Investigations on genetics of resistance to sterility mosaic (SM) disease in pigeonpea were carried out (1993-96) at ICRISAT Asia Center, Patancheru, India, to determine the inheritance of resistance for three different isolates of pigeonpea sterility mosaic pathogen and to study the combining ability of few resistant and tolerant lines.
In this direction, available lines (resistant/tolerant) were screened against two isolates of the SM pathogen. Breakdown of resistance was noticed in several lines, against isolate 2 of the pathogen. However, few lines resistant and tolerant to both the isolates were identified.
Inheritance of resistance and tolerance, in few of these lines was investigated. Screening was carried out in pots, using leaf-stapling technique for isolates 1 and 3 and infector-hedge, for isolate 2. Observations in F, and segregating generations indicated the recessive nature of resistance and role of two independent non-allelic genes for isolates 1 and 3. Resistance against these isolates appeared to be dependent on the presence of recessive alleles, at least at one of the loci. However, against isolate 2, resistance was observed recessive in some crosses and dominant in other crosses. Further, disease reaction for isolate 2, appeared to be governed by two independent non-allelic genes, with at least three multiple alleles, at one of the loci.
Combining ability studies of the resistant, tolerant and susceptible lines, included in the inheritance studies, were carried out with line x tester mating design, involving two male steriles and eleven pollen parents. The analysis of variance revealed significant differences for parents, hybrids, parents vs. hybrids and males, for all characters studied. Pre-ponderance of non-additive gene action was recorded for yield and all yield component characters studied.
ICP MS288 female was found to be a good combiner for early maturity, dwarf and compact growth habit while ICP MS3783 tolerant to isolate 1 of pigeonpea sterility mosaic pathogen and wilt disease was better combiner for seed yield, pods per plant, test weight, primary and secondary branches. Among the males, LRG 30 recorded high general combining ability, for seed yield and majority of yield components. The sterility mosaic resistant parents were however, poor combiners for yield and majority of the component characters.
Table of Contents
I. INTRODUCTION
II. REVIEW OF LITERATURE
III. MATERIALS AND METHODS
IV. RESULTS
V. DISCUSSION
VI. SUMMARY
LITERATURE CITED
Research Objectives and Focus
The primary research objective of this thesis is to investigate the genetic basis of strain-specific resistance to the sterility mosaic disease in pigeonpea, alongside evaluating the combining ability and genetic variability of various resistant and tolerant cultivars to facilitate effective breeding strategies for high-yielding, disease-resistant varieties.
- Determination of the inheritance patterns of strain-specific resistance to the sterility mosaic pathogen.
- Assessment of the combining ability of selected resistant and tolerant pigeonpea cultivars.
- Analysis of genetic variability and character associations for yield and other economic traits.
- Development of actionable breeding strategies for the creation of high-yielding, resistant pigeonpea genotypes.
Excerpt from the Book
GENETICS OF RESISTANCE
Resistance or susceptibility of a crop to a particular pathogen is the manifestation of host parasite interaction controlled by the co-evolving genetic systems of both the host and parasite. In centers of origin and crop diversity host population contains a wide spectrum of protective mechanisms that ensure survival against a high diversity of pathogenicity in the parasite. This results in a host/parasite equilibrium and most of the host genotypes have some degree of resistance against the parasite. However, in new areas of crop adaptation and intensive cultivation of a particular genotype genes for virulence to overcome the narrow genetic base of the host are favored causing susceptibility in the new cultivar. In the past pigeonpea cultivation in India and areas of Africa and Latin America had been confined to subsistence agriculture based on adapted landraces. The development of improved varieties by hybridization and selection under experimental conditions and cultivation in intensive production systems under irrigated conditions is a relatively recent phenomenon which has upset the delicate host/parasite equilibrium favoring the outbreak of diseases such as sterility mosaic. For planned disease management it is essential that genetic systems operating in a given host/pathogen environment are well understood. At present studies on genetics of resistance in pigeonpea are limited and preliminary.
Studies on inheritance of resistance to sterility mosaic disease of pigeonpea are also few and limited. Singh et al. (1983) studied the inheritance of resistance to sterility mosaic in 15 crosses involving five resistant and three susceptible genotypes F1, F2, BC1, and BC2 generations were studied. Resistance was under the control of four independent non allelic genes. The symbols Sv1, Sv2, sv3 and sv4 were assigned to the four resistance genes Sv1 and Sv2 were reported to exhibit duplicate dominant epistasis while, sv3 and sv4 exhibited duplicate recessive epistasis. It was further concluded that presence of at least one dominant allele at locus 1 or 2 and homozygous recessive genes at locus 3 or 4 were essential for resistance reaction.
Summary of Chapters
I. INTRODUCTION: This chapter provides an overview of the economic importance of pigeonpea in India and highlights the severe yield losses caused by the sterility mosaic disease, necessitating focused breeding for resistance.
II. REVIEW OF LITERATURE: This section summarizes existing research regarding the geographical distribution, pathogenic variability, identification of resistance sources, and genetic inheritance studies of the sterility mosaic pathogen.
III. MATERIALS AND METHODS: This chapter details the experimental setups, including the pathogen isolates, host materials, hybridization techniques, generation advancement, and the statistical methods utilized for data analysis.
IV. RESULTS: This section presents the comprehensive findings from screening experiments, inheritance studies across different isolates, and the evaluation of heterosis and combining ability in the tested hybrids.
V. DISCUSSION: This chapter interprets the experimental results, examining the genetics of resistance, the influence of pathogen variability, and the implications of heterosis and combining ability for future breeding programs.
VI. SUMMARY: This chapter offers a concise conclusion of the entire study, reiterating the findings on resistance inheritance and the potential for developing high-yielding, disease-resistant pigeonpea hybrids.
LITERATURE CITED: This section lists all scientific references and sources consulted during the course of the investigation.
Keywords
Pigeonpea, Cajanus cajan, Sterility Mosaic, Pathogen, Genetic Resistance, Inheritance, Heterosis, Combining Ability, GCA, SCA, Plant Breeding, Genetic Variability, Path Analysis, Disease Management, Yield Components.
Frequently Asked Questions
What is the core subject of this research thesis?
The research focuses on understanding the genetic mechanisms underlying resistance in pigeonpea against the sterility mosaic disease, which is a major constraint to pulse production in India.
What are the central themes of this study?
The central themes include the characterization of pathogenic variation, the inheritance patterns of resistance to specific viral strains, and the utilization of line x tester mating designs to assess combining ability and hybrid vigor.
What is the primary goal of the investigation?
The primary goal is to provide a systematic understanding of resistance genetics to facilitate the development of high-yielding, disease-resistant pigeonpea varieties suitable for commercial cultivation.
Which scientific methods were employed?
The study utilized standardized screening techniques like leaf-stapling and infector-hedge methods, hybridization in controlled environments, and statistical analyses including ANOVA, Chi-square testing, and path coefficient analysis.
What is covered in the main body of the work?
The main body covers the detailed screening of germplasm, the analysis of F1, F2, and backcross generations to identify gene action, and an extensive evaluation of yield components and heterotic performance in hybrid combinations.
Which keywords best characterize this work?
The work is characterized by terms such as pigeonpea, sterility mosaic, genetic inheritance, resistance, heterosis, combining ability, and crop improvement.
How does the pathogen's genetic plasticity affect the breeding strategy?
The reported genetic plasticity of the sterility mosaic pathogen necessitates a shift from general screening toward identifying strain-specific sources of resistance, as resistance effective against one isolate may fail against another.
What makes the identification of promising hybrids in this study significant?
The identification of specific hybrid combinations, such as ICP MS3783 x LRG 30, is significant because these crosses exhibit both desirable resistance traits and superior yield performance, providing a clear pathway for advanced generation breeding programs.
- Quote paper
- Srinivas Thati (Author), 1996, Genetics of resistance to sterility mosaic disease in pigeonpea, Munich, GRIN Verlag, https://www.grin.com/document/306846
