Publications of NIPGR Scientists
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Item High-Throughput SNP discovery and genotyping for constructing a saturated linkage map of Chickpea (Cicer arietinum L.)(Oxford University Press, 2012) Gaur, Rashmi; Azam, Sarwar; Jeena, Ganga; Khan, Aamir Waseem; Choudhary, Shalu; Jain, Mukesh; Yadav, Gitanjali; Tyagi, Akhilesh K.; Chattopadhyay, Debasis; Bhatia, SabhyataThe present study reports the large-scale discovery of genome-wide single-nucleotide polymorphisms (SNPs) in chickpea, identified mainly through the next generation sequencing of two genotypes, i.e. Cicer arietinum ICC4958 and its wild progenitor C. reticulatum PI489777, parents of an inter-specific reference mapping population of chickpea. Development and validation of a high-throughput SNP geno- typing assay based on Illumina’s GoldenGate Genotyping Technology and its application in building a high-resolution genetic linkage map of chickpea is described for the first time. In this study, 1022 SNPs were identified, of which 768 high-confidence SNPs were selected for designing the custom Oligo Pool All (CpOPA-I) for genotyping. Of these, 697 SNPs could be successfully used for genotyping, demonstrating a high success rate of 90.75%. Genotyping data of the 697 SNPs were compiled along with those of 368 co-dominant markers mapped in an earlier study, and a saturated genetic linkage map of chickpea was constructed. One thousand and sixty-three markers were mapped onto eight linkage groups spanning 1808.7 cM (centiMorgans) with an average inter-marker distance of 1.70 cM, thereby representing one of the most advanced maps of chickpea. The map was used for the synteny analysis of chickpea, which revealed a higher degree of synteny with the phylogenetically close Medicago than with soybean. The first set of validated SNPs and map resources developed in this study will not only facilitate QTL mapping, genome-wide association analysis and comparative mapping in legumes but also help anchor scaffolds arising out of the whole-genome sequencing of chickpea.Item EST-derived genic molecular markers: development and utilization for generating an advanced transcript map of chickpea(Springer Science, 2012) Choudhary, Shalu; Gaur, Rashmi; Gupta, Shefali; Bhatia, SabhyataWell-saturated linkage maps especially those based on expressed sequence tag (EST)-derived genic molecular markers (GMMs) are a pre-requisite for molecular breeding. This is especially true in important legumes such as chickpea where few simple sequence repeats (SSR) and even fewer GMM-based maps have been developed. Therefore, in this study, 2,496 ESTs were generated from chickpea seeds and utilized for the development of 487 novel EST-derived functional markers which included 125 EST-SSRs, 151 intron targeted primers (ITPs), 109 expressed sequence tag polymorphisms (ESTPs), and 102 single nucleotide polymorphisms (SNPs). Whereas ESTSSRs, ITPs, and ESTPs were developed by in silico analysis of the developed EST sequences, SNPs were identified by allele resequencing and their genotyping was performedusing the Illumina GoldenGate Assay. Parental polymorphism was analyzed between C. arietinum ICC4958 and C. reticulatum PI489777, parents of the reference chickpea mapping population, using a total of 872 markers: 487 new gene-based markers developed in this study along with 385 previously published markers, of which 318 (36.5%) were found to be polymorphic and were used for genotyping. The genotypic data were integrated with the previously published data of 108 markers and an advanced linkage map was generated that contained 406 loci distributed on eight linkage groups that spanned 1,497.7 cM. The average marker density was 3.68 cM and the average number of markers per LG was 50.8. Among the mapped markers, 303 new genomic locations were defined that included 177 gene-based and 126 gSSRs (genomic SSRs) thereby producing the most advanced gene-rich map of chickpea solely based on co-dominant markers.Item Development of SSR and gene-targeted markers for construction of a framework linkage map of Catharanthus roseus(Oxford University Press, 2011) Shokeen, Bhumika; Choudhary, Shalu; Sethy, Niroj Kumar; Bhatia, SabhyataBACKGROUND AND AIMS: Catharanthus roseus is a plant of great medicinal importance, yet inadequate knowledge of its genome structure and the unavailability of genomic resources have been major impediments in the development of improved varieties. The aims of this study were to develop co-dominant sequence-tagged microsatellite sites (STMS) and gene-targeted markers (GTMs) and utilize them for the construction of a framework intraspecific linkage map of C. roseus.Item Advancing the STMS genomic resources for defining new locations on the intraspecific genetic linkage map of chickpea (Cicer arietinum L.)(BioMed Central, 2011) Gaur, Rashmi; Sethy, Niroj K; Choudhary, Shalu; Shokeen, Bhumika; Gupta, Varsha; Bhatia, SabhyataChickpea (Cicer arietinum L.) is an economically important cool season grain legume crop that is valued for its nutritive seeds having high protein content. However, several biotic and abiotic stresses and the low genetic variability in the chickpea genome have continuously hindered the chickpea molecular breeding programs. STMS (Sequence Tagged Microsatellite Sites) markers which are preferred for the construction of saturated linkage maps in several crop species, have also emerged as the most efficient and reliable source for detecting allelic diversity in chickpea. However, the number of STMS markers reported in chickpea is still limited and moreover exhibit low rates of both inter and intraspecific polymorphism, thereby limiting the positions of the SSR markers especially on the intraspecific linkage maps of chickpea. Hence, this study was undertaken with the aim of developing additional STMS markers and utilizing them for advancing the genetic linkage map of chickpea which would have applications in QTL identification, MAS and for de novo assembly of high throughput whole genome sequence data.Item Development of chickpea EST-SSR markers and analysis of allelic variation across related species(Springer, 2009) Choudhary, Shalu; Sethy, Niroj Kumar; Shokeen, Bhumika; Bhatia, SabhyataDespite chickpea being the third important grain legume, there is a limited availability of genomic resources, especially of the expressed sequence tag (EST)-based markers. In this study, we generated 822 chickpea ESTs from immature seeds as well as exploited 1,309 ESTs from the chickpea database, thus utilizing a total of 2,131 EST sequences for development of functional EST-SSR markers. Two hundred and forty-six simple sequence repeat (SSR) motifs were identified from which 183 primer pairs were designed and 60 validated as functional markers. Genetic diversity analysis across 30 chickpea accessions revealed ten markers to be polymorphic producing a total of 29 alleles and an observed heterozygosity average of 0.16 thereby exhibiting low levels of intra-specific polymorphism. However, the markers exhibited high cross-species transferability ranging from 68.3 to 96.6% across the six annual Cicer species and from 29.4 to 61.7% across the seven legume genera. Sequence analysis of size variant amplicons from various species revealed that size polymorphism was due to multiple events such as copy number variation, point mutations and insertions/deletions in the microsatellite repeat as well as in the flanking regions. Interestingly, a wide prevalence of crossability-group-specific sequence variations were observed among Cicer species that were phylogenetically informative. The neighbor joining dendrogram clearly separated the chickpea cultivars from the wild Cicer and validated the proximity of C. judaicum with C. pinnatifidum. Hence, this study for the first time provides an insight into the distribution of SSRs in the chickpea transcribed regions and also demonstrates the development and utilization of genic-SSRs. In addition to proving their suitability for genetic diversity analysis, their high rates of transferability also proved their potential for comparative genomic studies and for following gene introgressions and evolution in wild species, which constitute the valuable secondary genepool in chickpea.Item Identification of microsatellite markers from Cicer reticulatum: molecular variation and phylogenetic analysis(Springer, 2006) Sethy, Niroj Kumar; Choudhary, Shalu; Shokeen, Bhumika; Bhatia, SabhyataMicrosatellite sequences were cloned and sequenced from Cicer reticulatum, the wild annual progenitor of chickpea (C. arietinum L.). Based on the flanking sequences of the microsatellite motifs, 11 sequence-tagged microsatellite site (STMS) markers were developed. These markers were used for phylogenetic analysis of 29 accessions representing all the nine annual Cicer species. The 11 primer pairs amplified distinct fragments in all the annual species demonstrating high levels of sequence conservation at these loci. Efficient marker transferability (97%) of the C. reticulatum STMS markers across other species of the genus was observed as compared to microsatellite markers from the cultivated species. Variability in the size and number of alleles was obtained with an average of 5.8 alleles per locus. Sequence analysis at three homologous microsatellite loci revealed that the microsatellite allele variation was mainly due to differences in the copy number of the tandem repeats. However, other factors such as (1) point mutations, (2) insertion/deletion events in the flanking region, (3) expansion of closely spaced microsatellites and (4) repeat conversion in the amplified microsatellite loci were also responsible for allelic variation. An unweighted pairgroup method with arithmetic averages (UPGMA)- based dendrogram was obtained, which clearly distinguished all the accessions (except two C. judaicum accessions) from one another and revealed intra- as well as inter-species variability in the genus. An annual Cicer phylogeny was depicted which established the higher similarity between C. arietinum and C. reticulatum. The placement of C. pinnatifidum in the second crossability group and its closeness to C. bijugum was supported. Two species, C. yamashitae and C. chorassanicum, were grouped distinctly and seemed to be genetically diverse from members of the first crossability group. Our data support the distinct placement of C. cuneatum as well as a revised classification regarding its placement.Item Development of sequence-tagged microsatellite site markers for chickpea (Cicer arietinum L.)(Wiley-Blackwell, 2006) Choudhary, Shalu; Sethy, Niroj K.; Shokeen, Bhumika; Bhatia, SabhyataMicrosatellite loci were identified from chickpea (Cicer arietinum L.), the third most important grain legume crop in the world. A total of 13 sequence-tagged microsatellite markers were developed using two different approaches: (i) amplification using degenerate primers and (ii) cloning of intersimple sequence repeat (ISSR)-amplified fragments. Thirty-five chickpea accessions were analysed, which resulted in a total of 30 alleles at the 13 loci. The observed heterozygosity ranged from 0.1143 to 0.4571 with an average of 0.2284. The cross-species transferability of the sequence-tagged microsatellite site (STMS) markers was checked in Cicer reticulatum, the wild annual progenitor of chickpea. These microsatellite markers will be useful for assessing the genetic diversity patterns within chickpea as well as aid in construction of intra- and interspecific genetic linkage maps.Item Development of STMS markers from the medicinal plant Madagascar periwinkle (Catharanthus roseus L.) G. Don(Wiley-Blackwell, 2005) Shokeen, Bhumika; Sethy, Niroj K.; Choudhary, Shalu; Bhatia, SabhyataWe report the isolation and characterization of the first set of sequence-tagged microsatellites sites (STMS) markers in Catharanthus roseus, a plant with a vast range of medicinal uses. The microsatellite loci were cloned from an enriched library constructed using degenerate primers. Based on the microsatellite motifs, seven STMS primer pairs were designed. They were used to amplify 32 accessions of C. roseus and one accession of Catharanthus trichophyllus. The primers amplified an average of 3.86 alleles per locus. The observed heterozygosity ranged from 0.2903 to 0.9688 with an average of 0.7511. The STMS markers of C. roseus also amplified corresponding loci in a related species (C. trichophyllus) suggesting conservation of the loci across the genus. These markers will prove useful for genetic diversity analysis and linkage map construction in C. roseus.