Many plants are at risk from hungry animals. With tomato plants a significant risk arises from nematodes, especially worms of the species Meloidogyne incognita. It is commonly called the “southern root-knot nematode” or the “cotton root-knot nematode.” Problems arise through the worms inducing the formation of galls (a kind of swelling growth on the external tissues of plants). The worms then inhabit these spaces and feast on the plant tissue, eventually killing the plant.
Tomato plants attempt a defense by secreting toxic chemicals which can either kill the worms or act as a form of deterrent. The production of the chemicals is regulated by hormones such as salicylic or jasmonic acid. This is not always effective.
Researching how some tomato plants are more robust than others, researchers have focused on a fungus called Trichoderma. This fungus is found inside the tissue of tomato plants. When present, the fungus aids the tomato plant in combating the parasitic worms.
In a research note, Dr. Ainhoa Martinez-Medina, from the German Center for Integrative Biodiversity Research (iDiv), explains how “the fungus boosts plant immunity by enhancing the production of toxic chemical compounds upon nematode attack.”
Dr. Martinez-Medina adds further: “this limits the invasion of the roots by nematodes, reduces the nematodes’ fecundity and compromises the formation of root galls.”
The relationship between the fungus, tomato plant and parasites was investigated under laboratory conditions. For this, tomato plants were divided into two groups. Half of the roots of their test plants were grown in one pot, and the other half in another pot.
Next, different combinations of infestation with nematodes and association with fungi were tested out. The experimental data revealed that the Trichoderma fungus functioned to prime the plant and this allowed the plant to defend itself faster against nematodes. Based on this research it may be possible to immunize a tomato plant against the worms by using the fungus.
The research has been published in the journal New Phytologist. The research paper is headed “Shifting from priming of salicylic acid- to jasmonic acid-regulated defences by Trichoderma protects tomato against the root knot nematode Meloidogyne incognita.”
