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<p>Cassava (<i>Manihot esculenta</i> Crantz) is a major global food crop, with Thailand as a leading producer. Plant growth-promoting rhizobacteria (PGPR) offer a sustainable alternative to chemical fertilizers, but the use of non-native PGPR may lead to poor efficacy and ecological disruption. To address this, we isolated and screened 110 native bacterial strains from arbuscular mycorrhizal (AM) fungal spores and rhizospheric soil (RS) collected from organic cassava fields in northeastern Thailand. Isolates were evaluated for IAA production, exopolysaccharide (EPS) production, ammonia production, siderophore production, and phosphorus and potassium solubilization. AM isolates showed higher siderophore production, while RS isolates exhibited greater EPS production. This work presents the first report of <i>Pantoea dispersa</i> isolated from cassava fields in Thailand, with strain CU_RS19 identified as a promising candidate due to its strong potassium-solubilizing ability and non-pathogenic status under the Pathogens and Animal Toxins Act of Thailand (2015). Outdoor pot experiments demonstrated that <i>P. dispersa</i> CU_RS19 significantly enhanced cassava growth, increasing root length (38.4%), root dry biomass (105%), stem diameter (30.3%), stem height (62.5%), stem dry biomass (68.1%), and leaf dry biomass (38.8%) compared to the control. Co-inoculation with <i>Serratia marcescens</i> CU_AM17 did not provide additional benefits, likely due to the absence of AM fungi in the experiment. These findings suggest that <i>P. dispersa</i> CU_RS19, a rhizospheric soil bacterium, is a promising PGPR for cassava cultivation. The absence of AM fungi treatments and the lack of bacterial colonization confirmation are limitations of this work. Future field studies incorporating <i>P. dispersa</i> CU_RS19, the AM-associated bacteria <i>S. marcescens</i> CU_AM17 and AM fungi are recommended to validate their efficacy under diverse agricultural conditions and explore tripartite interactions for enhanced plant growth.</p>

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Isolation and Characterization of Native Plant Growth-Promoting Rhizobacteria from Organic Cassava Fields in Thailand: Pantoea dispersa Enhances Cassava Growth

  • 期刊论文

  • 发表日期：

    2026年1月14日

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  • Kanapol Ketjarun,
  • Juthamas Chaiwanon,
  • Alisa Vangnai,
  • Pawara Pachit,
  • Jittra Piapukiew

摘要

Cassava (Manihot esculenta Crantz) is a major global food crop, with Thailand as a leading producer. Plant growth-promoting rhizobacteria (PGPR) offer a sustainable alternative to chemical fertilizers, but the use of non-native PGPR may lead to poor efficacy and ecological disruption. To address this, we isolated and screened 110 native bacterial strains from arbuscular mycorrhizal (AM) fungal spores and rhizospheric soil (RS) collected from organic cassava fields in northeastern Thailand. Isolates were evaluated for IAA production, exopolysaccharide (EPS) production, ammonia production, siderophore production, and phosphorus and potassium solubilization. AM isolates showed higher siderophore production, while RS isolates exhibited greater EPS production. This work presents the first report of Pantoea dispersa isolated from cassava fields in Thailand, with strain CU_RS19 identified as a promising candidate due to its strong potassium-solubilizing ability and non-pathogenic status under the Pathogens and Animal Toxins Act of Thailand (2015). Outdoor pot experiments demonstrated that P. dispersa CU_RS19 significantly enhanced cassava growth, increasing root length (38.4%), root dry biomass (105%), stem diameter (30.3%), stem height (62.5%), stem dry biomass (68.1%), and leaf dry biomass (38.8%) compared to the control. Co-inoculation with Serratia marcescens CU_AM17 did not provide additional benefits, likely due to the absence of AM fungi in the experiment. These findings suggest that P. dispersa CU_RS19, a rhizospheric soil bacterium, is a promising PGPR for cassava cultivation. The absence of AM fungi treatments and the lack of bacterial colonization confirmation are limitations of this work. Future field studies incorporating P. dispersa CU_RS19, the AM-associated bacteria S. marcescens CU_AM17 and AM fungi are recommended to validate their efficacy under diverse agricultural conditions and explore tripartite interactions for enhanced plant growth.