Reação de espécies, método de inoculação e avaliação de extratos vegetais no controle de Meloidogyne enterolobii em tomateiro

Abstract

The genus Meloidogyne contemplates the species of nematodes that most commonly affect crops around the world. The species M. enterolobii has been noted for affecting and causing serious losses in the production of guava trees and several other important crops in Brazil. The objective of this work was to evaluate the susceptibility of 10 plant species to M. enterolobii parasitism, the in vitro and in vivo effect of their leaf extracts on the pathogen and to evaluate the viability of two methods of inoculation of second stage juveniles (J2) In tomato. Initially seedlings of medicinal plants, toxic and ornamental Plumbago scandens; Ricinus communis; Dieffenbachia amoena; Datura stramonium; Solenostemon scutellaroides; Spigelia anthelmia; Chenopodium ambrosioides; Azadirachta indica; Jatropha curcas; Morinda citrifolia, were inoculated with 5,000 eggs / J2 of M. enterolobii to evaluate their susceptibility to nematode infection. In the in vitro test, leaf extracts were obtained by maceration of 1g of dried leaves in 10 ml of water (10% w / v), filtered and diluted with water (1: 1). 3 ml of each extract was added in Petri dishes, placing on each 50 Âμl plate of M. enterolobii, which were incubated for 48 hours for nematode mobility and mortality in the extracts. For the in vivo assay, extracts were also used in the final concentration of 5%, however, only seven of the most promising species in vitro. The application of the extracts occurred in the following sequence: inoculation of 5,000 eggs / J2 / vase in autoclaved and moistened soil; Application of 30 ml of extract to the soil 24 hours later; Transplanting of 'Santa Clara' tomato seedlings 24 hours after the addition of the extract; Repeated application of 30 ml of extract / pot at 7 and 14 days after the first application, and the results were evaluated 45 days counted from the inoculation of the nematoid. For the last assay, 300 J2 were inoculated in 21-day-old tomato seedlings kept in glass tubes with 10 ml of distilled water or in pots containing 0.5 kg of autoclaved soil. The seedlings were evaluated at 5, 10, 15, 20, 25 and 30 days after inoculation to compare the infestation in each environment. The results showed that R. communis; D. amoena; D. stramonium; A. indicates; J. curcas; M. citrifolia were considered highly resistant, since they did not allow the multiplication of the nematoid, presenting the reproduction factor equal to zero. P. scandens, S. anthelmia and C. ambrosioides were very resistant whereas S. scutelarioides was susceptible to the nematode. In the in vitro test, the extracts of seven of the 10 species, presented mortality values of J2 above 70%, highlighting C. ambrosioides that caused 97% of death. The application of leaf extracts to the soil was efficient to reduce infestation of M. enterolobii in tomato roots. The extracts of D. amoena and P. scandens were the most effective in the reduction of nematoid infection, but they affected the growth of the tomato. As for the inoculation methods, it was observed that the number of galls, females and egg masses was always higher in the roots of plants cultivated in soil when compared to the plants kept in water.