You Don't Have to Go Home but You Carrot Stay Here: Biological Control of the Root-Knot Nematode Meloidgyne Incognita in Carrots.

Root-knot nematodes cause tens of billions of dollars in damages to agricultural production annually. The enormous economic losses brought about by nematodes, combined with the downsides to current methods for handling them, have led to an increased focus in understanding natural plant defense mechanisms and finding alternative methods to lessen the damage done by root-knot nematodes. Endophyte biocontrol agents such as Trichoderma harzianum have shown promise in reducing nematode damage. Recent studies have demonstrated that soil management practices and plant genotype can influence endophyte community structure, but it is unclear whether such differences influence susceptibility to nematode damage. This study sought to better understand these dynamics by quantifying how differences in endophyte community structure influence nematode (Meloidgyne incognita) infection and plant performance in three carrot varieties that are susceptible, moderately resistant, and highly resistant to nematodes. The treatments were 1) unamended control, 2) Trichoderma spp., 3) microbes from an organically farmed field, 4) microbes from a conventionally farmed field, all applied at seeding, and 5) Trichoderma spp. applied after nematode infection. Carrot biomass and the level of nematode infection were affected by both treatment and genotype. Heavier tap roots were found to correspond with higher levels of infection in two of the three genotypes. Carrots inoculated with Trichoderma spp. after nematode infections had significantly greater tap root weights and lower galling compared to the control. Carrots treated at planting with Trichoderma spp. had significantly lower tap root weights and increased galling than most of the other treatments but also had significantly lower seedling mortality than the other treatments. Results of this study indicate that endophytic microbes can affect carrot susceptibility to nematode infection, and further research is warranted.