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Nitrogen transport is one of the most important processes in plants mediated by specialized transmembrane proteins. Plants have two main systems for nitrogen uptake from soil and its transport within the system—a low-affinity transport system and a high-affinity transport system. Nitrate transporters are of special interest in cereal crops because large amount of money is spent on N fertilizers every year to enhance the crop productivity. Till date four gene families of nitrate transporter proteins; NPF (nitrate transporter 1/peptide transporter family), NRT2 (nitrate transporter 2 family), the CLC (chloride channel family), and the SLAC/SLAH (slow anion channel-associated homologues) have been reported in plants. In our study, in silico mining of nitrate transporter genes along with their detailed structure, phylogenetic and expression analysis was carried out. A total of 412 nitrate transporter genes were identified in hexaploid wheat genome using HMMER based homology searches in IWGSC Refseq v2.0. Out of those twenty genes were root specific, 11 leaf/shoot specific and 17 genes were grain/spike specific. The identification of nitrate transporter genes in the close proximity to the previously identified 67 marker-traits associations associated with the nitrogen use efficiency related traits in nested synthetic hexaploid wheat introgression library indicated the robustness of the reported transporter genes. The detailed crosstalk between the genome and proteome and the validation of identified putative candidate genes through expression and gene editing studies may lay down the foundation to improve nitrogen use efficiency of cereal crops.

GRAS genes belong to the plant-specific transcription factors (TF’s) family that are known to be involved in plant growth and development. In this study, we have identified 37 genes from the bottle gourd genome that encodes for GRAS TF’s. Except for the SCLA, we were able to identify at least one gene from each of the 17 subfamilies. Gene structure and chromosomal analysis showed that maximum seven genes are present on Chr7 followed by six genes on Chr1. The subcellular location analysis revealed that most of the genes were localized in the nucleus, except for a few in chloroplast and mitochondria. Additionally, we have identified one tandem gene duplication event on Chr7 and three major motifs that were present in all the GRAS genes. Furthermore, the protein–protein interaction prediction and gene expression analysis showed five candidate hub-genes interact with various other genes and thus probably control the expression of interacting partners in different plant tissues. Overall, this study provides a comprehensive analysis of GRAS transcription factors in bottle gourd genome which could be further extended to other vegetable crops.

BackgroundThe lack of stable-high yielding and direct-seeded adapted varieties with better germination ability from deeper soil depth and availability of molecular markers are major limitation in achieving the maximum yield potential of rice under water and resource limited conditions. Development of high-throughput and trait-linked markers are of great interest in genomics-assisted breeding. The aim of present study was to develop and validate novel KASP (Kompetitive Allele-Specific PCR) markers associated with traits improving germination and seedling vigor of deep sown direct seeded rice (DSR).ResultsOut of 58 designed KASP assays, four KASP assays did not show any polymorphism in any of the eleven genetic backgrounds considered in the present study. The 54 polymorphic KASP assays were then validated for their robustness and reliability on the F1s plants developed from eight different crosses considered in the present study. The third next validation was carried out on 256 F3:F4 and 713 BC3F2:3 progenies. Finally, the reliability of the KASP assays was accessed on a set of random 50 samples from F3:F4 and 80–100 samples from BC3F2:3 progenies using the 10 random markers. From the 54 polymorphic KASP, based on the false positive rate, false negative rate, KASP utility in different genetic backgrounds and significant differences in the phenotypic values of the positive (desirable) and negative (undesirable) traits, a total of 12 KASP assays have been selected. These 12 KASP include 5 KASP on chromosome 3, 1 on chromosome 4, 3 on chromosome 7 and 3 on chromosome 8. The two SNPs lying in the exon regions of LOC_Os04g34290 and LOC_Os08g32100 led to non-synonymous mutations indicating a possible deleterious effect of the SNP variants on the protein structure.ConclusionThe present research work will provide trait-linked KASP assays, improved breeding material possessing favourable alleles and breeding material in form of expected pre-direct-seeded adapted rice varieties. The marker can be utilized in introgression program during pyramiding of valuable QTLs/genes providing adaptation to rice under DSR. The functional studies of the genes LOC_Os04g34290 and LOC_Os08g32100 possessing two validated SNPs may provide valuable information about these genes.

Background Improving the rate of genetic gain of cereal crop will rely on the accelerated crop breeding pipelines to allow rapid delivery of improved crop varieties. The laborious, time-consuming traditional breeding cycle, and the seasonal variations are the key factor restricting the breeder to develop new varieties. To address these issues, a revolutionized cost-effective speed breeding protocol for large-scale rice germplasm advancement is presented in the present study. The protocol emphasises on optimizing potting material, balancing the double-edged sword of limited nutritional dose, mode and stage of application, plant density, temperature, humidity, light spectrum, intensity, photoperiod, and hormonal regulation to accelerate rice growth and development. Results The plant density of 700 plants/m 2 , cost-effective halogen tubes (B:G:R:FR-7.0:27.6:65.4:89.2) with an intensity of ∼ 750–800 µmol/m 2 /s and photoperiod of 13 h light and 11 h dark during seedling and vegetative stage and 8 h light and 16 h dark during reproductive stage had a significant effect ( P  < 0.05) on reducing the mean plant height, tillering, and inducing early flowering. Our results confirmed that one generation can be achieved within 68–75 days using the cost-effective SpeedyPaddy protocol resulting in 4–5 generations per year across different duration of rice varieties. The other applications include hybridization, trait-based phenotyping, and mapping of QTL/genes. The estimated cost to run one breeding cycle with plant capacity of 15,680 plants in SpeedyPaddy was $2941 including one-time miscellaneous cost which is much lower than the advanced controlled environment speed breeding facilities. Conclusion The protocol offers a promising cost-effective solution with average saving of 2.0 to 2.6 months per breeding cycle with an integration of genomics-assisted selection, trait-based phenotyping, mapping of QTL/genes, marker development may accelerate the varietal development and release. This outstanding cost-effective break-through marks a significant leap in rice breeding addressing climate change and food security.

BackgroundOngoing large-scale shift towards direct seeded rice (DSR) necessitates a convergence of breeding and genetic approaches for its sustenance and harnessing natural resources and environmental benefits. Improving seedling vigour remains key objective for breeders working with DSR. The present study aims to understand the genetic control of seedling vigour in deep sown DSR. Combined genome-wide association mapping, linkage mapping, fine mapping, RNA-sequencing to identify candidate genes and validation of putative candidate genes were performed in the present study.ResultsSignificant phenotypic variations were observed among genotypes in both F3:4:5 and BC2F2:3 populations. The mesocotyl length showed significant positive correlation with %germination, root and shoot length. The 881 kb region on chromosome 7 reported to be associated with mesocotyl elongation. RNA-seq data and RT-PCR results identified and validated seven potential candidate genes. The four promising introgression lines free from linkage drag and with longer mesocotyl length, longer root length, semi-dwarf plant height have been identified.ConclusionThe study will provide rice breeders (1) the pre breeding material in the form of anticipated DSR adapted introgression lines possessing useful traits and alleles improving germination under deep sown DSR field conditions (2) the base for the studies involving functional characterization of candidate genes. The development and utilization of improved introgression lines and molecular markers may play an important role in genomics-assisted breeding (GAB) during the pyramiding of valuable genes providing adaptation to rice under DSR. Our results offer a robust and reliable package that can contribute towards enhancing genetic gains in direct seeded rice breeding programs.

Improving seedling vigour remains key objective for breeders working with direct-seeded rice (DSR). To understand the genetic control of seedling vigour in deep sown DSR, combined genome-wide association mapping, linkage mapping, fine mapping, RNA-sequencing to identify candidate genes and validation of putative candidate genes was performed. Significant phenotypic variations were observed among genotypes in both F3:4:5 and BC2F2:3 populations. The mesocotyl length showed significant positive correlation with %germination, root and shoot length. The 3.79 Mb region on chromosome 7 reported to be associated with mesocotyl elongation. RNA-seq data and RT-PCR results identified and validated seven potential candidate genes. The potential candidate gene, LOC_Os07g25150 codes for Myb-30-related transcription factor. The LOC_Os07g25150 codes for Myb 30-related transcription factor, LOC_Os07g17689 annotated as protein translation factor, LOC_Os07g17770 as tryptophanyl-tRNA synthetase, LOC_Os07g15440 as alanyl-tRNA synthetase family protein, LOC_Os07g24100 as retrotransposon protein and the remaining others as expressed proteins. The antagonistic relationship between Myb-30 and ethylene-mediated signalling (EIN-3) in regulating mesocotyl elongation have been observed. The functional characterization and knocking of LOC_Os07g25150 codes for Myb 30-related transcription factor may provide better understanding of the mechanism behind mesocotyl elongation. The four promising introgression lines with longer mesocotyl length, longer root length and semi-dwarf plant height have been identified.