The location for these new plantings or nursery would only be considered a safe place if the distance of the range, deter-mined for each genetic material, was respected between the old plantations and the new ones.By comparing data on the disease incidence and the number of diseased plants, total and per area among the genetic the disease was strongly expanded on the farm. Moreover, the disease initially spread in it, thus demonstrating its susceptibility to disease. Table 7 shows a comparative summary of the genetic material with the main statistical and geostatistical parameters analyzed.One of the main problems that appear in intensive monocropping systems, where the same cultivation is repeated continuously over time in the same plot, is the rise of soil-borne diseases . In crops such as strawberries, the high incidence of these diseases has led to a widespread use of soil disinfection practices. In this sense, fumigation of the soil with methyl bromide has been relied on to avoid the attack of pathogens in these crops. However, this practice has been prohibited due to its environmental risks . Until now, dazomet, metam sodium and metam potassium  were soil fumigants authorised in the Andalusian Integrated Production Regulations for strawberry, raspberry and blackberry. However, they did not pass the uniform principles established by Regulation  No. 1107/2009 in a recent revision. Hence, the authorisation for its use was cancelled by the General Directorate of Health of Agricultural Production. Also, 1,3 dichloropropene and chloropicrin, or their mixtures, are subject to the concession of exceptional uses by crop, area and problem. Furthermore, this concession is currently subject to various appeals. Therefore, with the current regulatory situation, and except for temporary authorisations, farmers lack chemical alternatives for soil disinfestation, which can compromise the productivity of these crops and their economic viability, in cases of high infestations by soil pathogens . In order to reduce the negative effects of soil-borne diseases for certain crops, a significant increase in production has been observed in soilless and hydroponic systems, which allow a greater control of plant health regardless of soil quality, while required nutrients are provided to plants with fertigation . By using a hydroponic system, a controlled amount of water and nutrients lead to high growth rates , reducing at the same time the chemical inputs . However, the change from soil-based production to hydroponic systems could lead to a significant risk of the occurrence of other pathogens especially adapted to aquatic environments, among which the Fusarium, Pythium and Phytophthora species stand out, since they could be easily spread through the recirculating fertiliser solution.

Particularly, the last two species,mobile grow system formerly considered chromista and currently classified in the Phylum Oomycota, have a superior advantage in liquid media because they present zoospores that facilitate the development of infection of new hosts within minutes . Phytophthora cactorum is a soil-borne pathogen that affects numerous herbaceous and woody species. In strawberry crops, it causes crown rot, loss of production, and plant death. The incidence of this disease has been observed also in soilless crops, introduced by infected runner plants and cold-stored plants or contaminated irrigation water . Fusarium oxysporum is a fungus that is widespread in different types of soil, presenting some pathogenic strains that affect many important crops around the world, causing significant economic loss since infected plants often collapse and die . Some studies have been carried out to identify the plant growth media that are most suppressive against the attacks of pathogenic F. oxysporum isolates . However, despite the ease of dispersion described above for some diseases in aqueous media, a lower incidence has been reported in closed hydroponic circuits. This could be related to microbiological activity and modulated by the type of substrate used and the plant species as a driving factor of the microflora and the hydroponic system . In the review by Stouvenakers et al. , the antagonistic microorganisms responsible for suppressive effects in hydroponic systems were grouped in the following categories: 1) competition for nutrients and niches; 2) parasitism; 3) antibiosis and 4) induction of disease resistance in plants. Trying to improve the sustainability of productions and to adjust to the paradigm of the circular economy, aquaponic systems have emerged as an interesting alternative to hydroponic systems. Aquaponic culture consists of a form of agriculture that combines aquaculture and hydroponics, where there is a recirculation of water through both subsystems, taking advantage of the metabolic waste of fish that serves as a nutrient for plants . In these systems, both circuits can be connected in a single loop, in coupled systems, where water continuously flows from one to the other , or in multiple loops, in decoupled systems, where flow goes just in one direction, from fish tanks to hydroponic beds . With this synergistic combination, savings in fertilisers and water are achieved, while reducing potential polluting discharges from both systems. Commercial large-scale aquaponics facilities are usually designed as decoupled systems, which is a great advantage in terms of management, since it is possible to modify the concentrations of nutrients, temperature and the pH of the water to adjust the values required by the plants without affecting the fish.

The fact that there is no water flow from hydroponic to aquaculture circuits also allows the applying of phytosanitary treatments, facilitating the cure of potential emerging diseases . On the contrary, in coupled aquaponic systems, which are commonly utilised in small-scale facilities, the use of pesticides to control plant diseases is not appropriate as they may affect fish or biofilter bacteria. Recent articles raise an interesting hypothesis about a natural protective action of aquaculture or aquaponic effluents against plant pathogens during in vitro tests . This phenomenon seems to be related to the presence of antagonistic microorganisms or inhibitory compounds in fish water.In the case of aquaponics, the presence of dissolved or suspended organic matter could also play an important role in the suppressiveness of some diseases, since it can modulate a microbial ecosystem which is less favourable for plant pathogens. This organic matter in the water comes not only from uneaten food debris and fish faeces, but also from organic plant growth media, root exudates and plant residues . The results of international surveys on aquaponics production developed in the USA  and Europe  have confirmed a lack of knowledge of producers about plant health and the incidence of plant diseases in the studied systems, as was reported by Stouvenakers et al. . Precisely, one of the challenges of aquaponic farming systems is related to disease control since pathogens can affect both fish and plants . For instance, an outbreak of Fusarium incarnatum, a grass fungus, could cause severe gill damage and even death to black tiger shrimps . Therefore, it is crucial to contribute to increasing knowledge in order to achieve the ideal conditions to improve the suppressive effect of aquaponic systems. Until now, there has been just one bibliographic reference comparing the suppressive effects in pure hydroponic systems and in aquaponic systems . However, this was carried out using small raft boxes with 4 lettuce plants to test the suppressiveness of Pythium aphanidermatum. Therefore, it could be very useful to determine the potential improvements against diseases achieved in the real conditions of aquaponic systems in relation to hydroponic production. For this reason, mobile vertical rack the following study is proposed. Its main goal is to compare the suppressive effects of these two culture systems for two pathosystems: P. cactorum –strawberry- and F. oxysporum f. sp. lycopersici – tomato.

As far as we know, this is the first time that the severities of two diseases in two crops have been compared between a hydroponic and an aquaponic system in real settings using systems under identical environmental conditions. This is essential to determine what fraction of the suppressive effect that has been referenced in the scientific literature is due to the presence of fish. Four blocks were determined in order to have four replications. Each of them included a hydroponic and an aquaponic system and their location within the block was decided randomly . A Nutrient Film Technique  system was used both for the hydroponic and aquaponic production of strawberry and tomato. To do so, 3 m long PVC pipes  were used, each of which had 28 holes  where the plants were inserted. The pipes were levelled with a 1% slope in order to allow the proper circulation of water. A thin water layer  was maintained inside the pipes, so the roots were in contact with the water but a correct aeration was ensured. In order to study the dynamics of disease transmission along the lines, each NFT channel was divided into four zones: 0, for the inoculated plants, and 1, 2 and 3 for the zones corresponding to increasing distances from the diseased plants . In the hydroponic systems, the nutrient solution was pumped by means of a 4000 L h− 1 submerged pump  from a 60 L sump into the NFT pipe, regulating the flow to the hydroponic line with a stopcock and pouring back to the sump. The aquaponic system was composed of a 250 L fish tank  sequentially connected to two smaller tanks  which acted as a clarifier and a biofilter, discharging fish effluents to the sump of the hydroponic subsystem, identical to the one described above. A stopcock on one of the extremes of a “T” fitting connected to the pump was used for sending 80% of the water from the biofilter back to the fish tank and the remaining 20% of the water to the NFT pipe. Again, the water was collected at the end of the pipe and returned to the sump. The water used for the experiment was obtained from the public network and dechlorinated by aerating it for 48 h prior to recharging the tanks. The fish used in this trial came from the university’s aquaponic facilities, located in a nearby greenhouse, where they were initially housed in an IBC tank similar to the models proposed by the FAO for small-scale aquaponics. At the beginning of both trials, 14–15 fish  were selected in order to achieve a total biomass of approximately 2.0 kg. The fish were placed in a container of 70 L provided with an aerator for each of the 4 aquaponic lines.

In order to acclimate the animals to the new environment, water from the destination tank was added to the fish container every 5 min, for a total time of 30 min. Once the pH and temperature values were close to those required, the fish were taken out with a net and placed in the new aquaponic tanks.The fish were fed twice a day with 24.4% protein feed by using the pond stick method.The daily amount of food applied in each tank was calculated as 2% of the total fish weight. This amount will result in a contribution of around 1.14 g of ammonia to the water . For the hydroponic culture, a Hoagland solution  was used to weekly refill the collector tanks. In the aquaponic systems, 0.3 L of chelated iron solution  was directly added to the clarifier tank  every fortnight.The plants were sprayed twice a week with 1% potassium sulphate to avoid possible deficiencies. When the plants started showing manganese deficiencies, they were sprayed with 1% manganese sulphate once a week. The maximum and minimum water temperature was measured twice a week with a Naterial® digital floating thermometer that worked with solar energy. The electrical conductivity was weekly monitored with an EC-Metro Basic 30 conductivity meter and the pH with a Hanna HI5221 pH meter. When the pH exceeded 7.5, citric acid at 1% was added in order to regain values between 6.5 and 7 for both the aquaponic and the hydroponic systems. The nitrate concentration was measured once a week by means of a Merck Millipore RQFlex reflectometer with a Reflectoquant test strip reader. For the first test, four isolates of P. cactorum  obtained from affected plants in Huelva  were selected for inoculation.