Characterization of heterosis and genomic prediction‐based establishment of heterotic patterns for developing better hybrids in pigeonpea

Whole-genome resequencing (WGRS) of 396 lines, consisting of 104 hybrid parental lines and 292 germplasm lines, were used to study the molecular basis of mid-parent heterosis (MPH) and to identify complementary heterotic patterns in pigeonpea [Cajanus cajan (L.) Millsp.] hybrids. The lines and hybrids were assessed for yield and yield-related traits in multiple environments. Our analysis showed positive MPH values in 78.6% of hybrids, confirming the potential of hybrid breeding in pigeonpea. By using genome-wide prediction and association mapping approaches, we identified 129 single nucleotide polymorphisms and 52 copy number variations with significant heterotic effects and also established a high-yielding heterotic pattern in pigeonpea. In summary, our study highlights the role of WGRS data in the study and use of heterosis in crops where hybrid breeding is expected to boost selection gain in order to ensure global food security

Enhanced modelling of doubly fed induction generator in load flow analysis of distribution systems

This paper presents an accurate framework for incorporating the doubly fed induction generator based wind farms in load flow analysis of distribution systems. The proposed model for doubly fed induction generator is based on an accurate equivalent circuit and also takes into consideration the voltage dependent reactive power limits associated with the doubly fed induction generator. In addition, the developed approach is capable of handling a doubly fed induction generator operating in either maximum power point tracking or non-maximum power point tracking modes. The proposed PQ model of doubly fed induction generator easily fits into the forward–backward technique that is typically employed for obtaining the load flow solution of distribution networks. Test results on 19-bus and 133-bus systems are reported to indicate the effectiveness of the proposed approach

Characterization and mapping of Dt1 locus which co-segregates with CcTFL1 for growth habit in pigeonpea

Pigeonpea (Cajanus cajan) is one of the most important legume crops grown in arid and semi-arid regions of the world. It is characterized with few unique features compared with other legume species, such as Lotus, Medicago, and Glycine. One of them is growth habit, an important agronomic trait. In the present study, identification of mutations affecting growth habit accompanied by a precise analysis of phenotype has been done which will shed more light upon developmental regulation in pigeonpea. A genetic study was conducted to examine the inheritance of growth habit and a genotyping by sequencing (GBS)-based genetic map constructed using F2 mapping population derived from crossing parents ICP 5529 and ICP 11605. Inheritance studies clearly demonstrated the dominance of indeterminate (IDT) growth habit over determinate (DT) growth habit in F2 and F2:3 progenies. A total of 787 SNP markers were mapped in the genetic map of 1454 cM map length. Growth habit locus (Dt1) was mapped on the CcLG03 contributing more than 61% of total phenotypic variations. Subsequently, QTL analysis highlighted one gene, CcTFL1, as a candidate for determinacy in pigeonpea, since an Indel marker derived from this gene co-segregated with the Dt1 locus. Ability of this Indel-derived marker to differentiate DT/IDT lines was also validated on 262 pigeonpea lines. This study clearly demonstrated that CcTFL1 is a candidate gene for growth habit in pigeonpea and a user-friendly marker was developed in the present study which will allow low-cost genotyping without need of automation

Analysis of Filter Design Approaches for Extraction of Instantaneous Symmetrical Components

Extraction of instantaneous symmetrical components plays a vital role in the operation of grid-connected converters. Conventionally, extraction of instantaneous symmetrical components is achieved by transforming the signal into a rotating reference frame and passing it through a digital filter. This work focuses on the design and performance of various digital filters adopted for the extraction of instantaneous symmetrical components. The design considerations and associated trade-offs involved in the design of digital filters are first outlined. Subsequently, the design procedure involved in commonly adopted filtering strategies is reviewed and their performance under various operating conditions is studied. In addition, this work also analyzes the impact of filter design on closed-loop applications such as phase locked loops. © 2022 IEEE

Identification of a virus naturally infecting sorghum in India as Sugarcane streak mosaic virus

The virus associated with mosaic disease of sorghum growing around the sugarcane fields in Andhra Pradesh state, India was found to be serologically related to the Sugarcane streak mosaic virus (SStMV) and Sorghum mosaic Parbhani virus (SMPV). The reverse transcription-polymerase chain reaction (RT-PCR) of the total RNA from the enzyme-linked immunosorbent assay positive sorghum samples with the potyvirus specific degenerate primers yielded an amplicon of ∼500 bp. This amplicon sequence had a 95% identity to the SStMV-Andhra Pradesh (SStMV-AP) and SStMV-Coimbatore isolates reported to naturally infect sugarcane in India. Further confirmation was made by RT-PCR of these samples with the SStMV-AP sequence specific primers that yielded ∼1,000 bp amplicon comprising the entire coat protein and 3′ UTR of the viral genome. This amplicon sequence also had a identity of 95% at nucleotide level with the SStMV-AP sugarcane isolate, but at the CP amino acid level it had 97.8% identity. This partial sequence data confirmed the association of SStMV with the mosaic disease of sorghum in Andhra Pradesh state, India. To our knowledge, this is the first report on association of SStMV with mosaic disease of sorghum and designated as SStMV-sorghum isolate

Genetic variability and correlation in pigeonpea genotypes

Forty nine pigeon pea genotypes were evaluated at Agricultural Research Station Tandur during kharif 2015-16. Genotypes were grouped into six clusters based on Mahalonobis D2 statistics. Days to maturity contributed to maximum genetic divergence followed by days to 50% flowering. Maximum inter cluster distance was observed between clusters II and VI and intra cluster distance in cluster I and II. Genotypes in cluster V recorded highest mean values for number of secondary branches/plant and number of pods/plant and seed yield. Broad sense heritability estimates were highest for days to maturity and days to 50% flowering. Significant and positive genotypic and phenotypic correlation was observed between seed yield and number of pods/plant and number of secondary branches/plant. The range of GCV observed was 4.55 to 22.07% for the traits under study indicating the extent of variability present among the pigeon pea genotypes. Path coefficient analysis revealed that days to maturity exhibited maximum direct effect followed by number of pods/plant

Translational Pigeonpea genomics consortium for accelerating genetic gains in Pigeonpea (Cajanus cajan L.)

Pigeonpea is one of the important pulse crops grown in many states of India and plays a major role in sustainable food and nutritional security for the smallholder farmers. In order to overcome the productivity barrier the Translational Pigeonpea Genomics Consortium (TPGC) was established, representing research institutes from six different states (Andhra Pradesh, Karnataka, Madhya Pradesh, Maharashtra, Telangana, and Uttar Pradesh) of India. To enhance pigeonpea productivity and production the team has been engaged in deploying modern genomics approaches in breeding and popularizing modern varieties in farmers’ fields. For instance, new genetic stock has been developed for trait mapping and molecular breeding initiated for enhancing resistance to fusarium wilt and sterility mosaic disease in 11 mega varieties of pigeonpea. In parallel, genomic segments associated with cleistogamous flower, shriveled seed, pods per plant, seeds per pod, 100 seed weight, and seed protein content have been identified. Furthermore, 100 improved lines were evaluated for yield and desirable traits in multi-location trials in different states. Furthermore, a total of 303 farmers’ participatory varietal selection (FPVS) trials have been conducted in 129 villages from 15 districts of six states with 16 released varieties/hybrids. Additionally, one line (GRG 152 or Bheema) from multi-location trials has been identified by the All India Coordinated Research Project on Pigeonpea (AICRP-Pigeonpea) and released for cultivation by the Central Variety Release Committee (CVRC). In summary, the collaborative efforts of several research groups through TPGC is accelerating genetics gains in breeding plots and is expected to deliver them to pigeonpea farmers to enhance their income and improve livelihood

Multiomics approach unravels fertility transition in a pigeonpea line for a two‐line hybrid system

Pigeonpea [Cajanus cajan (L.) Millsp.] is a pulse crop cultivated in the semi‐arid regions of Asia and Africa. It is a rich source of protein and capable of alleviating malnutrition, improving soil health and the livelihoods of small‐holder farmers. Hybrid breeding has provided remarkable improvements for pigeonpea productivity, but owing to a tedious and costly seed production system, an alternative two‐line hybrid technology is being explored. In this regard, an environment‐sensitive male sterile line has been characterized as a thermosensitive male sterile line in pigeonpea precisely responding to day temperature. The male sterile and fertile anthers from five developmental stages were studied by integrating transcriptomics, proteomics and metabolomics supported by precise phenotyping and scanning electron microscopic study. Spatio‐temporal analysis of anther transcriptome and proteome revealed 17 repressed DEGs/DEPs in sterile anthers that play a critical role in normal cell wall morphogenesis and tapetal cell development. The male fertility to sterility transition was mainly due to a perturbation in auxin homeostasis, leading to impaired cell wall modification and sugar transport. Limited nutrient utilization thus leads to microspore starvation in response to moderately elevated day temperature which could be restored with auxin‐treatment in the male sterile line. Our findings outline a molecular mechanism that underpins fertility transition responses thereby providing a process‐oriented two‐line hybrid breeding framework for pigeonpea

Construction of genotyping-by-sequencing based high-density genetic maps and QTL mapping for fusarium wilt resistance in pigeonpea

Fusarium wilt (FW) is one of the most important biotic stresses causing yield losses in pigeonpea. Genetic improvement of pigeonpea through genomics-assisted breeding (GAB) is an economically feasible option for the development of high yielding FW resistant genotypes. In this context, two recombinant inbred lines (RILs) (ICPB 2049 × ICPL 99050 designated as PRIL_A and ICPL 20096 × ICPL 332 designated as PRIL_B) and one F2 (ICPL 85063 × ICPL 87119) populations were used for the development of high density genetic maps. Genotyping-by-sequencing (GBS) approach was used to identify and genotype SNPs in three mapping populations. As a result, three high density genetic maps with 964, 1101 and 557 SNPs with an average marker distance of 1.16, 0.84 and 2.60 cM were developed in PRIL_A, PRIL_B and F2, respectively. Based on the multi-location and multi-year phenotypic data of FW resistance a total of 14 quantitative trait loci (QTLs) including six major QTLs explaining >10% phenotypic variance explained (PVE) were identified. Comparative analysis across the populations has revealed three important QTLs (qFW11.1, qFW11.2 and qFW11.3) with upto 56.45% PVE for FW resistance. This is the first report of QTL mapping for FW resistance in pigeonpea and identified genomic region could be utilized in GAB

Development of sequence-based markers for seed protein content in pigeonpea

Pigeonpea is an important source of dietary protein to over a billion people globally, but genetic enhancement of seed protein content (SPC) in the crop has received limited attention for a long time. Use of genomics-assisted breeding would facilitate accelerating genetic gain for SPC. However, neither genetic markers nor genes associated with this important trait have been identified in this crop. Therefore, the present study exploited whole genome re-sequencing (WGRS) data of four pigeonpea genotypes (~ 12X coverage) to identify sequence-based markers and associated candidate genes for SPC. By combining a common variant filtering strategy on available WGRS data with knowledge of gene functions in relation to SPC, 108 sequence variants from 57 genes were identified. These genes were assigned to 19 GO molecular function categories with 56% belonging to only two categories. Furthermore, Sanger sequencing confirmed presence of 75.4% of the variants in 37 genes. Out of 30 sequence variants converted into CAPS/dCAPS markers, 17 showed high level of polymorphism between low and high SPC genotypes. Assay of 16 of the polymorphic CAPS/dCAPS markers on an F2 population of the cross ICP 5529 (high SPC) × ICP 11605 (low SPC), resulted in four of the CAPS/dCAPS markers significantly (P < 0.05) co-segregated with SPC. In summary, four markers derived from mutations in four genes will be useful for enhancing/regulating SPC in pigeonpea crop improvement programs