In vitro and In planta Effect of Newer Synthetic Compounds against Rice Root Knot Nematode Meloidogyne graminicola in Rice Nurseries

A Laboratory experiments were carried out to evaluate the effect of newer synthetic chemicals compounds in the control of rice root knot nematode (Meloiodgyne graminicola). Ten chemicals of two series namely coumarin series (5 chemicals) and coumarin carbamate series (5 chemicals) were evaluated at different concentrations (1000ppm, 500ppm, 250ppm and 125ppm) against J2 and eggs of M. graminicola. Approximately 100 eggs and 100 juveniles were dispensed into separate tissue culture cavity block containing the dilutions of chemicals except the control which contained only Acetone distilled water mixture. In vitro experiment revealed that all the compounds resulted in nematode mortality ranging from 20-87% and inhibition of egg hatching from 10 to 78%; the higher concentrations (1000 and 500 ppm) were being most effective. In Coumarin carbamate, Series III (4, 5 dimethyl -2-oxo-2H-benzopyran-7yl-phenyl carbamate) 70 % mortality was observed even at lowest concentration of this chemical i.e. 125 ppm. The lowest mortality was observed in acetone and water mixture (control) alone (5.3%). Maximum larval mortality and inhibition of egg hatching was recorded in one of the Coumarin carbamate series III i.e., 4,5 dimethyl-2-oxo-2H-benzopyran-7yl phenyl carbamate (96.33% and 11%) respectively. Coumarin carbamate derivates proved more nematicidal than Coumarin series in both larval mortality and egg hatching experiments. Based on larval mortality and egg hatching experiments only promising synthetic chemicals with 500 ppm concentration were selected for screen house study. Chemicals were used @ 70 ml/pot as soil drenching and untreated check was also maintained. Among synthetic chemicals maximum seedling weight (10 plants) and shoot length (2.76 g and 19.10 cm) was recorded with Coumarin carbamate III (4,5 dimethyl-2- oxo-2H-benzopyran-7yl phenyl carbamate) followed by Coumarin carbamate V (2.71 g and 18.53cm) and Coumarin carbamate IV (2.35 g and 17.48 cm). The minimum number of galls per 10 plants were recorded with Coumarin carbamate III (64.25) followed by Coumarin carbamate V (64.50) and Coumarin carbamate IV (70.50). A similar trend was also recorded in nematode population per root. The results of present investigation suggest suitable chemicals for grower having nematode problem in field to incorporate it in management strategies.