Cereal cultivars can be ranked consistently for resistance to root-lesion nematodes (Pratylenchus thornei & P. neglectus) using diverse procedures

The root-lesion nematodes (RLN) Pratylenchus thornei and P. neglectus are widely distributed in Australian grain producing regions and can reduce the yield of intolerant wheat cultivars by up to 65 , costing the industry ~123 M AUD/year. Consequently, researchers in the northern, southern and western regions have independently developed procedures to evaluate the resistance of cereal cultivars to RLN. To compare results, each of the three laboratories phenotyped a set of 26 and 36 cereal cultivars for relative resistance/susceptibility to P. thornei and P. neglectus respectively. The northern and southern regions also investigated the effects of planting time and experiment duration on RLN reproduction and cultivar ranking. Results show the genetic correlation between cultivars tested using the northern and southern procedures evaluating P. thornei resistance was 0.93. Genetic correlations between experiments using the same procedure, but with different planting times, were 0.99 for both northern and southern procedures. The genetic correlation between cultivars tested using the northern, southern and western procedures evaluating P. neglectus resistance ranged from 0.71 to 0.95. Genetic correlations between experiments using the same procedure but with different planting times ranged from 0.91 to 0.99. This study established that, even though experiments were conducted in different geographic locations and with different trial management practices, the diverse nematode resistance screening procedures ranked cultivars similarly. Consequently, RLN resistance data can be pooled across regions to provide national consensus ratings of cultivars.

The shifting influence of drought and heat stress for crops in Northeast Australia

Characterization of drought environment types (ETs) has proven useful for breeding crops for drought-prone regions. Here we consider how changes in climate and atmospheric carbon dioxide (CO2) concentrations will affect drought ET frequencies in sorghum and wheat systems of Northeast Australia. We also modify APSIM (the Agricultural Production Systems Simulator) to incorporate extreme heat effects on grain number and weight, and then evaluate changes in the occurrence of heat-induced yield losses of more than 10, as well as the co-occurrence of drought and heat. More than six million simulations spanning representative locations, soil types, management systems, and 33 climate projections led to three key findings. First, the projected frequency of drought decreased slightly for most climate projections for both sorghum and wheat, but for different reasons. In sorghum, warming exacerbated drought stresses by raising the atmospheric vapor pressure deficit and reducing transpiration efficiency (TE), but an increase in TE due to elevated CO2 more than offset these effects. In wheat, warming reduced drought stress during spring by hastening development through winter and reducing exposure to terminal drought. Elevated CO2 increased TE but also raised radiation use efficiency and overall growth rates and water use, thereby offsetting much of the drought reduction from warming. Second, adding explicit effects of heat on grain number and grain size often switched projected yield impacts from positive to negative. Finally, although average yield losses associated with drought will remain generally higher than for heat stress for the next half century, the relative importance of heat is steadily growing. This trend, as well as the likely high degree of genetic variability in heat tolerance, suggests that more emphasis on heat tolerance is warranted in breeding programs. At the same time, work on drought tolerance should continue with an emphasis on drought that co-occurs with extreme heat. This article is protected by copyright. All rights reserved.

Legumes or nitrification inhibitors to reduce N2O emissions from subtropical cereal cropping systems in Oxisols?

The DAYCENT biogeochemical model was used to investigate how the use of fertilizers coated with nitrification inhibitors and the introduction of legumes in the crop rotation can affect subtropical cereal production and N2O emissions. The model was validated using comprehensive multi-seasonal, high-frequency dataset from two field investigations conducted on an Oxisol, which is the most common soil type in subtropical regions. Different N fertilizer rates were tested for each N management strategy and simulated under varying weather conditions. DAYCENT was able to reliably predict soil N dynamics, seasonal N2O emissions and crop production, although some discrepancies were observed in the treatments with low or no added N inputs and in the simulation of daily N2O fluxes. Simulations highlighted that the high clay content and the relatively low C levels of the Oxisol analyzed in this study limit the chances for significant amounts of N to be lost via deep leaching or denitrification. The application of urea coated with a nitrification inhibitor was the most effective strategy to minimize N2O emissions. This strategy however did not increase yields since the nitrification inhibitor did not substantially decrease overall N losses compared to conventional urea. Simulations indicated that replacing part of crop N requirements with N mineralized by legume residues is the most effective strategy to reduce N2O emissions and support cereal productivity. The results of this study show that legumes have significant potential to enhance the sustainable and profitable intensification of subtropical cereal cropping systems in Oxisols.

Ecological Networks in Stored Grain: Key Postharvest Nodes for Emerging Pests, Pathogens, and Mycotoxins

Wheat is at peak quality soon after harvest. Subsequently, diverse biota use wheat as a resource in storage, including insects and mycotoxin-producing fungi. Transportation networks for stored grain are crucial to food security and provide a model system for an analysis of the population structure, evolution, and dispersal of biota in networks. We evaluated the structure of rail networks for grain transport in the United States and Eastern Australia to identify the shortest paths for the anthropogenic dispersal of pests and mycotoxins, as well as the major sources, sinks, and bridges for movement. We found important differences in the risk profile in these two countries and identified priority control points for sampling, detection, and management. An understanding of these key locations and roles within the network is a new type of basic research result in postharvest science and will provide insights for the integrated pest management of high-risk subpopulations, such as pesticide-resistant insect pests.

The shifting influence of drought and heat stress for crops in Northeast Australia

Characterization of drought environment types (ETs) has proven useful for breeding crops for drought-prone regions. Here we consider how changes in climate and atmospheric carbon dioxide (CO2) concentrations will affect drought ET frequencies in sorghum and wheat systems of Northeast Australia. We also modify APSIM (the Agricultural Production Systems Simulator) to incorporate extreme heat effects on grain number and weight, and then evaluate changes in the occurrence of heat-induced yield losses of more than 10%, as well as the co-occurrence of drought and heat. More than six million simulations spanning representative locations, soil types, management systems, and 33 climate projections led to three key findings. First, the projected frequency of drought decreased slightly for most climate projections for both sorghum and wheat, but for different reasons. In sorghum, warming exacerbated drought stresses by raising the atmospheric vapor pressure deficit and reducing transpiration efficiency (TE), but an increase in TE due to elevated CO2 more than offset these effects. In wheat, warming reduced drought stress during spring by hastening development through winter and reducing exposure to terminal drought. Elevated CO2 increased TE but also raised radiation use efficiency and overall growth rates and water use, thereby offsetting much of the drought reduction from warming. Second, adding explicit effects of heat on grain number and grain size often switched projected yield impacts from positive to negative. Finally, although average yield losses associated with drought will remain generally higher than for heat stress for the next half century, the relative importance of heat is steadily growing. This trend, as well as the likely high degree of genetic variability in heat tolerance, suggests that more emphasis on heat tolerance is warranted in breeding programs. At the same time, work on drought tolerance should continue with an emphasis on drought that co-occurs with extreme heat. This article is protected by copyright. All rights reserved.

Managing resistance to chemical treatments in stored products pests

This review focuses on key trends in resistance to chemical treatments in stored product pests, and advances in resistance management, with an emphasis on resistance to the fumigant phosphine. Findings: Phosphine resistance continues to be a major concern. In particular, phosphine resistance in Cryptolestes ferrugineus has emerged as a serious issue, with some populations exhibiting the strongest level detected so far for this fumigant. In response, a 'quick knock down test' has been established to deliver industry and scientists 'same day' advice on the resistance status of field samples; sulfuryl fluoride is being developed as a 'resistance breaker' and phosphine dosages are being revised to manage this problem. There has been major progress in identifying the genes responsible for phosphine resistance and the development of molecular resistance diagnostics for key pests. Several studies on Rhyzopertha dominica have demonstrated that molecular screening can be used to determine the frequency of resistance alleles in samples collected from farm storages. Despite on-going research in several pests, there is no definitive answer to the question of whether there is a fitness cost associated phosphine resistance, with some studies showing a clear cost and others none. Evidence continues to emerge of resistance to grain protectants, including the juvenile hormone analogue methoprene. The development and adoption of spinosad, as a next generation 'green' treatment, and the use of protectant combinations provides opportunities to counter the problem of protectant resistance.Directions for future research: A uniform set of protocols should be developed for phosphine resistance detection for all major species. It should combine 'quick tests' and molecular diagnostics to be adopted internationally. Research is required on the establishment of a decision making system that integrates newly developed grain protectants and fumigants, other alternative control methods, as well as an accurate and rapid resistance detection system for early warning of the emergence of new resistances.

The effects of lupin (Lupinus angustifolius) addition to wheat bread on its nutritional, phytochemical and bioactive composition and protein quality

The grain legume Australian sweet lupin (Lupinus angustifolius; ASL) is gaining international interest as a functional food ingredient; however its addition to refined wheat bread has been shown to decrease bread volume and textural quality, the extent of which is influenced by ASL variety. The present study evaluated the effects of ASL incorporation (20% of total flour) of the six commercial varieties; Belara, Coromup, Gungurru, Jenabillup, Mandelup and Tanjil, on the level of nutritional, phytochemical and bioactive composition and protein quality of refined wheat flour bread. Protein, dietary fiber, phenolic and carotenoid content, antioxidant capacity and protein digestibility corrected amino acid score (PDCAAS) were higher (p < 0.05), whereas available carbohydrate level was lower (p < 0.05) in ASL–wheat breads than the wheat-only bread, regardless of the ASL variety used. In addition, the blood-glucose lowering bioactive peptide γ-conglutin was detected in all ASL–wheat breads but not in wheat-only bread. The ASL variety used significantly (p < 0.05) affected the dietary fiber, fat, available carbohydrates and polyphenolic level, the antioxidant capacity and the PDCAAS of the ASL–wheat breads. These findings demonstrate the potential nutritional and health benefits of adding ASL to refined wheat bread and highlight the importance of selecting specific ASL varieties to maximise its nutritional attributes.

Exotic plant pests–a threat to the sustainability of Australia’s grains industry

Exotic plant pests (EPPs) threaten production, market access and sustainability of Australian plant production systems. For the grains industry there are over 600 identified EPPs of which 54 are considered high priority, posing a significant threat. Despite Australia’s geographical isolation and strong quarantine systems, the threat from EPPs has never been higher with the increasing levels of travel and trade, emphasising the need for improving our efforts in prevention, preparedness and surveillance for EPPs.

Developing effective fumigation protocols to manage strongly phosphine-resistant Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae)

BACKGROUND The emergence of high levels of resistance in Cryptolestes ferrugineus (Stephens) in recent years threatens the sustainability of phosphine, a key fumigant used worldwide to disinfest stored grain. We aimed at developing robust fumigation protocols that could be used in a range of practical situations to control this resistant pest. RESULTS Values of the lethal time to kill 99.9% (LT99.9, in days) of mixed-age populations, containing all life stages, of a susceptible and a strongly resistant C. ferrugineus population were established at three phosphine concentrations (1.0, 1.5 and 2.0 mg L−1) and three temperatures (25, 30 and 35 °C). Multiple linear regression analysis revealed that phosphine concentration and temperature both contributed significantly to the LT99.9 of a population (P < 0.003, R2 = 0.92), with concentration being the dominant variable, accounting for 75.9% of the variation. Across all concentrations, LT99.9 of the strongly resistant C. ferrugineus population was longest at the lowest temperature and shortest at the highest temperature. For example, 1.0 mg L−1 of phosphine is required for 20, 15 and 15 days, 1.5 mg L−1 for 12, 11 and 9 days and 2.0 mg L−1 for 10, 7 and 6 days at 25, 30 and 35 °C, respectively, to achieve 99.9% mortality of the strongly resistant C. ferrugineus population. We also observed that phosphine concentration is inversely proportional to fumigation period in regard to the population extinction of this pest. CONCLUSION The fumigation protocols developed in this study will be used in recommending changes to the currently registered rates of phosphine in Australia towards management of strongly resistant C. ferrugineus populations, and can be repeated in any country where this type of resistance appears. © 2014 Commonwealth of Australia. Pest Management Science © 2014 Society of Chemical Industry

Response to deep placed P, K and S in central Queensland

Two field experiments were established in central Queensland at Capella and Gindie to investigate the immediate and then residual benefit of deep placed (20 cm) nutrients in this opportunity cropping system. The field sites had factorial combinations of P (40 kg P/ha), K (200 kg K/ha) and S (40 kg S/ha) and all plots received 100 kg N/ha. No further K or S fertilizers were added during the experiment but some crops had starter P. The Capella site was sown to chickpea in 2012, wheat in 2013 and then chickpea in 2014. The Gindie site was sown to sorghum in 2011/12, chickpea in 2013 and sorghum in early 2015. There were responses to P alone in the first two crops at each site and there were K responses in half the six site years. In year 1 (a good year) both sites showed a 20% grain yield response to only to deep P. In year 2 (much drier) the effects of deep P were still evident at both sites and the effects of K were clearly evident at Gindie. There was a suggestion of an additive P+K effect at Capella and a 50% increase for P+K at Gindie. Year 3 was dry and chickpeas at Capella showed a larger response to P+K but the sorghum at Gindie only responded to deep K. These results indicate that responses to deep placed P and K are durable over an opportunity cropping system, and meeting both requirements is important to achieve yield responses.

Fine Mapping of qDor7, a Major QTL Affecting Seed Dormancy in Sorghum (Sorghum bicolor (L.) Moench)

Seed dormancy is a key domestication trait for major crops, which is acquired in long-term systems development processes and enables the survival of plants in adverse natural conditions. It is a complex trait under polygenic control and is affected by endogenous and environmental factors. In the present study, a major seed dormancy QTL in sorghum (Sorghum bicolor (L.) Moench), qDor7, detected previously, was fine mapped using a large, multi-generational population. The qDor7 locus was delimited to a 96-kb region which contains 16 predicted gene models. These results lay a solid foundation for cloning qDor7. In addition, the functional markers tightly linked to the seed dormancy QTL may be used in marker-assisted selection for seed dormancy in sorghum.