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Can fungi protect eggplant from root-knot nematodes?
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In greenhouse pot tests by a Saudi team, two fungi isolated from root-knot nematodes cut the number of root galls on eggplant to 988 and 1,222 per root, against 2,754 on nematode-infected plants without a fungus.
Root-knot nematodes invade roots and make them swell into galls, which disrupt the plant's water and nutrient transport. With chemical nematicides increasingly restricted, a King Saud University team went looking for fungi that attack the nematodes themselves. They picked two promising strains from fungi growing on nematodes taken from infected tomato and eggplant roots, and tested them in the lab and then on potted eggplants (El-Qurashi et al., 2026).
What this means for your grow
Nothing you can buy yet: these are two newly isolated fungal strains, not commercial products. What the study adds is evidence that fungi living on root-knot nematodes can, in pots in a greenhouse, reduce galling and nematode numbers on eggplant while the plants grew as well or better. Even the best treatment left heavily galled roots by the paper's own index, and the authors say field trials are still needed, so for now it is a promising lead for biological control rather than a fix.
What did the team do?
The team collected nematode-infected tomato and eggplant roots from farms in Al-Uyayna village, Riyadh, and grew fungi from the nematodes. Two strains were identified as Cladosporium limoniforme (strain EF1, from nematode females on eggplant) and Plectosphaerella cucumerina (strain TJ5, from young nematodes on tomato).
- Lab tests: each fungus was grown on agar plates with nematode eggs or second-stage juveniles (the young, infective stage), and liquid filtrates from the fungal cultures were tested at 50% and 75% strength. They also checked that the fungi did not stop eggplant seeds germinating.
- Pot trial: pots of a 1:1 mix of sand and peat moss, sterilised with formalin, were inoculated with each fungus a week before planting. Twenty-five-day-old eggplant seedlings (cultivar Black Beauty) were planted in, and ten days later 1,500 juveniles of Meloidogyne javanica were added to each pot. The trial was stopped after 60 days in a greenhouse, and ran alongside untreated, nematode-only and fungus-only comparisons.
What did they find?
- Fewer galls: plants with C. limoniforme averaged 988 galls per root and those with P. cucumerina 1,222, against 2,754 on nematode-infected plants without a fungus.
- Fewer eggs and young nematodes: eggs per root fell to 26,047 and 33,846, against 62,602; egg masses to 1,148 and 1,379, against 2,774; and juveniles in the soil to 533 and 793 per 1,500 g, against 2,556.
- Reproduction factor: 1.24 with C. limoniforme and 1.33 with P. cucumerina, against 1.63, a significant drop. The root gall and egg mass indices (scored 0 to 5) were 4.6 to 4.8 with the fungi against 5.0, which was not a significant difference.
- Plant growth: C. limoniforme gave the heaviest shoots: 15.7 g dry weight on nematode-infected plants against 11.9 g on infected plants without a fungus, a significant difference, and 16.1 g on healthy plants against 14.2 g, which was not significantly different. P. cucumerina did not significantly change shoot or root weight.
- In the lab: egg hatching fell to 8.4% with P. cucumerina and 14% with C. limoniforme, against 46.6% without fungi, and juvenile deaths rose to 72.7% and 80%, against 19.1%. The culture filtrates stopped more than 95% of eggs from hatching.
- Seeds: eggplant seed germination was 90% with C. limoniforme and 70% with P. cucumerina, against 90% for the control, and the authors report no significant harmful effect.
What could it mean?
The authors conclude that both strains show promising potential as biological control agents against root-knot nematodes and as plant-growth-promoting fungi, and could become part of integrated pest management, with C. limoniforme giving the larger reductions in the pot trial, which the authors describe as superior. They say field trials must confirm whether the strains work in real soils and farming systems. For now the result is mostly of interest to researchers and biocontrol developers; it is not something to try at home.
What were the limitations?
The authors note that all the tests were in the lab and greenhouse, in sterile or semi-controlled potting mix. In open fields, results may change with temperature, soil moisture, pH and competition from other soil microbes. The compounds the fungi use against nematodes were not identified, and how much fungus to apply, how well it survives in natural soil and how to formulate it are still to be worked out.
Trial details
- Where: fungi isolated from root samples collected on farms in Al-Uyayna village, Riyadh, Saudi Arabia, and worked up in the Plant Nematology Laboratory, College of Food and Agriculture Sciences, King Saud University. Pot trial under greenhouse conditions.
- Who: Plant Protection Department, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.
- Crop: eggplant, cultivar Black Beauty, planted at 25 days old.
- Pest: the root-knot nematode Meloidogyne javanica, 1,500 second-stage juveniles per pot.
- Treatments: Cladosporium limoniforme EF1 and Plectosphaerella cucumerina TJ5, each grown on a barley and sand medium and mixed into the potting soil at 3% (wt/wt) a week before planting; untreated, nematode-only and fungus-only controls.
- How long: the pot trial was stopped after 60 days (the paper does not say from which point this was counted); fungi added a week before planting, nematodes 10 days after planting.
- System and substrate: plastic pots of 1,500 g of sand and peat moss (1:1 by volume), sterilised with 2% formalin for 10 days.
- Climate and lighting: 30 ± 2 °C, with 13.5 hours of daylight and 10.5 hours of dark.
- Nutrition: irrigated daily and fertilised as needed with NPK 20-20-20 plus trace elements.
- Design: pot trial in a randomised complete block design with five replicates per treatment; lab tests in a completely randomised design with three replicates; ANOVA with Fisher's protected LSD.
- Results: galls per root 988 (EF1), 1,222 (TJ5) and 2,754 (control); eggs per root 26,047, 33,846 and 62,602; reproduction factor 1.24, 1.33 and 1.63; root gall index 4.6, 4.8 and 5.0 (not significant); shoot dry weight on infected plants 15.7, 12.8 and 11.9 g.
- Funding and conflicts: Ongoing Research Funding program (ORF-2026-1565), King Saud University. The authors declare no commercial or financial conflicts of interest.
- Publication: Frontiers in Plant Science 17:1979971, published 11 November 2026, https://doi.org/10.3389/fpls.2026.1979971. Licence: CC BY.
- Not reported in the paper: pot volume or dimensions, greenhouse humidity and light intensity, the fertiliser rate, and yield.
Links
- The study: Biological control potential of nematophagous fungi, Cladosporium and Plectosphaerella, against Meloidogyne javanica infecting eggplant
- The institution: College of Food and Agriculture Sciences, King Saud University
References
- El-Qurashi, M. A., Al-Yahya, F. A., & Saleh, A. A. (2026). Biological control potential of nematophagous fungi, Cladosporium and Plectosphaerella, against Meloidogyne javanica infecting eggplant. Frontiers in Plant Science, 17, 1979971. https://doi.org/10.3389/fpls.2026.1979971