Project Type

Internacional / Público

Financial Program

PTDC - Projectos em todos os domínios científicos

Global Funding Value

184194.00 €

IPB Funding Value

86640.00 €

Research Project

Principal Investigator

Isabel Mourão

Start

2016-07-01

End

2019-06-30

Description

The sustainable management of economically important soilborne diseases, such as rootknot nematodes (RKN), Melopidogyne spp., calls for the integration of ecologically sound control strategies. The main goal of the Project is to develop a combined control strategy against RKN based on the use of the biological control agent, Pochonia chlamydosporia, the activation of natural plant defence mechanisms and the use of partially resistant rootstock. The fungus P. chlamydosporia is an ubiquitous egg parasite of RKN, but it is not able to prevent the initial root infection by the mobile nematode infective stage (J2). Application of this nematophagous fungus in the field requires the production and inoculation of very large numbers of spores that may not result in effective nematode control because fungal establishment and rhizosphere colonisation depend on fungal interactions with the plant Highly RKNsusceptible plants have a negative effect on the efficacy of P. chlamydosporia, as galls induced in roots tend to be larger, containing several nematode females that lay their eggs inside the roots and egg masses become protected from fungal attack. Therefore, biocontrol efficacy could be enhanced by the combination of control measures that prevent or reduce initial infestations such as the activation of natural plant defences. Natural plant defence can be triggered by the application of plant defence activators and, when integrated into good agricultural practices, both productivity and disease resistance can be improved. But, plant defence activators differ on their ability to induce defence against RKN and their efficacy may depend on the amount of compound absorbed by the plants. Our team has demonstrated the potential of a P. chlamydosporia isolate combined with the use of cisjasmone against RKN. Cisjasmone seemed to both reduce J2 penetration and increase parasitism by the fungus, enhancing its biocontrol efficiency. Studies on gene expression would provide a finer understanding of the underlying mechanisms responsible for the specific plantnematode interactions. Systemic defence may also play an important role as a result of grafting. Vegetable grafting is an emerging technique to tackle a wide range of soilborne pathogens. In Portugal, more than 50% of the area of cultivated tomato in protected crops is based on grafted plants. Many tomato rootstock cultivars are available from leading seed companies but rootstocks that are completely resistant to RKN are not available to date. Nevertheless, partially resistant or tolerant rootstocks reduce RKN infection and prevent the formation of large galls. A given rootstock can have varying degrees of RKN resistance depending on the RKN species/population and therefore, the RKN problem can only be temporarily alleviated by using grafted plants. Thus, combining vegetable grafting with a more generalist means of nematode control such a as the use of a (rootstock compatible) biological control agent and the activation of plant defence by e.g. cis jasmone would avoid this drawback. In fact, using grafted plants may further exacerbate the effect fungus + plant defence activator. Small scale trials will define and optimize the application method and concentration of plant defence activators against RKN in susceptible scions and commercially available RKN resistant rootstock cultivars alone or in combination with P. chlamydosporia. As rhizosphere colonization by the fungus varies among different plant species and cultivars, small pot bioassays will be performed to find a compatible match between P. chlamydosporia and tomato rootstock cultivars and to promote colonization of the rhizosphere very early on, before plantlets are transferred to the field. To clarify and understand the molecular mechanisms behind the improved nematode control obtained under laboratory conditions, pathogenicity and defencerelated genes upor downregulated, during the plantnematodefungus interactions, will be carried out using quantitative PCR. A large pot trial in field conditions (polythene tunnel, mimicking commercial cultivation) will be established using the management strategy with the most efficient combinations based on our assays and trials. An applied perspective will be considered, so parameters on tomato yield and fruit quality will be recorded. Knowledge acquired during the project will be used to raise public awareness of nematode problems and current alternative control strategies in an Exhibition/Open Day that will be held at IPVC. This will also serve as an opportunity to exchange knowledge and discuss ideas with nurseries, growers and collaborators.

Project Team

Isabel Mourão
Luís Miguel Cortez Mesquita de Brito
Maria Luísa Moura

Project Partners