Semina: Ciências Agrárias (Nov 2018)
Reaction of plant species to Meloidogyne enterolobii and the efficiency of their aqueous extracts in controlling the pathogen
Abstract
The genus Meloidogyne includes species of the most common nematodes to affect crops around the world. The species M. enterolobii is notable for affecting and causing serious losses in the production of guava trees and various other economically important crops in Brazil. The aim of this study was to evaluate the susceptibility of 10 plant species to parasitism by M. enterolobii, and the in vitro and in vivo effects of their leaf extracts on the pathogen. Initially seedlings of Solenostemon scutellarioides, Dieffenbachia amoena, Spigelia anthelmia, Plumbago scandens, Ricinus communis, Chenopodium ambrosioides, Azadirachta indica, Morinda citrifolia, Jatropha curcas and Datura stramonium were inoculated with 5,000 eggs of M. enterolobii to evaluate their susceptibility to nematode infection. For the test in vitro, a 5% concentration of the leaf extracts were added to Petri dishes, and 50 J2 of M. enterolobii were placed in each dish. After 48 hours incubation, the juveniles were evaluated for motility and mortality in the extracts. For the test in vivo, leaf extracts were used at the same concentration, however with only the seven most-promising in vitro species. This assay included the following sequence: inoculation of 5,000 eggs in autoclaved and moist soil contained in 1L pots; application of 30 ml of extract to the soil after 24 hours; transplanting of ‘Santa Clara’ tomato seedlings the following day; and reapplying the extract after 7 and 14 days. The results were evaluated 45 days after nematode inoculation. It was seen that the species D. amoena, R. communis, A. indica, M. citrifolia, J. curcas and D. stramonium displayed highly resistant behaviour; S. anthelmia, P. scandens and C. ambrosioides were very resistant, whereas S. scutelarioides was susceptible to the nematode. With the in vitro test, extracts from seven of the 10 species caused 70.4% to 97.4% J2 mortality. Applying the best leaf extracts to the soil was efficient in reducing M. enterolobii infestation in roots of the tomato.
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