Bio & Twitter

Dan Bebber is an ecologist studying the global distributions of crop pests and pathogens, in collaboration with Prof. Sarah Gurr at the University of Exeter, UK. Thomas Chaloner is a PhD student studying the response of a fungal pathogen of wheat to temperature, and the influence of climate change on fungal plant pathogens. The research group works closely with the organization CABI to understand the changing global burden of crop pests and pathogens on agriculture and food security.

Twitter: @danbebber @gurrlabexeter @thomaschaloner

Background and Aims

Anthropogenic climate change has pervasively altered ecological communities and the distributions of species on Earth. In agriculture, crop yields have been affected by shifting patterns of temperature and precipitation, and by extreme weather events. In addition, the distributions and impacts of crop pests and pathogens have been altered, and are expected to change in future. Farmers, agriculture businesses, plant protection organizations and other stakeholders will be faced with new threats, and the need for improved monitoring and control methods. In this talk, we will review recent work conducted in collaboration with the organization CABI and others, to understand how climate change is influencing the global burden of crop pests and pathogens, and consider the urgent research needs required to improve our response to this growing threat.

Methods

We use mathematical and statistical models to analyse past and future changes in the global burden of crop pests and diseases. Key to our analyses has been the CABI Knowledge Bank, perhaps the world's most comprehensive database on crop pest and disease distributions. We have compiled additional databases on plant pathogen ecophysiology, and have employed existing global estimates of crop production, past and future climates, and socioeconomic variables to understand what we know and don't know about the distributions and impacts of crop pests and diseases in a changing climate.

Results / Outcomes

Our analyses have shown that the geographical distributions of hundreds of crop pests and pathogens have shifted polewards in recent decades, at rates similar to those expected from global temperature changes (1). Mobile groups such as insects and fungi with airborne spores are moving fastest (1,2). We show that the current distributions of species whose life-cycles are strongly linked to the host plant, such as bacterial and fungal diseases, are less predictable by climate than those of free-living insects that are more exposed to external weather conditions (3). However, the rapid increase in new arrivals of pests and pathogens around the world cannot be explained by climate change alone. Globalization of trade and travel, along with increased technological capacity to identify and report pest incidences, dominate the increasing saturation of croplands with pests (2). We have shown that our knowledge of current distributions of pests and pathogens is highly biased, with better data in developed countries at higher latitudes (4). In response to this knowledge gap, we have developed a statistical model which is able to predict the presence of unreported pests and pathogens around the world using crop distributions, known pest distributions, and socioeconomic factors, thus enabling plant protection organizations to prioritize plant health risk analyses (5). Mathematical models allow us to investigate past and future climate effects on disease. We have developed epidemiological models for several fungal pathogens, based on temperature and moisture controls on the epidemiology of the disease (e.g. 6). One model shows that the spread of Black Sigatoka, the most damaging disease of bananas, across Latin America at the end of the 20th Century was facilitated by climate change (7). Conversely, our models suggest that the recent outbreak of coffee leaf rust in Colombia was probably triggered by weather conditions, but not by long-term climate change (8). In the case of new observations of wheat stem rust in the UK, the climate has become more conducive to the disease, but the main driver of re-emergence appears to be deliberate planting of the alternative host plant for conservation purposes (9). A major new analysis of the thermal physiology of fungal and oomycete pathogens suggests that the global burden of disease will fall more heavily at high latitudes than in the tropics through the 21st Century, tracking the expected climate-driven yield increases for many crops in the temperate zone (in prep). In addition, our data suggest that host and climate specialization by pathogens are independent and evolutionarily labile, meaning that new threats can easily emerge (10).

Conclusions

Our research demonstrates the interplay between climate, agricultural production and socioeconomic factors that will determine the global burden of crop pests and pathogens in the future. Climate change has affected, and will continue to affect, the distributions and impacts of these crop-destroying organisms. Improving our understanding of the current threat, through work conducted by organizations like CABI to collect and collate data, is a priority as we prepare for a warmer planet.

References

1. Bebber, D. P., Ramotowski, M. A. T., & Gurr, S. J. (2013). Crop pests and pathogens move polewards in a warming world. Nature Climate Change, 3, 985–988.

2. Bebber, D. P., Holmes, T., & Gurr, S. J. (2014). The global spread of crop pests and pathogens. Global Ecology and Biogeography, 23(12), 1398–1407.

3. Bebber, D., & Gurr, S. (2019). Biotic interactions and climate in species distribution modelling. BioRxiv, 520320. https://doi.org/10.1101/520320

4. Bebber, D. P., Holmes, T., Smith, D., & Gurr, S. J. (2014). Economic and physical determinants of the global distributions of crop pests and pathogens. New Phytologist, 202(3), 901–910.

5. Bebber, D. P., Field, E., Gui, H., Mortimer, P., Holmes, T., & Gurr, S. J. (2019). Many unreported crop pests and pathogens are probably already present. Global Change Biology, 25(8), 2703–2713.

6. Chaloner Thomas M., Fones Helen N., Varma Varun, Bebber Daniel P., & Gurr Sarah J. (2019). A new mechanistic model of weather-dependent Septoria tritici blotch disease risk. Philosophical Transactions of the Royal Society B: Biological Sciences, 374(1775), 20180266.

7. Bebber, D. P. (2019). Climate change effects on Black Sigatoka disease of banana. Philosophical Transactions of the Royal Society B: Biological Sciences, 374(1775), 20180269.

8. Bebber, D. P., Castillo, Á. D., & Gurr, S. J. (2016). Modelling coffee leaf rust risk in Colombia with climate reanalysis data. Philosophical Transactions of the Royal Society B: Biological Sciences, 371(1709), 20150458.

9. Lewis, C. M., et al. (2018). Potential for re-emergence of wheat stem rust in the United Kingdom. Communications Biology, 1(1), 13.

10. Chaloner, T. M., Gurr, S. J., & Bebber, D. P. (2019). Geometry and evolution of the ecological niche in plant-associated microbes. BioRxiv, 836411. https://doi.org/10.1101/836411

Bio & Twitter

Renu Pandey is working as a plant nutrition physiologist with the main emphasis on phosphorus and nitrogen in legumes and cereals. She has identified donors for nutrient use efficiency in wheat, soybean and green gram. Her group has developed rapid techniques for screening genotypes for PUE based on low P-induced total root carbon exudation by labeling shoot with 14CO2. Phosphorus nutrition under climate change has also been incorporated. She has guided/guiding nine M.Sc. and six Ph.D. students working on phosphorus and nitrogen and has published more than 70 research articles and book chapters in over 16 years. She has completed a dozen nationally and internationally funded projects on nitrogen and phosphorus as Principal Investigator. Twitter handle: @RenuPan276

Dr. Prem Bindraban is currently the Director of the European-Netherlands Office of IFDC. Before now, he was the Executive Director of the Virtual Fertilizer Research Center (VFRC) of IFDC. Prior to joining the VFRC, Bindraban had been the director of ISRIC World Soil Information at WUR in the Netherlands since 2009. He has also been a lecturer in Future Planet Studies at the University of Amsterdam since 2009, leader of international research at Agrosystems Research PRI at WUR since 2008, served as a professor in crop modeling at the University of São Paulo (Brazil) from 2008 to 2010 and as head of the Natural Resources unit of WUR’s Plant Research International from 2000 to 2008. He also served as a researcher at CIMMYT from 1993 to 1996 and at IRRI in 1991.

Dr. Christian Dimkpa is a plant-soil scientist with the International Fertilizer Development Center (IFDC), Muscle Shoals, Alabama, U.S.A. He is involved in the development of novel fertilizers and fertilizer delivery strategies to improve plant health and nutrient use by crops. He investigates a range of micronutrients interactions in soil-plant systems for crop yield enhancement, resilience to abiotic (drought) and biotic (disease) environmental stresses, and regulation of phosphorus flux. Notably, Christian also studies the role of micronutrients in improving the use efficiency of nitrogen and reducing nitrogen losses, with implications for climate change mitigation. Prior to joining IFDC in 2014, Christian was a Research Assistant Professor at the Biology Department of Utah State University Logan, Utah, USA. At USU, he was a co-Principal Investigator on the interactions of plants and plant-associated microbes with metallic nanoparticles in the context of ecotoxicology and plant protection.

Background and Aims

Anthropogenic activities have led to significant alteration in the climate change variables, resulting in an increase in surface temperature by 1.5 to 2°C, CO₂ up to 412 ppm, and interacting with non-climate variables to affect the food security and food production systems. The non-climate variables such as drought, flooding, nutrient availability, incidence of pests and diseases have adversely affected crop production and quality of produce. The direct climate extremes include rainfall, high night and extremely high day temperatures, increased CO₂ concentration, drought, heat, flooding, and chilling stresses whereas indirect extremes include outbreak of pests and diseases and increased salinity.

Similar to a healthy diet which protects the human body from numerous chronic diseases, plants also require a balanced nutrition, derived mostly from the soil, applied in soil as fertilizers, or directly on plants as foliar application, to cope with the direct or indirect effects of climate change. Higher atmospheric CO₂ though acts as CO₂ fertilization, stimulating growth, particularly in C3 crops. As a result, plants require adequate nutrient and water supply to match the positive growth response. The elevated CO₂-induced growth acceleration typically coincides with lower protein and micronutrients (Zn, Fe, Mn) contents in cereal grains by an amount sufficient to produce nutrition-related health risks for millions of people. Similarly, heat stress in plants induces the reactive oxygen species (ROS) thereby causing oxidative stress along with tissue dehydration. Limited availability of nutrients to plants often restricts growth, development, reproduction, yield and produce quality. Therefore, plant nutrition strategies have been proposed to address the effects of climate change on crop productivity. One such strategy, innovative fertilizers and application technologies (IFAT), is a set of balanced-nutrient fertilizer products and fertilization technologies aimed at addressing multiple challenges in crops posed by adverse climatic variables, including increased temperature and CO₂. Here, we present findings of how balanced crop nutrition helps plants to overcome the adverse effects of high temperature and elevated CO₂, and thereby improve their resilience to climate change variables.

Methods

Cereal species (Triticum aestivum, T. durum and Secale cereale) were grown in nutrient solution with optimum (500 μM) and low (2 μM) phosphorus (P) and exposed to elevated (700 ppm) and ambient (380 ppm) CO₂ to study the interactive effects of P and CO₂ on growth, rhizospheric processes and P use efficiency (PUE). In another experiment, effect of P supply on mitigation of high temperature stress on growth, antioxidant system and yield traits were studied in rice. Plants were grown in soil with optimum and low P and exposed to high temperature (45°C) from booting stage to physiological maturity by shifting them to high temperature tunnel while the other set was kept at natural ambient (36°C) temperature. Another experiment on rice seedlings was conducted under controlled condition with ambient (28°C/18°C day/night) and high (35°C/20°C day/night) temperature along with optimum (500 μM) and low (2 μM) P supply.

Results / Outcomes

Plants supplied with optimum P under elevated CO₂ resulted in increased dry matter accumulation. However, under low-P also the dry matter accumulation was stimulated by elevated CO₂. Leaf area increased (43%) under elevated CO₂ supplied with P. Lateral root density, length and surface area were higher at low-P with elevated CO_2, concomitant with a PUE increase of 59%. Hexaploid wheat was more responsive than tetraploid wheat to the interactive effects of elevated CO₂ under low P in terms of below ground processes such as increased efflux of organic acids, extracellular acid phosphatase activity and root traits which help the plants to mine fixed P from soil. We found that elevated CO₂ can partly counteract the effect of low-P supply because of improved PUE.

Application of P to rice seedlings grown at elevated temperature (35°C/20°C day/night) under controlled conditions resulted in increased biomass and leaf area. However, plants grown under natural ambient temperature and exposed to high temperature showed significant increase in yield components, namely panicle number and total grain weight when supplied with P as compared to without P. The activity of antioxidant enzymes and the concentration of corresponding metabolites were significantly altered by P nutrition and its interaction with temperature. Superoxide dismutase (SOD) and ascorbate peroxidase activities were highest under low P × elevated temperature which also showed higher hydrogen peroxide levels. The ascorbate concentration decreased under low P × elevated temperature whereas glutathione (GSH) increased. These findings demonstrate that elevated temperature-induced oxidative stress can be mitigated by P application.

Conclusions

Collectively, these findings indicate that sustaining enhanced crop growth and nutritional quality under elevated CO₂ or heat stress requires reassessing the rate of fertilizer dose and fertilizer-nutrient ratios, as well as supplying nutrients at the right crop growth stage. Foliar application of potassium (K), calcium (Ca), boron (B), selenium (Se), and manganese (Mn) are known to alter stomatal functioning by activating physiological and metabolic processes, thereby maintaining high tissue water potential that increases heat stress tolerance. Application of nutrients such as N, K, Ca, and Mg also reduces the toxicity of ROS by alleviating the concentration of antioxidant enzymes in plant cells. Zinc, Mn and copper are metal co-factors of SOD enzymes; therefore, foliar application of these nutrients on crops improves heat stress tolerance. Thus, packaging of these nutrients and delivery to plants as foliar products could improve stress tolerance capacity of plants under elevated CO₂ and temperature.

Bio & Twitter

Mamta Sharma is a leading Integrated Crop management Theme at ICRISAT (CGIAR institute). She is a Principal Scientist in Plant pathology and is working on legume crops specially chickpea and pigeonpea. Her areas of work include fungal pathology, biology and epidemiology of diseases, host x pathogen interactions, pathogenomics and climate change and emerging threats.

twitter handle: @MamtaSharma_1

Background and Aims

Background and aims: An increasing agricultural productivity is a critical first step in meeting the Sustainable Development Goals of ending hunger and poverty by 2030. The overwhelming majority of poor farmers survives in Sub-Saharan Africa and South Asia, overall loses of attainable yield from pest & disease (P&D) could actually be greater in these continents. In particular, significant damage has been caused globally by transboundary pests against the background of climate change and globalized movement of people and goods. We at ICRISAT works in a semi-arid tropic (less favored areas) region for adaptation of integrated genetic and natural resources to improve crop production and livelihood of farmers. Climate change, disruption of pest & diseases biological synchrony, promotion of minor pest into major, soil moisture deficit and lack or apparent failure of resistance cultivars seems to be major reasons for the production loss in pulses like chickpea and pigeonpea. Tailored research information on transboundary and emerging P&D, climate vulnerabilities for epidemics, crop resistant and new management technologies could essential to bring the transformation in poor farming families.

Methods

A working group was established to consensus these impacts by rendering intensive periodical surveillance, evaluation and risk prioritizations in pulse production systems specially targeting chickpea and pigeonpea. Additionally, historical pest and disease incidence on chickpea and Pigeonpea as well as weather data of different locations were curated from the available resources and analyzed the influences of variables of spread and incidences. Weather indices based regression models was utilized for developing forewarning models of pod borer (Egg and Larva) based on 20 years of data on egg (population /twigs), larve (population / plant) and trap catch (population in numbers) of pod borer to predict crop age at first appearance of egg / larve, crop age at peak population of egg/ larva and maximum population of egg/ larvae. Also, series of experiments were conducted under simulated conditions to study impact of elevated temperature and carbon dioxide on host and host x pest interactions in these pulses.

Results / Outcomes

Surveillance and comparison with historical reports illustrated the role of weather variables on emergence and re-emergence of minor pests to major viz., phytophthora blight, dry root rot, collar rot, spotted pod borer and viral diseases. Severity of these pests & diseases is increasing in major growing areas with high plant population. Further, virulence profiling of Fusarium wilt on host differentials reported the occurrence of more than one races in a location thus impeding the chickpea and pigeonpea production as well as pointing for existence of intra-population variability. Weather based forecast models developed to predict the pod borer infestation (peak severity and maximum population) to advise the farmers in advance (two weeks ahead) for timely management of insect populations. Model indicated that maximum temperature, relative humidity and bright sunshine hours from 42 to 51 standard meteorological week (SMW) are critical for pod borer (Helicoverpa) infestation/outbreak and dry root rot in Southern India. Future climate projections as well as trend analysis for these weeks depicted 2-3⁰C increase in maximum temperature in this region (2030-2050) indicating increased frequency of outbreak of these pests in future. Observed values are in close approximation to predicted value and further validation of the model in the field is in progress.

Conclusions

Accelerated pest’s damages prejudice the obligation of pest prioritization and risk assessment for optimization of the preemptive breeding in demarcated target population environments, determination of socio-economic condition of farmers and rapid action on climate smart crop management and adaptation. The forewarning models linked to the advisory will help in providing rapid response to the farmers for managing their crops in a real time manner.