Antagonistic and plant growth promotion of rhizobacteria against Phytophthora colocasiae in taro

Abstract

Taro leaf blight caused by Phytophthora colocasiae adversely affects the growth and yield of taro. The management of this disease depends heavily on synthetic fungicides. These compounds, however, pose potential hazards to human health and the environment. The present study aimed to investigate an alternative approach for plant growth promotion and disease control by evaluating seven different bacterial strains (viz., Serratia plymuthica, S412; S. plymuthica, S414; S. plymuthica, AS13; S. proteamaculans, S4; S. rubidaea, EV23; S. rubidaea, AV10; Pseudomonas fluorescens, SLU-99) and their different combinations as consortia against P. colocasiae. Antagonistic tests were performed in in vitro plate assays and the effective strains were selected for detached leaf assays and greenhouse trials. Plant growth-promoting and disease prevention traits of selected bacterial strains were also investigated in vitro. Our results indicated that some of these strains used singly (AV10, AS13, S4, and S414) and in combinations (S4+S414, AS13+AV10) reduced the growth of P. colocasiae (30−50%) in vitro and showed disease reduction ability when used singly or in combinations as consortia in greenhouse trials (88.75−99.37%). The disease-suppressing ability of these strains may be related to the production of enzymes such as chitinase, protease, cellulase, and amylase. Furthermore, all strains tested possessed plant growth-promoting traits such as indole-3-acetic acid production, siderophore formation, and phosphate solubilization. Overall, the present study revealed that bacterial strains significantly suppressed P. colocasiae disease development using in vitro, detached leaf, and greenhouse assays. Therefore, these bacterial strains can be used as an alternative strategy to minimize the use of synthetic fungicides and fertilizers to control taro blight and improve sustainable taro production.

Comparative transcriptome profiling provides insights into the growth promotion activity of Pseudomonas fluorescens strain SLU99 in tomato and potato plants

“…The activation of auxin biosynthesis genes and production of IAA by SLU99 ( Kelbessa et al., 2022 ) prompted us to analyze the differences in the expression of genes involved in auxin signaling pathways. Major auxin-responsive genes such as Gretchen Hagen 3 ( GH3 ) and small auxin up RNA ( SAUR ) are transcriptionally regulated by auxin at early stages of signal transduction.…”

“…Previous research found that bacterial consortiums aid plant growth by enhancing stress tolerance ( Silambarasan et al., 2019 ; Yang et al., 2021 ; Kelbessa et al., 2023 ). Recently, results from our group demonstrated that SLU99 is compatible with strains EV23 and AV10 ( Kelbessa et al., 2022 ), implying that these bacteria could co-exist as a consortium in the rhizosphere. Considering that all these strains are potent biocontrol agents ( Kelbessa et al., 2022 ), a bacterial consortium of these strains could act synergistically to contribute to reducing disease under natural conditions.…”

“…Recently, results from our group demonstrated that SLU99 is compatible with strains EV23 and AV10 ( Kelbessa et al., 2022 ), implying that these bacteria could co-exist as a consortium in the rhizosphere. Considering that all these strains are potent biocontrol agents ( Kelbessa et al., 2022 ), a bacterial consortium of these strains could act synergistically to contribute to reducing disease under natural conditions. Moreover, plant exudates attract rhizobacteria to colonize the roots ( Bais et al., 2006 ).…”

“…The strains used in this study were isolated from potato and tomato rhizosphere soils. In vitro antagonistic analysis indicated a strong activity against plant pathogens, including P. colocasiae ( Kelbessa et al., 2022 ) , P. infestans and R. solani (unpublished). To that end, we carried out a field trial with six bacteria with biological control activity on potato plants in a high disease pressure P. infestans infested field.…”

Comparative Transcriptome Profiling Provides Insights into the Growth Promotion Activity ofPseudomonas fluorescensstrain SLU99 in Tomato and Potato Plants

“…The strains used in this study were isolated from potato and tomato rhizosphere soils. In vitro antagonistic analysis indicated a strong antagonistic activity against plant pathogens, including P. colocasiae (Kelbessa et al, 2022), P. infestans and R. solani (unpublished). The aim of this study was to conduct a holistic study on the effect of PGPR on potato and tomato growth and select the best-performing PGPR to gain insights into their mechanism of action.…”