An investigation in rice (Oryza sativa L.) was carried out subjecting six ‘lines’ and 15 ‘testers’ crossed in a Line x Tester mating design to estimate gene action, combining ability and heterosis for yield and drought tolerant traits under aerobic condition. The 21 parents were also surveyed using SSR markers.
From the Line x Tester analysis, the hybrids exhibited significant variation among themselves for all the characters studied under aerobic condition. The study of gene action for drought tolerance and yield component traits revealed that all the traits exhibited dominant gene action which was predominant. Therefore, to harness the dominant gene effects, either heterosis breeding or selection at later generations would be an appropriate breeding methodology.
Based on the per se performance of lines and testers, the following parents i.e., IR79128A (L1), IR79156A (L2), COMS14A (L5), COMS24A (L6), IR 80286-22-3-6-1R (T3) and IR7925A-428-2-1-1R (T4) were adjudged as the best parents and crosses involving them would be expected to throw desirable segregants for both yield and drought tolerant traits under aerobic condition.
Based on the gca effects, the parents IR79128A (L1), IR70369A (L4), IR79156A (L2), BI-33 (T15), IR79582-21-2-2-1R (T5), KMP-105 (T11), T1 (IR 69726-29-1-2-2R) and MAS - 946-1 (T9) were the best general combiners and the crosses involving them would result in the identification of superior segregants with favourable genes for both drought and yield.
Out of 21 parents evaluated based on per se and gca effects, three
‘lines’ viz., IR79128A (L1), IR79156A (L2) and IR70369A (L4) and three ‘testers’ viz., IR7925A-428-2-1-1R (T11), KMP -148 (T12) and BI-33 (T15) were identified as the best genotypes which will be utilized in further breeding programmes as parents for improvement of yield and drought tolerance under aerobic conditions.
The cross combination IR70369A / MAS -26 (L4 x T10) was identified as the best for recombination breeding to get desirable segregants for yield and drought tolerant traits under aerobic conditions. The cross combinations viz., IR70369A / IR 7925A-428-2-1-1R (L4 x T4) and IR70369A / KMP-105 (L4 x T11) had high per se, sca effects and standard heterosis for drought tolerant and yield traits under aerobic conditions.
Table of Contents
I. INTRODUCTION
II. REVIEW OF LITERATURE
2.1. DROUGHT AND DROUGHT TOLERANCE IN RICE
2.2. NEED FOR AEROBIC RICE AND ITS IMPORTANCE
2.2.1. Aerobic rice breeding and its improvement
2.3. GENETICS OF DROUGHT TOLERANCE AND YIELD
2.4. DROUGHT TOLERANT TRAITS
2.5. ROLE OF SECONDARY TRAITS AND PUTATIVE TRAITS FOR DROUGHT TOLERANCE
2.5.1. Secondary traits
2.5.1.1. Days to 50 per cent flowering
2.5.1.2. Plant height
2.5.1.3. Number of productive tillers per plant
2.5.1.4. Panicle number per plant
2.5.1.5. Panicle length
2.5.1.6. Filled grains per panicle
2.5.1.7. Spikelet fertility
2.5.1.8. Total dry matter production (TDMP)
2.5.1.9. Hundred grain weight
2.5.1.10. Harvest index
2.5.1.11. Single plant yield
2.5.2. Putative traits
2.5.2.1. Root characters
2.5.2.1.1. Root length, dry root weight and dry shoot weight
2.5.2.1.2. Root – Shoot Ratio
2.5.2.1.3. Relative water content (RWC)
2.5.2.1.4. Chlorophyll stability index (CSI)
2.5.2.1.5. Proline content
2.5.2.1.6. SPAD chlorophyll meter reading
2.6. COMBINING ABILITY AND GENE ACTION
2.6.1. Gene action for different biometrical and physiological traits
2.7. VARIABILITY STUDIES
2.7.1. PHENOTYPIC AND GENOTYPIC CO EFFICIENT OF VARIATION
2.8. HERITABILITY AND GENETIC ADVANCE
2.9. HETEROSIS
2.10. ASSOCIATION ANALYSIS
2.10.1. Correlation studies
2.10.1.1. Correlation of grain yield with component traits
2.10.1.2. Inter correlation among yield components
2.10.2. Path analysis
2.10.2.1. Direct effects of different characters on grain yield
2.10.2.2. Indirect effects of different characters through other characters
2.11. GENETIC DISSECTION FOR DROUGHT TOLERANCE THROUGH MOLECULAR MARKERS
III. MATERIALS AND METHODS
3.1. MATERIALS
3.2. METHODS
3.2.1. HYBRIDIZATION PROGRAMME
3.2.2. Evaluation of F1 hybrids and parents for yield traits under aerobic condition
3.3. CHARACTERS STUDIED
3.3.1. YIELD AND ITS COMPONENTS
3. 3. 1.1. Days to 50 per cent flowering (DF):
3. 3.1.2. Plant height (PH):
3. 3. 1.3. Number of Productive tillers per plant (PT):
3.3.1.4. Number of panicles per plant (PP):
3. 3. 1.5. Panicle length (PL):
3. 3. 1.6. Filled grains per panicle (FG):
3. 3. 1.7. Spikelet fertility (SF):
3. 3. 1.8. Hundred grain weight (HGW):
3.3.1.9. Proline content (PC):
3.3.1.10. SPAD chlorophyll meter reading (SCMR):
3.3.1.11. Chlorophyll stability index (CSI):
3.3.1.12. Relative water content (RWC):
3. 3. 1.13. Biomass yield (BMY):
3. 3.14. Dry shoot weight (DSW):
3. 3. 15. Dry root weight (DRW):
3. 3. 16. Root / shoot ratio (RS):
3. 3. 1.17. Root length (RL):
3. 3.1.18. Harvest index (HI):
3.3.1.19. Single plant yield (YLD):
3.4. STATISTICAL ANALYSIS
3. 4. 1. Line x Tester analysis
3. 4. 1. 1. Analysis of variance
3.4.1.1.1. Phenotypic and genotypic variances
3.4.1.1.2. Phenotypic and genotypic co-efficient of variability (PCV and GCV)
3.4.1.2. HERITABILITY
3.4.1.3. GENETIC ADVANCE
3. 4. 1. 4. ANALYSIS OF COMBINING ABILITY AND GENE ACTION
3. 4. 1. 4. 1. ANOVA for combining ability
3. 4. 1. 4. 1.1. Estimation of combining ability effects
3. 4. 1. 4. 1.2. General combining ability effects
3. 4. 1. 4. 1.3. Specific combining ability effects
3. 4. 1. 4. 1.4. Test of significance of combining ability effects
3. 4. 1. 4. 2. ESTIMATION OF HETEROSIS
3. 4. 1. 4. 2.1. Heterobeltiosis (dii)
3. 4. 1. 4. 2.2. Standard heterosis (diii)
3. 4. 1. 4. 2.3. Test of significance
3. 4. 1. 4. 3. ASSOCIATION ANALYSIS
3. 4. 1. 4. 3.1. Correlation studies
3. 4. 1. 4. 3.2. Path coefficient analysis
3.5. Molecular characterization
3.5.1. Extraction of DNA
3.5.2. Quantification of DNA
3.5.3. Agarose gel electrophoresis
3.5.4. Molecular marker analysis
3.5.4.1. PCR amplification for SSR marker
3.5.4.2. Electrophoresis analysis
3.6. Scoring and statistical analysis of SSR data
3.6.1. Data scoring
3.6.2. Data analysis
3.6.3. Cluster analysis
IV. EXPERIMENTAL RESULTS
V. DISCUSSION
VI. SUMMARY
Research Objectives & Key Topics
The primary research objective of this thesis is to perform a comprehensive genetic and molecular analysis of various rice hybrids to identify the best parental combinations and genotypes that exhibit superior yield performance and drought tolerance under aerobic conditions.
- Line x Tester mating design for estimating combining ability and gene action.
- Assessment of heterosis for physiological, yield, and yield-contributing traits.
- Correlation and path analysis to determine the interrelationship between drought tolerance and yield.
- Molecular marker analysis using SSR markers to assess genetic polymorphism and similarity among parents.
Excerpt from the Book
3.2.1. HYBRIDIZATION PROGRAMME
The 21 parental seed materials [six Lines and 15 Testers (Testers = eight R lines and seven aerobic rice varieties)] were sown in a raised nursery bed during the month of June, 2009. The source materials of A, B and R lines with the above mentioned characteristic features were sown adopting line sowing in raised beds of one meter width and convenient length in a fertile well leveled plot. Thin sowing in the nursery was followed by good water and nutrient management to obtain healthy seedlings with three to four tillers at the time of planting.
Seedlings of A, B, R lines which attained the age of 29 days were transplanted in three meter length row with the spacing of 30 cm between rows and 15 cm between plants of each genotype in four rows. R lines were planted separately with an isolation of 300 meter. The row ratio obtained for planting the A and B lines was 8:2. Recommended package of practices and need based plant protection measures were adopted. Crosses were effected in a ‘Line x Tester’ mating design (Kempthorne, 1957).
The spikelets which were likely to open in the same day were selected during early hours between 6.30 and 8.30 A.M. in the female parents. Wet cloth method of emasculation as suggested by Chaisang et al. (1967) was followed to emasculate the selected spikelets. In this method, Panicles of the A lines on the 3rd or 4th day of its blooming were selected. The immature already opened top and lower spikelets were removed leaving only the middle spikelets. The panicle was covered with wet cloth and hot air was blown through the mouth. Due to increase in temperature and humidity inside the wet cloth, the spikelets were forced to open in the pre-anthesis time. All the six stamens that protruded out of the opened spikelets were removed one by one carefully by using a pointed forceps without damaging the style and stigma.
Summary of Chapters
INTRODUCTION: Provides an overview of the global importance of rice, the challenges of water scarcity, and the rationale for developing aerobic rice varieties.
REVIEW OF LITERATURE: Examines existing research on drought tolerance in rice, secondary traits, combining ability, heterosis, and molecular markers.
MATERIALS AND METHODS: Details the materials, hybridization techniques, characterization of traits, and statistical approaches used in the investigation.
EXPERIMENTAL RESULTS: Presents the statistical findings regarding variance, mean performance, combining ability, and heterosis of the rice genotypes studied.
DISCUSSION: Interprets the experimental results in the context of breeding strategies for yield improvement and drought tolerance in aerobic environments.
SUMMARY: Recaps the main findings of the research, emphasizing the effectiveness of specific hybrids and parental lines for future breeding programs.
Keywords
Aerobic rice, drought tolerance, Line x Tester analysis, combining ability, gene action, heterosis, SSR markers, genetic diversity, yield components, harvest index, SPAD chlorophyll meter, proline content, correlation analysis, path analysis, grain yield.
Frequently Asked Questions
What is the primary focus of this research?
The research focuses on the genetic and molecular improvement of rice for aerobic cultivation, specifically aiming to enhance yield and drought tolerance.
What are the core thematic areas covered in the thesis?
The thesis covers plant breeding methodologies, genetic variance estimation, heterosis exploitation, correlation and path analysis of yield components, and the use of molecular markers for genetic diversity assessment.
What is the main research objective?
The goal is to identify superior parental lines and hybrid combinations that maintain high productivity while using less water under non-flooded, aerobic conditions.
Which scientific method is utilized for breeding analysis?
The study employs a 'Line x Tester' mating design to estimate combining ability (GCA and SCA) and gene action in rice hybrids.
What topics are discussed in the main body chapters?
The main body chapters discuss experimental results related to mean performance, combining ability variance, heterosis, and association studies between various physiological and yield-related traits.
What keywords characterize the research?
The research is characterized by terms such as aerobic rice, drought tolerance, combining ability, heterosis, and molecular marker analysis.
What specific role does the 'Line x Tester' analysis play?
It provides critical information about the general combining ability (GCA) of parents and specific combining ability (SCA) of crosses, helping identify which parents contribute desirable traits for drought and yield.
How is molecular marker analysis applied in this study?
Molecular markers (SSRs) are used to screen 21 parents to determine genetic similarity and construct a dendrogram, which aids in selecting genetically diverse parents for cross-breeding.
- Quote paper
- Sathya Ramalingam (Author), 2012, Genetic and Molecular analysis of yield and physiological traits in three line hybrids in rice (Oryza sativa L.) under aerobic condition, Munich, GRIN Verlag, https://www.grin.com/document/201760
