Genetic Architecture of Spotted Stem Borer Resistance in Sorghum As Inferred From Qtl Mapping and Synteny with the Maize Genome

The present investigation was carried out to characterize the genetic architecture of spotted stem borer resistance and related agronomic and morphological traits in sorghum. The experimental material for this study consisted of 266 RILs derived from a cross between susceptible parent ICSV 745 and resistant parent PB 15520. These RILs were evaluated for phenotypic traits during the 2007 and 2008 rainy seasons under artificial infestation of stem borer, and were genotyped with 90 polymorphic SSR markers for linkage map construction and QTL analysis. The RILs exhibited wide variation for the observed traits across both of the screening environments. The mean performance of RILs for most of the spotted stem borer resistance except stem tunneling, neared the mid-parental value. Among the observed agronomic and morphological traits, except for testa (presence vs absence) and agronomic performance score, the means of RIL population were skewed towards that of one of the parents. High G×E interaction effects was observed in the RIL population progenies for all the resistance component, agronomic and morphological traits except plant color score and seedling basal pigmentation score, which are largely controlled by single major genes. Across-environment, heritability estimates for the resistance component traits were low to moderate, while for most of the agronomic and morphological traits they were high. From the frequency distributions polygenic inheritance was inferred for most of the observed spotted stem borer resistance and agronomic traits. Presence of transgressive segregation for all the observed resistance component traits except recovery resistance score and all observed agronomic traits — seedling vigor, plant height, time to 50% flowering and number of nodes suggesting that favorable and unfavorable alleles for these traits are dispersed between the two RIL parental lines. A significant and positive association was observed among all the observed resistance component traits, except stem tunneling. Significant association was also observed between various agronomic and morphological traits with resistance component traits such as plant height with stem tunneling, deadheart incidence with time to 50% flowering, plant color with leaf damage score and overall resistance score and recovery resistance score with both plant height and number of nodes

Construction of genetic linkage map and QTL analysis of sinksize traits in pearl millet (Pennisetum glaucum)

A linkage map, primarily based on SSCP-SNP markers, was constructed using 188 F2:3 (F2-derived F3) mapping population progenies derived from a cross between two pearl millet inbred lines having diverse pedigrees. The parents had large differences for two sink size traits (grain size and panicle diameter), and also differed for panicle length. The skeleton linkage map covered 1019 cM and it comprised of 44 loci (detected with 24 SSCP-SNP, 10 genomic SSR, 6 EST-SSR and 4 STS primer pairs) distributed across the seven linkage groups. Average adjacent-marker intervals ranged from 14 cM on LG1 to 38 cM on LG6, with an overall mean of 23 cM. Using the F2 linkage map and phenotypic data collected from the F2 and F2:3 generations of the mapping population, a total of 18 putative QTLs were detected for the three sink-size components. Eight QTLs explained 42.7% of observed phenotypic variation for panicle length, with individual QTLs explaining 6.1 to 18.2% using the F2:3 data set. For panicle diameter, 5 QTLs explained 45.8% of observed phenotypic variation with individual QTLs accounting for 6.3 to 30.2%. Similarly for grain size, 5 QTLs explained 29.6% of phenotypic variation with individual QTLs accounting for 6.1 to 8.9%. Genomic regions associated with panicle length, panicle diameter and grain size co-mapped on LG6 between Xpsms88 and Xpsms2270, indicating the existence of a gene or gene cluster with major effects involved in the control of significant proportions of the phenotypic variation for all three sink-size traits. The QTLs for panicle length on LG2 and LG6 (LOD>3 in both F2 and F2:3 data sets), for panicle diameter on LG2 and LG3 (LOD>14 in the F2:3 data set) and for grain size on LG3 and LG6 (LOD>3 in both F2 and F2:3 data sets) were identified as promising candidates for validation prior to possible application in marker-assisted breeding

Rechargeable Calcium–Sulfur Batteries Enabled by an Efficient Borate-Based Electrolyte

Rechargeable metal–sulfur batteries show great promise for energy storage applications because of their potentially high energy and low cost. The multivalent‐metal based electrochemical system exhibits the particular advantage of the feasibility of dendrite‐free metal anode. Calcium (Ca) represents a promising anode material owing to the low reductive potential, high capacity, and abundant natural resources. However, calcium–sulfur (Ca–S) battery technology is in an early R&D stage, facing the fundamental challenge to develop a suitable electrolyte enabling reversible electrochemical Ca deposition, and at the same time, sulfur redox reactions in the system. Herein, a study of a room‐temperature Ca–S battery by employing a stable and efficient calcium tetrakis(hexafluoroisopropyloxy) borate Ca[B(hfip)$_{4}$]$_{2}$ electrolyte is presented. The Ca–S batteries exhibit a cell voltage of ≈2.1 V (close to its thermodynamic value) and good reversibility. The mechanistic studies hint at a redox chemistry of sulfur with polysulfide/sulfide species involved in the Ca‐based system

Performance study of magnesium-sulfur battery using a graphene based sulfur composite cathode electrode and a non-nucleophilic Mg electrolyte

Here we report for the first time the development of a Mg rechargeable battery using a graphene–sulfur nanocomposite as the cathode, a Mg–carbon composite as the anode and a non-nucleophilic Mg based complex in tetraglyme solvent as the electrolyte. The graphene–sulfur nanocomposites are prepared through a new pathway by the combination of thermal and chemical precipitation methods. The Mg/S cell delivers a higher reversible capacity (448 mA h g−1), a longer cyclability (236 mA h g−1 at the end of the 50th cycle) and a better rate capability than previously described cells. The dissolution of Mg polysulfides to the anode side was studied by X-ray photoelectron spectroscopy. The use of a graphene–sulfur composite cathode electrode, with the properties of a high surface area, a porous morphology, a very good electronic conductivity and the presence of oxygen functional groups, along with a non-nucleophilic Mg electrolyte gives an improved battery performance

Construction of Genetic Linkage Map and QTL Analysis of Sink-Size Traits in Pearl Millet (Pennisetum glaucum)

A linkage map, primarily based on SSCP-SNP markers, was constructed using 188 F2:3 mapping population progenies produced from a cross between two pearl millet inbred lines having diverse parentage. The skeleton linkage map covered 1019 cM and it comprised of 44 markers distributed across the seven linkage groups. Average adjacent-marker intervals ranged from 14 cM on LG1 to 38 cM on LG6, with an overall mean of 23 cM. Using the F2 linkage map and phenotypic data from the F2 and F2:3 generations of the mapping population, a total of 18 putative QTLs were detected for the three sink-size components. Eight QTLs explained 42.7% of observed phenotypic variation for panicle length using the F2:3 data set. For panicle diameter, 5 QTLs explained 45.8% of observed phenotypic variation. Similarly for grain size, 5 QTLs explained 29.6% of phenotypic variation. Genomic regions associated with panicle length, panicle diameter, and grain size were comapped on LG6 between Xpsms88 and Xpsms2270, indicating the existence of a gene or gene cluster. The QTLs for panicle length on LG2 and LG6 ( in both F2 and F2:3 data sets), for panicle diameter on LG2 and LG3 ( in the F2:3 data set), and for grain size on LG3 and LG6 ( in both F2 and F2:3 data sets) were identified as promising candidates for validation prior to possible application in marker-assisted breeding

Genomic Regions Associated with Root Traits under Drought Stress in Tropical Maize (Zea mays L.)

An association mapping panel, named as CIMMYT Asia association mapping (CAAM) panel, involving 396 diverse tropical maize lines were phenotyped for various structural and functional traits of roots under drought and well-watered conditions. The experiment was conducted during Kharif (summer-rainy) season of 2012 and 2013 in root phenotyping facility at CIMMYT-Hyderabad, India. The CAAM panel was genotyped to generate 955, 690 SNPs through GBS v2.7 using Illumina Hi-seq 2000/2500 at Institute for Genomic Diversity, Cornell University, Ithaca, NY, USA. GWAS analysis was carried out using 331,390 SNPs filtered from the entire set of SNPs revealed a total of 50 and 67 SNPs significantly associated for root functional (transpiration efficiency, flowering period water use) and structural traits (rooting depth, root dry weight, root length, root volume, root surface area and root length density), respectively. In addition to this, 37 SNPs were identified for grain yield and shoot biomass under well-watered and drought stress. Though many SNPs were found to have significant association with the traits under study, SNPs that were common for more than one trait were discussed in detail. A total 18 SNPs were found to have common association with more than one trait, out of which 12 SNPs were found within or near the various gene functional regions. In this study we attempted to identify the trait specific maize lines based on the presence of favorable alleles for the SNPs associated with multiple traits. Two SNPs S3_128533512 and S7_151238865 were associated with transpiration efficiency, shoot biomass and grain yield under well-watered condition. Based on favorable allele for these SNPs seven inbred lines were identified. Similarly, four lines were identified for transpiration efficiency and shoot biomass under drought stress based on the presence of favorable allele for the common SNPs S1_211520521, S2_20017716, S3_57210184 and S7_130878458 and three lines were identified for flowering period water-use, transpiration efficiency, root dry weight and root volume based on the presence of favorable allele for the common SNPs S3_162065732 and S3_225760139

Genetic analysis of resistance to post flowering stalk rot in tropical germplasm of maize ( Zea mays L.)

Post flowering stalk rot (PFSR) is one of the major biotic constraints to maize production in tropical and sub-tropical environments. It is a complex disease caused by multiple pathogens, among which Fusarium moniliforme and Macrophomina phaseolina are the major ones that cause severe yield losses in the Asian tropics. A set of maize inbred lines was evaluated at two locations for Fusarium stalk rot (FSR) and Macrophomina stalk rot (MSR). Based on line evaluation trials, resistant and susceptible lines were selected and crossed following a Diallel mating design IV to study the gene action for resistance to these stalk rots and the estimating the combining ability of inbred lines. A 9 × 9 diallel (Diallel-A) produced 36 hybrids for studying FSR resistance, and a 12 × 12 diallel (Diallel-B) produced 66 hybrids to analyse the resistance towards both FSR and MSR. These hybrids were evaluated at two locations for MSR and one location for FSR with artificial inoculation. The hybrids differed significantly for FSR (p < 0.05), as was the general combining ability (GCA) effects (p < 0.01), while Specific combining ability (SCA) effects were found to be non-significant. The analysis of the trials under MSR, showed significant difference for GCA, SCA, GCA × environment (p < 0.01), and hybrid × environment (p < 0.05) while SCA × environment was non-significant. The Baker ratio, which shows the relative importance of GCA over SCA, was close to unity for both the stalk rots, and hence a predominant additive gene effect was inferred towards resistance to these diseases. Though the GCA × environment interaction was significant for MSR, this study identified lines and their cross combinations with high resistance and large GCA and SCA effects across environments for FSR and MSR This offers scope for source population improvement for resistance to these stalk rots, as well as developing maize hybrids with stable resistance to Post flowering stalk rot

Stress-resilient maize for climate-vulnerable ecologies in the Asian tropics

Most parts of the Asian tropics are hotspots of climate change effects and associated weather variabilities. One of the major challenges with climate change is the uncertainty and inter-annual variability in weather conditions as crops are frequently exposed to different weather extremes within the same season. Therefore, agricultural research must strive to develop new crop varieties with inbuilt resilience towards variable weather conditions rather than merely tolerance to individual stresses in a specific situation and/or at a specific crop stage. C4 crops are known for their wider adaptation to range of climatic conditions. However, recent climatic trends and associated variabilities seem to be challenging the threshold limit of wider adaptability of even C4 crops like maize. In collaboration with national programs and private sector partners in the region, CIMMYT-Asia maize program initiated research for development (R4D) projects largely focusing on saving achievable yields across range of variable environments by incorporating reasonable levels of tolerance/resistance to major abiotic and biotic stresses without compromising on grain yields under optimal growing conditions. By integrating novel breeding tools like - genomics, double haploid (DH) technology, precision phenotyping and reducing genotype × environment interaction effects, a new generation of maize germplasm with multiple stress tolerance that can grow well across variable weather conditions were developed. The new maize germplasm were targeted for stress-prone environments where maize is invariability exposed to a range of sub-optimal growing conditions, such as drought, heat, waterlogging and various virulent diseases. The overarching goal of the stress-resilient maize program has been to achieve yield potential with a downside risk reduction