Construction of a high-density genetic map and QTL analysis for yield, yield components and agronomic traits in chickpea (Cicer arietinum L.).

Unravelling the genetic architecture underlying yield components and agronomic traits is important for enhancing crop productivity. Here, a recombinant inbred line (RIL) population, developed from ICC 4958 and DCP 92-3 cross, was used for constructing linkage map and QTL mapping analysis. The RIL population was genotyped using a high-throughput Axiom®CicerSNP array, which enabled the development of a high-density genetic map consisting of 3,818 SNP markers and spanning a distance of 1064.14 cM. Analysis of phenotyping data for yield, yield components and agronomic traits measured across three years together with genetic mapping data led to the identification of 10 major-effect QTLs and six minor-effect QTLs explaining up to 59.70% phenotypic variance. The major-effect QTLs identified for 100-seed weight, and plant height possessed key genes, such as C3HC4 RING finger protein, pentatricopeptide repeat (PPR) protein, sugar transporter, leucine zipper protein and NADH dehydrogenase, amongst others. The gene ontology studies highlighted the role of these genes in regulating seed weight and plant height in crop plants. The identified genomic regions for yield, yield components, and agronomic traits, and the closely linked markers will help advance genetics research and breeding programs in chickpea.

Discovery of Putative Herbicide Resistance Genes and Its Regulatory Network in Chickpea Using Transcriptome Sequencing.

Background: Chickpea (Cicer arietinum L.) contributes 75% of total pulse production. Being cheaper than animal protein, makes it important in dietary requirement of developing countries. Weed not only competes with chickpea resulting into drastic yield reduction but also creates problem of harboring fungi, bacterial diseases and insect pests. Chemical approach having new herbicide discovery has constraint of limited lead molecule options, statutory regulations and environmental clearance. Through genetic approach, transgenic herbicide tolerant crop has given successful result but led to serious concern over ecological safety thus non-transgenic approach like marker assisted selection is desirable. Since large variability in tolerance limit of herbicide already exists in chickpea varieties, thus the genes offering herbicide tolerance can be introgressed in variety improvement programme. Transcriptome studies can discover such associated key genes with herbicide tolerance in chickpea. Results: This is first transcriptomic studies of chickpea or even any legume crop using two herbicide susceptible and tolerant genotypes exposed to imidazoline (Imazethapyr). Approximately 90 million paired-end reads generated from four samples were processed and assembled into 30,803 contigs using reference based assembly. We report 6,310 differentially expressed genes (DEGs), of which 3,037 were regulated by 980 miRNAs, 1,528 transcription factors associated with 897 DEGs, 47 Hub proteins, 3,540 putative Simple Sequence Repeat-Functional Domain Marker (SSR-FDM), 13,778 genic Single Nucleotide Polymorphism (SNP) putative markers and 1,174 Indels. Randomly selected 20 DEGs were validated using qPCR. Pathway analysis suggested that xenobiotic degradation related gene, glutathione S-transferase (GST) were only up-regulated in presence of herbicide. Down-regulation of DNA replication genes and up-regulation of abscisic acid pathway genes were observed. Study further reveals the role of cytochrome P450, xyloglucan endotransglucosylase/hydrolase, glutamate dehydrogenase, methyl crotonoyl carboxylase and of thaumatin-like genes in herbicide resistance. Conclusion: Reported DEGs can be used as genomic resource for future discovery of candidate genes associated with herbicide tolerance. Reported markers can be used for future association studies in order to develop marker assisted selection (MAS) for refinement. In endeavor of chickpea variety development programme, these findings can be of immense use in improving productivity of chickpea germplasm.

Genetic diversity assessment of Fusarium oxysporum f. sp ciceris isolates of Indian chickpea fields as revealed by the SRAP marker system.

An experiment was conducted to study the precise geographical distribution and racial complexity of Fusarium oxysporum f.sp ciceris (Foc) isolates representing 12 states of 4 agro-climatic zones of India at morphological, pathogenic and molecular level. The DNA based sequence related amplified polymorphism (SRAP) markers was employed to differentiate Foc isolates at genome level. The genotypic data output of the isolates was examined for diversity parameter as marker's Polymorphic percentage (PM %), Polymorphic Information Content (PIC), Marker Index (MI) and Gene Diversity Index (DI). As a result, 15 primers used in this study could generated total of 154 reproducible alleles ranging from 100-2100 bp (average allele per marker 10.26) in size, of that 149 (97%) were found to be polymorphic. The neighbor-joining analysis effectively classified the isolates of North East Plain Zone (NEPZ), Central Zone (CZ), North West Plain Zone (NWPZ) and South Zone (SZ) into four clusters. In summary, DNA based marker analysis could differentiate as per isolates geographical location, however pathogenic interaction of isolates from same geographical location could not match the genetic differentiation. Accordingly, considering the present complexity in racial profile, precise classification based on homologs virulence genes specific to races would give a more meaningful in correlating isolates with their native geographical distribution and helps in future resistance breeding programs for sustainable management of vascular wilt disease.

Population distribution and genetic relatedness in Indian Fusarium udum isolates based on ribosomal internal transcribe spacer and elongation factor.

With the objective to study the geographical distribution pattern and pathotype classification, isolates from 12 major pigeonpea growing states of India were examined at morphological and molecular levels. Two DNA based internal transcribe spacer (ITS) region derived primers FDP 3 (ITS1/ITS2), FDP 25 (mRNA, LOC100383610) and two elongation factors FDP 4 (F98-BKR5) and FDP 29 (M9968PY) were employed to genetically differentiate the isolates. As a result, each marker system gave an average of 3 alleles/marker. The higher efficiency of ITS over EF-1α marker was revealed using detailed comparative analysis that included various parameters like gene diversity index, effective marker ratio, and marker index. Neighbour Joining tree analysis grouped the isolates into three major clusters and showed narrow existence of genetic divergence. Combination of genotyping data with pathological measurements indicates dominance of variant 1 in the Central zone, South zone and North East Plain Zone, while North East Plain Zone and North West Plain Zone were largely dominated by variants 2 and 1, with strong possibility of evolving other variants. The present study would help in identifying specific isolate and patterns of its distribution in various pigeonpea growing regions thereby enhancing the scope for precise resistance breeding for crop improvement.