UC Riverside

Vermicompost teas (VCT) are documented to increase plant growth and yield and reduce plant fungal and bacterial diseases and nematode infestation in the soil. However, the underlying mechanisms for these results remain obscure. Radioimmnoassay was used to identify and quantify phytohormones present in commercially prepared "growth-promoting" VCT. Isopentenyladenine (IPA) and indole-3-acetic acid (IAA) were detected in VCT, along with a low amount of abscisic acid (ABA). Comparison of effects of VCT applied at the recommended rate with IPA applied at an amount equivalent to that supplied in the VCT treatment provided evidence that IPA increased Lycopersicon esculentum vegetative biomass, whereas the VCT increased fruit number per plant and fruit size. Comparison of a commercial "nematode-suppressing" nsVCT with treatments supplying equivalent amounts of IPA and IAA present in the VCT provided evidence that the nsVCT reduced galling and increased the growth of Lycopersicon esculentum plants inoculated with 5,000 and 10,000 eggs of root knot nematode (Meloidogyne incognita). The biomass plants of plants treated with nsVCT was greater or equal to that of control plants not inoculated with nematode eggs. Fungi and bacteria in the nsVCT were identified using rRNA gene analysis. Candida sp., Torulospora Sp., Saccharomyces sp. and some parasitic forms of Cladosporium sp. were dominant. The results provide the first evidence that plant hormones are present in VCT and document the growth promoting and nematode-suppressing capacity of vermicompost teas.