Location: Vegetable Crops Research
Project Number: 5090-21220-006-045-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 17, 2025
End Date: Sep 16, 2026
Objective:
Our project will identify differentially regulated responses following inoculation with root lesion nematode (RLN, V. dahlia, or in synergistic combination in different suppressive soil environments using potato cultivars with varying levels of potato early dying susceptibility and tolerance. We hypothesize that the soil microbiome and RLN manipulate plant defenses and nutrient management pathways, affecting host susceptibility or tolerance to V. dahliae. Understanding the molecular mechanisms regulating the synergism between these nematode and fungal pathogens would greatly aid in the development of more tolerant cultivars, inform management practices and disease risk predictions.
Research Objectives:
1. Assay the effect of suppressive soils on V. dahliae growth in infected and tolerant potato.
2. Determine the effect of suppressive soils on the population dynamics of V. dahliae and P. penetrans and on PED symptoms.
3. Identify key plant pathways that affect potato tolerance to PED in suppressive soil environments.
Approach:
Objective 1: In our previous work, we quantified the disease suppressive ability of several dozen agriculture soils using Verticillium-infected potato seedlings of susceptible Russet Norkotah, moderately resistant Russet Burbank, and tolerant Ranger Russet. Seedling tissues were harvested and stored at -80 °C. To determine the effect of soil suppressive ability on V. dahliae growth in these different potato varieties, we will determine the amount of V. dahliae in stem tissue using quantitative PCR.
Objective 2: We will conduct a new seedling assay to measure the effects of suppressive soils on pathogen population dynamics and PED development with increased nematode pressure. We will select three soils predicted to show high and three with low suppressiveness from previous study sites and grow a tolerant cultivar (Ranger Russet) and a susceptible cultivar (Russet Norkotah). Half of the seedlings will be treated with increased nematode pressure by soil inoculation of a pure culture of P. penetrans. Liquid culture of V. dahliae will be added into the soil. We will measure pathogen growth and soil/root nematode abundance. We will also measure plant tolerance, which describes the plant’s ability to continue growing despite infection and will be estimated as the disease severity per unit of pathogen infection. Finally, the rhizosphere soil microbial communities will be measured to investigate plant recruitment of beneficial microorganisms during PED suppression.
We will also measure nematode DNA in soil samples collected from previous studies in order to understand whether measured suppression has been influenced by the native soil nematode community. We will take advantage of established marker genes in our laboratory to quantify the nematode abundance using quantitative PCR.
Objective 3: Potato defenses to V. dahliae and P. penetrans have been studied extensively in the past and results suggest a synergistic effect of both pathogens that leads to increased susceptibility. But only limited data exists on global gene expression changes and no prior work has addressed differences between susceptibility and tolerance or the effect of suppressive soils. The identification of genes and genetic pathways correlated with PED tolerance will assist in future work to use genomic selection to develop improved varieties. RNA sequencing (RNAseq) is a relatively inexpensive method (<$100 per sample) to determine the expression of every gene within a sample. Our experiments will use different concentrations of V. dahliae and P. penetrans, individually and in combination, against Ranger Russet and Russet Norkotah plants. Because of the sensitive nature of this method, replication is a necessity. We will therefore analyze samples from five replications of each treatment. All experiments will be repeated with suppressive and non-suppressive soils for a total of 180 samples, resulting in a tremendous amount of data and an equally remarkable insight into the host responses to these pathogens. Standard bioinformatic analyses will be used to identify differentially regulated defense pathways.