Control potential of Meloidogyne javanica and Ditylenchus spp. using fluorescent Pseudomonas and Bacillus spp

ABSTRACT Plant Growth Promoting Rhizobacteria (PGPR) have different mechanisms of action in the development of plants, such as growth promotion, production of phytohormones and antibiotic substances and changes in root exudates. These help to control plant diseases. In order to evaluate the potential of microorganisms in the control of Meloidogyne javanica and Ditylenchus spp., five rhizobacteria isolated from rhizosphere of garlic cultivated in the Curitibanos (SC) region were tested. Hatching chambers were set on Petri dishes, in which were added 10 mL of bacterial suspension and 1 mL of M. javanica eggs suspension, at the rate of 4500, on the filter paper of each chamber. The same procedure was performed with 300 juvenile Ditylenchus spp. The experimental design was completely randomized, with four replications. The evaluations were performed every 72 h for nine days. The antagonized population of nematodes was determined in Peters counting chamber, determining the percentage hatching (for M. javanica) and motility (for Ditylenchus spp). Isolates CBSAL02 and CBSAL05 significantly reduced the hatching of M. javanica eggs (74% and 54.77%, respectively) and the motility of Ditylenchus spp. (55.19% and 53.53%, respectively) in vitro. Isolates were identified as belonging to the genera Pseudomonas (CBSAL05) and Bacillus (CBSAL02).

Fluorescent Pseudomonads associated with the rhizosphere of crops: an overview

Environmental concerns have led to the need of sustainable use of natural resources. The conventional agriculture caused considerable impacts on soils and waters. It is important to change certain agricultural managements to environmental cleaner techniques. The sustainable agriculture has pointed many approaches and techniques to reduce environmental impact. One of those strategies is the utilization of the soil microbiota to induce plant growth, control of plant diseases and biodegradation of xenobiotic compounds. Studies on the relationship between roots and microbiota are essential to achieve viable agricultural applications. These studies indicate that one of the most abundant microorganisms in the rhizosphere (area around the roots) is fluorescent Pseudomonas spp. They have been considered as an alternative to agrochemicals for controlling plant diseases and increasing plant development. This review addresses the main findings on fluorescent Pseudomonads. It summarizes and discusses significant aspects of this general topic, including (i) rhizosphere as a microhabitat; (ii) taxonomic, genetic and ecological aspects of fluorescent Pseudomonads in the rhizosphere; (iii) mechanisms of Plant Growth Promoting and Biological Control and (iv) commercial use of PGPR in agriculture.

As preocupações com o meio ambiente têm levado à necessidade do uso sustentável dos recursos naturais. A agricultura convencional tem causado impactos consideráveis no solo e nas águas. É importante mudar certas técnicas agrícolas por outras consideradas mais limpas para o meio ambiente. Uma estratégia é a utilização da microbiota do solo para induzir o crescimento de plantas, controlar fitomoléstias e para fazer a biodegradação de compostos xenobióticos. Estudos sobre a relação entre as raízes e a microbiota são essenciais para conseguir aplicações viáveis na agricultura. Estes estudos têm indicado que um dos mais abundantes microrganismos na rizosfera (região ao redor da raiz) é Pseudomonas spp. do grupo fluorescente. Estes têm sido considerados como alternativa tanto aos agrotóxicos no controle de doença de plantas como na indução do seu desenvolvimento. Esta revisão mostra os principais conhecimentos sobre Pseudomonas spp. do grupo fluorescente. Esta resume e discute aspectos significantes deste tópico, incluindo, (i) rizosfera como microhabitat; (ii) aspectos taxonômicos, genéticos e ecológicos de Pseudomonas spp. do grupo das fluorescentes na rizosfera; (iii) mecanismos de Promoção de Crescimento de Plantas e Controle Biológico e (iv) uso comercial de PGPR na agricultura.