Brief Summary of Minutes of Annual Meeting

STATE REPORTS

Haddish Melakeberhan – Michigan

Dr. Melakeberhan presented an informative overview of soil health.  Soil health is comprehensive, including biological, physiochemical, and structural components.  There is a lot of information published (information rich), but practical knowledge is limited due to a lack of integration of this knowledge.  Dr. Melakeberhan works with the soil food web model, Fertilizer use efficiency model, and integrated productivity efficiency model (all of which together have garnered 20,000 views on the website!). 

But what is meant by information rich, knowledge poor?  There are numerous indicators of soil health, for example reactive carbon, aggregate stability, and biological species.  But not a single indicator can be related to a specific soil health value. 

Dr. Melakeberhan finished his presentation by presenting data on a survey project to look at abundance of hapla in disturbed, healthy, degraded, and mature soils. 

Adrienne Gorny – North Carolina

Dr. Gorny presented on her team’s research in managing M. enterolobii in sweetpotato in North Carolina.  Continuing their yearly assessment of nematicides for short-term management of this species, they conducted an on-farm field trial to assess how well Tymirium is performing against other registered non-fumigant nematicides.  In the on-farm test, Tymirium performed equally as well as Velum and Salibro, with regard to increasing marketable yield and decreasing percent galled sweetpotatoes.  However, in this test, Telone II fumigant still performed the best. 

This year, Dr. Gorny and her team also conducted a unique field experiment to assess different fumigant application depths and rates.  They tested Telone II fumigant, applied in the bed at either 6 or 9 gal/acre, using shank depths of either 8 inches or 12 inches, in a fully crossed experiment.  Controls consisted on the shanks dragged at either 8 or 12 inches, with no fumigant delivered.   The plots in which fumigant was applied at 12 inches deep outperformed the plots in which fumigant was applied at 8 inches.  There was no significant affect of fumigant rate.  This is important information for growers in North Carolina to know, as application depth has a greater impact on fumigant efficacy than rate. 

Johan Desaeger – Florida

Dr. Desaeger presented on his group’s work with RKN.  Florida has a high diversity of RKN species, and M. enterolobii is just as common as M. incognita in the state.  Moreover, M. hapla was only found in fields with strawberries.  He and his students have been doing a lot of work with different nematicides in tomato, conducting their field trials at the research farm, evaluating Nimitz, Vydate, Salibro, Velum, and also overlaying fumigant on top of these non-fumigant nematicides.  The combination of chloropicrin + Telone is the better performing fumigant in their tests.  Dr. Desaeger presented some work on Purpurcillium lilacinum (MeloCon liquid formulation) – it is known that the efficacy of this product is associated with the movement of the fungal spores.  His student conducted a greenhouse study looking at the movement of this product.  The maximum number of spores was found within the first two weeks, then the spore density decreased.  How can we improve the activity of P. lilacinum with other biocontrol agents?  Dr. Desaeger also has a student looking at the combined application of P. lilacinum and Bacilum amyloliquefacianes for management of M. enterolobii in cucumber.  The combination of these products was more effective than a single product. 

Tristan Watson - Louisiana

In his presentation, Dr. Watson followed up with his work in reniform nematode in sweetpotato, which he presented at last year’s multi-state meeting.  Besides North Carolina, Louisiana and Mississippi are also big producers of sweetpotato, but reniform is more problematic than RKN in these states.  Out of 40 fields sampled in LA, 39 of them were infested with reniform, many of them over threshold.  Reniform results in smaller roots.  At this time, Dr. Watson is informing growers about this issue of reniform in sweetpotato, because it is relatively unknown.  To this end, his group published a mini-review in Plant Health Progress.  In 2024, they did an on-farm nematicide trial, when the growers handle and apply the products.  Tristan also conducted trials composed of large plots, 8 rows wide by 400 feet long.  The data showed that all nematicide fumigant and non-fumigant products were effective in reducing reniform eggs, and increased yields.  In 2025, they repeated this trial across the street from the 2024 trial (however, minus the Telone treatment because the grower couldn’t get Telone).  For context, 10,000 reniform per 500 cc soil is considered high density.  The Kpam fumigant treatment did reduce nematode counts at planting and 28 days after planting.  At 56 days after planting, populations increased for all treatments.   Late season reniform nematode development was extremely high.  However, yield was more variable, and from this trial work, Kpam, Salibro, and Vydate + Majestine were the better treatments.  Coming from Dr. Watson’s work, the grower recommendation for Louisiana for managing reniform is Kpam , Velum, and Salibro

Dr. Watson and his team is also screening sweetpotato cultivars for reniform resistance.  From this work, no commonly grown commercial sweetpotato cultivars were completely resistant, but Covington and Beauregard were highly susceptible.  However, some old cultivars are more resistant/tolerant, and studies are ongoing. 

Lei Zhang - Indiana

Everyone thinks of corn and soybean when they think of Indiana, yet as Dr. Zhang informed us, the state actually has a vegetable industry worth over $217 million.  Watermelon alone contributes $75 million!  Dr. Zhang’s work has been focusing on high tunnel production – specifically RKN has been found in over 50% of high tunnels in KY and OH.  In Indiana, their team found three populations of M. incognita that can overcome Mi-1 mediated resistance in tomato rootstocks.  Dr. Zhang and his lab tested all Mi-1 virulent isolates, and they all reproduce on Mi-1 tomato, however, they all failed to reproduce on pepper. They conducted penetration tests, and all five M. incognita isolates entered the pepper roots (both with the N gene and without the N gene).  They are continuing their work with these virulent populations to learn more about them.  Dr. Zhang is planning future work to look at the genome of the resistance breaking M. incognita stains to understand where these populations came from.  Did they arise from the same population, or separately? 

Dr. Zhang and collaborators also conducted a survey of nematodes on small vegetable farms in Indiana.  Almost all soil samples collected from the farms had PPN, with spiral, lesion, and dagger as the most prevalent. 

Amanda Hodson - California

Dr. Hodson shared two stories with us, one about organic amendments in olives in CA, and the other regarding RKN and Fusarium in processing tomatoes.  They looked at biochar applications in olives, as there is some research that suggests it suppresses PPN, yet some inconsistent claims.  They tested biochar and compost individually, the two together, and then a grower standard.  In the compost treatment, there was a short-term suppression of PPN.  With the biochar, there wasn’t much happening in the first year, but in the second year, the enrichment index increased.  There is some work showing that biochar could be serving as a microstructure, “housing” bacteria.  Yet in some work Dr. Hodson’s team did with almonds, biochar wasn’t great for soil health and nematode suppression – biochar treatment decreased nematode counts and was associated with lower Nitrogen pools. 

So what is a parasite?  E.O. Wilson told us that “parasites are predators that eat prey in units of less than one.”   

In the second part of her presentation, Dr. Hodson discussed resistance-breaking RKN in disease complexes with fusarium in tomato.  The RKN could be increasing root-exudates which could increase fungal spore germination.  The RKN may also reduce plant defenses.  Therefore, the order of infection seems important.  They conducted an experiment with resistance breaking isolates of M. javanica VW5.  There were no differences in fusarium symptoms with or without the RKN, and no difference in nematode symptoms with or without the fusarium.  But inoculation with both pathogens reduced plant biomass (this was when both pathogens were inoculated simultaneously).  In a second experiment, they inoculated the RKN first, then the Fusarium.  The combined infection of RKN+Fusarium resulted in greater chlorosis than just RKN alone.  There was no chlorosis with just Fusarium alone.  Were the RKN causing this chlorosis, or were the plants just stressed?  The question also becomes, what products might be helpful for managing both pathogens?  What is the effect of temperature on this disease complex experiments?  The resistance-breaking RKN populations seem to be able to completely overcome the resistance even in the absence of heat. 

Cynthia Gleason – Washington

Dr. Gleason provided us an overview of her lab, which works on RKN of potato, mainly M. chitwoodi and M. hapla.  Her lab researchers plant-nematode interactions to find better solutions for growers. They are working with effectors to understand what responses they induce. 

Dr. Gleason presented on her Litchi tomato project.  Litchi tomato has been shown to be very resistant to RKN, and serves as a trap crop.  In Litchi tomato, M. chitwoodi almost never enters the root, and M. hapla achieves only minor levels of penetration.  They looked at the transcriptome of Litchi tomato after infection with M. hapla.   Her student identified putative candidate resistant genes based on homology, cloned these genes, constructed potato hair root lines, and observed a reduction in galled roots.  Another area that Dr. Gleason’s lab is working in is identifying susceptibility genes, so that these may be edited for conferring resistance.  They are using nematode effectors to identify these susceptibility genes.  To illustrate, they are working on M. chitwoodi effector identification.  Yet they were running into some trouble – a bad genome can lead to bad gene models.  Her student worked on re-annotating the M. chitwoodi genome and achieved a better completeness (Busco score).  Now that the team has a better genome, they can ask some questions regarding the genome.  They compared the transcriptome from a pre-parasitic J2 vs. with just the esophageal glands.  This narrows the focus to effectors created in the gland and then excreted.  The identified McGland26, a brand new effector with no homology in any other nematode (it is M. chitwoodi specific).  Experimentation seems to suggest it is not suppressing plant defenses (callous deposition or ROS burst), and is not suppressing a hypersensitive response.  Check out their new paper about this out is PLOS! 

Louise-Marie Dandurand – Idaho

Dr. Dandurand presented her lab’s work on rotation trials for management of potato cyst nematode in Idaho.  About 3,000 acres are infested with PCN in Idaho, but this is a fairly concentrated area, two counties, 8 mile radius.  She shared with us the three steps to deregulate a field: 1) evaluate egg viability (no viable eggs detected), 2) a greenhouse bioassay must pass three rounds, and 3) an in-field bioassay in which a susceptible potato is planted and reproduction/viability is assessed (three rounds of in-field assay must be passed). 

Dr. Dandurand recently received an SCRI grant to address potato nematodes in the US.  There are four objectives on this project, but today Dr. Dandurand presented their objective on potato rotation plan research for PCN, specifically work with Litchi tomato and quinoa in rotation with potato.  Litchi tomato is reducing cysts by 82-99%, and quinoa is reducing cysts by ~45%.  Litchi tomato is therefore as effective as a fumigant!  From this Dr. Dandurand has developed recommendations, including using quinoa as a trap crop and Litchi tomato is the most effective eradication strategy.  Planting 2 years of susceptible pomato is unadvisable. 

Shifting gears, what is the impact of G. pallida on potato?  Dr. Dandurand and her team are using the DSSAT program to develop a predictive model for yield loss.  It was found that approx. 80 eggs / gram soil = 40% yield loss. There was significant yield loss in ‘Innovator’ and ‘Desiree’ when inoculated with 80 eggs / gram soil.  Yet, there was not a significant yield loss in ‘Russet Burbank’ at 80 eggs/g soil, which is a novel finding.  However, if looking at average tuber yield, PCN impacted the size of each tuber. 

Simon “Niels” Groen – California

Dr. Groen is working with tomato processors in the central valley of California.  The tomato rootstocks they are using should be resistant to M. incognita, resistance breaking strains have been observed.  In processing tomato, the introgression of Mi-1 was very effective, however recently this is starting to break down.  It is unknown whether the nematode is evading detection of the Mi-1 gene in plants, or if they are suppressing the immune response of the plant?  What is the genetic architecture of the resistance breaking phenotype?  Were these populations introduced from one source or did they evolve several times?  Antoon’s and Shahid’s lab have been collecting RKN populations from across California.  These populations were identified to species through PCR and perineal patterns.  All isolates were M. incognita except for one population.  Dr. Groen’s team is sequencing the genome of 20 isolates from CA and comparing these to other RKN genomes to identify variance.  They have found a couple of populations that are identified as M. javanica, yet are clustering away from the other known M. javanica clusters.  Can we identify structural variation in the genome of the M. incognita populations, especially those that are breaking resistance?  Are there any effector modifications or deletions that are shared across the resistance breaking isolates?  Dr. Groen’s team has found evidence that this is not the case, which suggests the resistance breaking strains rose independently among many different RKN isolates.  Virulence of resistance-breaking RKN populations may likely involved multiple genes.  There also appeared to be a latitudinal virulence gradient, as populations in the southern part of the state were more virulent, and those in the central and northern part were slightly less so.  Virulence appears to be a quantitative trait involving more than one gene. 

Joanna “Asia” Kud - Arkansas

Central questions to Dr. Kud’s lab include how do nematodes manipulate the host plant?  How many effectors do nematodes have?  How do we know which effectors are important?  We know that effectors are deployed over time, from hours after infection, to days later. 

Dr. Kud presented the concept of meta-effectors.  The cell is bombarded with many effectors at the same time – are there interactions between effectors deployed together?  Work on meta-effectors was initiated and groundwork done in Legionella bacteria.  For example, RHA1B effector is an E3 ubiquitin ligase, this effector is expressed in dorsal glands and is very disruptive to plant immunity.  It can degrade proteins used to look out for nematode pathogens!  RHA1B also contributes to cell cycle and growth, contributes to syncytium development.  However, because it is an E3 ligrase, does it impact other effectors, especially those localized into the same island?  Dr. Kud’s team’s research shows that yes, it was found that RHA1B degrades ME4 effector.  ME4 is a member of the flutathione synthetase effector family, and evidence shows it suppresses both PTI and ETI. 

Why would a nematode want to destroy its own effector?   Potentially because it functions as a spatio-temportal regulation.  Recall that the plant is “looking out” for nematodes at different times.  Perhaps it is in the nematode’s best interest to “clean up” after itself.    

Kathy Lawrence - Alabama

Dr. Lawrence and her team are working on greenhouse and field studies for management of RKN, and also tracking new PPN in Alabama.  They are working with diagnostic labs to identify new RKN populations in the state.  Of note, they identified M. enterolobii for the first time in Alabama.  They identified the M. enterolobii population based on morphological morphometric and molecular methods.  Since this species is new to Alabama, they conduced a host pathogenicity assay test and this isolate did not reproduce well on cotton and soybean, but had a high RF on pepper, tomato, sweetpotato, and tobacco.  The M. enterolobii isolate was identified in a Crepe Myrtle farm.   

Dr. Lawrence and her lab are also looking at yields of resistant and susceptible cotton varieties, either with or without nematicides under M. incognita pressure, including testing several ThriveOn cotton varieties.  Even with the resistant variety, there was a benefit of adding a Velum treatment, and there were similar results when considering pressure of both SRKN and reniform nematode.  They tested the effect of Tymirium as a seed treatment on cotton, and saw a numerical increase in yield with the use of Tymirium as a seed treatment.  They are excited to get this one registered for cotton growers.  Using resistance to reniform nematode, they are still seeing a reduction in yield under reniform pressure, whereas fields without reniform nematode are consistently yielding much better.  So, it is important to keep fields clean and nematode free.

Shahid Siddique – California

Dr. Siddique presented the two main themes in his lab: 1) genomics and biothenology for sustainable nematode management and 2) mechanisms of nematode infection and host response.  They are working on sequencing RKN populations, including resistance breaking strains and populations from across the US and globe.  They want to capture RKN genomic diversity across the US and create high quality reference genomes for those populations in California.  But how does this help farmers in CA?  This data can help with diagnostics and infection mechanisms, tracking RKN populations across California. 

Dr. Siddique and his lab have published M. incognita, M. javanica, M. floridensis, and M. hapla genomes.  The M. hapla genome is now available online.  In addition to RKN, they are also working on Pratylenchus vulnus and ring nematode M. xenoplax.  So what’s next?  They are expanding their sequencing project, so if you are in the US, consider donating your nematode populations. 

It seems as if RKN do not have traditional endings to the chromosomes, i.e. telomers and Shelterin complexes.  Instead, they seem to have 16-mer repeats at the end of the chromosomes, but just on one end.  Interestingly, Chromosome 1 has a 16-mer repeat in the middle, suggesting a chromosome fusion.  Most contiguous genome assembly for a PPN to date is their M. hapla genome. 

Dr. Siddique is also conducting studies with M. hapla VW9 (an avirulent strain), and M. hapla LM (a virulent strain), and differ in their ability to reproduce on snap bean variety NemaSnap.   They are working with “Unknown Candidate Gene Mh10” – multiple variants of this gene is present in the virulent population.  Silencing of this Mh10 gene enables the avirulent population (VW9) to infect nemaSnap bean. 

Dr. Sanabria-Velazquez gave us an overview of the anaerobic soil disinfestation (ASD) technique.  First, you need a carbon source – this is the main challenge, as we need to incorporate a lot of carbon.  The carbon source needs to be very cheap or free for the farmers.  The carbon source material is applied and then tarped or covered with plastic.  However, you can use the same plastic to then plant the veg, so the farmers don’t have to spend more.  While a postdoc at NCSU, he conducted an ASD trial – in this, PPN were reduced, but the other free-living nematodes were not really affected.  He would like to try this experiment on the muck soils in Ohio, looking at the main RKN in Ohio, M. hapla. 

Brent Sipes – Hawaii

Dr. Sipes presented on perhaps everyone’s favorite crops, coffee and cacao!  Their team conducted a survey on Hawaii’s Big Island for the coffee root-knot nematode, Meloidogyne konaensis.  In Oahu, there was less than 5% RKN incidence, but all samples were M. incognita.  No M konaensis found in Oahu.  But in Kona, 100% of coffee fields had M. konaensis.  Dr Sipes gave us an overview of coffee cultivation in Hawaii using the “pulapula” method (“pulling” method), which likely moved the M. konaensis across the coffee fields.  In Hawaii, M. konaensis is similar to a specimen collected from Brazil in 1980.  Very similar in morphometrics to M. paranaensis.  Perhaps a species complex is afoot?  However, the populations they are seeing are strictly M. konaensis, and there doesn’t seem to be mixing of populations of Mk and Mp.  Some comparison of the COX2-16S region indicated a diagnostic gap in the genome that is present in M. paranaensis is also present in the M. konaensis populations from Hawaii.  This has lead to the strong hypothesis that M. konaensis came to Hawaii from Brazil.  Mk and Mp are the same species, with Mp being a junior synonym. 

Dr. Sipes then presented another ongoing project on nematodes of cacao.  Hawaii is starting to grow cacao, but is pushing the limits on the climate region that it can grow.  Also noted is the interesting flavor profile of cacao from Hawaii.  Brent explained the different cultivars with red pods and yellow pods.  Cryptic above ground symptoms of nematode infection in cacao, browning and leaf edge burn.  His lab conducted a greenhouse study to inoculate the two varieties with Mi, Mj, and reniform nematode.  Both red and yellow pod cacao were good host to all three nematodes.  This indicates that nematodes may be a problem for growers and education efforts may be needed for cacao growers. 

Sushil Chhapekar (on behalf of Henry Nguyen) – Missouri

Dr. Chhapekar presented the lab’s work on estimating yield loss in soybean due to SCN, RKN, and other diseases.  Annual yield loss of $1.5 billion in the US alone.   We are in need of an alternative source of resistance, as 88788 (Rgh1 QTL) and Peking (Rgh4 QTL) are about 98% of the resistance on the market.  In their lab, they are identifying novel resistance alleles through genotyping and subsequent phenotyping, focusing on MG III-V.  However, they are mostly finding 88788 and Peking resistance, but on occasion they are come across novel resistance. 

Dr. Chhapekar and team identified a QTL qSCN10 candidate gene for SCN resistance.  They narrowed down the region and developed markers, and from this identified approx. 20 genes in this region.  They conducted an RNAseq experiment, and among the 20 genes, three genes were differentially expressed.  They then conducted haplotype clustering of the qSCN10 locus genes in different soybean lines, and conducted experiments to overexpress these genes in transgenic Williams 82.  Overexpression of these genes resulted in significantly reduced cyst counts. 

The Missouri team have also been working on RKN in soybean.  The major QTL for resistance to RKN in soybean was identified on Chr. 10 from their lab.  They have developed some NILs for this Chromosome 10.  They have identified the region responsible to approx. 30kb, however, there are no resistance genes predicted from this region.  They are working on evaluating the genes in this region and estimating which may be the most important towards RKN resistance.

General Discussion

Niels to Shahid: as a field (nematology), should we develop a website to bring together high quality morphometric and genetic data? 

Shahid: yes, I agree with this.  NCBI doesn’t always provide good quality results.  In our experience, using WormBase Parasite is much better than using NCBI. 

Will Rutter: I also agree with the need of a website to bring together this data. My initial thought is Nemaplex - can we link the morphological and genetic resources that we have high confidence in to that website? 

Niels: the stability of WormBase Parasite is also up in the air…. They are trying to find funds to maintain the site. 

Haddish: also consider Tom Power’s Nebraska website.  I think SON should take this seriously and devote some resources to this.  Generally, I agree that linking to other resource would be easier than starting from the ground up. 

Shahid: perhaps we should devote some time and discussion at the next SON meeting to this? (there was general agreement to this) 

Rutter:  perhaps also bring in Dorota’s mitochondrial database?  Perhaps increase membership fees for SON to cover costs? 

Action Item: have someone on the EB bring this up at the next SON EB meeting. 

S-1092 2025 Business Meeting (Fayetteville, AR  11/11/2025) 

1. State Reports

We began the S-1092 Business Meeting by discussing coordination and submitting the state reports.  Intiaz Chowdhury is the incoming Chair, so he will compile all the individual state reports for submission of the final report. 

2. New Vice-Chair

We then discussed who will be the next Vice-Chair.  Zane Grabau volunteered for this role. 

3. 2026 Meeting Site

We discussed where the multi-state meeting will be next year (in 2026).  Adrienne volunteered to host this meeting in Raleigh, since the 2025 meeting was held jointly in Fayetteville, AR.  Zane volunteered to organize the 2027 meeting in Gainesville.  We discussed the possibility of holding the multi-state meeting right after the Cotton Working Group meeting (also held in Raleigh), so that participants can combine travel.  However, it would be good to check when the ONTA meeting is scheduled for 2026, to make sure the timing does not overlap. 

4. New Hatch Project

At the 2026 meeting, we will need to begin talking about writing of the new hatch project, as the current S-1092 hatch project will end Sept 30, 2027. 

5. New Members

We discussed potential new members.  A new South Carolina representative may be needed upon the retirement of John Meuller.  Other potential members discussed were Shova Mishra, Deepak Haarith, Clemen Oliveira, Churamani Khanal, and Lesley Schumacher. 

W-5186 2025 Business Meeting (Fayetteville, AR  11/11/2025) 

1. State Reports

We began the W-5186 Business Meeting by discussing coordination and submitting the state reports.  Brent Sipes is the Secretary, so he will compile all the individual state reports for submission of the final report. 

2. New Secretary and Chair

We then discussed who will be the next Secretary.  Cynthia Gleason volunteered for this role; current Secretary Brent Sipes will move into the role of Chair next year. 

3. 2026 Meeting Site

We discussed where the multi-state meeting will be next year (in 2026).  Cynthia Gleason volunteered to host this meeting in Pullman, WA.

4. New Members

We discussed potential new members for W-5186: Deepak Haarith (FL), Bao Lam Huynh (CA), and Andres Sanabria-Velazquez (OH).