Effects of root exuded allelochemicals of linseed on egg hatch and mortality of juveniles of root-knot nematode (Meloidogyne javanica)

The effects of different polarity of allelocompounds of linseed (Linum usitatissinum L.) root exudates were evaluated on egg hatch and mortality of second stage juveniles of Meloidogyne javanica. Root exudates of linseed plants collected via root exudates trapping system on TLC revealed the presence of five allelocompounds viz., A, B, C, D and E of different polarity. Three emulsifiable concentrates (EC) and two emulsive water (EW) formulations developed from 95% pure compounds clearly revealed the role of polarity of isolated compounds in imparting their toxicity. EC formulation of A and B was found 100% toxic to the juveniles at 300 and 700 ppm, respectively at 24 and 48 hrs of incubation. EC and EW formulations of C and D showed 100% activity at 900 and 1400 ppm, respectively at an incubation period of 72 h, while EW formulation of E was found relatively ineffective as it could not produce significant mortality in all the test concentrations (600–1600 ppm). EC of A and B, respectively at 300 and 600 ppm concentrations also retarded egg hatching of test nematode up to 95%. At higher concentration, EC developed from compound A also caused permanent damage to eggs as there was no further egg hatching, when egg masses were transferred in ordinary water.