Effect of Sorghum Allelochemicals on the Mortality and Egg Hatching of Root-Knot Nematode, Meloidogyne javanica

Abstract

Root exudates of sorghum plants collected via root exudates trapping system after proper fractionation, give rise a total of five allelofractions of different polarity range i.e., polar to non-polar. The fractions were found to enrich about one major compound in each which was extracted out in purity of 95% by repeatedly following the fractional crystallization and column chromatographic techniques. All these five compounds viz., C, B, A, E and D were converted to three Emulsifiable Concentrate (EC) and two Emulsive Water (EW) formulations. Laboratory bioassay experiments conducted during 2009 and 2010 at IIPR, Kanpur revealed that the Polarity of the compounds used in formulations play key role in imparting  toxicity against second stage juveniles (J2) of Meloidogyne javanica.  EC formulation of fractions C and B (non-polar) was found 100% toxic to the juveniles at 300 and 700 µg ml-1 concentrations, respectively at the 24 and 48 hours of incubation. EC and EW formulations of the fractions A and E (medium polarity) showed 100% toxicity at 1100 and 1500 µg ml-1 concentrations respectively, at an incubation period of 72 h, while EW formulation of fraction D (completely polar) found  almost ineffective in all its test concentrations ranging from 1000-2000 µg ml-1. EC of C (highly non-polar)  at 250 µg ml-1 also retarded  in egg hatching of test nematode up to the extent of 98%. IR, 1HNMR, 13CNMR of C and B showed flavanol skeleton as a basic chemical moiety in their chemical structures, however, both differ structurally in respect of their functional substituents and the position of attachment at flavanol skeleton