QTL mapping and analysis
- 1. QTL Mapping MSc ag (2) year Agriculture Genetics and Plant Breeding Deen Dayal Upadhyaya Gorakhpur University Gorakhpur Submitted by. Shweta Kumari Submitted to Department of Genetics and plant breeding
- 2. Introduction ✩ QTL mapping ✩ QTL mapping is the process to identify the genomic region associated with desirable quantitative trait with the help of DNA marker ✩ In this process DNA markers are tested throughout the genome which are associated with QTLs.
- 3. Quantitative Traits Loci ✩ The loci controlling quantitative traits are called quantitative traits Ioci ( QTL) ✩ the term quantitative traits coined by Genderman. ✩ QTL is the region of genome which control quantitative trait ✩ QTL characteristics ✩ The QTLs are controlled by multiple genes ,each segregating according to Mendel's Law. ✩ These traits also a ected by environment to varying degrees ✩ QTL can show dominant or co-dominant
- 4. Objective of QTL mapping ✩ The basic objective is to detect QTL ✩ To identify the region of genome that a ects the trait of interest ✩ To analyse the e ect of the QTL on the trait ✩ How much variation for the trait is caused by a specific region ✩ What is the gene action associated with the QTL? ✩ Which allele is associated with the favourable e ect.
- 5. Procedure for QTL mapping ✩ Selection of diverse parental lines ✩ Creation of mapping population ✩ Phenotyping of the progeny ✩ Genotyping of the progeny ✩ Construction of linkage map.
- 6. Types of mapping population ✩ Recombinant Inbred line(RIL) ✩ Backcross ✩ F2 population ✩ Double haploid ✩ Near isogenic line(NIL)
- 7. Backcross mapping population ✩ Advantages: It is easier to identify QTL as there are less epistatic and linkage drag e ects; especially useful for crosses with wild species. ✩ Disadvantages: Di cult or impossible in species that are highly heterozygous and outcrossing. ✩ Use: best when inbred lines are available
- 8. F2 mapping Population ✩ Advantage: Fast and easy to construct. ✩ Disadvantage: F3 families are still very heterozygous; so the precision of the estimates can be low (because of the high standard error); can't be replicated
- 9. Recombinant Inbred Line ✩ RILs are produced by continuous selfing progeny of individual member of an F2 population until complete homozygous is achieved ✩ Advantages: fixed lines so can be replicated across many locations and/or years; can eliminate problem of background heterozygosity. ✩ Disadvantages: Can take a long time to produce. (Some species are not amenable)
- 10. Near Isogenic Line ✩ Advantage: Very precise and statistically strong, as background is constant; especially useful for validation experiments. ✩ Disadvantage: Can take time to construct; only useful for specific target QTL
- 11. Doubled Haploid Line ✩ Advantages: 1)Spontaneous chromosome doubling of ✩ Haploid microspores in in vitro culture ✩ 2)Homozygosity achieved in a single step Plants. ✩ Disadvantages: Less recombination between linked markers Not all systems are amenable to in vitro culture
- 12. Methods of QTL Detection ✩ Studying single markers one at a time. ✩ The simplest method for QTL analysis. ✩ Can be done by t-tests or ANOVA. ✩ Does not require a complete linkage map.
- 13. Simple Interval mapping ✩ Two markers at a time (flanking markers). ✩ Based on linkage mapping of markers. ✩ More accurate than single-marker analysis.
- 14. Composite interval mapping ✩ For detection of a QTL more than two markers are used ✩ It is based on linkage mapping of the marker.
- 15. Thank you
- 16. Zoho Show To create beautiful presentations, download Zoho Show from Play Store https://zoho.to/cy7 QTL mapping.pdf (This PDF has been generated using Zoho Show)