Root Knot Nematodes (Meloidogyne Incognita) Interaction with Selected Asteraceae Plants and their Potential use for Nematode Management

The southern root knot nematode (Meloidogyne incognita) is one of the highly polyphagous species of many cultivated plants. The losses associated with RKNs in small holder vegetable farms are not quantified but may range between 30-100% in tropical and subtropics. Application of broad spectrum nematicides is the common method of control and are to be highly toxic to humans and pollute the environment, hence the need for safer alternatives for small scale crop production systems. Biological control especially the use repellent plants is an environmentally safe option. Plants from the Asteraceae family have phytotoxic for nematode management. Investigations were conducted between June 2015 and January 2016 to determine the effect of four different Asteraceae species viz. Tagetes minuta, Artemisia annua, Bidens pilosa and Chrysanthemum cinerariaefolium on the behavior of M. incognita. The responses of Juveniles to odours from intact roots of the four asteraceous plant species were investigated. In addition, identification and quantification of volatile components present the in intact roots of Asteraceae plants. was also evaluated. Dual-choice soil olfactometer assays and gas chromatography-mass spectrometry (GC-MS) analysis were conducted in the laboratory. Root volatiles of 4 asteraceous plants antagonized the behavioral responses of M.incognita juveniles (repellence) (P = 0.05). Using the GC-MS analysis 59 volatile organic compounds were identified from intact roots of the Asteraceae plants; 30 from Tagetes minuta, 32 detected in Artemisia annua, 21 from Bidens pilosa and 12 from Chrysanthemum cinerariaefolium respectively. These findings suggest that the four asteraceous plants are repellent to M. incognita. Products from these plants may thus be incorporated in an integrated nematode management program for smallholder vegetable farming systems.