Nematotoxic potential of daikon, chinaberry and purslane herbal green manures against Globodera rostochiensis in vitro and microplot

The nematotoxic potential of water extracts and green manures prepared from three plant species, daikon Raphanus sativus var. longipinnatus L., purslane Portulaca oleracea L. and chinaberry Melia azedarach L., on Globodera rostochiensis was examined in vitro and in microplots. Significant alteration in J2 (second stage juvenile) activity and their hatching from eggs was observed with different exposure times by all plant species; more than 99% of the J2s were inactivated after 72h and the same degree of inhibition in hatching of the eggs occurred after exposure to the plant extracts. In microplots, the numbers of newly formed cysts and final nematode multiplication rates were reduced in unsterilized soil at 1, 3 and 5% (w:w) rates of amendment with fresh plant materials, and the infestation rates of potato plants did not differ significantly from those in soil treated with metham sodium 37%. The rate of emergence of J2 from cyst inocula declined by 36% in soil treated with chinaberry and purslane and by 71% in soil treated with daikon. The reduced availability of J2 in soil must be one of the reasons for decrease in nematode multiplication rates of 65% and 86% where soil was amended with chinaberry/purslane and daikon, respectively. In terms of plant growth improvement and nematode control, daikon amendment outperformed other treatments, including metham sodium.