Inter- and intra-specific variation in accumulation of cadmium by peanut, soybean, and navybean

Production of summer grain legumes like peanut, soybean, and navybean is expanding into irrigated or high rainfall areas on more acid, lighter textured soils in coastal areas of north-eastern Australia. A history of intensive use of phosphatic fertilisers, combined with soil properties which generally enhance phytoavailability of cadmium (Cd), have produced concerns about the likely quality of grain legumes produced in these areas. This paper reports field and pot experiments which examine the effect of grain legume species and variety on Cd accumulation when grown across a range of soil types. Results clearly show that both peanut and soybean accumulate Cd in seeds at levels greater than the maximum permitted concentration (MPC, 0·05 mg Cd/kg) even on soils with relatively low total or available Cd concentrations ( soybean > navybean, with the differences between peanut and navybean apparently correlated with differences in total plant Cd uptake. Cadmium concentrations in plant tops always exceeded that in seeds or kernel, and the testa in peanut kernel was shown to contain Cd concentrations that were 50 times greater than that in the embryonic axis and cotyledons. Significant (P < 0·05) variation in Cd content (at least 2-fold) was recorded among peanut varieties, with lesser variation evident among a limited sample of commercial navybean varieties. Comparison of results for 11 peanut varieties grown at each of 2 locations suggested strong genotype environment interactions determining kernel Cd concentration. Highly significant (P < 0·01) linear relationships were established between soil Cd in the cultivated layer (0-20 cm; 0·1 M CaCl2 extraction) and seed Cd content in field-grown soybean. However, despite observations of an apparent relationship between soil Cd (CaCl2 extraction) and peanut kernel Cd in pot studies, relationships between soil Cd in the cultivated layer and kernel Cd could not be reproduced in field trials. Kernel Cd concentrations from field-grown peanut plants were generally higher than those from pot trials, despite using soil collected from the cultivated layer (0-20 cm) of the field site for the potting medium. The presence of significant levels of Cd to approximately 60 cm in the soil profile and a general decline in pHw with depth suggest the lack of correlation between soil test Cd in the top 20 cm and kernel Cd in field-grown plants may be at least partly due to Cd uptake from deeper soil layers

Heritability of drought-Resistance traits in peanut

The paper presents results from a case study on genetic enhancement of drought resistance in peanut using combined physiological and breeding methods. Peanut genotypes with high levels of components of a resource capture model, transpiration (T), transpiration efficiency (TE) and harvest index (HI), were used as parents in a hybridisation program. F2-derived families of peanuts from 4 crosses were subjected to trait-based among family index selection in the F3 and F4. In order to calculate the selection index, estimates of harvest index, transpiration efficiency and transpiration were obtained. Heritability estimates for these traits were estimated using 3 different bases i.e. broad-sense heritability on an F3 row basis, broad-sense heritability on an F4 family mean basis using variance components and standard unit heritability estimates using correlation among generations. The heritability estimates varied significantly between crosses and traits depending on levels of genetic variation in parents. In some cases the variation seems to be caused by errors in sampling method. Kernel yield (KY) generally had the best correlations between F3 and F4 (maximum 0.65), HI and TE were intermediate and correlations for T were very poor (one cross in one environment 0.56 the remainder not significant). Consideration of these differences in heritability and the costs of sampling lead to the proposal that a simpler index based on KY and TE may be a useful compromise for selection of superior drought performance in peanut. Use of an index including TE would prevent selection for decreasing TE when selecting for KY, where there are casual negative associations between TE and the other two components. Media summary: It is possible to breed peanut varieties that produce more yield from the same amount of rainfall by selecting for a combination of high transpiration efficiency and kernel yield

A global resource for exploring and exploiting genetic variation in sorghum crop wild relatives

One response to mitigate the impact of climate change on agricultural systems is to develop new varieties that are tolerant to the new range of biotic and abiotic challenges this change causes. This requires access to novel variants of genes for complex adaptive traits. Crop wild relatives are a potentially valuable source of these genes however these materials are often difficult to work with and identifying valuable alleles is difficult without substantial investment in pre-breeding. In this study we describe the development of a nested association mapping population for sorghum using two cultivated grain sorghum reference parents and 9 wild and exotic sorghum accessions as donors. The donor parents come from the verticilliflorum, drummondii and margaritiferum taxa and were sampled from a range of environments across Africa. In total the resource of consists of 13 populations and a total of 1,224 lines. The population has been genotyped with DArT markers which produced 42,372 unique SNP markers covering the genome. We determine the utility of the resource for high resolution mapping of complex traits by demonstrating that the exotics contain unique alleles for some example adaptive trait loci and by using the population for GWAS. The resource should provide useful material for plant breeders attempting to deal with the challenges generated by climate change. This article is protected by copyright. All rights reserve

A structural comparison of salt forms of dopamine with the structures of other phenylethylamines

The structures of four salt forms of dopamine are reported. These are dopamine [2‐(3,4‐dihydroxyphenyl)ethan‐1‐aminium] benzoate, C8H12NO2+·C7H5O2−, I, dopamine 4‐nitrobenzoate, C8H12NO2+·C7H4NO4−, II, dopamine ethanedisulfonate, 2C8H12NO2+·C2H4O6S22−, III, and dopamine 4‐hydroxybenzenesulfonate monohydrate, C8H12NO2+·C6H5O4S−·H2O, IV. In all four structures, the dopamine cation adopts an extended conformation. Intermolecular interaction motifs that are common in the salt forms of tyramine can be found in related dopamine structures, but hydrogen bonding in the dopamine structures appear to be more variable and less predictable than for tyramine. Packing analysis discovered three dopamine‐containing groups of structures that can be described as isostructural with regards to the cation positions. Two of these groups contain both dopamine and tyramine species, and one of these is also highly variable in other ways too, containing anhydrous and hydrated forms, different anion types and ionized and neutral phenylethylamine species. As such, the group illustrates that packing behaviour can be robust and similar even where intermolecular interactions such as hydrogen bonds are very different

Two distinct classes of QTL determine rust resistance in sorghum

Background: Agriculture is facing enormous challenges to feed a growing population in the face of rapidly evolving pests and pathogens. The rusts, in particular, are a major pathogen of cereal crops with the potential to cause large reductions in yield. Improving stable disease resistance is an on-going major and challenging focus for many plant breeding programs, due to the rapidly evolving nature of the pathogen. Sorghum is a major summer cereal crop that is also a host for a rust pathogen which occurs in almost all sorghum growing areas of the world, causing direct and indirect yield losses in sorghum worldwide, however knowledge about its genetic control is still limited. In order to further investigate this issue, QTL and association mapping methods were implemented to study rust resistance in three bi-parental populations and an association mapping set of elite breeding lines in different environments. Results: In total, 64 significant or highly significant QTL and 21 suggestive rust resistance QTL were identified representing 55 unique genomic regions. Comparisons across populations within the current study and with rust QTL identified previously in both sorghum and maize revealed a high degree of correspondence in QTL location. Negative phenotypic correlations were observed between rust, maturity and height, indicating a trend for both early maturing and shorter genotypes to be more susceptible to rust. Conclusions: The significant amount of QTL co-location across traits, in addition to the consistency in the direction of QTL allele effects, has provided evidence to support pleiotropic QTL action across rust, height, maturity and stay-green, supporting the role of carbon stress in susceptibility to rust. Classical rust resistance QTL regions that did not co-locate with height, maturity or stay-green QTL were found to be significantly enriched for the defence-related NBS-encoding gene family, in contrast to the lack of defence-related gene enrichment in multi-trait effect rust resistance QTL. The distinction of disease resistance QTL hot-spots, enriched with defence-related gene families from QTL which impact on development and partitioning, provides plant breeders with knowledge which will allow for fast-tracking varieties with both durable pathogen resistance and appropriate adaptive traits

A physiological framework to explain genetic and environmental regulation of tillering in sorghum

Tillering determines the plant size of sorghum (Sorghum bicolor) and an understanding of its regulation is important to match genotypes to prevalent growing conditions in target production environments. The aim of this study was to determine the physiological and environmental regulation of variability in tillering among sorghum genotypes, and to develop a framework for this regulation. * Diverse sorghum genotypes were grown in three experiments with contrasting temperature, radiation and plant density to create variation in tillering. Data on phenology, tillering, and leaf and plant size were collected. A carbohydrate supply/demand (S/D) index that incorporated environmental and genotypic parameters was developed to represent the effects of assimilate availability on tillering. Genotypic differences in tillering not explained by this index were defined as propensity to tiller (PTT) and probably represented hormonal effects. * Genotypic variation in tillering was associated with differences in leaf width, stem diameter and PTT. The S/D index captured most of the environmental effects on tillering and PTT most of the genotypic effects. * A framework that captures genetic and environmental regulation of tillering through assimilate availability and PTT was developed, and provides a basis for the development of a model that connects genetic control of tillering to its phenotypic consequences

QTL analysis in multiple sorghum populations facilitates the dissection of the genetic and physiological control of tillering

Tillering in sorghum can be associated with either the carbon supply–demand (S/D) balance of the plant or an intrinsic propensity to tiller (PTT). Knowledge of the genetic control of tillering could assist breeders in selecting germplasm with tillering characteristics appropriate for their target environments. The aims of this study were to identify QTL for tillering and component traits associated with the S/D balance or PTT, to develop a framework model for the genetic control of tillering in sorghum. Four mapping populations were grown in a number of experiments in south east Queensland, Australia. The QTL analysis suggested that the contribution of traits associated with either the S/D balance or PTT to the genotypic differences in tillering differed among populations. Thirty-four tillering QTL were identified across the populations, of which 15 were novel to this study. Additionally, half of the tillering QTL co-located with QTL for component traits. A comparison of tillering QTL and candidate gene locations identified numerous coincident QTL and gene locations across populations, including the identification of common non-synonymous SNPs in the parental genotypes of two mapping populations in a sorghum homologue of MAX1, a gene involved in the control of tiller bud outgrowth through the production of strigolactones. Combined with a framework for crop physiological processes that underpin genotypic differences in tillering, the co-location of QTL for tillering and component traits and candidate genes allowed the development of a framework QTL model for the genetic control of tillering in sorghum

Chemical characterization of MEA degradation in PCC pilot plants operating in Australia

An important step towards commercial scale post-combustion CO2 capture from coal-fired power stations is understanding solvent degradation. Laboratory scale trials have identified three main solvent degradation pathways for 30% MEA: oxidative degradation, carbamate polymerization and formation of heat stable salts. This paper probes the semi-volatile organic compounds produced from a single batch of 30% MEA which was used to capture CO2 from a black coal-fired power station (Tarong, Queensland, Australia) for approximately 700 hours, followed by 500 hours at the brown coal-fired power station (Loy Yang, Victoria, Australia). Comparisons are made between the compounds identified in this aged solvent system with MEA degradation reactions described in literature. Most of semi-volatile compounds tentatively identified by GC/MS have previously been reported in laboratory scale degradation trials. Our preliminary results show low levels of degradation products were present in samples after its use in the pilot plant at Tarong (black coal) and consequent 13 months storage, but much higher concentrations were later found in the same solvent during its at use in the pilot plant at Loy Yang Power (brown coal). Further work includes identifying the cause of poor GC/MS repeatability and investigating the relative rates of reactions described in literature. The impact of inorganic anions and dissolved metals on MEA degradation will also be explored

Enhancement of sorghum grain yield and nutrition: A role for arbuscular mycorrhizal fungi regardless of soil phosphorus availability

Societal Impact Statement Sorghum is an important cereal crop that provides calories and nutrients for much of the world's population, and it is often grown with low fertiliser input. Optimising the yield, nutritive content and bioavailability of sorghum grain with minimal input is of importance for human nutrition, and arbuscular mycorrhizal (AM) fungi have previously shown potential to assist in this. Across sorghum genetic diversity, AM fungi improved the yield, nutrition and zinc and iron bioavailability of grain in a low phosphorus soil. Thus, food production systems that effectively manage AM fungi may improve consumer outcomes. Summary Sorghum is a C4 cereal crop that is an important source of calories and nutrition across the world, predominantly cultivated and consumed in low- and middle-income countries. Sorghum can be highly colonised by arbuscular mycorrhizal (AM) fungi, and the plant-fungal association can lead to improvements in biomass and nutrient uptake. High-throughput phenotyping allows us to non-destructively interrogate the ‘hidden’ effects of AM fungi on sorghum growth and phenology. Eight genetically diverse sorghum genotypes were grown in a soil amended with 2 or 20 mg P kg−1 and inoculated with an AM fungal culture of Rhizophagus irregularis. High-throughput phenotyping uncovered the ‘hidden’ effects of AM fungi on growth and phenology, while grain biomass, nutrition, Zn and Fe bioavailability and root AM colonisation was determined after destructive harvest. Sorghum plants colonised by AM fungi generally performed better than non-AM control plants, with greater yield, harvest indices, and grain P, Zn and Fe contents. During the early growth stages, AM colonisation led to temporary growth depressions. There were also AM fungal and P fertilisation effects on sorghum time-of-flowering. The sorghum genotype with the highest AM colonisation could barely produce grain when non-inoculated. The two genotypes that failed to mature had very low AM colonisation. Generally, the genetically diverse sorghum genotypes were highly responsive to AM colonisation and produced more grain of greater nutritive quality when colonised, without adverse consequences for micronutrient bioavailability

Genetic basis of sorghum leaf width and its potential as a surrogate for transpiration efficiency

Leaf width was correlated with plant-level transpiration efficiency and associated with 19 QTL in sorghum, suggesting it could be a surrogate for transpiration efficiency in large breeding program. Enhancing plant transpiration efficiency (TE) by reducing transpiration without compromising photosynthesis and yield is a desirable selection target in crop improvement programs. While narrow individual leaf width has been correlated with greater intrinsic water use efficiency in C4 species, the extent to which this translates to greater plant TE has not been investigated. The aims of this study were to evaluate the correlation of leaf width with TE at the whole-plant scale and investigate the genetic control of leaf width in sorghum. Two lysimetry experiments using 16 genotypes varying for stomatal conductance and three field trials using a large sorghum diversity panel (n = 701 lines) were conducted. Negative associations of leaf width with plant TE were found in the lysimetry experiments, suggesting narrow leaves may result in reduced plant transpiration without trade-offs in biomass accumulation. A wide range in width of the largest leaf was found in the sorghum diversity panel with consistent ranking among sorghum races, suggesting that environmental adaptation may have a role in modifying leaf width. Nineteen QTL were identified by genome-wide association studies on leaf width adjusted for flowering time. The QTL identified showed high levels of correspondence with those in maize and rice, suggesting similarities in the genetic control of leaf width across cereals. Three a priori candidate genes for leaf width, previously found to regulate dorsoventrality, were identified based on a 1-cM threshold. This study provides useful physiological and genetic insights for potential manipulation of leaf width to improve plant adaptation to diverse environments