In the greenhouses and fields of Andalusia, a different way of growing tomatoes is being tested : harnessing the power of soil fungi to obtain more nutritious fruit while simultaneously reducing reliance on chemical fertilizers. Far from being an isolated experiment, this line of research aligns with Europe's commitment to more sustainable agriculture.
The key lies in a kind of "natural vaccine" for tomato plants , which doesn't alter the crop's DNA or add artificial substances to the fruit. Instead, it activates the plant's own defense and nutrition mechanisms from very early stages through interaction with arbuscular mycorrhizal fungi , directly impacting the quality of the tomatoes that reach the consumer.
An Andalusian technique for healthier tomatoes with more antioxidants
The development of this strategy is being carried out by Andalusian research teams from the ZaidÃn Experimental Station (EEZ-CSIC) in Granada, in collaboration with the University of Seville and the agricultural cooperative SAT Hortoventas, located in Ventas de Zafarraya (Granada). The project has been funded by the Regional Ministry of Universities, Research and Innovation of the Andalusian Government, with support from the central government and European funds.
The technique involves inoculating tomato plants with beneficial soil fungi during the nursery phase, before they are transplanted to the field. These microorganisms, known as arbuscular mycorrhizal fungi, establish a symbiotic relationship with the roots: the plant shares some of the sugars it produces through photosynthesis with them, and in return, the fungus improves its access to water and nutrients.
Trials conducted on experimental plots at SAT Hortoventas have shown that tomatoes grown using this system contain between 30% and 40% more carotenoids than conventionally grown tomatoes. These compounds include lycopene and beta-carotene, natural antioxidants linked to protecting cells against aging and supporting cardiovascular health. This increase in carotenoids improves the nutritional value of the tomatoes that reach consumers.
According to those responsible for the study, the method does not genetically alter the tomato or incorporate external additives into the fruit; it simply stimulates metabolic pathways that the plant already possesses . Thus, the nutritional value of the fruit is increased without resorting to genetically modified organisms or extra chemical treatments beyond standard crop management.
This line of research has been described in the scientific article "Carotenoid biofortification in field-grown tomato fruits by early inoculation with arbuscular mycorrhizal fungi" , published in the Journal of Agricultural and Food Chemistry , which includes field data and analysis of the carotenoid content of the tomatoes produced.
A "plant vaccination" that activates defenses from the nursery
Researchers describe this strategy as a "plant vaccination" because the interaction between plant and fungus is established very early on, in the nursery, before transplanting. This way, when the tomato plants reach their final location, the symbiosis is already in place, regardless of the environmental conditions they encounter later.
When this early alliance forms, natural defense and antioxidant production pathways are activated , which the plant maintains throughout its development. It's not about injecting external products, but about triggering physiological responses that the tomato is capable of generating on its own, but which are often overshadowed in intensive agriculture due to the massive use of fertilizers.
The process can be explained simply as a strengthening of the plant's immune system: mycorrhizae help the crop respond better to water stress, the presence of pathogens or pests , and at the same time influence the synthesis of compounds of nutritional interest, such as carotenoids. The visible result for the farmer is a more resilient plant and fruit with a higher antioxidant profile. This responsiveness can reduce the incidence of pests under real-world conditions.
The researchers emphasize that for this fungus-plant interaction to be effective, over-fertilization with mineral fertilizers must be avoided . Excessive fertilizer can disrupt communication between the two organisms, as the plant no longer "needs" the fungus when the soil is saturated with readily available nutrients.
For this reason, the work protocol combines early fungal inoculation in the nursery with a reduction in traditional field fertilization. The goal is to maintain a balance that allows the plant to benefit from the symbiosis without sacrificing standard agricultural practices or competitive yields. More precise management of fertilization promotes the effectiveness of the mycorrhiza.
Mycorrhizal fungi: a natural extension of the roots
Arbuscular mycorrhizal fungi act as an extension of the plant's root system. Through a network of underground filaments, they explore soil volumes that the roots alone could not reach, resulting in better access to water and essential nutrients such as phosphorus, nitrogen, and certain micronutrients. In practice, these mechanisms are among the most common fungal processes involved in soil dynamics.
This network of hyphae functions, in practice, as an extension of the fine roots, increasing the effective absorption surface. Thanks to this, the plant can make better use of the soil's resources , especially in conditions of low nutrient availability or in soils with physical or chemical limitations.
In addition to improving resource uptake, this symbiosis helps activate defense and resilience mechanisms . Mycorrhizal plants often show greater tolerance to periods of drought, the presence of certain soil pathogens, and some pests, which, in the long term, can reduce the need for other inputs such as pesticides. This is relevant for combating diseases like Botrytis in tomatoes.
As part of the research conducted in Granada, the inoculation was carried out under real production conditions in an experimental field belonging to SAT Hortoventas, rather than in an isolated laboratory setting. This allows for the evaluation of plant and fungal behavior in scenarios similar to those encountered by farmers in their daily work.
The researchers' analyses show that, when the symbiosis is properly established and accompanied by moderate fertilization, the benefits are seen in both the agronomic productivity and the nutritional quality of the tomatoes, without penalizing the economic performance of the crop.
Fewer chemical fertilizers and agriculture more aligned with Europe
One of the aspects that has generated the most interest in the sector is the possibility of reducing the use of traditional fertilizers without jeopardizing production. Previous studies and the results of this project itself suggest that the combination of mycorrhizae and more precise management of nutrient applications could reduce the amount of mineral fertilizers used by between 25% and 50%.
This decrease has a double meaning: on the one hand, it represents a direct cost saving for farmers, in a context where fertilizers have experienced significant price increases; on the other hand, it helps to alleviate environmental problems associated with over-fertilization, such as groundwater contamination and soil degradation.
This approach is fully aligned with the goals of the European Green Deal and the UN Sustainable Development Goals, which promote a reduction in the use of chemical inputs in agriculture and encourage more environmentally friendly production models. For horticultural regions like southern Spain, where the intensive use of fertilizers is common, these alternatives can make all the difference.
The Andalusian Regional Government emphasizes that the initiative not only improves the quality of the final product, but also offers practical tools to move towards more sustainable horticulture without losing competitiveness compared to other tomato-producing origins in Europe.
The project is funded by the Regional Ministry of University, Research and Innovation , the Ministry of Science, Innovation and Universities and the European Regional Development Fund, under the motto "A way of making Europe", which reinforces the strategic nature of these lines of research for the whole of the European Union.
Results, next steps and potential applications
The work developed by the MycoStress group , from the Department of Soil and Plant Microbiology of the EEZ-CSIC, has made it possible to demonstrate under field conditions that the "natural vaccine" based on mycorrhizal fungi results in tomatoes with more carotenoids and in plants better prepared to face stress situations.
The data obtained indicate a consistent increase in the lycopene and beta-carotene content of the fruit, compounds associated with a healthy diet and widely studied for their role as antioxidants. Although the research has focused on measuring the tomato's composition, the team is already working to assess whether this enrichment has direct effects on human health when it is part of a regular diet.
Another area of ​​focus is analyzing the extent to which this symbiosis can help reduce the impact of pests and diseases on the crop, something especially relevant in the context of climate change, with more frequent heat and water stress scenarios in much of Spain and southern Europe. The study of pests and diseases remains a priority for implementing this technique in widespread production.
If these additional benefits are confirmed, the technique could be progressively extended to other production systems and other vegetables that are also grown intensively, taking advantage of the same principle: strengthening the plant from the root with the help of soil microorganisms, instead of depending exclusively on external inputs.
Taken together, the results position this "plant vaccination" approach as a promising way to produce healthier tomatoes and more sustainable crops , combining scientific knowledge, collaboration with the Andalusian agricultural sector and alignment with European strategies for reducing fertilizers and improving food quality.
