rubber trees in the NMR One of the proposed solutions is to select suitable rubber varieties (good growth, high yield and cold tolerance), accompanying with breeding and cultivation techniques to develop rubber in the Northern mountainous areas Meanwhile, the research results on rubber trees in the NMR are limited in terms of quantity and research time, and to our knowledge, there has not been any systematic study to deal with such challenges Therefore, the study of the topic: "Research on technical measures to develop rubber trees in the northern mountainous provinces" is very necessary The objects of the research Successfully select cold-tolerant rubber lines and identify suitable breeding and cultivation techniques to meet the requirements of sustainable rubber development in the Northern Mountainous Region The subjects and scope of this research 3.1 Research subjects The study conducted on 13 common rubber clones: IAN 873, RRIC 100, RRIC 121, GT1, RRIM 600, RRIM 712, RRIV 1, RRIV 106, RRIV 124, LT 74, VNg 77-2, VNg 77 -4, VN 73-46 and 28 newly created domestic rubber clones (detailed in the introduction of rubber varieties, appendix 2) 3.2 Research scope - Assess the cold tolerance of clones planted in nursey gardens at the establishment stages of aged and Materials for analyzing physiological and biochemical indicators including morphological and anatomical characteristics of leaves were sourced from 1- whorl leaf polybag rubber seedlings in the nursery gardens and grafted branches in the breeding gardens - Research on rubber tree development is limited to selective breeding methods, breeding techniques, cultivation methods in the immature stages, aiming at increasing growth ability, latex yield and shorten the immature period At the same time, it aims to increase the capacity of supplying cold-tolerant rubber varieties to meet the demand of expanding rubber growing areas in the Northern mountainous provinces The research content of this thesis does not aim to develop rubber trees in a multi-purpose direction In addition, in order to meet the research objectives, this study inherited the research experiments and results, which were already conducted and implemented during 2011-2015 by the author of this research These inheritances have been agreed and allowed by the Northern Mountainous Agriculture and Forestry Science Institute (NOMAFSI) The scientific and practical significance of the research Scientific significance The thesis is a systematic study on the botanical characteristics of rubber trees with a focus on finding the relationships between morphological, leaf anatomy and physiological and biochemical criteria in relation to low temperature tolerance This is the basis for the rapid selection of individuals oriented to the goal of selecting coldtolerant rubber varieties, contributing to reducing the breeding time The research results of the thesis have provided the basis for completing the rubber tree breeding technique, which is the foundation for the continuation of research on rubber breeding techniques in the ecological conditions of the Northern mountainous areas; as well as plays as reference materials for educational purposes regarding rubber trees in the Northern mountainous areas Through nutritional field experiments, the thesis has sugguested the hypotheses about the effect of fertilizer quantities on the changes of mineral nutrient contents in rubber leaves and some soil chemical characteristics These are good suggestions for further research Practical significance The study sucessfully selected cold-tolerant, high-yield rubber clones to recommend for rubber mass production in the NMR The study has completed the breeding process; supplementing some technical measures in rubber production in the NMR such as selecting suitable intercropped crops on immature rubber gardens and appropriate fertilizer quantity These are useful recommendations for provinces where rubber tree are planting, both for rubber farmers and staff involved in directing the rubber production Novel contribution of the study The dissertation is the firstly comprehensive research project on newly created and imported rubber genetic resources tested in the NMR, selected some recommended rubber lines for production: DVT 27, RRIV 124 and VNg 77-4 In particular, VNg 77-4 has been recognized as cold tolerant rubber varieties and are allowing to use for mass production in the Northern moutanous region The desertation is also the first research in Vietnam to study cold tolerance of rubber varieties in combination with assessing morphological expression, leaf anatomical characteristics and changes of biochemical and biochemical indicators under the effects of low temperature conditions; establishing a multivariate correlation function which reflects the relationship of damage index of some leaf anatomy with physiological and biochemical criteria The thesis has clarified the differences in the breeding season compared to the traditional region; techniques for planting and tending nursery gardens; the important role of potassium fertilizer in increasing cold tolerance for rubber in nursery stage The study also sucessfully recommended a technical process of propagating rubber trees for the NMR (recognized by the Ministry of Agriculture and Rural Development as a technical advance) The research results of the thesis initially affirmed that: galangal (Alpinia officinarum) is an efficiently intercropping crop during the period of from closed canopy to the early commercial stage of rubber tress; the 1.5 time increased amount of fertilizer compared to the technical procedure issued on 2012 (60 kg N + 60 kg K2O + 30 kg K2O / ha) resulted in the increased growth of rubber trees in the immature period, and significantly increased latex yield in the first exploited years; establishing a linear relationship between yield and rubber perimeter; suggesting initial assesments on leaf nutrient content and soil chemistry characteristics of fertilization treatments Chapter LITERATURE REVIEW AND SCIENTIFIC BACKGROUND OF THE RESEARCH The scientific background of the research Rubber trees have requirements on climatic conditions such as evenly distributed rainfall of over 2,000 mm / year without dry season, the number of rainy days is from 125-150 days /year; maximum temperature from 29-340C, minimum about 200C with average monthly temperature from 25-280C The main difference in climatic conditions in rubber plantations in traditional and nontraditional regions is the low average temperature It causes not only morphological damages on the visible parts of rubber trees: leaves, stems, roots but also directly affect the physiological processes in plants: photosynthesis, respiration and water exchange Each rubber variety has different leaf morphological characteristics (varies with cultivated conditions and the environment) This feature is the difference between varieties and is used in the evaluation and identification of varieties at nursery and rubber plantations at immature stages Rubber propagation by grafting is still the main breeding method, which is applied to produce leafy seedlings for new planting in the world as well as in Vietnam The two important plant materials used are the scion cuttings taken from the breeding garden and the rootstock The compatibility of these two materials plays a critical role in deciding the survival rate of rubber trees after transplantation Prolonging the standard rootstock will extend the seed production time Fertilizers have been shown to be able to improve growth ability, shorten growth duration in unfavorable growing areas, and contributing to latex yield improvement Rubber trees need fertilizer mainly with macronutrients: N, P, K and partly Mg Potassium plays a role in increasing plant tolerance in low temperatures.In addition, unfavorable condition increases the demand for fertilizers for rubber trees Appropriate intercropping on rubber plantations can bring economic benefits, improve plant growth, maintain and improve the physical and chemical characteristics of the soil Moreover, based on the characteristics of each type of crop and the growth stage of the rubber plantation to choose suitable intercropping crops Some comments are drawn from the literature review Suitable variety is the most important factor for growing rubber in unfavorable areas Evaluation of newly created and imported rubber clone lines is still the method of selecting rubber varieties being used in the world Some of the main criteria used in evaluating variety selection in non-traditional areas are: growth ability, latex yield and cold tolerance based on the method of Huang & Pan introduced in 1992 Aside, some physiological and biochemical indicators are also used to assess the cold tolerance of rubber trees such as relative water content, chlorophyll fluorescence, photosynthetic pigment (chlorophyll a and chlorophyll b, total chlorophyll and carotenoid), proline and catalase content Some of the criteria used in the anatomy of the leaves are: thickness of the main veins and lamella, the lamina layer and the chlorenchyma Cloning by grafting is still the main method used to create materials for new plantation In order to sustainably develop rubber trees in the Northern region, the selection of suitable varieties and breeding techniques that suits natural and socio-economic conditions of the region plays an important role Currently, the research of variety sustability for the NMR is poorly implemented, especially in terms of research duration to evaluate the performance of newly created domestic clones as well as new imported varieties To date, there has not been any studies on cold tolerance of varieties regarding physiological, biochemical criteria and leaf defoliant characteristics In addition, solutions to deal with the effects of low temperature conditions to the breeding processes such as preparation of scion cuttings, planting time, seedling care have not yet been identified In the NMR, studies on inorganic fertilizer application were only evaluated its effect during the first years of applications (1-2 years) and there are no outcomes of soil nutrient composition and rubber leaf evaluation A number of studies on intercropping have shown to be effective when rubber trees are intercropped in the early stage in the region However, there has not been any studies on intercropping with rubber trees during the first plantation years when the tree canopy begins to close until it is fully closed Chapter MATERIAL, CONTENT AND RESEARCH METHOD 2.1 Research material - Rubber variety: - Rubber varieties: IAN 873, RRIC 100, RRIC 121, GT 1, RRIM 600, RRIM 712, RRIV 1, RRIV 106, RRIV 124, VNg 77-4, VNg 77-2, LT 74 and VN 73-46 - Clone lines: 28 new domestic hybrid clones provided by the Vietnam Rubber Research Institute - Fertilizers: Nitrogen Ha Bac (46% N), Lam Thao phosphate (Supephosphate 16% P2O5), Kaliclorua (60% K2O), Maggie phosphate (16% MgO) - Intercropping crops: Mulato (Brachiaria mulato), Brizantha (Brachiaria brizantha), Galangal (Alpinia officinarum), Turmeric N8 (Curcuma longa) Mondograss (Ophiopogon japonicus Wall.) - Other materials: Seed rubber tree, grafted rubber tree branches (4-5 whorl leaves), grafted buds, 1- whorl leaf polybag rubber seedlings 2.2.Time and research location 2.2.1 Research time: All the research components were undertaken from 2011- 2019 2.2.2: Research locations: NOMAFSI; Chieng Ban and Chieng Kheo communes, Mai Son district, Son La province; Khong Lao commune, Phong Tho district, Lai Chau province; and Minh Quan commune, Tran Yen district, Yen Bai province 2.3 Research content Content 1: Study on agro-biological characteristics and cold tolerance of some rubber clones in the NMR; Content 2: Research on rubber breeding techniques; Content 3: Research on some cultivation techniques for rubber trees 2.4 Research method 2.4.1 Research method of content 1: Study on agro-biological characteristics and cold tolerance of some rubber clones in the NMR 2.4.1.1 Experiment design Experiment 1: Research cold tolerance in the field In the variety comparison experiment, assess the level of damage to the entire number of plants in the treatment On the nursery and the plantation demonstration, randomly evaluate the level of morphological damage of rubber morphology with replicates (each replicate with rubber rows, 10 trees in each row) Experiment 2: Research on growth ability and latex yield of some rubber clones The experiement consists of treatments, each treatment is a clone Each treatment includes plants with three replicates and was completely randomized block designed, which ended up with a total 15 plants Design density of 571 trees / (spacing of x 2.5 m) Plants used for the experiment were the polybag rubber seedlings with stabe whorl leaves Experiemental clones were including DVT 27, DVT 30, DVT 54, RRIV 124, VNg 77-2, VNg 77-4 and LT 74 Experiement 3: Study on morphological and anatomical characteristics of leaves of some rubber varieties The varieties selected for research include: IAN 873, RRIC 121, RRIV 1, RRIV 124 and VNg 77-4 Varieties on the nusery fields were uniformly cut in February The timing to select and eveluate morphological criteria was when the grafted branches had stable whorl leaves The leaflets selected for morphological evaluation were typical leaves in the middle of the selected leaf layers Leaf samples were also taken for anatomical analysis The experiment was arranged in completely randomized blocks of 10 plants / variety x replicates Experiement 4: Research some physiological and biochemical criteria in rubber leaves Experiement 4a Assess the relative water content of some rubber clones Five varieties were selected for the research including: IAN 873, RRIC 121, RRIV 1, RRIV 124 and VNg 77-4 Two factors experiment were arranged in completely randomized block with rubber varieties, thresholds for low temperature processing time of 80C for 60 hours, 120 hours and replicates Number of experimental leaves: leaves / variety / replicate Experimental leaves were collected at 40 days of age The sample preparation and determination of relative water content processes used the method of Balsamo, RA (2006) (Appendix 16) Experiement 4b Study the response of some biochemical and biochemical indicators of some rubber clones in low temperature conditions The studied rubber varieties including: IAN 873, RRIC 121, RRIV 106, RRIV 124 and VNg 77-4 Each variety is a treatment, each treatment consists of plants (2 whorl leaf) placed under 80C for 60 hours Methods of Sarkar.J (2013) was used for sample 10 The treatments were: T1: Grafting in June T4: Grafting in September T2: Grafting in July T5: Grafting in October T3: Grafting in August Experiment 7: Effects of potassium fertilization quantity on some biochemical and biochemical indicators of rubber seedlings in low temperature conditions The experiment was designed in randomized complete blocks, in which each variety was seperately arranged The experiment included treatments (changing the concentration of K2O) Each treatment had 10 plants with replicates The total number of experimental plants was 150 trees /variety After being fertilizered with amount of gN + g P2O5/seedling, the polybag rubber seedlings then were applied with potassium fertilizer by the amount of 0,00, 0,25, 0,50, 0,75, 1,00 g K2O/ each seddling, depending on the treatments Rubber trees were fertilized at 35 days after grafting, and 20 days after fertilizing, the plants were measured for growth and heat stress treatment at 8°C (12h for RRIV 124 and 48 hours for VNg 77-4) using the method of Sarkar.J (2013) (Appendix 17) 2.4.2.2 Parameters and observation methods Agronomic parameters Diameter of grafted buds, diameter of grafted branches, number of whorl leaf, grafting survival rate were evaluated based on the technical standard 10 TCN 9002: 2006 Some other criteria: Number of horizontal buds (buds), height of grafted branches (cm), sufficient rate of woody graft (%), number of sufficient grafted cuttings / 1m of grafted branches (cuttings), sufficient rate of grafted branches (%), total meters of branches / (m), height of grafted buds (cm), leaf size, successful seedling rate (%), propagation coefficient (ha / year) Biochemical and physiological criteria Photosynthesis pigments, chlorophyll fluorescence (Fv / Fm), proline content (µg / g of fresh leaves), catalase enzyme activity (U / g of fresh leaves) were conducted using the method described in the subheading 2.4.1.2 11 2.4.3 Research method for contents Research on some cultivation techniques for rubber trees 2.4.3.1 Experiment design Experiment 8: Determination of suitable fertilization time for immature rubber trees The experiment included fertilizer time treatments, each time was a treatment with replicates, each replicate had 15 trees The total number of experimental plants was 225 The amount of fertilizer used in this experiemnt was followed the the rubber tree technical document issued in 2012, in which 60 Kg N + 60 kg P2O5 + 30 kg K2O/ were equally divided into applications for each season Experiment treatments included: T1: Applied in April and in October (Control) T2: Applied in April and in September T3: Applied in March and in August T4: Applied in May and in September T5 : Applied in April and in July Experiment 9: Effect of chemical fertilizer quantity on the grow capability in the immature period and latex yield in the early harvest period The experiment consists of treatments, designed in a randomized complete block with replicates, each replicate had 10 trees Experiment treatments included: T 1: 60 Kg N + 60 kg P2O5 + 30 kg K2O/ha (Control) T 2: 60 Kg N + 60 kg P2O5 + 30 kg K2O + 15 kg MgO/ha T 3: 90 Kg N + 90 kg P2O5 + 45 kg K2O /ha T 4: 90 Kg N + 90 kg P2O5 + 45 kg K2O + 22,5 kg MgO/ha T 5: 120 Kg N + 120 kg P2O5 + 60 kg K2O /ha T 6: 120 Kg N + 120 kg P2O5 + 60 kg K2O + 30 kg MgO/ha Experiment 10: Crop choice for intercropping with rubber trees when its canopy was fully closed Some crops that were experimentally evaluated including: Mulato grass, Brizanthag grass, Galangal Mondograss MulatoII, Brizantha, Turmeric N8 and Mondograss Each crop was experiemntally arranged separately on a big spot without repetition (40m2/crop) Experiement 11: Effect of row space and harvesting time on galangal growth and productivity On the years old VNg 77-4 rubber field, galangal is arranged to intercrop in every rubber rows (plant row then skip row) with space of 1.5m, 2m, 2.5m and 3m (planting distance: 70 x 50 cm) Each intercropping space is a treatment, arrnaged as randomzied 12 complete block with replicates and 40m2 / replicate Galangal was harvested at 18, 24 and 36 months after planting 2.4.3 Parameters and observation methods Agronomic parameters - The growth indicators (stem perimeter and primary bark thickness), latex yield (gram/tree/cut) was examined using the same method described in subheading 2.4.1.2 Nutrient content in soil and in rubber leaves - Soil sampling methods: described by Tong Viet Thinh (2014) Indicators for analyzing included pH, soil organic matter, total N, total P, total K, available P, Ca2+, Mg2+available K, and CEC - Methods of analyzing leaf nutrient content (N, P, K, Mg and Ca) based on the standard: 10 TCN 451: 2001, 10 TCN 453: 2001 10 TCN 454: 2001 and TCVN 9015-2: 2011 Evaluation criteria and methods for intercropping crops - Plant height of each crop type, yield (turmeric, grass and galangal) The yield of turmeric N8 and galangal (tons / ha) was assessed using the descriptive and evaluation forms for ginger genome gene source of the Plant Resource Center The economic efficiency was assessed using the CIMMYT method (1988) 3.2.5 Statistical analysis - Data were analyzed using the Excel, Statistix 8.2, SPSS and R Software Basic statistical parameters: average, percentage (%), standard deviation, coefficient of variation, correlation coefficient (r), determination coefficient R, Lmg index Analysis of variance (ANOVA), group analysis, assessment of differences by Duncan test, LSD0.05, assessment of the correlation among parameters Chapter RESULT AND DISCUSSION 3.1 Agro-biological characteristics and cold tolerance of some rubber clones in the Northern region 3.1.1 Evaluation of the field cold tolerance The statistics show that: In early 2011, the NMR experienced a cold stress lasting for more than 30 consecutive days The average temperature in the month ranged from - 15.20C, except for Muong Te Lai Chau, where the average temperature was 16.10C The absolute minimum temperature was from 0.7 - 10.50C The number of days with absolute minimum temperature were from 11 to 16 days The sunny hours in the month was very low (0 - 61 hours) These 13 factors were ideal conditions to evaluate the effects of cold stress on rubber trees Some results of assessing the damage degree of the cold condition are as follow: a For clones that are newly domestic created: The damage degree of the clones were ranging from 24.4 to 96.0% Good coldtolerant clones are: 27, 30, 40 and 54 By contrast, poor cold-tolerant clones are: 23, 24, 25, 26, 34, 37, 38, 39, 44, 45, 48, 55, 58 b For the popular rubber varieties: Results from the the damage degree assessment of 11 rubber varieties on the nursery garden in Phu Ho - Phu Tho indicated that the varieties that are slightly affected (damage level