Hatching and Mortality of Meloidogyne enterolobii Under the Interference of Entomopathogenic Nematodes In vitro

Abstract

Plant parasitic nematodes have become one of the main problems in the tomato cultivation. Among these, Meloidogyne enterolobii presents great challenges to the farmer, since it is a polyphagous species and difficult to control. The entomopathogenic nematodes (EPNs) present as potential for biological control of this pathogen. The objective of the study was to evaluate the interference of EPNs S. brazilense, S. feltiae, S. rarum, H. amazonensis and H. bacteriophora on hatching and mortality of M. enterolobii. 500 eggs of this nematode and 1.000 infective juveniles of each EPN species were placed in a plastic pot totaling 25 mL of suspension and kept in an incubator at 25°C. The number of juveniles hatched in the suspension was counted every 2 days, until 10 days. After 10 days of evaluations, the remaining suspension (15 mL) containing M. enterolobii and EPNs was inoculated into Rutgers tomato seedlings. The suspension contained approximately in 300 eggs of M. enterolobii occasional juveniles and 600 IJ of each nematode species. Sixty days after inoculation were evaluated gall indexes, egg mass indexes, total number of eggs and juveniles of M. enterolobii and reproductive factor was calculated. In the mortality experiment, 500 infective juveniles of M. enterolobii and 1.000 juveniles of each EPN species were placed in a plastic pot totaling 25 mL of suspension. The evaluation of juvenile mortality was performed by counting of the mobile and immotile nematodes, by adding two drops of NaOH to the nematode suspension. It was verified that on the 10th day all ENPs provided reduction in the hatching of M. enterolobii. In the pot experiment it was found thato gall index, egg mass indexm, nematodes total number and reproduction factor were significantly reduced in treatments with all species of EPNs tested. However, in the mortality test, only EPNs S. brazilense and S. rarum provided mortality on the second day and H. bacteriophora affected mortality on the 4th day. In the other evaluations, there was no statistical difference. The results highlight the potential of the use of EPNs in programs of integrated management of M. enterolobii in tomato.

Resistance induction and nematicidal activity of certain monoterpenes against tomato root-knot caused by Meloidogyne incognita

“…The hatched juveniles were counted under a stereo microscope (Commack, NY, United States) after incubation for 7 days at room temperature (25 ± 2°C). The rate of hatching inhibition was calculated, and Probit analysis was used to measure the inhibition concentration for half of eggs hatching (IC 50 ) values ( Finney, 1971 ; Damascena et al, 2019 ).…”

Direct antagonistic effect of entomopathogenic nematodes and their symbiotic bacteria on root-knot nematodes migration toward tomato roots

“…Four Philippine EPN isolates signi cantly reduced the extent of root penetration and gall development of M. incognita in tomato roots (Felicitas et al 2021). Similarly, Steinernema brazilense, Steinernema rarum, S. feltiae, Heterorhabditis amazonensis and Heterorhabditis bacteriophora were all observed to reduce galls, egg mass, egg hatching, and reproduction of M. enterolobii (Damascena et al 2019). Moreover, it has been shown that EPN-infected insect cadavers themselves are able to reduce root colonization by RKNs (Caccia.…”

“…This is the only free-living stage; the IJs persist in soil for several days or months without food (Poinar 1990). Interestingly, EPNs have been shown to have antagonistic effects on RKNs (Grewal et al 1997;Sayedain et al 2021), but these effects vary depending on the EPN species (Damascena et al 2019;Lewis and Grewal, 2005). For instance, when Steinernema feltiae EPNs were present in the rhizosphere of tomato plants, the galling and egg hatching of M. incognita RKNs was reduced by 34.12% and 62.42%, respectively (Lewis et al 2001).…”