Pseudomonas Strains that Exert Biocontrol of Plant Pathogens

Abstract

An increasing number of strains of Pseudomonas spp. are being studied for the known benefits they provide to plants. Many of them are natural inhabitants of plant roots and the soil area influenced by them: the rhizosphere. Some are even capable to colonize the root interior and, occasionally, to spread to above-ground organs establishing themselves as beneficial endophytes. The artificial introduction of these strains into target agro-ecosystems can lead to enhanced growth and improved fitness of host plants. These positive effects are usually a consequence of the capacity of bacteria to suppress the attacks by phytopathogenic microorganisms, a phenomenon known as biological control activity. In this chapter, the main modes of action that biocontrol Pseudomonas strains can deploy against plant pathogens are reviewed: antibiosis, competition for nutrients and niches, induction of defense responses, etc. How these bacteria are able to colonize plant and pathogen structures, as prerequisite for effective disease suppression, will be also discussed. A concise section devoted to the complex regulatory networks controlling biological control traits is included as well. Finally, the potential that biocontrol pseudomonads pose as marketable products is briefly presented. The underlying idea is that a much better understanding of the complex, multitrophic interactions taking place among the plant, the pathogen(s), the biocontrol pseudomonads and the environment is instrumental for commercial exploitation, aiming to overcome the frequently-observed problem of biocontrol performance inconsistency. The powerful '-omics' and microscopy approaches currently available are providing fundamental information to acquire such knowledge. The use of biocontrol agents as a complementary measure within integrated disease management strategies should have a promising future in modern sustainable agriculture.

When Genome-Based Approach Meets the “Old but Good”: Revealing Genes Involved in the Antibacterial Activity of Pseudomonas sp. P482 against Soft Rot Pathogens

“…Representatives of the genus include pathogens affecting humans and animals ( Pseudomonas aeruginosa ; Sadikot et al, 2005 ), insects ( Pseudomonas entomophila ; Vodovar et al, 2005 ) and plants (mainly Pseudomonas syringae ; Young, 2010 ; Baltrus et al, 2011 ). However, most pseudomonads are harmless commensals, some of which show plant-beneficial or biodegradation properties valuable for biotechnological applications (Adesemoye and Kloepper, 2009 ; Mercado-Blanco, 2015 ; Novik et al, 2015 ). Pseudomonas spp.…”

“…produce a diverse array of biologically active metabolites, including antibiotics, bacteriocins, biosurfactants, toxins, volatiles, and iron-scavenging siderophores (Gross and Loper, 2009 ; Silby et al, 2011 ; Schulz-Bohm et al, 2015 ). Many of these metabolites increase the competitive potential of Pseudomonas spp., either by facilitating the colonization of a given niche and nutrient uptake, or through direct influence on the coexisting (micro)organisms (Pliego et al, 2011 ; Mercado-Blanco, 2015 ). This competitive edge is of particular importance in environments such as soil and the rhizosphere, where local “hot spots” of microbial activity are formed due to limited and uneven distribution of nutrients.…”

“…In the light of limited measures available to protect plants from soft rot (Czajkowski et al, 2011 ), as well the long history of Pseudomonas spp. strains as effective biological control agents against fungal diseases in agriculture and horticulture (Mercado-Blanco, 2015 ), the discovery of P482 with its novel antibacterial activity is potentially significant. Currently, the only chemically defined Pseudomonas -derived compound with antibacterial activity against soft rot bacteria is 2,4-diacetylphloroglucinol (2,4-DAPG).…”

Plant-Microbe Interactions: A Molecular Approach

“…Moreover, its genome can be easily manipulated. Pseudomonas is competitive with a number of nutritional sources and can easily thieve in new nutritional and environmental conditions (Mercado-Blanco 2015 ). In nature, pseudomonads have been found to carry a strictly regulated antibiosis controlling system.…”

Desenvolvimento de pacote biotecnológico para tratamento de sementes de soja.

“…Por outro lado, diversos microrganismos possuem mecanismos de biocontrole que protegem as plantas contra patógenos e doenças (PRATT; CENTER, 2012). Os agentes de biocontrole podem atuar por meio de vários mecanismos, como: produção de sideróforos, antibióticos e bacteriocinas, competição por substrato, parasitismo, indução de resistência e proteção cruzada (BERG, 2015;MERCADO-BLANCO, 2015;WHITTLE et al, 2015).…”