Nghiên cứu cải tiến các giống đậu tương DT2008, DT96 và đt26 bằng phương pháp xử lý đột biến tia gamma nguồn co60 tt tiếng anh

i MINISTRY OF EDUCATION MINISTRY OF AGRICULTURE AND TRAINING AND RURAL DEVELOPMENT VIETNAM ACADEMY OF ARICULTURAL SCIENCES -* - NGUYEN VAN MANH RESEARCH ON IMPROVING SOYBEAN VARIETIES DT2008, DT96 AND ĐT26 THROUGH 60Co GAMMA IRRIGATION Research: Genetics and Crop breeding Code: 9620111 DOCTORAL THESIS SUMMARY OF AGRICULTURE Hanoi - 2020 The Doctoral thesis was completed in: VIETNAM ACADEMY OF AGRICULTURAL SCIENCES Supervisors: Prof PhD Le Huy Ham PhD Le Duc Thao Objection 1: …………………………… Objection 2: …………………………… Objection 3: ………………………… The Doctoral thesis is defended at Institute Committee of PhD Dissertation Examination: Vietnam Academy of Agricultural Sciences At ……………… day……………month………… 2020 PhD thesi can be found at: National Library of Vietnam Library of Vietnam Academy of Agricultural Sciences INTRODUCTION Imperativeness of the thesis Soybean (Glycine max (L.) Merrill), a short-day crop, has high nutrient content (Protein 30 - 45%, lipit 18 – 22% ), easy cultivation, wide adaptation, effect on land reclamation and insect limitation in the rotation of other crops In Vietnam, soybean is a traditional crop and grown in 28 of 63 provinces/cities It plays an important role in agricultural production and has high economic value and efficiency in crop restructing but its area is decreasing In 2018, soybean production reached at only 53.1 thounsand hecta with the productivity of 80.8 thounsand tons (https://www.gso.gov.vn), only met about 8% of domestic demand, the rest had to imported The causes of decrease in soybean production are the lack of soybean varieties with high yield, good quality and good resistance; difficult condition of cultivation; backward cultivation techniques and low intensive investment Therefore, it is urgent and necessary to create new soybean varieties with high yield, good quality and suitable for many different crops In soybean, it is hard to eliminate anthers because its flowers are small, perishable and vulnerable In addition, its completely self-fertilization results in being difficult to create heritable variations by hybridization Therefore, mutation method through 60Co gamma irradiation is so efficient to generate new heritable variations in soybean, contributing to diversifying genetic variations, shortening the time to select a new variety, and especially improving existing soybean varieties In order to diversity soybean varieties in production, contributing to expanding the area and developing soybean production in Vietnam, the thesis “Research on improving soybean varieties DT2008, DT96 and ĐT26 through 60Co gamma irradiation” has been carried out Objectives Improving soybean varieties in the goals of shortening the growth duration and stem height, increasing the resistance to lodging and seed quality…through 60Co gamma irradiation to create and select new soybean varieties, meeting the demand of current production Scientific and Practical Significances 3.1 Scientific Significances Results of the thesis would be the basic for creating new soybean varieties by mutation method through 60Co gamma irradiation in the goals of shortening the growth duration and stem height, increasing the resistance to lodging and seed quality… Through conducting the thesis, the highly effective irradiation doses of gamma ray (60Co) have been identified for creating new mutant soybean varieties The data published in this work can be used as a guide material for teaching and research on soybean breeding in agricultural universities and research institutes 3.2 Practical Significances New soybean mutants including 01 self- declared circulation variety DT215 and 02 promising lines DT96ĐB and ĐT26ĐB have been created They have high yield (>2.5 tons/ha), good quality (protein > 40%, lipid >18%), good resistance to rust and powder mildew, meeting the demand of current production The group of 234 mutant soybean lines in the M7 generation divided from soybean virieties DT2008, DT96 and ĐT26 with improved traits are signigicant materials for creating and selectiong new soybean varieties Research Materials and Scope 4.1 Research Materials Soybean varieties DT2008, DT96 and ĐT26 Mutagen of gamma ray from the source of Cobalt 60 (60Co) 4.2 Research Scope Creating soybean mutants through gamma irradiation (Co60) on dry seeds, germination seeds and flowering plants Evaluating the impact of gamma irradiation (Co60) on the growth and development of the soybean varieties Selecting new soybean lines significant for creating and selecting new soybean varieties Testing and trial production of new promising mutant soybean varieties Significant Contribution Effective gamma irradiation doses (60Co) in soybean have been indentified at the doses of 150Gy, 200Gy and 250Gy on dry seeds, 25Gy and 50Gy on germination seeds and 10Gy and 20Gy on flowering plants A collection of 234 mutant soybean lines with one or some improved traits compared to the original varieties such as growth duration, stem height, seed cover colour… have been created and used as significant materials for new soybean breeding A new mutant soybean variety DT215 (the yield of 2.71 – 3.32 tons/ha but black seed coat different from DT2008’s yellow seed coat, – 10 days shorter growth duration in the range of 90 – 95 days) which was selfrecognized for introducing into the production and promising mutant soybean varieties DT96ĐB (the growth duration of 90 – 94 days, the height of 52.1 – 59.9 cm and the yield of 2.22 – 3.06 tons/ha but better lodging resistance compared to the origin DT96) and ĐT26ĐB (the yield of 2.23 – 2.55 tons/ha but black seed coat different from ĐT26’s yellow seed coat, the growth duration of 86 – 91 days) have been produced They have good growth and development, good resistance to deseases, high yield… and satisfy the demand of current produciton Thesis structure The thesis consists of 140 pages (excluding illustrations and Appendices) including Introduction (4 pages); Chapter 1: Literature Review (35 pages); Chapter 2: Materials, Contents and Research Methods (12 pages); Chapter 3: Research Results and Discussion (68 pages); Conclusions and Recommendations (2 pages); List of published works related to the thesis (1 page); References (18 pages) with 85 Vietnamese documents, 49 English documents and websites The thesis has 53 data tables, 12 pictures, 35 appendices and published works CHAPTER I LITERATURE REVIEW The literature review presents the following contents of (1) Introduction of soybean, (2) Research situation of soybean breeding in the world and in Vietnam, (3) Mutaiton and applications in plant breeding, (4) Research on mutant soybean breeding Thereby, some following comments have been drawn: Soybean is the main source of protein and vegetable oil for the whole world It is used as food for human and livestocks, for soil conditioning… In Vietnam, soybean is a traditional crop but its production has met only about 8% of domestic demand with the decrease in area because of low yield, backward cultivation techniques, low investment, especially the lack of new soybean varieties… Mutation method is so effective to improve plant varieties and has created over 3,200 varieties of 220 plant species It has produced a rich source of genetic variation, especially unavailabe traits in nature In Vietnam, there has been 61 mutant crop varieties of rice, flower, soybean… Currently, there has been 171 mutant soybean varieties in the world, mainly created through gamma irradiation (66 varieties) with the improved traits of yield, growth duration, stem height, seed coat colour and resistance In Vietnam, there has been 11 mutant soybean varieties, of which varieties created through gamma irradiation such as DT84, DT90, DT99, DT2008, AK06… However, these varieties has been mainly created through gamma irradiation on dry seeds There has been still the limitation on studies of gamma irradiation on germination seeds and flowering plants have been still limited CHAPTER II MATERIALS, CONTENTS AND RESEARCH METHODS 2.1 Materials 2.2.1 Soybean varieties: DT2008, DT96, ĐT26 and DT84 (control) 2.2.2 Mutagenic agent: 60 Cobalt source (60Co) of gamma ray - Irradiation doses on dry seeds: (control), 100, 150, 200, 250, 300 and 350 Gy - Irradiation doses on germination seeds: (control), 25, 50, 75, 100, 125 and 150 Gy - Irradiation doses on flowering plants: (control), 10, 20, 30, 40, 50 and 60 Gy 2.2 Contents Content 1: Research on the effect of gamma irradiation (60Co) on the growth and development of soybean varieties Effect of gamma irradiation (60Co) on the growth and development of soybean varieties Effect of gamma irradiation (60Co) on variation frequency and spectrum of soybean varieties Evaluating the inheritance of morphological variations derived from soybean varieties which were irradiated with gamma ray (60Co) Content 2: Research on selecting significant mutant soybean lines for soybean breeding Selecting mutant individuals and soybean lines significant for soybean breeding Evaluating and comparing promising mutant soybean lines Evaluating the genetic diversity of some mutant soybean lines by SSR markers Content 3: Testing the production trials of promising mutant soybean varieties 2.3 Research Methods 2.3.1 Gamma irradiation method soybean varieties DT2008, DT96 and ĐT26 a) Gamma irradiation on dry seeds Dry seeds of soybean varieties were irradiated at the doses of (control), 100, 150, 200, 250, 300 and 350 Gy with the source power of 64.8 kCi during 30 minutes Each treatment used 600 seeds b) Gamma irradiation on germination seeds Dry seeds of soybean varieties were soaked in fresh water during hours, and then put into the incubator at 260C during 2, 4, 6, and 10 hours The seeds after incubating were irradiated at t0he doses of (control), 25, 50, 75, 100, 125 and 150 Gy during 30 minutes with the source power of 62.3 kCi Each treatment used 500 seeds c) Gamma irradiation on flowering plants Dry seeds of soybean varieties were sown in pots At the blooming stage (50% of plants in bloom), flowers, pods and buds on each plant of pots were marked with thread separately and irradiated at the doses of (control), 10, 20, 30, 40, 50 and 60 Gy during 30 minutes, the source power of 61.1 kCi Each treatment used pots 2.3.2 Research on the effect of gamma irradiation (60Co) on the growth and development of soybean varieties a) Experimental design Treatments were designed in sequence without replication and with the alternation of the controls of original varieties The plot area was 8.5 m2 (5m x 1.7m) Seeds were sown in the density of 35-40cm in row distance and 10cm in hole distance, one seed per hole * M1 generation: Gamma irradiation on dry seeds: After irradiaton, 100 seeds of each treatment were taken and sown on the tray with sterilized sand at 26oC during days to evaluate the germination rate The remaining seeds of each treatment were sown in the experimental field to evaluate the growth and development At the harvesting stage, variant individuals were collected separately The mixture of remaning plants were collected in each treatment Gamma irradiation on germination seeds: Seeds after irradiation were sown in the experimental field to evaluate the growth and development At the harvesting stage, variant individuals were collected separately The mixture of remaning plants were collected in each treatment Gamma irradiation on flowering plants: After irradiaton, soybean varieties were observated and evaluated on the growth and development in green house At harvesting stage, seeds from marked flowers, pods and buds were collected separately in each treatment * M2 generation: Seeds collected from M1 generation were sown in M2 generation in each treatment Seeds of M1 individuals were sown in separate rows b) Effect of gamma irradiation (60Co) on germination and survival rate of soybean varieties c) Effect of gamma irradiation (60Co) on the growth and development of soybean varieties The growth and development of soybean varieties were observed continuously from seedling stage to harvesting stage on traits of stem height, a number of branches, a number of pods, a number of fertile pods, 1000-seed weight… d) Effect of gamma irradiation (60Co) on variation frequency and spectrum of soybean varieties Observating and detecting morphological variations and agronomic traits such as leaflet shape, stem colour, seed coat colour, growth duration, stem height… e) Evaluating the inheritance of morphological variations derived from soybean varieties irradiated with gamma ray (60Co) The inheritance of morphological variations was evaluated and monitored over generations M1 to M2, M2 to M3 and M3 to M4 2.3.3 Research on selecting significant mutant soybean lines for soybean breeding a) Research on selecting significant mutant soybean lines for soybean breeding Pedigree method was used to select mutant soybean lines based on bioagrobiological traits such as stem shape, leaflet shap, pubescence colour, growth duration, lodging resistance, 1000-seed weight, seed coat colour… b) Evaluating and comparing promising mutant soybean lines Promising mutant soybean lines were evaluated and compared under the national standard QCVN 01-58:2011/BNNPTNT by Ministry of Agriculture and Rural Development on the value of cultivation and use of soybean varieties Experiments of comparing mutant soybean lines were designed in RCB with three replications on the plots with the area of 8.5 m2 c) Evaluating the genetic diversity of some mutant soybean lines by SSR markers 2.3.4 Testing the production trials of promising mutant soybean varieties Promising mutant soybean varieties were tested under the national standard QCVN 01-58:2011/BNNPTNT by Ministry of Agriculture and Rural Development on the value of cultivation and use of soybean varieties 2.3.5 Analysis of grain nutrition content 2.3.6 Observation traits Observation traits and evaluation methods under the national standard QCVN 01-58:2011/BNNPTNT by Ministry of Agriculture and Rural Development on the value of cultivation and use of soybean varieties 2.3.7 Data Analysis Data analysis was processed by Excel 2016 and IRRISTAT 5.0 2.4 Research time and place 2.4.1 Research time From 2012 to 2019 2.4.2 Research place Field experiments were conducted in Dan Phuong district, Hanoi city Production trials of promising mutant soybean varieties were conducted Hanoi, Vinh Phuc CHAPTER III RESEARCH RESULTS AND DICUSSIONS 3.1 Research on the effect of gamma irradiation (60Co) on the growth and development of soybean varieties 3.1.1 Research on the effect of gamma irradiation (60Co) on the growth and development of soybean varieties irradiated on dry seeds a) Effect of gamma irradiation (60Co) on germination and survival rate of soybean varieties irradiated on dry seeds There was a little effect of gamma irradiation on germination rate in M1 and M2 generations in soybean varieties irradiated on dry seeds The germination rate ranged from 98 to 100% (the rate of 100% at the control) in M1 generation and from 98.3 to 100% (the rate of 100% at the control) in M2 generation Table 3.1 Effect of gamma irradiation (60Co) on germination rate of soybean varieties in M1 and M2 generations Unit: % M generation M generation Radiation doses DT2008 DT96 ĐT26 DT2008 DT96 ĐT26 0Gy (control) 100 100 100 100 100 100 100Gy 100 100 100 100 100 99.7 150Gy 100 100 100 98.7 99.7 100 200Gy 99.0 99.0 99.0 100 99.7 99.3 250Gy 100 100 100 99.0 98.7 99.7 300Gy 99.0 98.0 99.0 99.3 99.3 99.3 350Gy 98.0 99.0 100 99.3 98.3 98.7 The survival rate of soybean varieties decreased with the increase of radiation doses The effect of gamma irradiation on survival rate was much in M1 generation but little in M2 generation In M1 generation, survival rate decreased rapidly with the increase of radiation doses from 200 Gy to 350 Gy The survival rate in soybean variety DT2008, DT96 and ĐT26 ranged from 26.4-94.2% (the rate of 97.6% at the control), 20.8-94.0% (the rate of 94.6% at the control) and 20.2-96.2% (the rate of 96.4% at the control) respectively Lethal dose 50% (LD50) was indentified at 300 Gy In M2 generation, the survival rate in soybean variety DT2008, DT96 and ĐT26 ranged from 81.9-85.7% (the rate of 85.2% at the control), 73.7 – 81.1% (the rate of 80.6% at the control) and 78.3 – 83.2% (the rate of 83.1% at the control) respectively Table 3.2 Effect of gamma irradiation (60Co) on survival rate of soybean varieties irradiated on dry seeds in M1 and M2 generations Unit: % M1 generation M2 generation Radiation doses DT2008 DT96 ĐT26 DT2008 DT96 ĐT26 0Gy (control) 97.6 94.6 96.4 85.2 80.6 83.1 100Gy 94.2 94.0 96.2 85.7 81.1 83.2 150Gy 89.6 87.4 91.6 85.3 74.5 83.1 200Gy 81.4 73.6 84.4 85.0 76.8 82.1 250Gy 68.2 56.8 68.4 84.6 74.9 81.8 300Gy 45.6 39.4 45.2 82.3 74.6 80.6 350Gy 26.4 20.8 20.2 81.9 73.7 78.3 60 b) Effect of gamma irradiation ( Co) on growth and development indicators of soybean varieties irradiated on dry seeds Gamma irradiation on dry seeds prolonged the growth duration and reduced quantity traits such as stem height, a number of fertile pods, individual yield in soybean varieties The decrease of quantity traits was much in M1 generation but little or negligible in M2 generation c) ) Effect of gamma irradiation (60Co) on variation frequency and spectrum of soybean varieties irradiated on dry seeds 50 100 50 0 100 150 200 250 300 350 (Đ/c) M1 generation DT2008 DT96 100 150 200 250 300 350 (Đ/c) M2 generation DT2008 DT96 ĐT26 ĐT26 Figure 3.1 Effect of gamma irradiation (60Co) on variation frequency of soybean varieties irradiated on dry seeds in M1 and M2 generations Variation frequency was on the increase of radiation doses from 100 Gy to 350 Gy In M1 generation, variation frequency of soybean varieties DT2008, DT96 and ĐT26 ranged from 0.6 – 58.8% (the rate of 0.4% at the control), 0.2 – 54.6% (the rate of 0.2% at the control) and 0.4 – 52.6% (the rate of 0.2% at the control) respectively In M2 generation, variation frequency of soybean varieties DT2008, DT96 and ĐT26 ranged from 6.1 – 36.1% (the rate of 0.8% at the control), 6.4 – 39.8% (the rate of 0.6% at the control) and 6.4 – 37.7% (the rate of 0.5% at the control) respectively 11 Variation frequency of soybean varieties was on the increase with the rise in gamma irradiation dose In M1 generation, variation frequency of soybean varieties DT2008, DT96 and ĐT26 ranged from 24.1 – 100, 25.3 – 100.0 and 20.4 – 100% (the rate of 0% at the control) respectively From 100Gy and over doses, variation frequency was 100% (mainly sterile variations and late maturation) In M2 generation, variation frequency of soybean varieties DT2008, DT96 and ĐT26 ranged from 10.3 – 58.1, 23.9 – 88.0 and 16.9 – 68.7% respectively There was a little effect of different incubation times on the variation frequency in soybean varieties 200 100 100 50 0 DT2008 DT96 ĐT26 DT2008 DT96 ĐT26 M1 generation M2 generation Figure 3.2 Effect of gamma irradiation (60Co) on variation frequency of soybean varieties irradiated on germination seeds in M1 and M2 generations Table 3.18 Effect of gamma irradiation (60Co) on variation spectrum of soybean varieties irradiated on dry seeds in M1 and M2 generations Unit: number of variations M generation M2 generation Radiation doses DT2008 DT96 ĐT26 DT2008 DT96 ĐT26 0Gy (control) 0 4 25Gy 10 10 10 17 17 16 50Gy 10 10 10 17 17 16 75Gy 10 10 10 14 13 16 100Gy 7 12 13 125Gy 7 10 10 150Gy 6 9 A number of variations of soybean varieties ranged from 7-10 in M1 generation and 8-17 in M2 generation In M1 generation, the number of variations of soybean varieties DT2008, DT96 and ĐT26 ranged from 7-10, 6-10 and 6-10, respectively There was no variation at the control In M2 generation, the number of variations of soybean varieties DT2008, DT96 and ĐT26 ranged from 8-17, 9-17 and 9-16, respectively The radiation dose with 12 the most number of variations was 25 and 50 Gy (the number of variations was 10 in M1 generation and 16-17 in M2 generation At the same irradiation dose, there was no effect of incubation times on variation spectrum in soybean varieties Some significant variations for soybean breeding were selected such as straight stem (acute-angled branching angle), short stem, branchiness, early maturation… 3.1.3 Research on the effect of gamma irradiation (60Co) on the growth and development of soybean varieties irradiated on flowering plants a) Effect of gamma irradiation (60Co) on germination and survival rate of soybean varieties irradiated on flowering plants Table 3.19 Effect of gamma irradiation (60Co) on germination rate of soybean varieties irridiated on flowering plants in M2 generation Unit: % M1 generation M2 generation Radiation doses DT2008 DT96 ĐT26 DT2008 DT96 ĐT26 0Gy (control) 99.6 99.1 99.3 93.2 90.6 94.8 10Gy 99.2 99.3 99.0 79.3 73.8 81.6 20Gy 98.5 98.5 98.2 41.2 31.2 39.9 30Gy 98.4 98.5 98.4 22.5 21.5 20.6 Note: No seed harvested at the doses of 40, 50 and 60Gy M1 generation The plants irradiated at the doses 40, 50 and 60 Gy were sterile and didn’t have any seed in M1 generation In M2 generation, the germination rate of soybean varieties DT2008, DT96 and ĐT26 ranged from 98.4 – 99.2% (the rate of 99.6% at the control), 98.5 – 99.3% (the rate of 99.1% at the control) and 98.2 – 99.0% (the rate of 99.3% at the control), respectively The survival rate of soybean varieties at treatments was lower than that at the control and on the rapidly decrease with the increase of radiation doses from 10 Gy to 30 Gy (No seed harvested at the doses of 40, 50 and 60Gy M1 generation), and was the lowest at 30 Gy The survival rate of soybean varieties DT2008, DT96 and ĐT26 ranged from 22.5 – 79.3% (the rate of 93.2% at the control), 21.5 – 73.8% (the rate of 90.6% at the control) and 20.6 – 81.6% (the rate of 94.8% at the control), respectively The survival rate was the lowest of the plants derived from marked flowers and the highest of the plants derived from marked pods All seeds collected from marked flowers at the dose of 20 Gy, and from marked flowers and pods at the dose of 30 Gy had no survival 13 b) Effect of gamma irradiation (60Co) on growth and development indicators of soybean varieties irradiated on flowering plants Gamma irradiation on flowering plants prolonged the growth duration and reduced quantity traits such as stem height, a number of fertile pods, individual yield in soybean varieties The higher the dose of gamma irradiation was, the greater the effect of gamma irradiation on growth and development was in M1 generation There was little difference of growth and development among treatments and the control in M2 generation c) Effect of gamma irradiation (60Co) on variation frequency and spectrum of soybean varieties irradiated on flowering plants Variation frequency of soybean varieties was on the increase with the rise in gamma irradiation dose and reached at 100% from 30 Gy and over doses Variation frequency of soybean varieties DT2008, DT96 and ĐT26 ranged respectively from 31.5 – 100, 14.6 – 100 and 21.3 – 100% (the rate of 0.0% at the control) in M1 generation, and from 30.1 – 100, 36.9 – 100 and 37.5 – 100% in M2 generation, and higher than the control (0 Gy) 200 200 100 100 0 (Đ/c) DT2008 DT96 M1 generation ĐT26 10 DT2008 20 DT96 30 ĐT26 M2 generation Figure 3.3 Effect of gamma irradiation (60Co) on variation frequency of soybean varieties irradiated on germination seeds in M1 and M2 generations Gamma irradiation on flowering plants affected greatly on plant parts, caused many morphological variations in M1 generation such as leaflet variations (changed leaflet shape, blistered leaflet surface, enlarged or elongated leaflet size, decreased number of leaflets), stem variations (enlarged nodes, soft and slow-aging stem), pod variations (more than valves, small pods) Especially, there were different variations on the same plant In M2 generation, there were 11 variations A number of variations were the most at the dose of 10 Gy (11 variations) and the lowest at the dose of 30 Gy with only variations of late maturation and sterileness (100%) At the same time, significant variations for soybean breeding were selected such as branchiness, short stem and fruitfulness at the doses of 10 and 20 Gy 14 Table 3.25 Effect of gamma irradiation (60Co) on variation spectrum of soybean varieties irradiated on flowering plants in M1 and M2 generations Unit: number of variations M1 generation M2 generation Radiation doses DT2008 DT96 ĐT26 DT2008 DT96 ĐT26 0Gy (control) 0 1 10Gy 2 11 11 11 20Gy 4 8 30Gy 4 2 40Gy 3 50Gy 3 60Gy 3 3.1.4 Evaluating the inheritance of morphological variations derived from soybean varieties which were irradiated with gamma ray (60Co) To evaluate the inheritance of morphological variations selected in M1 generation into M2 generation, variant individuals in M1 generation were selected separately and sown in separate rows in M2 generation In M1 generation, there were many morphological variations such as stem shape (curved stem, flat stem, double stem), stem height (higher or shorter than the origin), first branch (no branch, branchiness, branching at the cotyledon node, symmetrically branches at the same node, double branches), leaflet (leaflet shape, number of leaflet…) However, all these variations didn’t inherited into M2 generation Therefore, these variations were modifications To evaluate the inheritance of morphological variations selected in M2 generation into M3 generation, variant individuals in M2 generation were selected separately and sown in separate rows in M3 generation In M2 generation, there were also morphological variations such as stem shape (flat stem, double stem), first branch (branching at the cotyledon node, symmetrically branches at the same node, double branches…) and these variations didn’t inherited into M3 generation either Therefore, these variations were modifications In addition, in M2 generation there were some new morphological variations not found in M1 generation such as pubescence colour, pod coat colour, seed coat colour, hilum colour These variations were different to the origins and inherited at the rate of 100% into M3 and M4 generations Therefore, these variations were genetic variations or mutants The new morphological variations which didn’t appear in M1 generation but come out in M2 generation and inherited into M3 and M4 generations would be the 15 action of gamma causing changes in genetec structure, producing recessive mutant alleles in M1 generation In M2 and M3 generations, recessive homozygotes appeared due to the self-pollination resulting in the appearance of mutants These mutants inherited completely into M3 and M4 generations The inheritance of these mutants could be explained as follows: Table 3.26 The inheritance of morphological variations of soybean varieties in M2, M3 and M4 generations Ord Variations Black seed coat colour (the origin’s yellow) Gray pubescence colour (the origin’s brown) Brown hilum colour (the origin’s black) Number of variant individuals in M2 The rate of mutant individuals in M3 100% The rate of mutant individuals in M4 100% ĐT26 100% 100% DT96 100% 100% ĐT26 100% 100% ĐT26 100% 100% Varieties DT2008 Mutants of black seed coat colour were derived from DT2008 and ĐT26 at the doses 200 and 150 Gy, respectively through irradiated on dry seeds Seed coat colour is a single gene characteristic controled by a gene pair In particular, green or yellow seed coat colour is dominant, black or brown seed coat colour is recessive So it can be assumed that yellow seed coat colour controled by dominant allele Ri, black seed coat colour controled by recessive allele ri Black seed coat colour is controled by a pair of recessive homozygous alleles riri, yellow seed coat colour is controled by pairs of dominant alleles RiRi or heterogeneous alleles Riri Mutation Self-polination Self-polination Self-polination RiRi Riri ri ri ri ri ri ri M0 M1 M2 M3 M4 (Yellow) (Yellow) (Black) (Black) (Black) Mutants of gray pubescence colour were derived from the origins DT96 and ĐT26 at the dose of 200 Gy and 10 Gy through gamma irradiation on dry seeds and on flowering plants, respectively Pubescence colour is 16 controled by a single gene pair In particular, brown pubescence colour is dominant and gray pubescence colour is recessive (Pham Thi Bao Chung, 2015) So it can be assumed that brown pubescence colour controled by dominant allele Wpi, gray pubescence colour controled by recessive allele wpi Gray pubescence colour is controled by a pair of recessive homozygous alleles wpiwpi Brown pubescence colour is controled by pairs of dominant alleles WpiWpi or heterogeneous alleles Wpiwpi WpiWpi M0 (Brown) Mutation Self-polination Self-polination Wpiwpi wpiwpi wpiwpi M1 M2 M3 (Brown) (Gray) (Gray) Self-polination wpiwi M4 (Gray) Mutants of brown hilum colour derived from the origin ĐT26 at the dose of 150 Gy through gamma irradiation on dry seeds Black hilum colour is dominant and brown hilum colour is recessive Hilum colour in soybean is controlled by pairs of genes The presence of dominant genes at the same time will produce the interaction between them and create black hilum colour But the separate presence of two dominant genes will produce brown hilum colour So it can be assumed that black hilum colour controled by two pairs of dominant alleles RtRtW1W1, brown hilum colour controled by pairs of alleles RtrtW1W1, RtrtW1w1, rtrtW1W1, rtrtW1w1, rtrtw1w1 * Mutagenesis at the first gene pair (Rt rt): Mutation Self-polination Self-polination Self-polination RtRtW1W1 RtrtW1W1 rtrtW1W1 rtrtW1W1 rtrtW1W1 M0 M1 M2 M3 M4 (Black) (Black) (Brown) (Brown) (Brown) * Mutagenesis at the secondary gene pair (W1 Mutation RtRtW1W1 M0 (Black) w1): Self-polination Self-polination Self-polination RtRtW1w1 RtRtw1w1 RtRtw1w1 RtRtw1w1 M1 M2 M3 M4 (Black) (Brown) (Brown) (Brown) Therefore, induced mutation through gamma irradiation on soybean varieties created many different variations In particular, there were variations that were modifications and not inherited to the next generation such as stem shape (curved stem, flat stem, double stem), first branch (no branch, branching at cotyledon node, symmetrically branches at the same node, double branches), leaflet (number of leaflets…) But there were variations that were mutants and inherited to the next generation such as seed coat colour, pubescence colour, hilum colour 3.2 Research on selecting significant mutant soybean lines for soybean breeding 3.2.1 Selecting mutant soybean lines significant for soybean breeding 17 The process of selecting mutant soybean lines was carried out continuously from M2 to M7 generations based on observation and evaluation of morphological characteristics, growth and development, resistance to diseases… to identify mutant traits and select mutants significant for soybean breeding a) Selecting mutant lines derived from the origin DT2008 Table 3.27 Number of mutant individuals or lines selected from treatments of 60Co gamma irradiation on soybean variety DT2008 Unit: individual/line Generations M2 M3 M4 M5 M6 M7 Gamma irradiation on dry seeds 150Gy 17 161 46 22 14 11 200Gy 31 392 136 69 51 46 250Gy 25 229 39 20 16 14 Gamma irradiation on germination seeds 25Gy 50Gy 20 12 265 198 66 68 30 36 16 14 10 12 Gamma irradiation on flowering plants 10Gy 20Gy 40 10 117 73 43 29 22 17 Total 155 1435 427 216 125 103 In M7 generation, 103 mutant lines were selected including 10 mutant lines derived from treatments of gamma irradiation on flowering plants (7 lines at the dose of 10 Gy and lines at the dose of 20 Gy), 22 mutant lines derived from treatments of gamma irradiation on germination seeds (10 lines at the dose of 25 Gy and 12 lines at the dose of 50 Gy) and 71 mutant lines derived from treatments of gamma irradiation on dry seeds (11 lines at the dose of 150 Gy, 46 lines at the dose of 200 Gy and 14 lines at the dose of 250 Gy) In particular, compared to the origin DT2008, there were 28 mutant lines with 5.1 – 6.9cm higher stem height, 12 mutant lines with 1.2 – 1.8 more branches, 26 mutant lines with higher yield, 19 mutant lines with – days shorter growth duration and 18 mutant lines with black seed coat b) Selecting mutant lines derived from the origin DT96 In M7 generation, 58 mutant lines were selected including mutant lines derived from treatments of gamma irradiation on flowering plants (4 lines at the dose of 10 Gy and lines at the dose of 20 Gy), 25 mutant lines derived from treatments of gamma irradiation on germination seeds (16 lines at the dose of 25 Gy and lines at the dose of 50 Gy) and 24 mutant lines derived from treatments of gamma irradiation on dry seeds (4 lines at the dose of 150 Gy, 13 lines at the dose of 200 Gy and lines at the dose of 250 18 Gy) In particular, compared to the origin DT96, there were mutant lines with straight growth habit, mutant lines with – 6.1 cm shorter stem height, 12 mutant lines with 1.2 – 1.8 more branches, 17 mutant lines with higher yield, mutant lines with – days shorter growth duration, mutant lines with gray pubescence and mutant lines with different pod colour Talbe 3.29 Number of mutant individuals or lines selected from treatments of 60Co gamma irradiation on soybean variety DT96 Unit: individual/line Generations M2 M3 M4 M5 M6 M7 Gamma irradiation on dry seeds 150Gy 71 23 11 200Gy 23 246 54 33 17 13 250Gy 30 273 28 14 10 Gamma irradiation on germination seeds 25Gy 50Gy 21 16 296 206 77 52 41 31 16 10 15 10 Gamma irradiation on flowering plants 10Gy 20Gy 29 10 59 45 29 23 14 17 Total 137 1196 286 161 72 58 c) Selecting mutant lines derived from the origin ĐT26 Table 3.31 Number of mutant individuals or lines selected from treatments of 60Co gamma irradiation on soybean variety ĐT26 Unit: individual/line Generations M2 M3 M4 M5 M6 M7 Gamma irradiation on dry seeds 150Gy 148 114 52 35 35 200Gy 59 30 12 250Gy 51 23 12 7 Gamma irradiation on germination seeds 25Gy 50Gy 17 223 131 52 37 27 23 13 12 Gamma irradiation on flowering plants 10Gy 20Gy 42 10 81 89 29 22 18 15 10 10 Total 94 782 307 159 80 73 In M7, 73 mutant lines were selected including 15 mutant lines derived from treatments of gamma irradiation on flowering plants (10 lines at the dose of 10 Gy and lines at the dose of 20 Gy), 13 mutant lines derived from treatments of gamma irradiation on germination seeds (12 lines at the dose of 25 Gy and lines at the dose of 50 Gy) and 45 mutant lines derived from treatments of gamma irradiation on dry seeds (35 lines at the dose of 150 Gy, lines at the dose of 200 Gy and lines at the dose of 250 Gy) 19 Therefore, nduced mutation through gamma irradiation on soybean varieties DT2008, DT96 and ĐT26 created 234 mutant lines in M7 generation including 103 mutant lines derived from the origin DT2008, 58 mutant lines derived from the origin DT96 and 73 mutant lines derived from the origin ĐT26 Mutant soybean lines have improved traits compared to the origins such as shorter growth duration, higher yield, shorter stem height, black seed coat… 3.2.2 Evaluating and comparing promising mutant soybean lines To identify promising mutant soybean lines, promising mutant soybean lines derived from DT2008 (8 lines), DT96 (6 lines) and ĐT26 (5 lines) were evaluated and compared in crops of spring, summer and winter a) Evaluating and comparing promising mutant lines derived from soybean variety DT2008 Table 3.35 The yield components and yield of promising mutant lines derived from soybean variety DT2008 in Hanoi Ord 10 Lines/Varieties 08200-2/8 08200-25/24 08200-25/26 08200-9/1 08200-29/3 08200-26/11 08-2-25/4-10 08-6-25/3-8 DT2008 (đ/c 1) DT84 (đ/c 2) LSD0,05 CV(%) Number of fertile pods per plant (pod) S A W 44.3 62.7 30.2 43.5 62.9 30.8 44.9 61.8 28.7 45.1 63.2 29.2 45.3 62.8 29.7 45.7 63.4 29.5 44.7 65.2 30.8 45.3 64.8 31.4 45.3 64.5 30.4 24.3 37.8 19.6 3.54 6.39 3.71 4.8 6.1 5.5 Number of seeds per pod (seed) S 2.02 2.01 2.03 2.02 2.02 2.02 2.03 2.02 2.02 2.03 0.09 2.8 A 2.04 2.02 2.03 2.04 2.02 2.01 2.03 2.02 2.03 2.12 0.10 2.9 W 1.98 1.97 1.95 2.01 1.99 1.96 1.98 1.96 1.98 1.96 0.10 3.0 Real yield (tons/ha) S 2.84 2.87 2.79 2.84 2.87 3.00 2.76 2.77 3.03 1.89 0.15 3.1 A 3.12 3.08 2.95 2.96 2.88 3.18 2.91 2.83 3.34 2.68 0.16 3.0 W 2.44 2.56 2.35 2.46 2.38 2.46 2.41 2.34 2.68 1.82 0.13 3.2 S = Spring crop, A = Summer crop, W = Winter crop Three promising mutant lines derived from the origin DT2008 were selected including mutant line 08200-26/11 with black seed coat and shortest growth duration, mutant line 08200-2/8 with 11.5 - 17.4 cm shorter stem height compared to the origin DT2008, and mutant line 08200-25/24 with – days shorter growth duration compared to the origin DT2008 The line 08200-26/11, named as DT2008ĐT first and then DT215, was tested in the value of cultivation and use in national testing and production trials 20 b) Evaluating and comparing promising mutant lines derived from soybean variety DT96 Three promising mutant lines derived from the origin DT96 were selected including mutant line 96-2-25/1-10 with better lodging resistance and straight growth habit, mutant line 96-6-25/5-3 with light brown pod coat, and the most promising mutant line of 96200-13/2 with gray pubescence Table 3.39 The yield components and yield of promising mutant lines derived from soybean variety DT96 in Hanoi Ord Lines/Varieties 96-2-25/1-10 96-6-50/1-9 96-6-25/5-2 96-6-25/5-3 96200-13/1 96200-13/2 DT96 (đ/c 1) DT84 (đ/c 2) LSD0,05 CV(%) Number of fertile pods per plant (pod) S A W 30,3 41,8 27,8 29,7 40,8 26,3 29,7 40,2 26,5 31,3 42,5 28,6 29,3 38,9 27,2 28,3 38,5 27,4 29,7 40,6 27,5 24,8 36,5 20,4 2,86 4,86 2,19 5,7 6,9 4,7 Number of seeds per pod (seed) S 2,12 2,08 2,09 2,11 2,10 2,12 2,11 2,03 0,14 3,8 A 2,23 2,24 2,20 2,22 2,24 2,23 2,24 2,13 0,13 3,3 Real yield (tons/ha) W 2,05 2,04 2,06 2,03 2,05 2,04 2,04 1,95 0,11 3,1 S 2,69 2,58 2,56 2,77 2,44 2,62 2,52 1,96 0,12 2,7 A 2,91 2,89 2,85 3,01 2,86 2,98 2,94 2,35 0,16 3,2 W 2,42 2,38 2,31 2,45 2,30 2,47 2,42 1,91 0,14 3,2 S = Spring crop, A = Summer crop, W = Winter crop c) Evaluating and comparing promising mutant lines derived from soybean variety ĐT26 Table 3.43 The yield components and yield of promising mutant lines derived from soybean variety ĐT26 in Hanoi Ord 26-2-25/2-6 26-4-25/3-10 26150-2/24 26150-1/3 26150-1/12 ĐT26 (đ/c 1) DT84 (đ/c 2) LSD0,05 CV (%) Lines/Varieties S 32,3 40,1 30,3 33,3 32,7 33,3 25,6 A 28,5 33,4 29,2 28,8 29,6 29,0 33,8 W 27,1 30,2 27,8 27,5 26,4 27,4 21,1 Number of fertile pods per plant (pod) S A W 2,48 2,42 2,61 2,52 2,43 2,62 2,50 2,41 2,58 2,49 2,40 2,61 2,51 2,43 2,60 2,51 2,42 2,60 2,02 2,10 1,96 Real yield (tons/ha) S 2,24 2,56 2,17 2,36 2,26 2,38 1,92 0,14 3,4 A 2,04 2,36 1,97 2,18 2,05 2,14 2,26 0,19 5,0 W 2,23 2,48 2,10 2,26 2,13 2,25 1,88 0,18 4,6 S = Spring crop, A = Summer crop, W = Winter crop 21 Three promising mutant lines of 26-2-25/2-6, 26-4-25/3-10 and 26150-1/3 derived from the origin ĐT26 were selected In particular, mutant line 26-2-25/2-6 has shorter stem height and better lodging resistance with the yield of 2.04 – 2.24 tons/ha equal to the origin ĐT26’s Mutant line 264-25/3-10 has the yield of 2.36 – 2.56 tons/ha, 7-10% higher than the origin’s And mutant line 26150-1/3 has black seed coat with the equal growth and development and yield compared to the origin ĐT26’s 3.2.3 Evaluating the genetic diversity of some mutant soybean lines by SSR markers Figure 3.5 Diagram of genetic relationship between promising mutant soybean lines and the origins The genetic diversity of promising mutant lines including lines derived from DT2008 (08200-26/11 named as DT2008ĐB, 08200-2/8, 08200-25/24), lines derived from DT96 (96-2-25/1-10, 96-6-25/5-3, 96200-13/2 named as DT96ĐB), lines derived from ĐT26 (26-2-25/2-6, 26-4-25/3-10, 26150-1/3 named as ĐT26ĐB), line derived from DT2003 (2003-10n/8) and origin varieties (DT2008, DT2003, DT96 and ĐT26) were evaluated by SSR markers The result showed that the genetic similarity coefficient of mutant lines derived from the same ogirin was high and ranged from 0.67 to 1.00, and higher than that of mutant lines derived from different origin The genetic similarity coefficient of mutant lines derived from DT2008, DT96, ĐT26 was high and ranged 0.74 – 1.00, 0.78 – 1.00 and 0.64 – 0.88, respectively In particular, the genetic similarity coefficient of mutant lines DT2008ĐB and 08200-25/24, DT96ĐB and 96-2-25/1-10, 26150-1/3 and 26-2-25/2-6 was the highest It was the lowest at mutant lines 26-2-25/2-6 and 26-4-25/3-10 3.3 Testing the production trials of promising mutant soybean varieties Promising mutant soybean varieties DT215 (DT2008ĐB), DT96ĐB (96200-13/2) and ĐT26ĐB (26150-1/3) were tested in production trials in Hanoi and Vinh Phuc 22 3.3.1 Morphological characteristics Mutant soybean variety DT215 has the same morphological characteristics of purple flowers, brown pubescence, brown pod cover, black hilum, pointed-egg shape leaflets, semi-straight growth habit and limited growth type as the origin DT2008 but difference from seed coat colour DT215 has black seed coat different from DT2008’s yellow seed coat Mutant soybean variety DT96ĐB has the same morphological characteristics of purple flowers, medium brown pod cover, yellow seed coat, gray hilum, pointed-egg shape leaflets, semi-straight growth habit and limited growth type but difference from the colour of hair of main stem DT96ĐB has gray pubescence different from DT96’s brown pubescence Mutant soybean variety ĐT26ĐB has the same morphological characteristics of white flowers, brown pubescence, dark brown pod cover, black hilum, semi-straight growth habit and limited growth type but difference from seed coat colour ĐT26ĐB has black seed coat different from ĐT26’s yellow seed coat 3.3.2 Growth and development traits Promising mutant soybean varieties have higher growth and development but longer growth duration compared to soybean variety DT84 (check) The growth duration of varieties DT215, DT96ĐB and ĐT26ĐB ranged from 90 – 100, 90 – 94 and 86 – 91 days, compared to the growth duration of the origins DT2008, DT96, ĐT26 and the check DT84 of 95 – 100, 89 – 95, 87 – 91 and 83 – 88 days, respectively The range of the growth duration of the origins DT2008, DT96, ĐT26 and the check DT84 was 95 – 100, 89 – 95, 87 – 91 and 83 – 88 days, respectively The stem height of promising mutant soybean varieties was higher than DT84’s and the highest in summer crop The stem height of DT215, DT96ĐB and ĐT26ĐB ranged from 61.5 – 70.8, 52.1 – 59.8 and 41.8 – 51.6 cm, respectively, compared to the stem height of the origins DT2008, DT96, ĐT26 and the check DT84 of 62.4 – 71.1, 50.6 – 58.2, 41.5 – 53.2 and 35.5 – 47.0 cm 3.3.3 Resistance The resistance of promising mutant soybean varieties is higher than or equal to the origins’ but higher than the check DT84’s They have mild infection of rust (score 1) and powder mildew (score 1-2), and good lodging resistance (score 1-2) 3.3.4 Yield components and yield Mutant soybean variety DT215 had the real yield similar to DT2008’s but higher than the check DT84’s In Hanoi, DT215 had the real yield of 2.71 – 3.32 tons/ha (38.8 – 51.4% higher than the check DT84), DT2008 had the real yield of 2.65 – 3.35 tons/ha In Vinh Phuc, DT215 had the real yield of 2.72 – 3.31 tons/ha (32.6 – 51.1% higher than the check DT84), DT2008 had the real yield of 2.75 – 3.92 tons/ha 23 Mutant soybean variety DT96ĐB had the real yield similar to DT96’s but higher than the check DT84’s In Hanoi, DT96ĐB had the real yield of 2.22 – 3.06 tons/ha (20.6 – 29.1% higher than the check DT84), DT96’s had the real yield of 2.26 – 2.95 tons/ha In Vinh Phuc, DT96ĐB had the real yield of 2.46 – 2.88 tons/ha (19 – 38% higher than the check DT84), DT96’s had the real yield of 2.58 – 2.78 tons/ha Table 3.51 The real yield of promising mutant soybean varieties Unit: tons/ha Varieties DT215 DT2008 (origin) DT96ĐB DT96 (origin) ĐT26ĐB ĐT26 (origin) DT84 (check) LSD0,05 CV% Spring 2.81 2.84 2.58 2.65 2.48 2.52 1.98 0.19 4.2 Hanoi Summer 3.32 3.35 3.06 2.95 2.35 2.26 2.37 0.22 4.5 Winter 2.71 2.65 2.22 2.26 2.23 2.32 1.79 0.20 4.9 Spring 2.87 2.92 2.65 2.72 2.55 2.65 1.92 0.17 3.7 Vinh Phuc Summer Winter 3.21 2.72 3.24 2.75 2.88 2.46 2.78 2.58 2.38 2.28 2.42 2.20 2.42 1.80 0.24 0.23 4.9 5.3 Mutant soybean variety ĐT26ĐB had the real yield similar to ĐT26’s but higher than the check DT84’s The real yield of ĐT26ĐB ranged 2.23 – 2.48 tons/ha in Hanoi (ĐT26’s yield of 2.26 – 2.52 tons/ha) and 2.28 – 2.55 tons/ha in Vinh Phuc (ĐT26’s yield of 2.22 – 2.65 tons/ha), 15.9 – 32.8 and 24.6 – 28.6% higher in spring and summer, respectively, compared to the check DT84 Among three promising mutant soybean varieties, black soybean variety DT215 with yield potential and good resistance was tested in national testing VCU in 2018-2019 The result showed that variety DT215 had good growth and development, high stem, branchiness, mild infection of rust, downy mildew, brown spots (score 1-3), good lodging resistance (score 1-2) and non-splitting pods (score 1) with the average yield of 2.32 – 2.56 tons/ha, 9.9 – 28.4% higher than DT84’s Variety DT215 was recognized as a selfdeclared circulation variety under the notice No 654/TB-TT-CLT dated June 8, 2020 of Department of Crop Production, Ministry of Agriculture and Rural Development 3.3.5 Nutritional content Promising mutant soybean varieties have high nutritional content and equal to the origins’ with the protein content of over 40% (DT215, DT96ĐB and ĐT26ĐB have the protein content of 42.26, 40.10 and 40.50%, respectively), lipid content of over 18% (DT215, DT96ĐB and ĐT26ĐB have the lipid content of 18.24, 18.09 and 21.65%, respectively), glucid over 25% (DT215, DT96ĐB and ĐT26ĐB have the glucid content of 25.13, 26.50 and 25.59%, respectively) Therefore, these varieties can be used as materials to produce soymilk, tofu… 24 CONCLUSIONS AND RECOMMENDATIONS Conclusions 1) Induced mutation through 60Co gamma irradiation on dry seeds, germination seeds and flowering plants in soybean varieties caused the growth decline of traits at sharp level in M1 generation, but little or nonsignificant level in M2 generation, created benefitcial mutants for soybean breeding such as early maturation, short stem, black seed coat… - Lethal dose 50% (LD50) of gamma irradiaton on dry seeds, germination seeds and flowering plants was identified at 300, 100 and 20 Gy, respectively - The doses, having the most viriation spectrum, of gamma irradiaton on dry seeds, germination seeds and flowering plants were identified at 200, 50 and 10 Gy, respectively - The efficient doses of gamma irradiaton on dry seeds, germination seeds and flowering plants were identified at 200, 25 and 10 Gy, respectively, 2) In M7 generation, 234 mutant soybean lines were selected including 103, 58 and 73 lines derived from DT2008, DT96 and ĐT26, respectively They have improved traits compared to the origins such as earlier maturation, shorter stem, changed colour of seed coat, hilum… and are so significant materials for soybean breeding 3) Three mutant soybean varieties with high yield (much higher than DT84’s), good quality (protein >40%, lipid >18%, glucid >25%), good resistance were selected They are promising mutant soybean varieties for the production - Mutant soybean variety DT215, recognized as a self-declared circulation variety, has the equal growth and resistance with the yield of 2.71 – 3.32 tons/ha but black seed coat different from DT2008’s yellow seed coat, – 10 days shorter growth duration in the range of 90 – 95 days (the range of DT2008’s growth duration of 95 – 110 days) - Mutant soybean variety DT96ĐB has the equal growth and development with the growth duration of 90 – 94 days, the height of 52.1 – 59.9 cm and the yield of 2.22 – 3.06 tons/ha, but better lodging resistance (score 1) compared to the origin DT96 (score 1-2), gray pubescence different from DT96’s brown pubescence - Mutant soybean variety ĐT26ĐB has the equal growth and development compared to the origin ĐT26 with the yield of 2.23 – 2.55 tons/ha but black seed coat different from ĐT26’s yellow seed coat Recommendations 1) Selecting and utilizing continously the collection of mutatn soybean lines as initial materials for new soybean breeding 2) Conducting the production trials and VCU for mutant soybean varieties DT96ĐB and ĐT26ĐB to release as self-declared circulation varieties 3) Comleting the technical process and developing the production of black soybean variety DT215, contributing replacing old soybean varieties and increasing the yield and quality of soybean in Vietnam 25 THE PUBLISHED ARTICLES IN RELATION TO THE THESIS Le Duc Thao, Pham Thi Bao Chung, Nguyen Van Manh (2015), “The effect of 60Co gamma irradiation on creating variations beneficial for soybean breeding”, Journal of Vietnam Agricultural Science and Technology, 2(9), p.5-9 Le Duc Thao, Nguyen Van Manh, Pham Thi Bao Chung, Pham Thi Phuong Thu (2015), “Research on improving soybean variety DT96 through gamma irradiation (60Co) on dry seeds”, Journal of Vietnam Agricultural Science and Technology, (57), p.18 – 21 Nguyen Van Manh, Le Duc Thao, Pham Thi Bao Chung, Le Thi Anh Hong, Le Huy Ham (2016), “Research result of creating and selecting black soybean variety DT2008ĐB”, Secondary National Conference of Plant Science, Can Tho, 11-12 August, p.488-493 Nguyen Van Manh, Le Duc Thao (2016), “Result of evaluating promising mutant soybean lines derived from DT2008 through gamma irradiation (60Co), Journal of Agriculture and Rural Development, Volume of Cultivar and Breed, 2, p 162-165 Le Duc Thao, Nguyen Van Manh (2017), “Research on improving soybean variety ĐT26 through 60Co gamma irradiation on dry seeds”, Journal of Agriculture and Rural Development, Volume of Cultivar and Breed, 1, p.65-68 Le Duc Thao, Nguyen Van Manh (2017), “Result of evaluating promising mutant soybean lines derived from DT96 through gamma irradiation (60Co), Tạp chí Nơng nghiệp & Phát triển nông thôn, Journal of Agriculture and Rural Development, Volume of Cultivar and Breed, 1, p.6971 ... variations of soybean varieties DT2008, DT96 and ĐT26 ranged from 2-9, 1-9 and 2-9 respectively In M2 generation, the number of variations of soybean varieties DT2008, DT96 and ĐT26 was more than in M1... varieties DT2008, DT96 and ĐT26 ranged from 7-10, 6-10 and 6-10, respectively There was no variation at the control In M2 generation, the number of variations of soybean varieties DT2008, DT96 and ĐT26. .. Effect of gamma irradiation (60Co) on germination rate of soybean varieties in M1 and M2 generations Unit: % M generation M generation Radiation doses DT2008 DT96 ĐT26 DT2008 DT96 ĐT26 0Gy (control)