Isolation of root exuded allelochemicals of marigold (Tagetes erecta) and their effect on the mortality and egg hatching of root knot nematode (Meloidogyne javanica)

Root exudates of marigold (Tagetes erecta), collected from intact live plants via root exudate trapping system after proper fractionation gave five different allelofractions viz., C, B, A, E and D of different polarity (non-polar to polar). Three Emulsifiable Concentrate (EC) and two Emulsive Water (EW) formulations developed from 90% pure fractions clearly revealed the role of polarity of isolated fractions in imparting their toxicity against second stage juveniles (J2) of Meloidogyne javanica. EC formulations of fractions A and B (non-polar) was found 100% toxic to the juveniles at 200 mg ml−1 of concentrations after an incubation period of 24 h. EC and EW formulations of the fractions C and D (medium polarity) showed approximately 70 and 80% juvenile mortality respectively at 700 and 1200 mg ml−1 concentrations, at an incubation period of 72 h, while EW formulation of fraction D (polar) found least effective against juveniles in all its test concentrations (8001200 mg ml−1). EC formulations of A and B at their higher concentrations of 150 & 200 μg ml−1, were not only found extremely effective in retarding egg hatch of the test nematode up to an extent of more than 98% but also caused permanent damage to the exposed eggs.