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Towards utilization of genome sequence information for pigeonpea improvement By ICAR institutes, SAUs and ICRISAT
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A major source of protein to about 20% of the world population (Thu et al., 2003) An abundant source of minerals and vitamins (Saxena et al., 2002) Most versatile food legume with diversified uses such as food, feed, fodder and fuel It is hardy, widely adaptable crop with better tolerance to drought and high temperature Belongs to family Leguminosae with chromosome no. 2n=22 and genome size of ~833 Mbp Pigeonpea (Cajanus cajan L. Millsp)
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Climate change!
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Pigeonpea – production trends (last five decades) Unfortunately, no increase has been witnessed in its productivity (yield kg ha-1), which in the past five decades has remained stagnant at around 700 kg ha-1
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Some constraints in pigeonpea production Sterility mosaic disease (SMD) Fusarium wilt (FW)
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A route developed and taken by breeders: From germplasm to variety/hybrid Germplasm Superior variety
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Genomics-assisted breeding: Predicting the phenotype Genotype Gene(s) Trait/QTL Phenotype Transcriptomics Proteomics Metabolomics TILLING EcoTILLING EST Sequencing Genome Sequencing Map-based Cloning Genetic Mapping Physical Mapping Genetic Mapping Association Mapping QTL Mapping Trait Correlations Genetic Resources Improved germplasm Trends Pl Science 2005; Trends Biotech 2006
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A variety of approaches (cars) MAS: MARKER-ASSISTED SELECTION - Plants are selected for one or more (up to 8-10) alleles MABC: MARKER-ASSISTED BACKCROSSING –One or more (up to 6-8) donor alleles are transferred to an elite line MARS: MARKER-ASSISTED RECURRENT SELECTION –Selection for several (up to 20-30) mapped QTLs relies on index (genetic) values computed for each individual based on its haplotype at target QTLs GWS: GENOME-WIDE SELECTION –Selection of genome-wide several loci that confer tolerance/resistance/ superiority to traits of interest using GEBVs based on genome-wide marker profiling
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Example of development of a submergence tolerant version of Swarna, a widely grown variety, in 2½ years Marker-assisted backcrossing IR49830-7: tolerant Swarna-Sub1 Swarna: Non-tolerant Sub1 Target gene selection Recombinant selection Recombinant selection Background selection Background selection BC2 or BC3 X Courtesy of David Mackill, IRRI
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New Sub1 lines (in yellow) and recurrent parents (in white) after 17 days submergence in field at IRRI, 2007DS Samba Samba-Sub1 IR64-Sub1 IR49830 (Sub1) IR64 IR42 IR64 IR64-Sub1 Samba-Sub1 IR49830 (Sub1) Samba IR64 IR64-Sub1 IR49830 (Sub1) IR42 IR64-Sub1 IR64 IR49830 (Sub1) IR42 Samba IR42 Samba Courtesy of David Mackill, IRRI
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Swarna-Sub1 in U.P. (Faizabad area) Courtesy of David Mackill, IRRI, The Philippines
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Challenges in genomics- assisted crop improvement Narrow genetic base in the primary gene pool Very few molecular (SSR) markers Non-availability of appropriate germplasm such as mapping populations Intraspecific genetic map with low marker density Non-availability of trait-associated markers in breeding Issues of costs and expertise in molecular breeding
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Germplasm Superior variety
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Developing infrastructures and sign posts for providing directions (Indo-US AKI, CGIAR-GCP, US-NSF)
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ResourcePigeonpea SSRs29,000 SNPs35,000 GoldenGate768 SNPs KASPar assays1,616 SNPs DArT arrays15,360 Sanger ESTs~20,000 454 /FLX reads496,705 TUSs21,432 Illumina reads (million reads) >160 (14 parents) Gene/transcriptomic/ SNP resources
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CMS and mt genome sequencing of pigeonpea Production of A- line seeds Production of hybrid seeds for commercial crop Commercial pigeonpea hybrids production ICPA 2039, ICPB 2039, ICPH 2433 & ICPW 29 sequenced using 454 technology
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From Orphan crop- genomic resources rich crop
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Phylogenetic analysis of Cajanus spp. using KASPar assays Cluster-I Cluster-II Cluster-III
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How to use this genome information…
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Objectives Molecular mapping of resistance to biotic and abiotic stresses - Mapping populations available - Genotyping and phenotyping - Marker trait association for resistance to FW, SMD and Rf Enhancing the genetic base of pigeonpea genepool by developing multi-parents populations - MAGIC population (2000 lines) developed using 8 parents - NAM population (50 crosses-1000 lines) with 50 parents - High density genotyping or genotyping by sequencing of 3000 lines - Phenotyping of MAGIC and NAM populations (each population at least in 3 environments) - Marker trait association analysis for traits of interest
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Genome wide association studies based on re- sequencing and phenotyping of germplasm set - Germplasm set of 300-500 lines assembled - Genotyping-by-sequencing of the germplasm set - Precise phenotyping of the germplasm set by different partners - Fine mapping of traits of interest for breeders Bioinformatics analysis to improve the quality of draft genome - Two genome assemblies need to be merged - Defining a consensus genes set - Breeders-friendly genome databases
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Validation and characterization of 1213 disease resistance genes - Genetic mapping of disease resistance genes - Association of genes with disease resistance traits - Functional validation of selected set of candidate genes - Mining of superior allleles/haplotypes for disease resistance Validation and characterization of ca. 200 abiotic stress tolerance genes - Genetic mapping of abiotic stress tolerance genes - Association of genes with abiotic stress tolerance traits - Functional validation of selected set of candidate genes - Mining of superior allleles/haplotypes for abiotic stress tolerance genes
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Possible outcomes Superior breeding lines for traits of interest with enhanced genetic diversity Molecular markers associated with resistance to biotic stresses and tolerance to abiotic stresses Alleles and haplotype information available on germplasm set so that breeders can use informative lines Set of well characterized disease resistance and abiotic stress tolerance genes Breeder-friendly genome database of pigeonpea
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Possible partners NRCPB, New Delhi NBPGR, New Delhi IIPR, Kanpur IARI, New Delhi Uni Agril Sciences- Bangalore Banaras Hindu University ANGRAU- Hyderabad
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