Combined use of plant extracts and arbuscular mycorrhizal fungi to reduce root-knot nematode damage in tomato

The effects of mycorrhization by Funneliformis mosseae alone and combined with soil applications of plant extracts from garlic, neem, quassia, and thyme on the damage caused by Meloidogyne incognita in tomato were studied in pot experiments under greenhouse conditions. The nematode reduced shoot fresh weight of tomato by 15% compared with that of nematode-free plants. Nutrient and water stress in M. incognita-infested tomato were detected by measuring the leaf chlorophyll content and canopy temperature, as early as 21days after nematode inoculation. Mycorrhization by F. mosseae offset the damage caused by the nematode with a general positive effect on plant growth, representing a 17% increase over non-mycorrhized plants. Nematode densities were reduced by garlic, neem, and thyme extracts. Several interactions between treatments proved positive or negative for tomato plant growth, mycorrhization, and nematode reproduction. The most favourable treatment for nematode suppression was a combination of mycorrhization by F. mosseae and application of garlic extract, which increased plant growth by 52%, reduced root galling by 50% and lowered the final nematode population by 51%, when compared to nematode-infested non-treated plants. Neem and thyme extracts showed a negative interaction with F. mosseae, reducing mycorrhization frequency.