Mixtures of Plant-Growth-Promoting Rhizobacteria Enhance Biological Control of Multiple Plant Diseases and Plant-Growth Promotion in the Presence of Pathogens

Abstract

Several studies have shown that mixtures of plant-growth-promoting rhizobacteria (PGPR) could enhance biological control activity for multiple plant diseases through the mechanisms of induced systemic resistance or antagonism. Prior experiments showed that four individual PGPR strains—AP69 (Bacillus altitudinis), AP197 (B. velezensis), AP199 (B. velezensis), and AP298 (B. velezensis)—had broad-spectrum biocontrol activity via antagonism in growth chambers against two foliar bacterial pathogens (Xanthomonas axonopodis pv. vesicatoria and Pseudomonas syringae pv. tomato) and one of two tested soilborne fungal pathogens (Rhizoctonia solani and Pythium ultimum). Based on these findings, the overall hypothesis of this study was that a mixture of two individual PGPR strains would exhibit better overall biocontrol and plant-growth promotion than the individual PGPR strains. Two separate greenhouse experiments were conducted. In each experiment, two individual PGPR strains and their mixtures were tested for biological control of three different diseases and for plant-growth promotion in the presence of the pathogens. The results demonstrated that the two individual PGPR strains and their mixtures exhibited both biological control of multiple plant diseases and plant-growth promotion. Overall, the levels of disease suppression and growth promotion were greater with mixtures than with individual PGPR strains.

Aspergillus terreus Inhibits Growth and Induces Morphological Abnormalities in Pythium aphanidermatum and Suppresses Pythium-Induced Damping-Off of Cucumber

“…Various studies were carried out to characterize the biocontrol efficacy against P. aphanidermatum damping-off by multiple microorganisms such as Trichoderma harzianum (Sivan et al, 1984), Pseudomonas chlororaphis , and Bacillus subtilis (Nakkeeran et al, 2006) and endophytic actinomycetes (El-Tarabily et al, 2009). Some studies used several biocontrol species, which led to greater disease suppression (Szczech and Shoda, 2004; Liu et al, 2017). Other studies used seed treatment with biocontrol agents which proved its effectiveness in damping-off control (Lifshitz et al, 1986; Callan et al, 1990).…”

Combination of biocontrol bacteria for rice seeds microbiolization: incidence and transmission of Bipolaris oryzae, and plant growth

“…The use of biocontrol combinations, as studied here, is justified by the premise that compatible combinations may intensify the biocontrol effect and/or broaden the spectrum of controlled pathogens, in addition to offering stability in terms of effect under different adverse conditions in the field (Liu et al, 2018). In fact, several studies report such behavior, including for the combination of Pseudomonas and Bacillus isolates (such as the DFs-C4 combination), as Journal of Seed Science, v.40, n.4, p. [378][379][380][381][382][383][384][385][386][387]2018 well as the treatment of Setaria italica seeds with a quadruple mix to control blast (P. grisea) in the field (Karthikeyan and Gnanamanickam, 2008) and Brassica campestris seeds with a double combination to control Xanthomonas campestris pv.…”

Biological control in the germination of seeds from two species native of the Cerrado region

“…The use of specific microorganisms for the biological control of phytopathogens has proven to be efficient against certain fungi and bacteria owing to the production of antimicrobial substances (Rocha et al, 2009;Yuan et al, 2017;Saito et al, 2018;Liu et al, 2018), which leads to an alternative to the chemical control of diseases. These biological control agents can act directly and indirectly by inducing the plant's defense mechanisms in the control of fungal diseases (Benítez et al, 2004).…”