Asparagus is one of the outdoor horticultural species with the largest cultivated area in the European Union, with more than 62,000 hectares dedicated to cultivation. Germany and Spain are included in the list of the five countries with the highest production worldwide. However, the crop is threatened by the “decay syndrome”, a gradual loss of vigor, which constitutes one of the main phytosanitary problems of this crop worldwide and which can even lead to the death of the affected plants.

The key question that has long been unanswered is: which fungi are causing the death of asparagus plants?

A team that includes researchers from the Sustainable Plant Production and Protection Group of the Polytechnic University of Madrid (UPM), together with researchers from the Andalusian Institute for Agricultural and Fisheries Research and Training (IFAPA), in Spain all the aforementioned institutions, set out to search the answer. The researchers, after analyzing farm fields in three producing provinces in Spain, have identified seven different specific complexes of the Fusarium fungus and modeled the severity of the disease. Likewise, they have managed to determine the importance of climatic factors in its expression.

The work carried out in the ETSIAAB Plant Protection Laboratory, under the direction of Professor Daniel Palmero, has made it possible to know the microbiota associated with plants affected by the decay syndrome in northern and central Spain. In this way, 13 species of the genus Fusarium have been identified. After determining the pathogenicity of the different species, the three most prevalent species have been identified (Fusarium oxysporum, Fusarium redolens and Fusarium proliferatum), which play a predominant role in the development of the disease in these plants.

General view of the soil disinfection test carried out by UPM researchers. (Photo: Plant Protection Laboratory, ETSIAAB)

The results of the study have made it possible to establish a relationship between the severity of the disease (observed in the field) and factors such as temperature, planting date or the density of fungal inoculum (microorganisms capable of causing infection) in the soil. As Daniel Palmero, a researcher at the UPM who participated in the study, indicates, “this information will be vital to address the effective control of the disease.”

Work is currently continuing to explore effective disease control measures through crop rotations, green manures, or soil disinfection treatments. Specifically, researchers are using anaerobic soil disinfection techniques together with the use of organic amendments or the use of Biological Control Agents to reduce the amount of pathogens in soils and thus be able to control the disease.

The study is titled “Fusarium Consortium Populations Associated with Asparagus Crop in Spain and Their Role on Field Decline Syndrome”. And it has been published in the academic journal Journal of Fungi. The research is part of the “Intelligent Growth Operational Program” INIA-FEDER 2014-2020. RTA2015-00008-C02-01 / 02 / National Institute of Agricultural and Food Research and Technology. (Source: UPM)