The effect of 1-Octen-3-ol and 3-Octanone on plant parasitic nematodes

The nematicidal effect of two volatile organic compounds (1-Octen-3-ol and 3-Octanone) was assessed under in vitro conditions against Meloidogyne incognita, Pratylenchus thornei and Xiphinema index. The assays were carried out in Petri dishes with 3.8% water agar. Each Petri was divided into 6 circles which served as nematode sampling zones. Each circle was inoculated with 20 ml of a water nematode suspension. The number of the juveniles was variable according to the tested nematode. A 22 x 22 mm glass slide holding a round piece of filter paper was placed in the center of the Petri dish lid. Different amounts (2.5, 5, 10 and 20 mL) of each VOC were deposited onto the filter paper. Petri dishes were closed and sealed with parafilm. Five replications were considered for each combination concentration x exposure time. Only one control (0 concentration and 5 replications) was used for both VOCs and for each nematode species. Survival and mortality of the nematodes was assessed after 45 min, 90 min, 3, 6, 12 and 24 h. The percentage mortality was corrected by eliminating the natural death in the control according to the Schneider Orelli's formula. Probit analysis was used to calculate lethal doses (LD50) for each exposure time (from 45 min to 24 h). For the root-knot nematode M. incognita, LD50 ranged from 10.1 to 0.2 mL and from 8.5 to 0.6 mL for 1-Octen-3-ol and 3-Octanone, respectively. P. thornei was less susceptible to the VOCs in comparison to M. incognita showing values of LD50 ranging from 50.8 to 0.01 mL for 1-Octen-3-ol and from 389 to 1 mL for 3-Octanone. The dagger nematode X. index showed a LD50 from 12.1 to 0.5 mL and from 2.1 to 0.2 mL for 1-Octen-3-ol and 3-Octanone, respectively. Therefore, 1-Octen-3-ol resulted more effective than 3-Octanone in the control of M. incognita and P. thornei. By contrast, 3-Octanone was more effective against X. index