Genes involved in nutrient competition by Pseudomonas putida JBC17 to suppress green mold in postharvest satsuma mandarin

Abstract

Understanding the mechanisms underlying biocontrol activity in biocontrol agents is indispensable to implement biological control. However, the understanding of specific mechanisms for nutrient competition in nutrient limited environments is still limited. This study was performed to control green mold of postharvest satsuma mandarin (mandarin) using Pseudomonas putida JBC17 (JBC17), and identify the genes involved in nutrient competition. Treatment with JBC17 on wounded mandarin fruits at a concentration of 10(6) and 10(7) cfu ml(-1) suppressed the incidence of green mold with efficacy of 74.1 and 91.4%, respectively, compared to the untreated control. In spite of there being no antifungal activity in a dual culture test, JBC17 significantly inhibited the conidial germination of Penicillium digitatum. The results from the nutrient competition assay revealed that the inhibition of conidial germination was exerted by nutrient starvation. From the constructed transposon (Tn) library of JBC17, exopolyphosphatase (ppx) and Xaa-Pro aminopeptidase (pepP) were recognized as potential factors responsible for the inhibition of conidial germination. In conclusion, the understanding of nutrient depletion specific to the inhibition of conidial germination by JBC17 may ultimately lead to a deeper understanding of the bacterial metabolism and conidial metabolism for germination as well as biocontrol activity.

Biocontrol of Postharvest Fruit Fungal Diseases by Bacterial Antagonists: A Review

“…Phytopathogen inhibition can be greater if the cellular dose of the antagonist increases; thus, there is a need to perform studies on the application of different bacterial doses on the host to determine the minimum concentration required to inhibit the phytopathogen [34]. Yu and Lee [35] demonstrated that the bacteria Pseudomonas putida inhibited spore germination of Penicillium digitatum due to nutrient availability of the host. Other bacteria have inhibited different Agronomy 2019, 9, 121 4 of 15 phytopathogen fungi by carbon sources, such as Pseudomonas syringae, Pantoea agglomerans [24], Pseudomonas fluorescens [30] and Bacillus megaterium [16].…”

In vitro study of biocontrol potential of rhizospheric Pseudomonas aeruginosa against Fusarium oxysporum f. sp. cucumerinum

“…include phenazines (Hu et al 2014), 2,4-diacetylphoroglucinol (Zhang et al 2016), pyoluteorin (Wu et al 2011), pyrrolnitrin (Zhang et al 2016), cyclic lipopeptides (Michelsen et al 2015), siderophores (Sulochana et al 2014), volatile compounds (Mannaa et al 2017), hydrolytic enzymes (Solanki et al 2014), and so on. Fluorescent pseudomonads, for example, Pseudomonas aeruginosa (Fatima and Anjum 2017), Pseudomonas putida (Yu and Lee 2015), and Pseudomonas fluorescens (Zhang et al 2016), are well-known to protect plants from fungal infections.…”

High-throughput identification of genes influencing the competitive ability to obtain nutrients and performance of biocontrol in Pseudomonas putida JBC17

“…In our previous studies, Pantoea agglomerans 59–4 and Pseudomonas putida JBC17 (JBC17WT) suppressed postharvest blue mold and green mold diseases of Citrus unshiu (Satsuma mandarin) by nutrient competition 16 , 17 . A complex and large mutant library with a high insertion frequency aids in precisely identifying regions of interest 18 .…”

“…A complex and large mutant library with a high insertion frequency aids in precisely identifying regions of interest 18 . Hence, we analyzed 2,804 Tn mutants of JBC17WT and identified genes, including exopolyphosphatase ( ppx ) and Xaa-Pro aminopeptidase ( pepP ), which are involved in nutrient competition 17 . Our previous results strongly suggested the role of nutrient competition in the biocontrol ability of JBC17WT.…”