New Variety Testing in Phytotrons
by Rasmus Madsen
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Climate-controlled greenhouses, or ‘phytotrons’, are controlled-environment research facilities used in plant science to study plant growth, development, and physiology under highly controlled environmental conditions. These facilities allow us to manipulate factors such as light, temperature, humidity, atmospheric gas levels, and even soil status or nutrient availability to study how plants respond to different environmental stimuli and stresses.
The global coffee production is threatened by global climate change, including increasing temperatures, erratic rainfall, and shifts in growing zones. Phytotrons enable us to simulate future climate scenarios, testing how coffee plants might respond to these challenges. It may also be used to develop strategies and techniques to mitigate the impacts of climate change, such as new agricultural practices or selecting or breeding coffee varieties that thrive in more variable conditions and to develop the best agronomical practices for those.
In field studies, variables like weather and soil conditions can vary widely, making it difficult to replicate results. These phytotrons ensure consistent, controlled conditions, allowing for reproducible studies and more reliable conclusions about how specific factors affect coffee plants.
Coffee plants are vulnerable to diseases like coffee leaf rust, which thrives under specific environmental conditions. Phytotrons can be used to simulate these conditions and to test resistant varieties or study the effectiveness of disease management strategies. By isolating environmental factors in phytotrons, we can identify the specific conditions under which diseases flourish and struggle and develop more effective countermeasures.
Additionally, coffee bean quality is strongly influenced by environmental factors. By precisely simulating these variables in the phytotrons, we can study how different conditions impact bean development and quality, leading to improved cultivation practices or the selection of high-quality varieties, which is equally important to the specialty coffee market.
Stress Testing New Varieties
Stress testing coffee plants in phytotrons is vital for understanding how new coffee varieties respond to various environmental stresses, such as drought, heat, heavy rainfalls, and their susceptibility to diseases and pests. It enables us to screen large numbers of new coffee varieties quickly and efficiently under various stress conditions with a high reproducibility. This accelerates the breeding process by allowing early identification of varieties with the most promising traits. This research helps implement coffee varieties that are more resilient and sustainable in the face of a changing climate.
Water Stress Simulation
By controlling water availability in phytotrons, we can simulate both moderate and severe drought conditions at different phenological stages to test the resilience of new coffee varieties. Key outcomes include:
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Identifying varieties that can survive or maintain high productivity during prolonged dry periods.
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Understanding how water stress affects different reproductive growth stages, such as flowering and seed development.
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Developing and implementing drought-resistant varieties that are suitable for water-scarce regions or future climate scenarios.
Temperature Stress Simulation
Coffee plants, particularly Arabica, are sensitive to temperatures above 30°C. Phytotrons allow us to expose coffee plants to extreme heat conditions at different phenological stages to assess:
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The upper temperature limits at which coffee plants can thrive.
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How heat stress impacts photosynthesis, flowering, and fruiting.
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Which new coffee varieties can withstand heat and still produce high-quality seeds.
Although most coffee plants are sensitive to cold, especially frost, certain varieties or hybrids may be more tolerant. Phytotrons can simulate cold stress to:
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Test new coffee varieties for cold resistance.
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Explore how low temperatures during different growth stages (e.g., germination, flowering) affect productivity.
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Develop strategies for growing coffee in cooler climates or at higher altitudes, extending the growing range.
Salinity and Soil Quality
In regions where soil salinity is an issue, phytotrons can be used to study how new coffee varieties respond to increased salt levels in the soil. In the phytotrons we are testing the tolerance of coffee plants to saline conditions, the effects of salt stress on plant water uptake, growth, and seed quality, and test new varieties that can grow in marginal soils or saline regions.
Diseases
Testing new coffee varieties for disease resilience and developing mitigation practices in phytotrons is a critical aspect of improving coffee production, particularly given the threats posed by diseases like coffee leaf rust (Hemileia vastatrix). Phytotrons allow us to closely mimic the environmental conditions that promote the spread of these pathogens, providing a controlled setting to evaluate how new coffee varieties respond and helping to develop strategies to mitigate their effects. We can expose new coffee varieties to different levels of humidity, temperature, and light intensity to assess how quickly the disease spreads under varying conditions, the severity of the infection in different environmental scenarios, and whether some varieties exhibit natural resistance or slower progression of the disease under the same conditions. Phytotrons are ideal for screening large numbers of coffee varieties to identify those that possess genetic resistance to pathogens. Screening involves deliberately exposing different coffee varieties to pathogens under controlled conditions to determine their resilience
Once a variety is confirmed to be disease-resistant through phytotron testing and field trials, it can be propagated and introduced to coffee-growing regions where disease pressure is high, while farmers should be trained to adopt improved cultural practices or integrated pest management strategies.
Data collected from phytotron studies, such as how temperature and humidity affect disease development, can be used to create predictive models that help farmers anticipate disease outbreaks. This information is vital for implementing early warning systems in coffee-growing regions.
Developing Best Practices for New Varieties
By simulating a range of conditions (environmental, soil status, nutrients availability etc.), we can develop the best growing practices tailored to specific varieties, helping to maximize yield, quality, and economic sustainability in production. Different varieties react strongly very different to agricultural practices. Phytotrons provide the ideal setting for testing and developing best agricultural practices for each specific variety, which can be rolled out in the field to increase productivity and quality.
Phytotrons allow for precise control of nutrient levels, making it possible to study the impact of various nutrients and fertilizer regimes on coffee plants and specific varieties. We vary the pH of the soil and availability of micro- and macronutrients and observe how different concentrations affect plant growth, flowering, and bean quality. We can compare the effectiveness of organic fertilizers (e.g., compost, coffee pulp) with synthetic fertilizers in terms of how well they provide nutrients to coffee plants and impact soil health. Additionally, in many coffee-growing regions, water availability is a critical issue, and nutrient uptake is strongly influenced by soil moisture levels. Phytotrons enable precise control over both irrigation and nutrient availability, allowing us to study their interactions.
We can also simulate various fungicides and biological control agents under controlled environmental conditions to see how effective they are at different stages of infection and in different environmental scenarios. Testing under different temperature and humidity regimes simulates real-world variability, helping to determine the best timing and application rates for disease control in the field. We can also simulate how changes in plant spacing, shade management, or pruning might affect disease prevalence and severity. As an example, Denser planting might increase humidity within the canopy, promoting disease spread, while wider spacing might improve airflow and reduce moisture levels, thus limiting pathogen growth.
Real-Life Implementation
Moving from phytotron research to real-life implementation at the farm level involves a multi-step process that bridges the controlled environment of the phytotron with the complex and dynamic conditions of actual coffee farms. The key challenge is to translate the insights gained from highly controlled experiments into practical, scalable, and economically viable strategies that farmers can adopt.
Once key insights have been identified in the phytotrons, the next step is to validate these findings in field trials under real-world conditions. This phase involves:
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Small-scale testing on farms: collaborate with farmers to conduct small-scale trials on farms that represent various geographical locations, soil types, and climatic conditions.
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Adjusting variables to field realities: Field trials help account for uncontrolled factors such as weather variability, soil variability, and farmer practices that were not present in the phytotrons. The trials typically assess: