Chromosome-specific potential intron polymorphism markers for large-scale genotyping applications in pomegranate

Despite the availability of whole genome assemblies, the identification and utilization of gene-based marker systems has been limited in pomegranate. In the present study, we performed a genome-wide survey of intron length (IL) markers in the 36,524 annotated genes of the Tunisia genome. We identified and designed a total of 8,812 potential intron polymorphism (PIP) markers specific to 3,445 (13.40%) gene models that span 8 Tunisia chromosomes. The ePCR validation of all these PIP markers on the Tunisia genome revealed single-locus amplification for 1,233 (14%) markers corresponding to 958 (27.80%) genes. The markers yielding single amplicons were then mapped onto Tunisia chromosomes to develop a saturated linkage map. The functional categorization of 958 genes revealed them to be a part of the nucleus and the cytoplasm having protein binding and catalytic activity, and these genes are mainly involved in the metabolic process, including photosynthesis. Further, through ePCR, 1,233 PIP markers were assayed on multiple genomes, which resulted in the identification of 886 polymorphic markers with an average PIC value of 0.62. In silico comparative mapping based on physically mapped PIP markers indicates a higher synteny of Tunisia with the Dabenzi and Taishanhong genomes (>98%) in comparison with the AG2017 genome (95%). We then performed experimental validation of a subset of 100 PIP primers on eight pomegranate genotypes and identified 76 polymorphic markers, with 15 having PIC values ≥0.50. We demonstrated the potential utility of the developed markers by analyzing the genetic diversity of 31 pomegranate genotypes using 24 PIP markers. This study reports for the first time large-scale development of gene-based and chromosome-specific PIP markers, which would serve as a rich marker resource for genetic variation studies, functional gene discovery, and genomics-assisted breeding of pomegranate

Size-dependent structural transition from multiple-twinned particles to epitaxial fcc nanocrystals and nanocrystal decay

The size dependence of structural transition from multiple-twinned particles (MTP) to epitaxial face centered cubic nanocrystals was investigated for Ag nanoparticles formed on Si(001) surfaces by in situ reflection high-energy electron diffraction and ex situ transmission electron microscopy. The transition from MTP to nanocrystals was promoted by postdeposition annealing. Clear particle size dependence is found in the epitaxial formation temperatures (TE), which is about 2/3 of the calculated, size-dependent, melting temperature (TM) using the value of surface energy γS =1.2 J m² for larger particles (>2 nm). Once nanocrystals are formed, they decay and disappear in a narrow temperature range between 795 and 850 K. No evidence of nanocrystal melting was detected from the reflection high-energy electron diffraction observations. © 2007 The American Physical Society.K. Sato, W. J. Huang, F. Bohra, S. Sivaramakrishnan, A. P. Tedjasaputra, and J. M. Zuo, Phys. Rev. B 76, 144113, 2007

Genomic interventions for sustainable agriculture

Agricultural production faces a Herculean challenge to feed the increasing global population. Food production systems need to deliver more with finite land and water resources while exerting the least negative influence on the ecosystem. The unpredictability of climate change and consequent changes in pests/pathogens dynamics aggravate the enormity of the challenge. Crop improvement has made significant contributions towards food security, and breeding climate-smart cultivars are considered the most sustainable way to accelerate food production. However, a fundamental change is needed in the conventional breeding framework in order to respond adequately to the growing food demands. Progress in genomics has provided new concepts and tools that hold promise to make plant breeding procedures more precise and efficient. For instance, reference genome assemblies in combination with germplasm sequencing delineate breeding targets that could contribute to securing future food supply. In this review, we highlight key breakthroughs in plant genome sequencing and explain how the presence of these genome resources in combination with gene editing techniques has revolutionized the procedures of trait discovery and manipulation. Adoption of new approaches such as speed breeding, genomic selection and haplotype-based breeding could overcome several limitations of conventional breeding. We advocate that strengthening varietal release and seed distribution systems will play a more determining role in delivering genetic gains at farmer’s field. A holistic approach outlined here would be crucial to deliver steady stream of climate-smart crop cultivars for sustainable agriculture

Genomics and breeding innovations for enhancing genetic gain for climate resilience and nutrition traits

Key message Integrating genomics technologies and breeding methods to tweak core parameters of the breeder’s equation could accelerate delivery of climate-resilient and nutrient rich crops for future food security. Abstract Accelerating genetic gain in crop improvement programs with respect to climate resilience and nutrition traits, and the realization of the improved gain in farmers’ fields require integration of several approaches. This article focuses on innovative approaches to address core components of the breeder’s equation. A prerequisite to enhancing genetic variance (σ2g) is the identification or creation of favorable alleles/haplotypes and their deployment for improving key traits. Novel alleles for new and existing target traits need to be accessed and added to the breeding population while maintaining genetic diversity. Selection intensity (i) in the breeding program can be improved by testing a larger population size, enabled by the statistical designs with minimal replications and high-throughput phenotyping. Selection priorities and criteria to select appropriate portion of the population too assume an important role. The most important component of breeder′s equation is heritability (h2). Heritability estimates depend on several factors including the size and the type of population and the statistical methods. The present article starts with a brief discussion on the potential ways to enhance σ2g in the population. We highlight statistical methods and experimental designs that could improve trait heritability estimation. We also offer a perspective on reducing the breeding cycle time (t), which could be achieved through the selection of appropriate parents, optimizing the breeding scheme, rapid fixation of target alleles, and combining speed breeding with breeding programs to optimize trials for release. Finally, we summarize knowledge from multiple disciplines for enhancing genetic gains for climate resilience and nutritional traits

Strategies for breeding, production and promotion of pigeonpea hybrids in India

With the release of GTH-1 the world’s first CMS hybrid in pigeonpea [Cajanus cajan (L.) Millsp.], the breeding of hybrids in this important pulse crop has become a reality. At present three early duration pigeonpea hybrids with yield advantage of >30% have been identified/released in India.This has been possible due to breeders’ success in developing stable cytoplsmic nuclear male sterility (CMS) system and selection of stable restorers. The large-scale hybrid seed production is facilitated by insect-aided natural out-crossing and hybrid yields of 1000-1500 kg /ha have been harvested by the growers. To sustain this breakthrough in pigeonpea it is necessary to identify, evaluate and maintain the perfect CMS line (A and B lines) along with good restorers on a regular basis. In this paper, an attempt has been made to consolidate strategies related to the development of new hybrids, their seed production technology and promotion in the country

Interior Weyl-type Solutions of the Einstein-Maxwell Field Equations

Static solutions of the electro-gravitational field equations exhibiting a functional relationship between the electric and gravitational potentials are studied. General results for these metrics are presented which extend previous work of Majumdar. In particular, it is shown that for any solution of the field equations exhibiting such a Weyl-type relationship, there exists a relationship between the matter density, the electric field density and the charge density. It is also found that the Majumdar condition can hold for a bounded perfect fluid only if the matter pressure vanishes (that is, charged dust). By restricting to spherically symmetric distributions of charged matter, a number of exact solutions are presented in closed form which generalise the Schwarzschild interior solution. Some of these solutions exhibit functional relations between the electric and gravitational potentials different to the quadratic one of Weyl. All the non-dust solutions are well-behaved and, by matching them to the Reissner-Nordstr\"{o}m solution, all of the constants of integration are identified in terms of the total mass, total charge and radius of the source. This is done in detail for a number of specific examples. These are also shown to satisfy the weak and strong energy conditions and many other regularity and energy conditions that may be required of any physically reasonable matter distribution.Comment: 21 pages, RevTex, to appear in General Relativity and Gravitatio

Advances in Pigeonpea Genomics

Pigeonpea, a member of family Fabaceae, is one of the important food legumes cultivated in tropical and subtropical regions. Due to its inherent properties to withstand harsh environments, it plays a critical role in ensuring sustainability in the subsistence agriculture. Furthermore, plasticity in the maturity duration imparts it a greater adaptability in a variety of cropping systems. In the post genomics era, the importance of pigeonpea is further evident from the fact that pigeonpea has emerged as first non-industrial legume crop for which the whole genome sequence has been completed. It revealed 605.78 Mb of assembled and anchored sequence as against the predicted 833 Mb genome consequently representing 72.8 % of the whole genome. In order to perform genetic and genomic analysis various molecular markers like random amplified polymorphic DNA (RAPD), restriction fragment length polymorphism (RFLP), amplified fragment length polymorphism (AFLP), simple sequence repeat (SSR), diversity array technology (DArT), single feature polymorphism (SFP), and single nucleotide polymorphism (SNP) were employed. So far four transcriptome assemblies have been constructed and different sets of EST-SSRs were developed and validated in a panel of diverse pigeonpea genotypes. Extensive survey of BAC-end sequences (BESs) provided 3,072 BES-SSRs and all these BES-SSRs were further used for linkage analysis and trait mapping. To make the available linkage information more useful, six intra-specific genetic maps were joined together into a single consensus genetic map providing map positions to a total of 339 SSR markers at map coverage of 1,059 cM. However, earlier very few linkage maps were available in the crop because of non-availability of genomic resources. Several quantitative trait loci (QTLs) associated with traits of agronomic interest including QTLs for sterility mosaic disease, fertility restoration, plant type and earliness have been identified and validated. To strengthen the traditional breeding, plenty of genomics tools and technologies are now available for integration in regular pigeonpea breeding schemes. This article presents the progress made in the area of pigeonpea genomics and outlines its applications in crop breeding for pigeonpea improvement

Toward the sequence-based breeding in legumes in the post-genome sequencing era

Efficiency of breeding programs of legume crops such as chickpea, pigeonpea and groundnut has been considerably improved over the past decade through deployment of modern genomic tools and technologies. For instance, next-generation sequencing technologies have facilitated availability of genome sequence assemblies, re-sequencing of several hundred lines, development of HapMaps, high-density genetic maps, a range of marker genotyping platforms and identification of markers associated with a number of agronomic traits in these legume crops. Although marker-assisted backcrossing and marker-assisted selection approaches have been used to develop superior lines in several cases, it is the need of the hour for continuous population improvement after every breeding cycle to accelerate genetic gain in the breeding programs. In this context, we propose a sequence-based breeding approach which includes use of independent or combination of parental selection, enhancing genetic diversity of breeding programs, forward breeding for early generation selection, and genomic selection using sequencing/genotyping technologies. Also, adoption of speed breeding technology by generating 4–6 generations per year will be contributing to accelerate genetic gain. While we see a huge potential of the sequence-based breeding to revolutionize crop improvement programs in these legumes, we anticipate several challenges especially associated with high-quality and precise phenotyping at affordable costs, data analysis and management related to improving breeding operation efficiency. Finally, integration of improved seed systems and better agronomic packages with the development of improved varieties by using sequence-based breeding will ensure higher genetic gains in farmers’ fields