Yellow wilting in corn salad

Project period
2016 - 2019

Yellow wilting in corn salad: Investigation of possible causes and management strategies

Since several years the occurrence of a symptom called “Gelbe Welke” (Yellow Wilting) is a problem during the winter cultivation of corn salad (Valerianella locusta). At the beginning of cultivation the plants develop normally, but about two weeks after planting, respective plants show root reductions followed by typical wilt symptoms like yellow, chlorotic and limp leaves. The yellowing spreads from the external and older leaves to the internal and younger ones. Because of root reduction and decreased photosynthesis symptomatic plants are significantly smaller at the end of the cultivation period than those that develop normally.

Symptoms of this wilting occur both in greenhouse and open field cultivation. Abiotic factors like press pot consistency, insufficient water supply or factors derived by cultivation of tomatoes as a previous crop as well as common soilborne plant pathogens can be excluded as causative for the respective symptoms. Also nematodes, soil-borne fungal pathogens (Pythium spp., Phytophthora spp., etc.) and viruses could be excluded as possible pathogens of the Yellow Wilting on corn salad. Our previous studies have shown that Yellow Wilting symptoms are transferable from infected to uninfected plots via soil, pointing to the fact that the causal agent is soilborne and has most probably a biotic origin. Yet, respective organisms and/or causal agents of Yellow Wilting in corn salad are not identified and proper and effective control measures are so far not available for growers.

Within the framework of the European Innovation Partnerships (EIP Agri) an Operational Group (OG) has been set up, consisting of members and associated partners from science, breeding, consulting and vegetable practice. The aim is the continuous exchange of experience in order to find constructive solutions, which can be continuously adapted to new knowledge and changing production conditions. A systematic as well as result-oriented approach to the problem is to be developed. Creating an innovative solution for the problem of Yellow Wilting in corn salad without chemical plant protection as well as establishing an exchange and communication platform for the handling of the Yellow Wilting for the future is the additional aim of this cooperation and the practical innovation project.

In the practical innovation project we conduct greenhouse experiments to assess the effects of an annual soil solarization on soil temperatures and symptom development of Yellow Wilting in corn salad plants as well as on plant development and growth. Initial results show that soil disinfection by solarization repeatedly applied for three or more consecutive years is a cost-efficient and effective approach to reduce or inhibit the symptoms of Yellow Wilting in corn salad plants under greenhouse cultivation. Moreover, we aim at identifying the causal agent(s) of Yellow Wilting using metagenomics and metabolomics analysis of various soil samples obtained from greenhouses in Geisenheim and other locations.

Project coordination
Yvonne Rondot