Biocontrol of Orchid-pathogenic Mold,Phytophthora palmivora, by Antifungal Proteins fromPseudomonas aeruginosaRS1

Abstract

Black rot disease in orchids is caused by the water mold Phytophthora palmivora. To gain better biocontrol performance, several factors affecting growth and antifungal substance production by Pseudomonas aeruginosa RS1 were verified. These factors include type and pH of media, temperature, and time for antifungal production. The results showed that the best conditions for P. aeruginosa RS1 to produce the active compounds was cultivating the bacteria in Luria-Bertani medium at pH 7.0 for 21 h at 37 °C. The culture filtrate was subjected to stepwise ammonium sulfate precipitation. The precipitated proteins from the 40% to 80% fraction showed antifungal activity and were further purified by column chromatography. The eluted proteins from fractions 9–10 and 33–34 had the highest antifungal activity at about 75% and 82% inhibition, respectively. SDS-PAGE revealed that the 9–10 fraction contained mixed proteins with molecular weights of 54 kDa, 32 kDa, and 20 kDa, while the 33–34 fraction contained mixed proteins with molecular weights of 40 kDa, 32 kDa, and 29 kDa. Each band of the proteins was analyzed by LC/MS to identify the protein. The result from Spectrum Modeler indicated that these proteins were closed similarly to three groups of the following proteins; catalase, chitin binding protein, and protease. Morphological study under scanning electron microscopy demonstrated that the partially purified proteins from P. aeruginosa RS1 caused abnormal growth and hypha elongation in P. palmivora. The bacteria and/or these proteins may be useful for controlling black rot disease caused by P. palmivora in orchid orchards.

Bacillus velezensis CE 100 Inhibits Root Rot Diseases (Phytophthora spp.) and Promotes Growth of Japanese Cypress (Chamaecyparis obtusa Endlicher) Seedlings

“…The experiment was repeated three times with three replications per treatment. The growth inhibition of oomycete pathogens was calculated using the following formula: Inhibition (%) = [(α − β)/α] × 100, where α was the radial growth of phytopathogenic oomycete on the control plate and β was the radial growth of phytopathogenic oomycete on the dual culture plate [ 24 , 26 , 27 , 28 ].…”

“…Among the various methods, the use of plant growth-promoting rhizobacteria (PGPR) has attracted attention of many researchers. PGPR can control pathogenic oomycetes and increase plant growth [ 23 , 24 , 25 , 26 , 27 , 28 ]. Moreover, PGPR are well-known non-toxic bacteria that enhance soil fertility without causing negative effects on human health and the environment [ 28 ].…”

“…Moreover, PGPR are well-known non-toxic bacteria that enhance soil fertility without causing negative effects on human health and the environment [ 28 ]. In addition, PGPR can effectively boost plant health by limiting the growth of plant pathogens through the production of antagonistic substances, antibiotics and cell wall degrading enzymes [ 25 , 26 , 27 , 28 ]. Lytic enzymes, such as β-1,3-glucanase and protease produced by PGPR are key players in the degradation of oomycete cell walls, which are mainly composed of β-glucan and protein [ 23 , 25 , 26 , 28 , 29 ].…”

“…In addition, PGPR can effectively boost plant health by limiting the growth of plant pathogens through the production of antagonistic substances, antibiotics and cell wall degrading enzymes [ 25 , 26 , 27 , 28 ]. Lytic enzymes, such as β-1,3-glucanase and protease produced by PGPR are key players in the degradation of oomycete cell walls, which are mainly composed of β-glucan and protein [ 23 , 25 , 26 , 28 , 29 ]. On the other hand, PGPR provides plants with phytohormones, such as auxins, gibberellins and cytokinins, which regulate plant growth [ 24 , 28 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ].…”

Biocontrol and Action Mechanism of Bacillus amyloliquefaciens and Bacillus subtilis in Soybean Phytophthora Blight

“…BS1 inhibited the zoosporangium formation and zoospore germination of P. sojae , and the inhibition rate of stock solutions reaches 95.9% [13]. Sowanpreecha and Rerngsamran [14] found that the antibacterial protein from P. aeruginosa RS1 can effectively inhibit P. palmivora , and the molecular weight of the antibacterial protein is about 20 kDa to 54 kDa. According to LC/MS, these proteins may be catalase, chitin-binding protein, and protease.…”