Variation in chlorophyll content per unit leaf area in spring wheat and implications for selection in segregating material

Reduced levels of leaf chlorophyll content per unit leaf area in crops may be of advantage in the search for higher yields. Possible reasons include better light distribution in the crop canopy and less photochemical damage to leaves absorbing more light energy than required for maximum photosynthesis. Reduced chlorophyll may also reduce the heat load at the top of canopy, reducing water requirements to cool leaves. Chloroplasts are nutrient rich and reducing their number may increase available nutrients for growth and development. To determine whether this hypothesis has any validity in spring wheat requires an understanding of genotypic differences in leaf chlorophyll content per unit area in diverse germplasm. This was measured with a SPAD 502 as SPAD units. The study was conducted in series of environments involving up to 28 genotypes, mainly spring wheat. In general, substantial and repeatable genotypic variation was observed. Consistent SPAD readings were recorded for different sampling positions on leaves, between different leaves on single plant, between different plants of the same genotype, and between different genotypes grown in the same or different environments. Plant nutrition affected SPAD units in nutrient poor environments. Wheat genotypes DBW 10 and Transfer were identified as having consistent and contrasting high and low average SPAD readings of 52 and 32 units, respectively, and a methodology to allow selection in segregating populations has been developed. © 2014 Hamblin et al

Dynamics of nitrate and nitrite in saturated sand filters with enhanced substrate conditions for denitrifying bacteria

Substrate conditions for denitrifying bacteria were enhanced by adding carbon sources to a laboratory-scale sand filter system. Temperature, oxidation–reduction potential, and hydrogen ion concentration were measured through the recirculation of nitrogen-dosed wastewater and carbon sources that were mixed to encourage microbial growth, with denitrifying bacteria identified by standard plate counts. Two different external carbon sources (sucrose and ethanol) were added, with and without activated sludge amendments. Nitrate, nitrite, and chemical oxygen demand (COD) concentrations were monitored relative to an untreated control and a treatment with activated sludge under an initial hydraulic loading rate of 0.508 m3 /m2 d and a hydraulic retention time of 2.5 h. Nitrate decay rates were only significantly enhanced for the ethanol treatment without addition of activated sludge. Nitrite initially accumulated when carbon sources were added, but no accumulation was evident by the end of the experiment after 150 min. COD declined when carbon sources were added, but activated sludge had no effect on the rate at which the COD declined. The increased rate of nitrate removal with the addition of ethanol is of technical interest, as the volume of wastewater treated in a unit volume of filter medium for denitrification doubled with ethanol compared with sucrose at the same concentration

Phenotypic Evaluation and Genetic Analysis of Seedling Emergence in a Global Collection of Wheat Genotypes (Triticum aestivum L.) Under Limited Water Availability

The challenge in establishing an early-sown wheat crop in southern Australia is the need for consistently high seedling emergence when sowing deep in subsoil moisture (>10 cm) or into dry top-soil (4 cm). However, the latter is strongly reliant on a minimum soil water availability to ensure successful seedling emergence. This study aimed to: (1) evaluate 233 Australian and selected international wheat genotypes for consistently high seedling emergence under limited soil water availability when sown in 4 cm of top-soil in field and glasshouse (GH) studies; (2) ascertain genetic loci associated with phenotypic variation using a genome-wide association study (GWAS); and (3) compare across loci for traits controlling coleoptile characteristics, germination, dormancy, and pre-harvest sprouting. Despite significant (P 85%) across nine environments. Moreover, 21 environment-specific quantitative trait loci (QTL) were detected in GWAS analysis on chromosomes 1B, 1D, 2B, 3A, 3B, 4A, 4B, 5B, 5D, and 7D, indicating complex genetic inheritance controlling seedling emergence. We aligned QTL for known traits and individual genes onto the reference genome of wheat and identified 16 QTL for seedling emergence in linkage disequilibrium with coleoptile length, width, and cross-sectional area, pre-harvest sprouting and dormancy, germination, seed longevity, and anthocyanin development. Therefore, it appears that seedling emergence is controlled by multifaceted networks of interrelated genes and traits regulated by different environmental cues

Reducing insecticide use in broad-acre grains production: An Australian study

Prophylactic use of broad-spectrum insecticides is a common feature of broad-acre grains production systems around the world. Efforts to reduce pesticide use in these systems have the potential to deliver environmental benefits to large areas of agricultural land. However, research and extension initiatives aimed at decoupling pest management decisions from the simple act of applying a cheap insecticide have languished. This places farmers in a vulnerable position of high reliance on a few products that may lose their efficacy due to pests developing resistance, or be lost from use due to regulatory changes. The first step towards developing Integrated Pest Management (IPM) strategies involves an increased efficiency of pesticide inputs. Especially challenging is an understanding of when and where an insecticide application can be withheld without risking yield loss. Here, we quantify the effect of different pest management strategies on the abundance of pest and beneficial arthropods, crop damage and yield, across five sites that span the diversity of contexts in which grains crops are grown in southern Australia. Our results show that while greater insecticide use did reduce the abundance of many pests, this was not coupled with higher yields. Feeding damage by arthropod pests was seen in plots with lower insecticide use but this did not translate into yield losses. For canola, we found that plots that used insecticide seed treatments were most likely to deliver a yield benefit; however other insecticides appear to be unnecessary and economically costly. When considering wheat, none of the insecticide inputs provided an economically justifiable yield gain. These results indicate that there are opportunities for Australian grain growers to reduce insecticide inputs without risking yield loss in some seasons. We see this as the critical first step towards developing IPM practices that will be widely adopted across intensive production systems. © 2014 Macfadyen et al

Response of chickpea (Cicer arietinum L.) to terminal drought: Leaf stomatal conductance, pod abscisic acid concentration, and seed set

© 2016 The Author. Flower and pod production and seed set of chickpea (Cicer arietinum L.) are sensitive to drought stress. A 2-fold range in seed yield was found among a large number of chickpea genotypes grown at three dryland feld sites in south-Western Australia. Leaf water potential, photosynthetic characteristics, and reproductive development of two chickpea genotypes with contrasting yields in the feld were compared when subjected to terminal drought in 106kg containers of soil in a glasshouse. The terminal drought imposed from early podding reduced biomass, reproductive growth, harvest index, and seed yield of both genotypes. Terminal drought at least doubled the percentage of flower abortion, pod abscission, and number of empty pods. Pollen viability and germination decreased when the fraction of transpirable soil water (FTSW) decreased below 0.18 (82% of the plant-available soil water had been transpired); however, at least one pollen tube in each flower reached the ovary. The young pods which developed from flowers produced when the FTSW was 0.50 had viable embryos, but contained higher abscisic acid (ABA) concentrations than those of the well-watered plants; all pods ultimately aborted in the drough t treatment. Cessation of seed set at the same soil water content at which stomata began to close and ABA increased strongly suggested a role for ABA signalling in the failure to set seed either directly through abscission of developing pods or seeds or indirectly through the reduction of photosynthesis and assimilate supply to the seeds

Incorporating organic matter alters soil greenhouse gas emissions and increases grain yield in a semi-arid climate

© 2016 The Authors Increasing soil organic matter (OM) is promoted as a strategy for improving the resilience of coarse-textured cropping soils in semi-arid climates. While increasing soil OM can benefit crop productivity, it can also enhance nitrous oxide (N2O) emissions in temperate climates. Our objective was to investigate if increasing soil OM affected soil greenhouse gas (GHG) fluxes and grain production in a semi-arid region in south-western Australia. We firstly measured N2O and methane (CH4) fluxes from a free-draining sandy soil with contrasting soil OM content for 2.5 years using automated soil chambers. The randomized block design included two OM additions (no OM, plus OM) by two nitrogen (N) fertilizer rates (0, 0N; 100 kg N ha-1 yr-1, +N) by three replicate plots. Organic matter (chaff) had been applied to the plus OM treatments every three years since 2003, with 80 t OM ha-1applied in total. Secondly, we investigated the interaction between soil OM content and N fertilizer addition on grain yield for two growing seasons. The randomized split-plot design included two OM treatments by five N fertilizer rates (0, 25, 50, 75 and 100 kg N ha-1), by three replicates. Increasing soil OM increased grain yields and soil mineral N, but also enhanced soil N2O emissions. Nitrous oxide emissions were low by international standards (<0.12% of the N fertilizer applied), with total N2O emissions after two years ranked: plus OM (+N; 427 g N2O-N ha-1) > plus OM (0N; 194 g N2O-N ha-1) > no OM (+N; 41 g N2O-N ha-1) = no OM (0N; 14 g N2O-N ha-1). Increasing soil OM also decreased CH4uptake by 30%. Management practices that increase soil OM in sandy-textured rainfed, cropping soils in semi-arid regions should be encouraged as they can improve grain yield without substantial increases in soil N2O or CH4emissions

Crop Updates - 2003 Lupins

This session covers twenty one papers from different authors LUPIN ISSUES AND R & D DIRECTIONS Mark Sweetingham, Department of Agriculture ACKNOWLEDGEMENTS VARIETIES AND BREEDING New lupin line for release – WALAN2141, Bevan J, Buirchell, Mark Sweetingham, Geoff Thomas, Amelia McLarty, Harmohinder Dhammu and CVT and Lupin Breeding teams, Department of Agriculture Lupin variety trial, Martin Harries and Wayne Parker, Department of Agriculture Herbicide tolerance of new lupins, Harmohinder S. Dhammu, Terry Piper and David Nicholson, Department of Agriculture YELLOW AND ALBUS LUPINS Selection for high lupin yield under terminal drought, Jairo A. Palta1&2, Neil C. Turner1&2 Bob French2&3 and Bevan Buirchell2&3 , 1CSIRO Plant Industry, Floreat, WA, 2CLIMA, University of Western Australia, Crawley, WA, 3Department of Agriculture Outcrossing and isolation distance in yellow lupins, Kedar Adhikari, Bevan Buirchell and Katia Stefanova, Department of Agriculture Development of aphid tolerant yellow lupins in Western Australia, Kedar Adhikari, Bevan Buirchell, Mark Sweetingham and Françoise Berlandier, Department of Agriculture ESTABLISHMENT Development of anthracnose resistant albus lupins for Western Australia, Kedar Adhikari, Bevan Buirchell, Mark Sweetingham and Geoff Thomas, Department of Agriculture Lupin sowing methods for improved yields, Glen Riethmuller, Department of Agriculture Moisture delving = more reliable lupin establishment, Paul Blackwell and Wayne Parker, Department of Agriculture Effect of time of sewing, plant density and row orientation on lupins at various row spacings, Geoff Fosbery, Farm Focus Consultants, Bill Crabtree, Crabtree Consulting and Tracy Gilham, WANTFA Influence of row spacing on water stress and water use of lupins, Bob French and Laurie Wahlsten, Department of Agriculture AGRONOMY Effect on lupin protein and yield from variety, planting time and seed rate, Pierre Fievez, Pierre Fievez and Associates Lupin row cropping: herbicides to band, shield design and economics, Mike Collins, WANTFA and John Holmes, 4 Farmers Harvest options for narrow leaf lupins, Martin Harries and Dirranie Kirby, Department of Agriculture NUTRITION Additional nutrients on lupin yield and protein, Pierre Fievez, Pierre Fievez and Associates Demonstrating the effect of phosphorous placement on yields of narrow leaf lupin and yellow lupin on high phosphorus retention soils, Martin Harries and Wayne Parker, Department of Agriculture PESTS AND DISEASES How far are anthracnose spores spread by rain splash? Geoff Thomas, Mark Sweetingham and Ken Adcock, Department of Agriculture Height of cereal stubble affects spread of lupin anthracnose, Geoff Thomas, Bill MacLeod and Ken Adcock, Department of Agriculture Controlling non-necrotic strains of bean yellow mosaic virus in lupins by cultural methods, Roger Jones and Rohan Prince, Department of Agriculture, and Centre for Legumes in Mediterranean Agriculture MARKET DEVELOPMENT Australian sweet lupin – is it the next human health food? Stuart Johnson, Deakin University; Ramon Hall, ARC SPIRT PhD Scholar; Madeleine Ball, University of Tasmania; Sofia Sipsas and David Petterson; Department of Agriculture CONTACT DETAILS FOR PRINCIPAL AUTHOR

Approaches to scheduling water allocations to kikuyugrass grown on a water repellent soil in a drying-climate

Water allocation is a principal planning method for managing water supplies to agricultural and horticultural land in drying climates. Regulatory bodies often establish the water allocation amount, but its distribution during the irrigation season is left to the land manager’s discretion. We evaluated approaches to best manage water allocations to a warm-season turfgrass [Pennisetum clandestinum (Holst. Ex Chiov)] grown on a free-draining sand prone to surface (0–25 mm) soil water repellence in a Mediterranean climate in south-western Australia under ‘deficit irrigation’, in a two-year field study. The three factorial experiment consisted of three levels for each treatment applied to plots (10 m2) of kikuyugrass: water allocation (5000, 6250 or 7500 kL ha−1 yr−1), irrigation schedule, and soil wetting agent rate (nil, recommended ‘label’ rate, double recommended ‘label’ rate), and was replicated three times. The irrigation schedules were based on historical net evaporation at the site, and then refined monthly using in-season net evaporation data or measurements of soil water content. Kikuyugrass growth and color was adequate when irrigated using the current regional water allocation (7500 kL ha−1 yr−1) under a low wear situation and to a lesser extent when the water allocation was lowered to 6250 kL ha−1 yr−1. Application of a soil wetting agent diminished water repellence and improved kikuyugrass color for 7500 or 6250 kL ha−1 yr−1 water allocations. Distributing a water allocation based on historical monthly net evaporation rates was a simple and effective scheduling approach to maintaining a warm-season turfgrass