Quantitative relationships of Pseudomonas chlororaphis 63-28 to Pythium root rot and growth in hydroponic peppers

Abstract

The ability of Pseudomonas chlororaphis 63-28 to suppress Pythium root rot (Pythium aphanidermatum) and promote plant growth was investigated in hydroponic peppers that were predisposed or not predisposed to the disease. The biocontrol agent was introduced into the nutrient solution 10 days before the roots were inoculated with the pathogen. The root zone was maintained at 23ºC except when roots were exposed to 33ºC for three days before inoculation to induce predisposition to root rot. At constant 23ºC (no predisposition) application of P. chlororaphis at 10 7 CFU mL -1 nutrient solution delayed root browning more effectively than did higher or lower densities. In predisposed plants, densities of 10 6 , 10 7 and 10 8 CFU mL -1 were equally superior. When applied at 10 7 CFU mL -1 , the density of P. chlororaphis on roots of the two temperature regimes ranged from log 10 5.88 to 6.45 CFU g -1 fresh roots at seven to 19 days after application. The agent delayed root browning, re-mediated predisposition to root rot, and increased growth of inoculated and noninoculated plants. Leaf expansion was a sensitive marker of root rot and remediation by P. chlororaphis. We conclude that P. chlororaphis 63-28 has substantial potential for managing the disease regardless of predisposition. Key words: Capsicum annuum, Pythium aphanidermatum, disease predisposition, biological control, leaf expansion. RESUMO Relações quantitativas de Pseudomonas chlororaphis 63-28 com a podridão radicular causada por Pythium e ao crescimento de pimentão hidropônicoA supressão da podridão de raiz (Pythium aphanidermatum) e a promoção de crescimento de pimentão hidropônico por Pseudomonas chlororaphis 63-28 foram avaliadas em plantas predispostas ou não ao patógeno. O bioagente foi introduzido na solução nutritiva 10 dias antes das raízes serem inoculadas com o patógeno. A zona radicular foi mantida a 23ºC, exceto nos três dias antes da inoculação quando as plantas foram expostas a 33ºC. Na temperatura de 23ºC (sem predisposição), P. chlororaphis na concentração de 10 7 UFC mL -1 , aplicada na solução nutritiva, atrasou o aparecimento dos sintomas da doença. As concentrações de 10 6 , 10 7 e 10 8 UFC mL -1 do bioagente foram mais eficientes em controlar a doença nas plantas inoculadas com o patógeno. A densidade do bioagente nas raízes, nos dois regimes de temperatura, variou de 5,88 a 6,45 log da UFC g -1 de raiz fresca, do sétimo ao 19º dia após a aplicação de 10 7 UFC mL -1 Nas plantas inoculadas ou não, o bioagente atrasou o aparecimento do escurecimento radicular, remediou a predisposição a doença e incrementou o desenvolvimento das plantas. A expansão foliar foi um indicador adequado para a podridão de raiz e a remediação com P. chlororaphis. Conclui-se que P. chlororaphis 63-28 tem potencial para o manejo da podridão da raiz em sistemas hidropônicos, independentemente da predisposição. Palavras-chave: Capsicum annuum, Pythium aphanidermatum, controle biológico, expansão foliar, predisposição a doença.

Aquaponics Food Production Systems

“…In soilless culture, several antagonistic microorganisms can be picked due to their biological cycle being similar to root pathogens or their ability to grow in aqueous conditions. Such is the case of nonpathogenic Pythium and Fusarium species and bacteria, where Pseudomonas, Bacillus and Lysobacter are the genera most represented in the literature (Paulitz and Bélanger 2001;Khan et al 2003;Chatterton et al 2004;Folman et al 2004;Sutton et al 2006;Liu et al 2007;Postma et al 2008;Postma et al 2009;Vallance et al 2010;Sopher and Sutton 2011;Hultberg et al 2011;Lee and Lee 2015;Martin and Loper 1999;Moruzzi et al 2017;Thongkamngam and Jaenaksorn 2017). The direct addition of some microbial metabolites such as biosurfactants has also been studied (Stanghellini and Miller 1997;Nielsen et al 2006;Nielsen et al 2006).…”

Plant Beneficial Bacteria and Their Potential Applications in Vertical Farming Systems

“…Bacillus has been shown to control Pythium spp., Cryptococcus coccoides , Fusarium oxysporum f. spp., and Rhizoctonia solani for tomato, chrysanthemum, peppers, and lettuce [ 194 , 195 , 196 , 197 , 198 ]. Inoculations of tomato with Bacillus amyloliquefaciens can increase yield; however, the benefits were dependent on an open-loop hydroponic system, and inoculations seemed to be harmful in a closed-loop system, which may suggest that potential nutritional imbalances in a system may affect the outcome of plant–PGPB relationships [ 199 ].…”

The Use of PGPB to Promote Plant Hydroponic Growth

“…A study of hydroponically grown Chrysanthemums concluded that Pseudomonas chlororaphis and Bacillus cereus were the best PGPB for Pythium biocontrol after they reduced pathogen root colonization by 72–91% [ 130 ]. Pseudomonas chlororaphis also effectively prevented Pythium infection in Romaine lettuce [ 16 ] and Cubico sweet peppers [ 131 ]. In Cortina lettuce, the commercial product “Boost” containing Bacillus subtilis was more effective than other products with Enterobacter , Trichoderma , or Gliocladium [ 132 ].…”