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Exploitation of natural variation
- 1. Exploitation of naturalvariation – attempts to increase variation Sri Subalakhshmi V K I 2019608015 I Ph.D (GPB)
- 2. Introduction • Natural variation– genome encoded differences for phenotypic variation • Enrolls for adaptation and species formation • More valuable and acts as reservoir of genes for plant improvement
- 3. Exploitation of naturalvariation – early attempts • Domestication • Selection • Hybridization
- 4. Landraces • Earliest formof cultivar • Closely related to wild ancestor • Highly heterogeneous and have broad genetic base • Represents first step in domestication process
- 5. Characteristics of landraces •High level of genetic diversity within populations • Adaptation to soil and climatic conditions • pest and disease resistance
- 6. Maize • 12000 years •Accumulation of spontaneous mutation Domestication
- 9. Selection • Pure lineselection • Mass selection
- 10. Hybridization • Crossing parentsand generating segregating populations • Pedigree breeding – qualitative traits (disease resistance, color, shape of plant parts, plant architecture) • Ideotype breeding – for improvement of quantitative traits
- 11. Cont. • Population breeding– improves phenotypic performance of intermating population by increasing the frequency of favourable alleles. • Inter-species / inter generic hybridization plays a crucial role in exploiting natural variation.
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- 13. Examples S. officinarum xS.barberi (adaptation to NI) F1 x S.spontaneum (resistance to pest &diseases) Noble canes
- 14. Exploiting natural variationfor insect defence – backcross breeding • Expression level polymorphism DNA polymorphism in regulatory genes or mutation, DNA methylation, interference of small RNAs, copy number of gene
- 15. Example • Maize –expression of herbivore induced TPS23 (terpene synthase 23) – produce volatile compounds (E)-β-caryophyllene – attracts natural enemies • Glucosinolates in Brassicaceae plants confers resistance against insects.
- 16. Cont. • Backcross breedinghelps in transfer of R-gene for resistance • WKS1 gene confers partial and temperature-dependent resistance - stripe rust, Puccinia striiformis – produce lipid signals/autoflourscent cells are formed around infecion sites- but is absent in commercial wheat varieties and introgressed from the ancestral wheat accession Triticum turgidum L. ssp. Dicoccoides
- 17. QTL • QTL isthe chromosomal region that contains a gene(s) that affects the quantitative trait. • Information obtained on QTL analysis is used in crop improvement programme.
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- 20. Allele mining –Eco-TILLING • Involves detection of naturally occuring allelic variation from landraces, cultivars, germplasms • Presence of point mutation or SNPs will be detected
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- 23. Findings • DEP 1(Dense and Erect Panicle 1) is pleotropically responsible for dense panicle, high grain number per panicle, erect panicle. • Mapped on chromosome 9 • DEP1 encodes unknown PEBP (phosphatidylethanolamine- binding protein) like domain protein
- 25. • The dominantallele at the DEP1 locus cause truncating mutation in phosphatidylethanolamine-binding protein- like domain protein. • enhance meristematic activity, resulting in a reduced length of the inflorescence internode, an increased number of grains per panicle thereby increase in grain yield.