Location: Horticultural Crops Disease and Pest Management Research Unit
Project Number: 2072-22000-046-004-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2021
End Date: Oct 31, 2025
Objective:
Objective 1: To identify, purify, and concentrate nematicidal toxins from litchi tomato.
Objective 2. Characterize the potential nematicidal activity of toxins produced by litchi tomato on hatch and reproduction of G. pallida and M. chitwoodi.
Approach:
Objective 1: Our approach will be to fractionate S. sisymbriifolium plant tissues and test the toxicity of fractions to nematodes by using standard hatching assays. To achieve this goal, a series of extracts will be prepared from flowers, leaves, and roots of freeze-dried plant material at the semi-preparative scale (Gurbuz et al., 2015). After the screening of the extracts for nematode toxicity, the most potent extracts will be fractionated using analytical preparative techniques such as liquid-liquid extraction, column separation, and solid-phase extraction. The most potent fractions will be analyzed by high resolution mass spectrometry for specific chemical groups identification. Upon toxicity confirmation, bioactive molecules will be isolated and identified; and extraction procedures for these potential nematicidal compound(s) will be developed thus allowing us to obtain enough material for hatching assays and other bioassays. Once nematicidal activity is confirmed, further purification will be conducted, and assessment of large scale production will be made including feasibility of synthesis of nematicidal compounds.
Objective 2: In the absence of its potato host, encysted PCN eggs are protected from the soil environment and can lie dormant 20 or more years in wait for a susceptible host. For Idaho, the encysted eggs are the life stage that need to be attacked because planting potato is prohibited in infested fields. Fractions obtained from Objective 1 will be evaluated against eggs of PCN and CRKN in a 96-well microwell assay. CRKN will be included in these studies to demonstrate the potential application of S. sisymbriifolium to control a plant-parasitic nematode commonly found in PNW potato production fields. Toxicity confirmation of specific groups of chemicals extracted from litchi tomato will be assessed through in vitro hatching assays with both PCN and CRKN. Approximately 100 eggs will be added to microwells and then the fraction will be added, for a total volume of 200 ul. The plate will be incubated at 25 C for 1 week after which the number of hatched juveniles will be counted. All experiments for both PCN and CRKN will include water controls and treatments will be replicated at least five times and repeated. Impact of fraction on reproduction of PCN will be measured in our standard bioassay conducted on a susceptible potato in the greenhouse. Because initial experiments indicate that both the timing of exposure and the concentration may have an impact on egg viability and hatching, the concentration of the extracts will be varied, and the eggs will be exposed to the extracts and the hatching stimulus found in potato or litchi tomato root diffusates. Data analyzed with Statistical Analysis Systems.
Once fractions with nematicidal activity are identified, field trials will be conducted in established microplots in infested fields in Shelley Idaho to confirm toxicity under field conditions.
