Biological Products Precondition Field Soil and Induce Changes in Bacterial Communities to Reduce Root‐Knot Nematode Symptoms in Tomato Crops

Abstract

Root‐knot nematodes ( Meloidogyne spp., RKNs) cause significant yield losses in tomato crops and current chemical control methods have limitations. For example, the use of nematicides have associated safety concerns for both environmental and human health. Some biological products are promising sustainable alternatives to chemicals. The present study investigated whether field application of selected biological products could precondition the soil, altering bacterial communities, which in turn could reduce Meloidogyne javanica infestation of tomatoes in the greenhouse. Soil was collected from a tomato field site where commercially available biological products, Popul8 (microbial), Eco‐Humate (organic acid) and Eco‐Vital (fish + seaweed), were applied throughout the growing season. Tomato cv. Moneymaker seedlings were transplanted into free‐draining plastic pots filled with 80:20 (v:v) field soil:river sand and inoculated with viable M. javanica eggs (~10,000/pot). At 11 weeks post‐inoculation, the roots were washed free of soil and scored for RKN‐induced galling and egg counts. Rhizosphere soil and root samples were then sequenced to identify bacterial communities. Tomato plants grown in preconditioned field soil had significant reductions in RKN galling (31.8% [microbial], 26.3% [fish + seaweed] and 25.4% [organic acid]) compared to untreated control soil. Amplicon sequencing of the 16S rRNA gene showed significant differences in bacterial community composition between the plants grown in preconditioned soil and the controls. These findings suggest that the biological products created a potential legacy effect that contributed to RKN suppression and highlight the potential of the products for integrated management of RKNs, and the need for further investigation in replicated field trials.