Search

Biological control is an environmentally safe alternative in the management of nematodes. The selection of new biocontrol agents has focused on the potential of Bacillus species in in vitro and in vivo studies. In this study, twenty-three local Bacillus isolates were characterised and evaluated for metabolisable carbon source, secondary metabolite production and nematicidal action. The in vitro antagonism studies were evaluated after direct confrontation between infecting juveniles of M. enterolobii and bacterial isolates. In a greenhouse, nematicidal activity was evaluated 51 days after nematode inoculation in melon plants previously inoculated with the bacteria and cultivated in pots. The numbers of egg masses, galls, J2 and eggs in the root, J2 in the soil, the reproduction factor and the biomass yield of the plants were evaluated. From the results obtained in the laboratory experiments, it was observed that five carbon sources (D-glucose, N-acetyl-glucosamine, D-maltose, malic acid and trisodium citrate) were common to all isolates, with variation in the production of secondary metabolites. The sum of nematostatic and nematicidal effects was above 90%. In the pot experiment, a significant reduction in the number of galls was observed with the treatments LCB 03, LCB 40, LCB 45, LCB 47, LCB 51, LCB 56 and LCB 5(3) and there was no increase in plant biomass. Root protection may be associated with effective colonisation through biofilm formation and the action of metabolites with nematicide and disorientation action. However, it is necessary to carry out further studies. Made available in DSpace on 2022-05-11T11:13:33Z (GMT). No. of bitstreams: 1 Melao-Fungo-para-controle-biologico-2022.pdf: 5957977 bytes, checksum: 3573acb8639845fa39fede25201f01fb (MD5) Previous issue date: 2022

Root-knot nematodes (RKNs) (Meloidogyne spp.) are well known disease problem causing major losses in vegetable crops. Although, chemical nematicides have been used as one of the primary means for controlling RKNs, reliance on these nematicides is associated with heavy costs and negative effects on human health and environment. In this research, the suppressing potential of 6 Iranian commercial fertilizers on RKNs was investigated in laboratory and greenhouse conditions as an alternative to reduce the use of chemical nematicides. For this purpose, M. javanica inoculum was thoroughly mixed with autoclaved sandy loam soil. Then, 6 fertilizers (biofertilizer, phosphate chemical fertilizer (phosphate), potassium chemical fertilizer (potassium), peat moss, vermicompost, and leaf mold) were added individually to the inoculated soil, according to the defined treatments. The nematicide Cadusafos was used as a positive control. A negative control was also included in the experiment (including no fertilizer and no nematicide). Four-leaf seedlings of the tomato (Super Chief cv.) were transferred to the pots filled using 2 kg of the treated soil. After 60 days, reproduction factor (RF), egg mass, and root galling of the nematode were recorded. The results showed that, fertilizer-treated soils had significantly (P≤0.05) lower root galling, egg mass, and RF compared to the negative control. After the nematicide treatment, the highest suppression capability on the RKN was obtained in treatments of phosphate, biofertilizer, potassium, vermicompost, peat moss, and leaf mold, respectively. It can be concluded that, replacing chemical nematicides with fertilizers may be considered as a successful nematode management in tomato fields. Resumo Nematoides-das-galhas das raízes (RKNs) Meloidogyne spp. causam perdas consideráveis na produção de hortaliças em todo o mundo. Embora o uso de nematicidas químicos seja um dos principais meios de controle de RKNs, a dependência nesses nematicidas está associada aos altos custos e impactos negativos à saúde humana e ao meio ambiente. No presente estudo, foi investigado o potencial de supressão de seis fertilizantes comerciais iranianos em RKNs em condições de laboratório e estufa, a fim de reduzir o uso de nematicidas químicos. Para este propósito, o inóculo de M. javanica foi totalmente misturado com o solo franco-arenoso autoclavado. Em seguida, os fertilizantes (biofertilizante, fertilizante químico de fosfato (fosfato), fertilizante químico de potássico (potássio), musgo de turfa, vermicompostagem e bolor) foram adicionados e misturados individualmente ao solo inoculado, de acordo com os tratamentos definidos. O nematicida Cadusafós foi utilizado como controle positivo. Um controle negativo também foi considerado (sem fertilizante e sem nematicida). Mudas de quatro folhas do tomate (Super Chief cv.) foram transferidas para vasos cheios de 2 kg de solo tratado. Após 60 dias, o fator de reprodução (FR), a massa de ovos e o número de galhas foram registrados. Os resultados mostraram que os tratamentos com fertilizantes apresentaram significativamente (P≤0,05) menor número de galhas nas raízes, massa de ovos e FR, em comparação com o controle negativo. Depois do controle positivo, a maior capacidade de supressão de M. javanica foi obtida nos tratamentos com fosfato, biofertilizante, potássio, vermicompostagem, turfa e bolor, respectivamente. Conclui-se que a substituição de nematicidas químicos por fertilizantes pode ser uma estratégia aceitável para se alcançar uma gestão bem-sucedida de nematoides em campos de tomate.