Tài liệu Nghiên cứu chọn tạo giống ngô năng suất cao chống chịu bệnh gỉ sắt (Puccinia sp.) cho vùng Tây Nguyên (TTTA)

MINISTRY OF EDUCATION MINISTRY OF AGRICULTURE AND TRAINING AND RURAL DEVELOPMENT VIETNAM ACADEMY OF AGRICULTURAL SCIENCES ******* TRAN THI PHUONG HANH MAIZE HYBRID BREEDING FOR HIGH YIELD AND RUST (puccinia sp.) TOLERANCE IN THE CENTRAL HIGHLANDS Major Field: Genetics and Plant Breeding Code: 62.62.01.11 DOCTORAL THESIS SUMMARY Ha Noi - 2015 The Doctoral thesis was completed in: VIETNAM ACADEMY OF AGRICULTURAL SCIENCES Scientific Supervisors: 1: Dr. Bui Manh Cuong 2: Dr. Tran Quang Tan Reviewer 1: Reviewer 2: Reviewer 3: The thesis is defended at Council for Thesis Assessment at University/Institutional level, held at: Vietnam Academy of Agricultural Sciences At hours day month year The Ph.D thesis may be found at: Vietnam National Library The Library of Vietnam Academy of Agricultural Sciences The Library of National Maize Resarch Institute 1 INTRODUCTION 1. THESIS URGENCY Maize (Zea may L.) is considered as one of the most important cereal crops in the world and the second after rice in Vietnam. The Central Highlands is of soil and climate very favorable for maize. However, maize cultivars still don’t fully express its potential yield due to drought and diseases, especially rust (Puccinia sp.). Annually, there may be of 15 - 20% loss in the first crop season and about 25 - 40%, even up to 60% in the second ones. In order to explore potential and advantages of the Central Highlands, it is necessary to use high yield and rust tolerant maize hybrids to improve maize yield and production for the Central Highlands. From reasons mentioned above, It would be urgent to carry out the thesis “ Maize hybrid breeding for high yield and rust (puccinia sp.) tolerance in the central highlands” 2. RESEARCH OBJECTIVES Developing inbred lines and selecting some promising crosses with high yield, tolerance to rust and suitability for ecological conditions and cultivation habits in the Central Highlands. 3. Scientific and practical significances  Scientific significance Providing data, scientific facts and applicability of materials in breeding maize hybrids with high yield, rust tolerance for the Central Highlands  Practical significance - Selecting a nursery of materials including 28 inbred lines with high yield and rust tolerance in the Central Highlands; - Introducing some promissing crosses: VN5885 recognized as trial production, VN665 and VN667 tested in the official testing system with high yield, rust tolerance for maize production in the Central Highlands, contributing into improving maize yield and production in this region. 2 4. MATERIALS AND SCOPE OF RESEARCH * Materials - Including inbred lines derived from commercial hybrids such as NK67, NK66, C919, CP888, CP999, P4097, DeKalbgold, Pacific 747, LVN10 and LVN4; top-croses, dialell crosses, promissing crosses; local checks: LVN4, LVN99, LVN885, C919, DK9901, CP888, NK67. - Rust disease on maize. * Scopes - Experiments of evaluating lines and crosses, genetic diversity using SSR markers; - Evaluating combing ability, heterosis, adaptability, stability of crosses in the Central Highlands and other ecological zones. 5. NEW CONTRIBUTIONS OF THE THESIS The research in the dissertation found a nursery consisting of 28 inbred lines with rust tolerance as materials for developing high yield hybrids with rust tolerance and developing a new hybrid namely VN5885, of wide adaptability, early medium maturity, hard stalks, especially good rust tolerance that recognized as trial production in 2013 by The Ministry of Agriculture and Rural Development (Decision No. 627/QĐ-TT-CLT dated 30 Dec, 2013) and tested with two promising crosses (VN665 and VN667) in the Central Highlands and other ecological zones. 6. STRUCTURE OF THE THESIS The thesis consists of 133 pages, 37 tables, 15 pictures presented in 5 sections: Introduction (3 pages); Chapter 1: Scientific basis and review of literature (42 pages); Chapter 2: Materials, contents and research methods (13 pages); Chapter 3: Research results and discussions (61 pages); Conclusions and suggesions (1 page); References including 142 documents with 27 in Vietnamse, 109 in English and 6 from websites. There are two publications related to the dissertation in domestic journals. 3 CHAPTER I SCIENTIFIC BASIS AND OVERVIEWS 1.1. SCIENTIFIC BASIS The Central Highlands is very potential zone for agricultural development and the second major maize area in the country. Maize is mainly used for livestock and partly food for the ethnic minorities here. However, maize production in the Central Highlands is still inadequate and unsustainable, because most of maize areas are mountainous with highly steep slopes, rainfed condition and low intensive farming. Moreover, due to warm climate, high rainfall and humidity, it is very favorable for development of diseases harmful to maize especially rust, which causes major damage on maize in the Central Highlands (loss of production annually from 15-20 % in the summer - autumn, and 25- 40% even up to 60% in some areas in autumn- winter crop season). In addition, current maize cultivars still are not good at tolerance to diseases so not able to meet requirements of maize development in the Central Highlands. Thus, drought and diseases especially rust are major reasons for the reducted maize production in the Central Highlands. Therefore, it is necessary to have a set of maize hybrids with high yield, early maturity, rust tolerance etc in order to decrease the losses of maize production for the Central Highlands. 1.2. FOREIGN RESEARCH WORKS RELATED TO THE THESIS 1.2.1. Maize production and usage in the world Due to important role in the global economy, there should always be great interests in and more and more continuous development of maize production. In 2001, globle maize area is 140.2 million ha with an average yield of 4.3 tons.ha-1 and an output of over 600 million tons. The proportion of maize area accounts for 20 % of the total area of cereal crops. The level of average annual growth in maize production worldwide during 2000 2010 is 1.8 % of area, 2.1 % of yield and 4.3% of production. By 2013, corn area in the world is 184.19 million ha with average yield of 5.52 tons.ha-1 and production of more than 1016.74 million tons. 4 1.2.2. Heterosis and its application in maize breeding Heterosis is defined as the superiority of a hybrid cross over its two parents in vitality, adaptability, productivity and quality. Until now, heterosis has been researched in details, divided into five types: heterosis of morphology, productivity, adaptability, early maturity and physiology, biochemistry. 1.2.3. Inbred lines, methods of selection and evaluation 1.2.3.1. Definition of inbred lines Inbred lines are relative concepts to refer to self-pollinated lines at a level of high homozygosity and genetic stability in many traits. For maize, it takes 7-9 self-fertilized generations to obtain inbred lines. 1.2.3.2. Methods of inbred line development Selfing, sib-mating (sib or fullsib), additivo accumulative, selection of similar lines, backcross, etc. Besides, some methods of new line development such as gamete selection, DH lines via anther or unfertilized ovule culture, inducers use, etc. 1.2.3.3. Combing ability Combination ability is an inherited characteristic, passed down progenies through selfing and crossing. Combination ability is determined by evaluating general and specific combining ability. 1.2.3.4. Evaluation of combing ability: Top-crossing, dialell-crossing 1.2.4. Genetic diversity and its implications into maize hybrid breeding Maize is typically a cross pollinated plant, very diverse populations and heterozygous individuals. So the database about the genetic diversity of germplasm is essential and extremely useful in the evaluation of lines, determination of heterotic groups and prediction of promissing high yield test-crosses. To evaluate genetic diversity, there are many methods such as morphological markers, biochemical markers, DNA molecular markers. 1.2.5. Rust disease on maize 1.2.5.1. Pathogens: Puccinia sorghi, Puccinia polysora, Physopella zeae. 5 1.2.5.2. The environmental influence on the infection and development of the disease The infection as well as the dispersity of Puccinia sorghi and Puccinia polysora is affected by environmental conditions. Favourable temperature: Puccinia sorghi from 15 to 25°C, Puccinia polysora between 23 and 28°C. 1.2.5.3. The influence of rust disease on maize: causing a reduction or loss in photosynthetic capacity, an increase in respiratory rate, strong evaporation, water transportation interruption, resulting in the loss of plant water balance, making plants withered and reducing grain yield. 1.2.5.4. The variety of pathogens Various biological types of Puccinia sorghi, which causes impacts on hosts, are calculated in the amount of spores dispersing on sensitive seedlings. For Puccinia polysora, there are at least 10 races and known as EA1, EA2, EA3, PP.3, PP.4, PP.5, PP.6, PP.7 and PP.8, PP.9, PP.10. 1.2.5.5. The inheritance of rust resistance in maize Qualitative resistance is controled by single dominant genes. Rust resistance by Puccinia polysora: 11 genes (Rpp1 - Rpp11). Rust resistance by Puccinia sorghi: 25 Rp dominant genes. Quantitative resistance: polygene traits and inheritance to the next generation is in accordance with additive principles and of high general combining ability. 1.2.5.6. The management of rust in maize In order to control rust resistance in corn, there should be with resistant varieties, chemical measures and cultivation methods. 1.2.5.7. The study of breeding maize varieties with high yield and rust tolerance Worldwide, there have been many research works on rust and breeding high-yielding maize varieties resistant to rust. These studies are generally carried out by traditional methods, mainly in India. Recently, the combination of traditional methods and biotechnology also has identified a number of high-yielding maize cultivars resistant to rust. However, these studies are still of limitation. 6 1.3. DOMESTIC RESEARCHES RELATED TO THE THESIS 1.3.1. Maize production and usage in Vietnam Maize hybrids have played a major role in an increase in maize productivity and yield in Vietnam. During 1960 - 1980, maize yield of Vietnam only reached 0.8 -1.1 tons.ha-1 due to using local varieties and obsolete cultivation techniques. In 1990, applying improved maize varieties, grain yield gained 1.5 tons.ha-1. In 1991, maize hybrid area accounted for only less than 1% of 447,000 ha. In 2000, hybrids accounted for 65% of total maize acreage and contributed in improving average yield of 2.75 tons.ha-1. In 2013, the maize area is 1.17 million ha, of which hybrids are more than 95%. The success in hybrid maize program has significantly contributed in increasing nationwide average yield of 4.44 tons.ha-1. 1.3.2. Maize production in the Central Highlands The Central Highlands is of 243.9 thousand ha maize, accounting for 20.6% maize area. In 2013, maize area of the Central Highlands was 252.4 thousand ha, mainly in three provinces DakLak (123.4 thousand ha), GiaLai (52.6 thousand ha) and DakNong (52.9 thousand ha). Maize yield in the region is 51.7 quintals.ha-1, ranked third among maize regions in Vietnam, higher than the nationwide average yield (44.4 quintals.ha-1) and equivalent to the world average (55.2 quintals.ha-1). Due to an increase in area and productivity, maize production in the region has been increased by 7.56% compared to in 2012, with 1,306.1 thousand tons and 25.14% of national production. 1.3.3. Inbred lines and evaluation In Vietnam, since 1990, it has focused on making inbred lines to develop hybrids. Until now, there have been many inbred lines with high yield made by traditional methods. In addition, many high-yielding inbred lines has been also created by appying biotechnology. 1.3.4 Genetic diversity and its implications in maize breeding In Vietnam, based on morphological criteria, a number of authors have studied the genetic diversity of maize germplasm. DNA molecular markers have also been used to 7 support the development of hybrids such as using RAPD, SSR markers in analyzing the genetic diversity of line nursery, clustering and predicting heterosis as well. 1.3.5. Researches on rust and breeding high-yielding maize varieties tolerant to rust In Vietnam, researches on maize rust are still limited and until now there have been have two determined species of rust fungi on maize. These are Puccinia polysora and Puccinia sorghi. This dissertation is the first work of maize hybrid breeding for high yield and rust (puccinia sp.) tolerance in the central highlands in Vietnam. CHAPTER 2 MATERIALS AND METHODS 2.1. RESEARCH MATERIALS The inbred lines derived from commercial hybrids such as NK67, NK66, C919, CP888, CP999, P4097, DeKalbgold, Pacific 747, LVN10 and LVN4; Checks in the experiments of test-cross selection as NK67 and C919: Checks used in official testing, breeding testing are NK67, C919, DK9901, CP888, LVN4, LVN885, LVN99. 29 SSR primers from Invitrogen company announced at website: http://www.maizegdb.org/ssr.php 2.2. RESEARCH CONTENTS - Investigation of damage on corn caused by rust in the Central Highlands; - Evaluation of agronomical characteristics, tolerance of rust tolerant lines; - Evaluation of genetic diversity, genetic purity and combing ability of the nursery of rust tolerant lines; - Evaluation of agronomical characteristics, tolerance, heterosis of top-crosses, dialell crosses, and selection of promising crosses; - Testing of maize hybrids tolerant to rust in the Central Highlands and other ecological zones. 8 2.3. METHODOLOGY 2.3.1. Investigating methods on the production and diseases on corn • Interview • Method of assessment and investigation in field Applying methods of research, investigation and detection of diseases under “Plant protection Research Methods” of the Institute of Plant Protection, 2003. 2.3.2. Methods of artificial infection According to the method of artificial infection by Meena Shekhar, Sangit Kumar and Nguyen Thi Binh (1990). 2.3.3. Method of assessing lines, top-crosses and dialell crosses Evaluating agronomical characteristics, tolerance, yield of lines and crosses as well; and data collection under the guidance of CIMMYT (1985); Evaluating top-crosses, dialell crosses according to the model of Griffing 4 (1956). 2.3.4 Methods of assessing genetic diversity by SSR markers Evaluating genetic diversity under the guidance of AMBIONET-CIMMYT (2004) 2.3.5. Testing methods Applying the procedures for maize testing No.10 BC-341-2006 by The Ministry of Agriculture and Rural Development 2.3.6. Data processing The experimental results processed by the program Excel 5.0, MSTAT 4.0, SAS 9.1; Combining ability for yield in top crosses and dialell crosses in according to model Griffing 4 analyzed by Nguyen Dinh Hien’s Diallel program version 2.0; Tree genealogical mapping with specific software NTSYS pc version 2.1. 2.4. LOCATIONS AND TIME • Time: from 2009 to 2014 - During 2009-2011: Investigating of damage on corn caused by rust in the Central Highlands; Having selected a nursery of rust tolerant lines, evaluated the genetic diversity by molecular markers, developed the combing ability by top-crossing and dialell -crossing, tested hybrid crosses. - During 2011-2014: Having evaluated the growth and development of some promising crosses. • Locations: in the Central Highlands and Hanoi. 9 CHAPTER 3 RESULTS AND DISCUSSION 3.1. DAMAGES CAUSED BY RUST ON MAIZE IN THE CENTRAL HIGHLANDS 3.1.1. Current status of diseases harmful to maize in the Central Highlands To assess the prevalence of harmful diseases on maize in the field, conducting surveys at summer-autumn and autumn-winter crop seasons in 2009 in the Central Highlands showed that most of diseases such as rust, sheath blight, northern corn leaf blight, southern corn leaf blight and stalk rot are popular on maize. The prevalence of these diseases is only 5 - 25% in Autumn-Winter, but much higher in the Autumn-Winter crop season with 25 50%), in which rust is the most remarkable. 3.1.2. Current status of maize rust in the Central Highlands Rust disease often takes place in Autumn-Winter rather than in Summer-Autumn crop season. Depending on local areas but the prevelance is from 5 to 25% in Summer-Autumn while in the range of about 25 - 50% in Autumn-Winter crop season. Rust disease is a main cause of reducing maize yield in the Central Highlands. The losses caused by rust are estimated as about 14.44% in summer-autumn and 27.46% in autumn-winter crop seasons and depend on each cultivar. Therefore, it should be necessary to have a set of high-yielding maize cultivars with rust tolerance for reducing yield loss in the Central Highlands. 3.2. AGRONOMICAL CHARACTERISTICS, TOLERANCE OF RUST TOLERANT LINES 3.2.1. Results of selecting a nursery of rust tolerant lines for the Central Highlands Through evaluating tolerance ability of 40 lines via artificial infection as well as accessment in field, it showed that there are 28 lines expressing good rust tolerance as B67a, B67c, M67a, M67b, G2, G3, G17, G31, G40, G41, G43, G45, G46, G47, G286, G288, G289, G1234, G1235, G1237, G1238, C4N, C10N, C2N, C3N, C90N, C89N, C88N. These lines may be used as materials for high yield and rust tolerance maize hybrid breeding in the Central Highlands. 3.2.2. Agronomical characteristics and tolerance of the nursery of rust tolerant lines Evaluation results on agronomical characteristics and tolerance of lines in Autumn 10 Winter season 2009 at two locations: Dan Phuong - Ha Noi and Buon Ma Thuot - DakLak. It should be presented in table 3.7 while yield components and yield in the Central Highlands are shown in Table 3.11 Table 3.7. Tolerance ability of studied lines No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Name of lines Lodging ĐP B67a 1 B67c 1 M67a 3 M67b 3 G2 2 G3 2 G17 2 G31 2 G40 2 G41 2 G43 2 G45 2 G46 2 G47 2 G286 3 G288 3 G289 3 G1234 3 G1235 3 G1237 3 G1238 3 C2N 2 C3N 2 C4N 3 C10N 1 C89N 3 C90N 3 C88N 2 T5 (Check) 1 DF2 (Check) 3 BMT 1 1 2 2 1 1 1 2 2 2 1 1 1 1 2 2 2 2 2 2 2 2 2 3 1 3 3 2 1 2 Tolerance ability (1- 5) Drought Leaf blight Sheath blight Rust tolerrance ĐP BMT ĐP BMT ĐP BMT ĐP BMT 1 1 2 2 2 2 1 2 1 1 2 2 2 2 1 2 2 3 2 3 2 3 1 2 2 3 2 3 2 3 1 2 2 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 2 2 2 3 2 3 2 2 2 2 2 3 2 3 2 2 2 2 1 2 2 3 2 2 2 2 1 2 2 3 2 2 2 2 1 2 2 2 1 2 2 2 2 2 1 2 1 1 2 2 2 2 1 2 1 2 2 2 1 2 2 2 1 1 2 3 1 1 2 3 1 2 2 2 1 1 2 3 1 1 2 3 1 3 2 3 1 1 2 1 1 1 2 2 1 1 2 2 1 1 2 2 1 1 2 1 1 2 1 2 1 1 2 2 2 3 1 2 1 1 3 3 3 3 3 3 2 2 3 3 3 3 3 3 2 2 3 3 2 2 1 1 2 2 2 2 2 2 1 1 1 1 2 2 1 2 2 2 3 3 2 2 1 2 1 2 2 2 2 2 1 2 1 1 2 2 1 1 2 2 1 1 1 1 2 3 2 3 2 3 3 3 Notice: Point 1-5: best - worst DP: Dan Phuong and BMT: Buon Ma Thuot 11 Table 3.11. Yield components and grain yield of lines in BuonMaThuot- DakLak Name Ear Length No. of lines Cm CV% 1 B67a 12.8 7.3 2 B67c 13.3 6.1 3 M67a 14.3 7.0 4 M67b 16.1 8.3 5 G2 12.8 7.2 6 G3 12.8 6.1 7 G17 12.6 3.7 8 G31 14.0 6.1 9 G40 14.8 7.3 10 G41 12.1 6.1 11 G43 12.8 5.8 12 G45 13.0 5.8 13 G46 13.6 6.3 14 G47 12.0 4.3 15 G286 13.8 5.6 16 G288 13.6 11.4 17 G289 12.7 10.7 18 G1234 12.3 8.7 19 G1235 13.8 5.8 20 G1237 13.6 8.0 21 G1238 12.7 6.7 22 C2N 11.3 10.2 23 C3N 11.2 5.8 24 C4N 14.7 6.1 25 C10N 14.6 3.7 26 C89N 13.7 5.8 27 C90N 14.3 6.3 28 C88N 14.3 4.5 T5 29 13.5 6.1 (Check) DF2 30 14.4 5.6 (Check) CV% LSD 0.05 Ear Diameter Cm CV% 3.4 4.6 3.4 5.6 3.8 4.3 3.8 6.3 3.4 5.1 3.6 6.6 3.2 7.6 3.6 10.2 3.4 8.2 3.7 6.1 3.3 8.3 3.6 8.3 3.6 10.6 3.4 4.5 3.3 5.8 3.2 6.2 3.6 3.3 3.7 6.6 3.8 5.8 4.0 7.3 3.9 6.3 4.4 6.3 4.4 4.2 4.4 8.3 4.5 6.7 4.3 5.8 3.8 3.4 4.1 3.7 Rows CV% Kernels 12.0 11.7 22.3 14.0 8.9 28.3 14.0 7.9 21.5 12.0 14.4 27.1 12.0 10.2 25.9 12.0 13.5 24.0 12.0 12.4 21.0 12.0 8.6 27.6 12.0 10 25.2 12.0 8.6 25.6 12.0 8.3 25.5 14.0 10.0 27.1 12.0 10.2 24.0 12.0 14.1 20.6 12.0 8.3 23.6 12.0 3.9 27.1 14.0 4.0 22.0 14.0 7.8 24.9 14.0 8.6 21.6 14.0 7.1 22.3 14.8 5.8 20.4 14.8 3.3 21.9 14.4 3.7 27.1 13.6 6.1 32.7 14.0 7.3 28.1 12.0 10.2 30.0 12.0 7.1 26.1 12.0 6.6 27.3 3.7 8.0 12.0 8.6 22.8 7.6 261.7 24.7 3.1 6.3 12.0 8.2 25.3 4.8 233.5 22.4 Kernel rows Kernels per row CV% 13.9 4.5 12.6 10.5 4.9 10.7 17.3 13.6 8.9 11.4 10.4 4.9 12.7 14.1 8.9 5.4 8.5 15.0 12.9 6.9 11.4 5.7 8.2 6.6 5.4 6.7 8.1 9.1 P.1000 Yield kernels (Quintal/ha) (g) 239.3 23.6 242.0 24.8 258.0 38.6 260.0 32.5 242.0 28.6 257.6 29.8 252.5 28.3 240.0 30.0 252.6 30.7 248.6 32.4 243.3 35.6 242.2 36.6 243.3 33.3 251.1 34.7 256.8 29.6 244.9 36.3 254.0 34.5 244.0 30.3 234.5 34.7 242.0 27.6 237.6 30.7 310.0 32.1 299.1 30.4 333.7 36.3 334.1 38.5 310.2 36.5 293.6 35.5 285.5 30.3 6.48 3.331 In Autumn- Winter 2009 The results of the overall assessment of agronomical characteristics and tolerance show that selected 28 lines for development of early mature varieties with rust 12 tolerance and maturity (108 -118 days in the Central Highlands, 112-106 days in Northern Vietnam), which are of healthy seedling stage, uniformity in morphological traits, good resistance especially rust (point 1 - 2) and quite high yield (23.6 to 36.6 quintals.ha-1), meet the requirements of the program on developing rust tolerant maize hybrid for the Central Highlands. 3.3. GENETIC DIVERSITY AND COMBINING ABILITY OF THE NURSERY OF RUST TOLERANT MAIZE LINES 3.3.1 Genetic diversity of the nursery of rust tolerant maize lines All of lines with rust tolerance ability are satisfactory to the requirements in the study of genetic diversity, to the proportion of homozygous genotypes more than 80%. PIC value of 29 studied loci which is in the range of 0.124 to 0.809 and of 0.523 on average demonstrates that it is quite diverse in the level of genetic diversity in the nursery of studied lines. Through the tree genealogical chart of studied lines, it should be indicated that these 30 lines are clearly divided into two groups at the degree of similarity as 0.272 (27.2%). - Group I: including 22 lines and 4 subgroups as following: Subgroup 1.1: 8 lines, consisting of G1238, G1237, M67a, M67c, G31, G3, G17 and G2. Subgroup 1.2: 3 lines as G40, G41 and G43. Subgroup 1.3: 9 lines, these are G45, G46, G47, G1234, G1235, G286, G288, G289 and T5. Subgroup 1.4: 2 lines, B67a and B67c. - Group II: including 6 lines: C4N, C89N, C2N, C3N, C90N and C88N. - C10N and the check DF2 are classified separately from the rest of the lines at the degree of similarity as 0.21 (21%). Based on the results of genetic clustering with 29 SSR loci combined with the results of an assessment of agronomical characteristics, these lines were divided into two sets of experiments in order to make an evaluation of combining ability of yield: - Experiment 1: Mainly consisting of lines of group I (21 lines, excluding line T5) and line DF2, using top-cross method because of a large number of lines; - Experiment 2: Including lines of group II, C10N and T5 lines, applying Griffing 4 13 diagram of dialell- crossing. Evaluating results are presented in the next sections. G1238 G1237 M67a M67b G31 G3 G17 G2 G40 G41 G43 G45 G46 G47 G1234 G1235 G286 G288 G289 T5 B67a B67c C4N C89N C2N C3N C90N C88N DF2 C10N G1238 0.20 0.38 0.56 0.74 0.92 Coefficient Figure 3.8. Tree genealogical chart on genetic relationship of 30 lines based on the analysis of 29 SSR loci 3.3.2. Combining ability of rust tolerant line nursery for grain yield The experiment on evaluating combining ability was implemented in summer-autumn season 2010 at two locations: Cu M'gar and Buon Ma Thuot. 3.3.2.1. Combining ability evaluation of rust tolerant line nursery for grain yield by top-crossing The results of assessing combining ability of 20 lines by top-crossing with 2 testers B67a and G2 should be represented in table 3.14. 14 Table 3.14. Combining ability of 20 experimental lines for grain yield General No. Name of lines Specific combing ability combining ability Variance of specific Tester 1 (B67a) Tester 2 (G2) combing ability 1 M67a 4.574 -4.523 4.522 40.906 2 M67b -1.209 0.994 -0.994 1.977 3 G3 -19.976 0.527 -0.528 0.557 4 G17 -10.526 -8.256 8.256 136.318 5 G31 -7.492 -12.856 12.856 330.545 6 G40 -10.326 11.111 -11.111 246.901 7 G41 -13.742 7.094 -7.094 100.654 8 G43 -9.659 3.177 -3.178 20.193 9 G45 4.208 -2.256 2.256 10.178 10 G46 14.258 2.027 -2.028 8.222 11 G47 9.441 -0.989 0.989 1.957 12 G286 10.158 3.627 -3.628 26.318 13 G288 1.141 0.344 -0.344 0.237 14 G289 -10.059 2.644 -2.644 13.983 15 G1234 5.724 -4.139 4.139 34.265 16 G1235 1.658 -2.539 2.539 12.895 17 G1237 10.524 1.261 -1.261 3.179 18 G1238 10.641 1.777 -1.778 6.319 19 B67c 9.208 -1.089 1.089 2.373 20 DF2 1.458 2.061 -2.061 8.494 In summer-autumn crop season 2010 at Cu M'gar 3.3.2.2. Combining ability evaluation for grain yield by dialell-crossing The results of evaluating the combining ability of 8 lines by dialell-crossing are shown 15 in table 3.15. Table 3.15: Combining ability of 8 experimental lines for grain yield Variance of combing ability No. Name of lines General combining ability (gi) 1 C3N 2.838 11.525 2 C2N -4.340 44.234 3 C4N 5.665 37.054 4 C10N 5.010 3.126 5 C88N -5.951 20.457 6 C89N -8.474 69.422 7 T5 5.854 24.773 8 C90N -0.601 82.073 (si2) In summer-autumn season 2010 at Buon Ma Thuot Based on the results of line evaluation on agronomical traits, tolerance and combing ability for grain yield, it should be determined that some lines are of maturity, agronomical traits, tolerance satisfactory to the objectives of the thesis, in which 11 lines carry precious traits such as rust tolerance, high general combining ability, high variance of specific combining ability for grain yield, these are G2, G45, G46, G47, G286, G1237, G1238, B67a, B67c, C4N and C10N. 3.4. THE RESULTS OF EVALUATING AGRONOMICAL TRAITS, TOLERANT ABILITY, HETEROSIS OF TOP CROSSES, DIALELL CROSSES AND SELECTION OF PROMISSING CROSSES Testing top-crosses and dialell crosses was carried out in summer-autumn season 2010 at 2 locations Cu M'gar and Buon Ma Thuot with two checks NK67 and C919. 3.4.1. The evaluation of agronomical traits, tolerant ability, hetorosis of top-crosses The tolerant ability of top-crosses should be presented in table 3.17. 16 Table 3.17. Tolerant ability of top-crosses (scale of 1-5) No. Names of crosses 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 M67a X M67b X G3 X G17 X G31 X G40 X G41 X G43 X G45 X G46 X G47 X G286 X G288 X G289 X G1234 X G1235 X G1237 X G1238 X B67c X DF2 X M67a X M67b X G3 X G17 X G31 X G40 X G41 X G43 X G45 X G46 X G47 X G286 X G288 X G289 X G1234 X G1235 X G1237 X G1238 X B67c X DF2 X NK67 C919 B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 Rust Sheath Blight 3 2 2 2 3 2 1 2 3 1 2 1 1 2 1 2 2 2 2 2 2 2 2 2 3 1 2 3 2 1 2 3 1 2 2 2 2 2 2 2 2 2 2 2 1 2 2 2 2 1 2 2 2 2 2 1 2 2 2 2 1 1 1 2 2 1 2 1 1 3 2 2 2 2 1 2 2 3 2 2 1 2 1 2 Northern corn Southern corn leaf blight leaf blight 2 2 2 2 2 2 2 2 2 2 2 2 2 2 1 2 2 3 2 2 1 2 1 2 1 2 1 2 2 2 2 2 1 2 2 2 1 2 1 2 1 2 1 2 2 2 1 2 2 2 1 2 1 2 2 3 2 2 1 2 2 2 2 2 1 2 2 3 2 2 1 2 2 2 2 2 2 3 2 2 2 3 2 2 Notice: Point 1-5: best – worst In summer-autumn season 2010 at Cu M'gar Grain yield and yield heterosis of top crosses are available in table 3.19. 17 Table 3.19. Grain yield and yield heterosis of top crosses No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Name of lines M67a M67b G3 G17 G31 G40 G41 G43 G45 G46 G47 G286 G288 G289 G1234 G1235 G1237 G1238 B67c DF2 M67a M67b G3 G17 G31 G40 G41 G43 G45 G46 G47 G286 G288 G289 G1234 G1235 G1237 G1238 B67c DF2 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X NK67 C919 CV% LSD0.05 B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a B67a G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 G2 Grain yield (Quintals/ha) 76.7 76.4 57.2 57.9 56.3 77.4 70.0 70.2 78.6 92.9 85.1 90.4 78.1 69.2 78.2 75.8 88.4 89.1 84.8 80.2 88.8 77.5 59.2 77.4 85.1 58.3 58.9 66.9 86.2 91.9 90.1 86.2 80.5 67.0 89.6 83.9 89.0 88.6 90.0 79.1 76.4 73.2 3.87 4.903 Hmp (%) 143.1 157.9 95.4 92.9 92.3 172.2 139.9 119.3 146.7 200.9 176.6 205.9 155.5 115.7 158.6 159.2 191.4 188.7 201.7 181.4 177.6 157.8 99.3 154.4 186.3 101.7 98.8 106.2 166.8 193.6 188.9 187.4 159.5 105.9 191.9 182.8 189.0 183.1 215.4 173.5 Notice: Hmp- Average heterosis; Hs - Standard heterosis; In summer-autumn crop season 2010 at Cu M’gar Hs (%) (NK67) 0.4 0.0 -25.1 -24.3 -26.3 1.4 -8.4 -8.2 2.9 21.6 11.4 18.4 2.3 -9.4 2.4 -0.8 15.8 16.6 11.0 4.9 16.2 1.4 -22.5 1.4 11.3 -23.7 -22.9 -12.5 12.8 20.3 18.0 12.9 5.4 -12.3 17.2 9.8 16.4 15.9 17.8 3.5 Hs (%) (C919) 4.8 4.4 -21.9 -20.9 -23.1 5.8 -4.4 -4.1 7.4 27.0 16.3 23.5 6.7 -5.4 6.9 3.5 20.8 21.7 15.8 9.5 21.3 5.9 -19.1 5.8 16.2 -20.4 -19.6 -8.7 17.7 25.6 23.1 17.8 10.0 -8.5 22.4 14.6 21.5 21.0 23.0 8.0 18 Based on the results of testing top-crosses in experiment 1, it must be found that two crosses G46 x B67a and G46 x G2 are of precious agronomical traits such as time early medium maturity, compact plants, long cylindrical ears, quite good tolerance, especially rust (point 1), yields more than 90 quintals/ha higher than checks NK67 and C919. 3.4.2. Evaluation of tolerance ability, heterosis of dialell- crosses The tolerance ability of of crosses is presented in table 3.21. Table 3.21. The tolerance ability of of crosses (scale of 1 – 5) No. Names of crosses Rust Sheath Blight 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 C3N x C2N C3N x C10N C3N x C4N C3N x C88N C3N x C89N C3N x T5 C3N x C90N C2N x C10N C2N x C4N C2N x C88N C2N x C89N C2N x T5 C2N x C90N C10N x C4N C10N x C88N C10N x C89N C10N x T5 C10N x C90N C4N x C88N C4N x C89N C4N x T5 C4N x C90N C88N x C89N C88N x T5 C88N x C90N C89N x T5 C89N x C90N T5 x C90N NK67 C919 1 1 2 1 1 2 2 2 1 2 2 1 2 1 1 1 1 1 1 2 2 2 2 1 1 2 2 2 2 3 1 1 2 2 2 2 2 2 2 2 2 1 2 2 3 3 3 3 3 2 2 2 2 2 2 2 3 3 2 2 Northern corn leaf blight 1 2 2 2 1 2 2 2 2 1 2 1 2 1 2 2 2 2 2 2 2 2 2 3 1 2 3 3 2 1 Southern corn leaf blight 1 2 2 2 2 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Notice: point 1-5: Best - Worst In summer-autumn crop season 2010 at Buon Ma Thuot Grain yield and heterosis for yield of dialell crosses are shown in table 3.23.