Drought tolerance indexes of 20 sesame varieties One day after drought treatment Three days after drought treatment Five days after drought treatment Drought tolerance ranking % UWP:
Trang 1MINISTRY OF EDUCATION AND TRAINING
HA NOI NATIONAL UNIVERSITY OF EDUCATION
-
TRAN THI THANH HUYEN
RESEARCH ON SOME PHYSIOLOGICAL AND BIOCHEMICAL
INDEXES RELATED TO DROUGHT TOLERANCE,
PRODUCTIVITY AND QUALITY OF SOME SESAME VARIETIES
(SESAMUM INDICUM L.) CULTIVATED IN HANOI
Major: Plant physiology Code: 62 42 30 05
Summary of doctoral thesis of biology
HA NOI - 2011
Trang 2The thesis completed at
Hanoi National University of Education
Scientific supervisor:
1 Prof Dr NGUYEN NHU KHANH
2 As Prof Dr NGUYỄN VAN MUI
Reviewer 1: Prof Dr Hoang Minh Tan
Reviewer 2: Prof Dr Do Ngoc Lien
Reviewer 3: Prof Dr Le Tran Binh
Thesis defense will be at the Council for State Level Thesis Marking at Hanoi National University of Education
At (time) on … (date) …… 2011
The thesis can be found at:
- National Library of Viet Nam
- Library, Hanoi National University of Education
Trang 3Publications related to the thesis
1 Tran Thi Thanh Huyen, Nguyen Nhu Khanh, Nguyen Thi Lan Phuong,
Hoang Thi Thu Phuong (2008), “Comparison of amino acid composition, nutritional value of sesame seed proteins in some local and imported
sesame cultivars in Vietnam”, Journal of Science, Ha Noi National
2 Tran Thi Thanh Huyen, Nguyen Nhu Khanh, Nguyen Thi Lan Phuong,
Hoang Thi Thu Phuong (2008), “Seed quality of some local and imported
black sesame (Sesamum indicum L.) cultivars in Vietnam”, Proceedings of the 4th National Coference on Biochemistry and Molecular Biology, pp
183-186, Science and Technics Publishing House
3 Tran Thi Thanh Huyen, Lê Thi Thuy, Nguyen Nhu Khanh (2010), “
Fluctuation of proline content in relationship to drought resistance ability at
the young age of 20 sesame varieties in artificial drought condition”, Journal
137-142
4 Tran Thi Thanh Huyen, Chu Thi Ngoc, Trinh Thi Thu Phuong (2010),
“Evaluation of drought tolerance of 20 sesame varieties (Sesamum indicum L.)”, Journal of Science, VietNam National University, HaNoi, Volume 26,
No 2S, pp 145-151
5 Tran Thi Thanh Huyen, Nguyen Nhu Khanh, Nguyen Thi Thanh Thuy,
Nguyen Thi Minh Nguyet (2010), “Study in genetic diversity of sesame
(Sesamum indicum L.) using RAPD”, Journal of Biotechnology, Volume
Trang 5INTRODUCTION
During the living process, plants are always influenced by external factors such
as drought, cold weather, heat, salinity, flooding, insects, etc Among these factors, high temperature, cold weather, wind and drought are considered the main causes to the dehydration in plants A long drought can affect relevant metabolistic reactions, different stages of plant growth and development leading to low productivity and quality of agricultural products and possible dead plants Drought is a complicated phenomenon and is widely regarded as the most important factor to optimise plant production
Sesame (Sesamum indicum L.) is among terrestrial plants with a wide range of
adaptation and traditionally cultivated in different types of soil Sesame is known as
“the queen of oil producing plants” with high nutritional values In sesame seeds, the high lipid content of 45 – 54%, especially with presence of unsaturated fatty acids (oleic, linoleic, linolenic), essential amino acids, antioxidant compounds (sesamin, sesamol, sesamolin and vitamin E), has increased values of sesame seeds Many studies in the world have been carried out to evaluate these characteristics of sesame
In Vietnam, few studies on sesame has been conducted so far, especially typical features of sesame on drought tolerance have not been systematically explored in depth In the mean time, there have been quite many studies on drought tolerance in other cropping plants such as sweet grass, paddy rice, mung bean, tobacco, green bean, maize, etc Drought tolerance of a plant depends on its own genotypes, agrobiological charateristics, physiological and biochemical characteristics Therefore, it is necessary to study on the relationship between physiological and agrobiolocial characteristics, and further more at the molecular level, the characteristics related to drought tolerance of sesame Moreover, since Vietnam is located in the monsoon tropical region, drought which is a frequently found factor that affects growth and development of crop plants, crop production and its quality Therefore, studying to analyse influences of droughts, to assess and select varieties which are of high drought tolerance is an effective and necessary measure to minimise drought effects on crop plants in general, and sesame, in particular On that basis, drought tolerance mechanisms, directions to improve and to select potential sesame varieties with high drought tolerance, high yield, stability and adaptability for unfavourable natural conditions in a range of different ecological regions will be identified
From the above reasons, we have carried out the study:
“Research on some physiological and biochemical indexes related to drought tolerance, productivity and quality of some sesame varieties (Sesamum indicum L.) cultivated in Hanoi”
2 Objectives of the study
- To identify differences between some physiological and biochemical criteria related to drought tolerance of sesame varieties of good and poor drought tolerance
Trang 6Through this study, to recommend criteria which are characterised by drought tolerance of sesame varieties to be as a basis for selection of sesame varieties of high
drought tolerance
- To identify genetic relationships between sesame varieties of good and poor
drought tolerance among the 20 pre-screened sesame varieties
- To assess yield and seed quality of some drought tolerant sesame varieties
selected during experiments of the study conducted in Hanoi
3 Scientific and practical significance of the study
Scientific significance
- Data collected in the study will be scientific evidence on physiological and biochemical reactions related to drought tolerant ability of sesame varieties under the study
- Study results identified the genetic relationship between sesame varieties of high and poor drought tolerance among 20 sesame varieties under the study
- The results of sesame seed analysis will have additional contributions of scientific evidence, which is significantly important to nutritional values and uses of sesame seeds
Practical significance
- Differences between physiological and biochemical criteria of high and poor drought tolerant varieties can be used for selection and generation of high drought tolerant varieties with high yield and good quality so as to reduce input materials and labour in selecting drought tolerant varieties
- Study results on sesame seeds are also a criterion of reference for selections
of sesame varieties with both drought tolerance and good seed quality to be used in industries of sesame exploitation and processing as well as in medicine and pharmacy
4 New contributions of the thesis
- Identified physiological and biochemical differences between high and poor drought tolerant varieties On that basis, classified sesame into different groups of sesame with drought tolerance at different levels Proposed V5 and V14 varieties which are highly drought-tolerant but can give stable production and good seed quality
- Combined the assessment of drought tolerance with the analysis of genotypes with RAPD techniques and showed different sesame varieties with genetically high and poor drought tolerance
- Analysed some criteria on nutritional quality of sesame seeds such as contents of minerals, amino acids, lipids, acid indexes, especially 3 unsaturated fatty acids (oleic, linoleic and linolenic)
CHAPTER I RESEARCH REVIEW 1.1 General introduction on sesame
1.2 Crops’ drought tolerance
1.3 Research situation of genetic diversity of sesame
Trang 7CHAPTER II RESEARCH SUBJECT AND METHODOLOGY 2.1 Research subject
Sesame varieties were obtained from Department of Seed Gene Bank – Vietnam Institute of Agriculture Science and Technology
2.2 Methodology
2.2.1 Identification of physiological criteria: Rapid assessment of drought
tolerance, identification of soil’s wilting coefficient, water content in tissues when plants are withered, and associated water content were performed applying Dhopte method Leaf tissues’ water-retaining capacity (identified with Kozushco method), osmotic pressure of cells, fluorescent chlorophyll were identified by OPTI-Sciences OS-30 Chlorophyll Flourmeter Total chlorophyll content was identified with methods of Wintermans, De Mots, while associated chlorophyll content was identified based on Shmatco
2.2.2 Identification of biochemical criteria: saccharose content and α-amylase
activity were determined by Miller G.L method; proline content, by Bates method; lipid content, by Soxlet method Amounts of minerals and unsaturated fatty acids were analyzed by gas chromatography Total essential amino acid content in sesame
seeds was identified by HP-Amino Quant series II
2.2.3 Identification of genetic diversity by RAPD (Random Amplified Polymorphic DNA): DNA isolation was based on Doyle method; RAPD-PCR was
carried out using the method of William et al with 26 random primers
CHAPTER III RESULTS AND DISCUSSIONS 3.1 Assess dehydration resistance of 20 sesame varieties in researched area 3.1.1 Impacts of drought on physiological criteria
3.1.1.1 Rapid assessment of drought tolerance
We rapidly assessed drought tolerance of 20 sesame genotype during seedling period in laboratory including: rate of un-withered plant, rate of recovered plant and drought tolerance indexes V14 and V5 had the highest drought tolerance indexes, which reached 22085 and 21541, respectively Two varieties had the lowest drought tolerance indexes were V4, V8, which reached 13675 and 12646 (the higher the drought tolerance index is, the higher the drought tolerance capacity is)
Based on drought tolerance indexes in the table 3.1, initially we divided 20 varieties into three groups: the good drought tolerance group has two varieties: V14 and V15; low drought tolerance group has two varieties: V4 and V8; other 16 varieties have medium drought tolerance indexes including: V18, V17, V13, V16, V12, V19, V11, V6, V15, V2, V1, V9, V10, V3, V7, V20 varieties
Trang 8Table 3.1 Drought tolerance indexes of 20 sesame varieties One day after
drought treatment
Three days after drought treatment
Five days after drought treatment
Drought tolerance ranking
(% UWP: rate of un-withered plant; % RP: rate of recovered plant)
3.1.1.2 Soil’s wilting coefficient
We identified soil’s wilting coefficient in order to determine water absorption capacity from the soil of different sesame varieties The minimal point of soil moisture the plant requires not to wilt is defined as soil’s wilting coefficient If moisture decreases to this or any lower point a plant wilts and thus can no longer recover its turgidity The physical definition of the wilting point (symbolically expressed as θpwp or θwp) is defined as the water content at −1500 J/kg (or −15 bars)
of suction pressure, or negative hydraulic head The results are indicated in the Table 3.2
For soil’s wilting coeficient, V5 and V14 were withered when water content in soil was low, which was only 10.89% and 11.04% compared to undried soil V3 and V8 were withered when water content in soil was higher, reaching 14.92% and 15.08%, respectively
Trang 9Table 3.2 Humidity of withered plants and soil’s wilting coefficient
Wilting coeficient of 20 sesame varieties fluctuated from 3.41 – 4.85g H2O/100g dried soil Wilting coeficients were lowest for V5 and V14 varieties Of which V5 had the lowest wilting coeficient, which was 3.41g H2O/100g dried soil Two varieties V3 and V8 showed the highest wilting coeficients, which were 4.85 and 4.80g H2O/100g dried soil, respectively That means, water content in soil, which V5 and V14 could not absorb, was lower than water content in soil, which V3 and V8 varieties could not absord In the same soil type, the variety which can survive with lower water content in the soil, have better drought tolerance and vice versa The results showed that V5 and V14 have the best drought tolerance and V3 and V8 have the worst drought tolerance
3.1.1.3 Impacts of drought on water content in tissues
At diferent drought levels, water content in tissues is different between varieties Water content in tissues inffluences physical actitives in general and in leaf tissues in particular Therefore, the water content in plant at wilting point is critial for
Varieties
Humidity of withered plant
Soil’s wilting coefficient (g
H 2 O/100g dried soil)
Drought tolerance ranking
Trang 10supplementary water for plants, minimizing harmful effects of drought on crops and through this amount of water we can assess water dificit torelance capacity
Table 3.3 Water content in leaf tissues when plant withered
Water content in tissue when plant withered (%) Sesame
condition
Drought condition
Rate comparing with normal condition
(%)
Drought tolerance ranking
3.1.1.4 Impact of drought on associated water content in leaf
In the drought condition, water in plant has a trend to increase associated water content and increase free water content Therefore, associated water content and water-retaining capacity of leaf tissue have very important meaning for tolerance
Trang 11capacity in water deficit condition Associated water content in normal and drought condition is presented in table 3.4
Table 3.4 Associated water content in sesame leaf in normal and drought
condition Associated water content in sesame leaf (%) Sesame
varieties
Normal condition
Drought condition
Rate to compare with normal condition (%)
Drought tolerance ranking
Under the drought condition, to reduce dehydration, a part of water in tissues shifts to associated water At the same time dehydration also increases the ratio of associated water in plants Moreover, the increased associated water ratio in tissue under the drought condition can be explained by the increase of dissolved molecular concentration (ions of minerals, saccharose, organic acids, amino acids…) The
Trang 12drought condition also increases the content of absorption associated water This is absorption adjustment, and is the main mechanism to maintain turgor pressure in almost all plants to deal with dehydration and helps plant continuously absorb water and maintain water for metabolism
3.1.1.5 Impact of drought on water-retaining capacity of leaf tissue
Under drought condition, water-retaining of leaf tissue is a mechanism to support plants to resist water deficit Content of water loss during the same period from one amount of sample higher, the water-retaining capacity is lower and lead to resistant capacity to disadvantage environment is lower and otherwise hydration of plant tissue slower, water-retaining capacity is higher, resistance capacity to stress environment higher When leaf tissue lost water to one restriction level, leaf cells produce water-retaining mechanism to sustain water to assist plants to against water deficit
Table 3.5 Water-retaining capacity of leaf tissue in drought condition of 20
researched sesame varieties Water-retaining capacity of leaf tissue (% content of lost water/ total
water content) Sesame
varieties
One day after drought treatment
Drought tolerance ranking
Three days after drought treatment
Drought tolerance ranking
Five days after drought treatment
Drought tolerance ranking
Trang 13Water-retaining capacity of leaf tissue is expressed by amount of lost water (% water lost/ total water content) Therefore, to assess water deficit resistance of researched sesame varieties, we identified water-retaining capacity of leaf tissue at different period after drought treatment (one day, three days and five days)
Data collected in the table 3.5 indicates that water-retaining capacity of leaf tissue changes over time (number of days) of droughts
Amount of lost water after three drought treatment days of all 20 researched varieties is less than content of lost water after one drought treatment day indicating water-retaining capacity increased However, after 5 drought treatment days, content
of lost water increases more than the content of lost water after three drought treatment days, or after five drought treatment days Water-retaining capacity of leaf
of all researched varieties is reduced At the same drought treatment period, the varieties which have smaller content of lost water/ total water content will have better water-retaining capacity
Collected data illustrated that: at three point of time, after 1, 3 and five drought treatment days, content of lost water is the smallest for V14 variety; following is V5 meaning that these two varieties have the best water-retaining capacity
The group, which has the worst water-retaining capacity, does not identically fluctuate In particular: after one drought treatment day, position of ranking order 20 belongs to V8; after three drought treatment days this position belongs to V20; and after five drought treatment days is V3 Therefore, it is clear that all three varieties V3, V8, and V20 belong to groups, which have the worst water-retaining capacity or the lowest drought tolerance
Together with relative drought tolerance capacity, the water-retaining capacity
of leaf tissue also has similar results for some groups such as: V5, V14 which have the highest water-retaining capacity while V3, V8, V20 have the worst water-retaining capacity
3.1.1.6 Impacts of drought on content of chlorophyll and fluorescent chlorophyll
of sesame leaf
In the drought condition, then content of chlorophyll is different in each
variety The indicator of chlorophyll content, especially the content of relative pigments can be used to evaluate photosynthesis activity and resistance capacity of crop We calculated content of total chlorophyll and content of relative chlorophyll of
20 researched sesame varieties and realized that:
The content of total chlorophyll of all 20 sesame varieties is reduced when drought occurs The two varieties V5 and V14 reaches the highest value of chlorophyll content (1.934 mg/g leaf and 1.930 mg/g leaf) These two varieties are also slightly impacted by water deficit (reached 90.53% and 88.44% in comparison to the normal condition) Therefore, they rank the first and the second position respectively V3 and V13 are the most seriously influenced by water deficit, which have amount of total chlorophyll reduced to 67.49% and 74.29% as compared with normal condition