The Endophytic Plant Growth Promoting Methylobacterium oryzae CBMB20 Modulates Plant Defense Responses while Integrating Naturally with the Seed-borne Endophytic Bacterial Community of Rice

Denver I. Walitang,Tongmin Sa(사동민) 한국토양비료학회 2021 한국토양비료학회 학술발표회 초록집 Vol.2021 No.11

Inoculation with the endophytic plant growth promoting bacteria (PGPB) leads to plant responses concurrent to the integration of the bioinoculum to the native endophytic bacterial community of the host plant. The interaction of the bioinoculum on the community of the native endophytic bacteria of the host plant is also understudied but should be an essential factor when assessing effects of bioinoculants. The study evaluated the modulation of host defense responses in rice when it is inoculated by Methylobacterium oryzae CBMB20. The effect of inoculation on the diversity and community structure of the root and shoot bacterial endophytes in Oryza sativa L. spp. indica cv. IR29 was also investigated. The defense responses observed in IR29 measured in terms of ROS and PR protein production significantly increased, but was eventually modulated by Methylobacterium oryzae CBMB20. Using Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis, CBMB20 was shown to integrate with the native endophytic bacterial community of rice without causing significant changes in the bacterial diversity and community structure. The endophytic bacterial community of the rice seedling could be traced to the original seed community suggesting that they are seed-borne endophytes. The dominant bacterial communities in rice are mainly represented by bacterial genera associated to Microbacterium, Delftia, Pseudomonas, Xanthomonas and Stenotrophomonas, Herbaspirillum, Enterobacter and Sphingomonas. In addition, Curtobacterium, Enterobacter, Stenotro-phomonas and Xanthomonas were observed in both the root and shoot community. The results showed that Methylobacterium oryzae CBMB20 could modulate defense responses and non-antagonistically integrate with the native endophytic bacterial community of the rice host opening another area on the mechanism of plant growth promotion by the bioinoculum.

Endophytic Colonization of Pseudomonas vancouverensis OB155 and Pseudomonas frederiksbergensis OS261 in Multiple Crops

Lee, Kyung Mok - Denver I. Walitang 충북대학교 농업과학기술연구소 2022 農業科學硏究 Vol.38 No.1

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Methanogenesis and Methane Oxidation in Paddy Fields under Organic Fertilization

( Chungwoo Kim ),( Denver I. Walitang ),( Tongmin Sa ) 한국환경농학회 2021 한국환경농학회지 Vol.40 No.4

BACKGROUND: Global warming is one of the most pressing environmental issues which concomitantly complicates global climate change. Methane emission is a balance between methanogenesis and methane consumption, both of which are driven by microbial actions in different ecosystems producing methane, one of the major greenhouse gases. Paddy fields are major sources of anthropogenic methane emissions and could be compounded by organic fertilization. METHODS AND RESULTS: Literature reviews were conducted to give an overview of the global warming conditions and to present the relationship of carbon and methane to greenhouse gas emissions, and the need to understand the underlying processes of methane emission. A more extensive review was done from studies on methane emission in paddy fields under organic fertilization with greater emphasis on long term amendments. Changes in paddy soils due to organic fertilization include alterations of the physicochemical properties and changes in biological components. There are diverse phylogenetic groups of methanogens and methane oxidizing bacteria involved in methane emission. Also, multiple factors influence methanogenesis and methane oxidation in rice paddy fields under organic fertilization and they should be greatly considered when developing mitigating steps in methane emission in paddy fields especially under long term organic fertilization. CONCLUSION(S): This review showed that organic fertilization, particularly for long term management practices, influenced both physicochemical and biological components of the paddy fields which could ultimately affect methanogenesis, methane oxidation, and methane emission. Understanding interrelated factors affecting methane emission helps create ways to mitigate their impact on global warming and climate change.

Seedling Growth Enhancement by Indole Acetic Acid (IAA) Producing Plant Growth-Promoting Pseudomonas spp.

Kyungmok Lee, Geon Choi, Bowon Jeong, and Denver I. Walitang 충북대학교 농업과학기술연구소 2022 農業科學硏究 Vol.38 No.2

A plethora of environmental stresses can reduce the early seedling growth leading to decrease in crop productivity. Priming of seeds with beneficial endophytic bacterial strains to induce early germi- nation and enhance their growth is a sustainable and eco-friendly agricultural practice. Hence, this study was conducted to evaluate the enhancement of seedling growth in three different crops, namely onion, green onion and zucchini under gnotobiotic conditions, mediated by bacterial inoculation. Two bacterial strains, Pseudomonas frederiksbergensis OS261 and Pseudomonas vancouverensis OB155 were used in this study. Both bacterial strains are characterized as psychrotolerant and have ACC deaminase activity and IAA production ability. The P. frederiksbergensis OS261 inoculation had shown significant increase in root length, shoot length, and total dry weight of onion and green onion seedlings. The inoculation didn’t show any significant effect on the growth parameters of zucchini plants suggesting the effective- ness of bacterial strains in particular plant species. On the other hand, the seedling vigor index was only recorded to be significantly higher in OS261 inoculated onion seedlings. Collectively, this study suggests that higher IAA production by bacterial strains is a determinant trait in enhancing seedling growth under normal environmental conditions and there can be bacteria-plant specificity for effective enhancement of plant growth and productivity.

Accumulation of compatible solutes in rice (Oryza sativa L.) cultivars by inoculation of endophytic plant growth promoting bacteria to alleviate salt stress

Ahmed Shamim,Heo Tae-Young,Roy Choudhury Aritra,Walitang Denver I.,Choi Jeongyun,Sa Tongmin 한국응용생명화학회 2021 Applied Biological Chemistry (Appl Biol Chem) Vol.64 No.5

Salinization of agricultural lands, particularly rice paddies, results in the drastic decline of crop yields. Soil salinization impacts the plant physiology by inducing salt stress which may leads to osmotic stress, ionic stress and water-related nutrient imbalance. These imbalances necessitate the need for plants to produce osmolytes including proline and glycine betaine. This study aimed to elucidate the dynamic changes in proline and glycine betaine accumulation modulated by the inoculation of Brevibacterium linens RS16 in salt-sensitive and moderately salt-tolerant rice plants under salt stress conditions. This study showed the interaction of four major factors including rice genotypes with differing tolerance to salt stress, length of exposure to salt stress, level of salt stress and effects of inoculation. Salt stress resulted in significant reduction in plant growth parameters with the salt-sensitive rice genotype (IR29) having a more significant growth reduction. Both the salt-sensitive and salt-tolerant rice genotypes increased in total proline and glycine betaine accumulation at 3 days and 10 days after subjecting under 50 mM and 150 mM salt stress conditions. A significant increase in proline and glycine betaine was observed in the salt-sensitive genotype after 10 days under 50 mM and 150 mM salt stress conditions. Inoculation of the rice genotypes with B. linens RS16 resulted in the improvement of plant growth parameters in both rice genotypes, and total proline and glycine betaine accumulation, especially in IR29. This study showed that proline and glycine betaine are compatible osmolytes of rice under salt stress, and that inoculation of rice genotypes with B. linens RS16 mediated salt tolerance through improvement of plant growth parameters and proline and glycine betaine accumulation in rice plants.