Prof. Nantakorn Boonkerd

Year	Title	Journal
2010	Changes in bacterial community composition in the system of rice intensification (SRI) in Chiang Mai, Thailand Sooksa-Nguan T., Gypmantasiri P., Boonkerd N., Thies J.E., Teaumroong N.	Microbes and Environments
Abstract: The factors of alternating flooding and draining during the vegetative growth phase and applying compost to investigate changes in bacterial community composition between the system of rice intensification (SRI) and conventionally managed rice were investigated. 16S rRNA gene T-RFLP analysis showed the major changes in the bacterial communities from the beginning of cultivation to vegetative phase, at which time the groups formed remained consistent until the end of cropping season. Significant and consistent separations of microbial communities between the two systems were revealed. These results suggested that the differences in rice cultivation practice can cause the changes in microbial communities. Keyword: 16S rRNA; Soil bacterial community; SRI; System of rice intensification; T-RFLP Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-77957042883&doi=10.1264%2fjsme2.ME09184&partnerID=40&md5=301c02c2c8a620ad381ef29645dee05e DOI: 10.1264/jsme2.ME09184
2009	Cyanobacterial akinete induction and its application as biofertilizer for rice cultivation Innok S., Chunleuchanon S., Boonkerd N., Teaumroong N.	Journal of Applied Phycology
Abstract: Nostoc sp. VICCR1-1 was induced in order to form akinetes on the basis of nutrient modification. Phosphorus and iron were found to be the critical for akinete differentiation, especially when both elements were omitted. The number of akinete cells increased up to 20% when compared with culturing in BG110 medium (without N source). In addition, CaCl2 played a role in heterocyst differentiation, and was able to induce heterocyst ranging between 30% and 46%. In order to prepare akinetes as inoculum, the dried form of akinetes was prepared by mixing it with montmorillonite clay. The inoculum with the amount of 2.8 × 106 cells m-2 was applied to rice (Oryza sativa) fields. After harvesting, the grain yields from chemical N fertilizer, vegetative cells, and akinete inoculum treatments were not significantly different. To monitor the persistence of Nostoc sp. VICCR1-1 after harvesting, the most probable number-denaturing gradient gel electrophoresis technique using 16S rRNA gene was employed. The results indicated that the remaining population is at 2.5 × 105 and 1.62 × 106 cells m-2 in treatments supplied with vegetative cells and akinete inocula, respectively. Akinete induction might be one of the appropriate approaches for producing cyanobacterial inoculum. © Springer Science + Business Media B.V. 2009. Keyword: Akinete induction; Akinete inoculum; Montmorillonite clay; MPN-DGGE; Nostoc sp.; Rice cultivation Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-77349100184&doi=10.1007%2fs10811-009-9409-x&partnerID=40&md5=94d05698848e75de2abd42441ed3eeb8 DOI: 10.1007/s10811-009-9409-x
2009	Effect of rice cultivation systems on nitrogen cycling and nitrifying bacterial community structure Sooksa-nguan T., Thies J.E., Gypmantasiri P., Boonkerd N., Teaumroong N.	Applied Soil Ecology
Abstract: The system of rice intensification (SRI) has been reported to increase yields by up to 5-10 t ha-1 when compared with practices used in conventional rice cultivation. Changes in root length, root distribution and mineral nutrient cycling leading to increased crop nutrient uptake have been suggested as mechanisms responsible for the dramatic yield increases reported for SRI. In this study, we focused on the SRI practices of alternating soil flooding and draining during vegetative growth, use of young seedlings and applying compost to investigate soil microbial processes that may be involved in the SRI yield phenomenon. Nitrogen (N) mineralization, short-term nitrification, N2 fixation and denitrification potentials were measured. Potentially mineralizable N differed significantly between the two soil depths and between rice cultivation systems in soil sampled from 0 to 10 cm. Nitrification rates were consistently significantly higher in the SRI system. No differences in potential rates of denitrification or nitrogen fixation were observed between the two cultivation systems. Because nitrification rates were significantly higher in the SRI system, the ammonia-oxidizing bacterial (AOB) communities were evaluated by denaturing gradient gel electrophoresis (DGGE) of PCR amplicons as well as cloning followed by sequencing of the ammonia monoxygenase gene (amoA) from both soil depths. Cluster analysis of amoA gene revealed a clear cluster associated with SRI-managed plots in April at the 30% level of similarity. Phylogenetic analysis of amoA sequences cloned from DNA extracted from field soils revealed a few Nitrosospira-like sequences associated with the SRI system with compost applied and one Nitrosomonas-like sequence associated with the conventional rice cultivation system. Rice yields from the conventionally managed plots (5.92 and 5.47 t ha-1) were significantly higher than those obtained from the SRI-managed plots (3.67 and 3.58 t ha-1) with and without compost applied, respectively. Nematode galls were observed on roots of SRI-managed rice during the vegetative growth phase under intermittent irrigation and could be a factor in the low yields observed in the SRI plots. SRI practices resulted in yield losses at this location, most likely due to root infestations by parasitic nematodes that were able to establish when the soils were drained. Practitioners should use caution and monitor carefully for parasitic nematodes when first adopting SRI. Increased nitrification rates and changes in dominant AOB populations have the potential to change N dynamics in the SRI system that could lead to improved yields when other factors are not limiting. © 2009 Elsevier B.V. Keyword: Ammonia monooxygenase; amoA; Denitrification; N-mineralization; Nitrification; Nitrogen fixation; Soil microbial activity; SRI; System of rice intensification Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-70149117943&doi=10.1016%2fj.apsoil.2009.06.013&partnerID=40&md5=38612b645e001e96cdef37ec2d811bca DOI: 10.1016/j.apsoil.2009.06.013
2009	The communities of endophytic diazotrophic bacteria in cultivated rice (Oryza sativa L.) Prakamhang J., Minamisawa K., Teamtaisong K., Boonkerd N., Teaumroong N.	Applied Soil Ecology
Abstract: Even though attempts have been made to use endophytic diazotrophic bacteria as biofertilizers for rice cultivation, their community structure and complexity in rice tissues is not well understood. In this study, the diversity and the community structure of endophytic diazotrophs as well as the nifH gene expression within each plant part and growth stage of rice under different soil conditions were investigated. The population of viable endophytic diazotrophic bacteria in cultivated rice (Oryza sativa L. cultivar KDML-105) was investigated under different soil conditions and the N2-fixing ability of selected consortia and single isolates was assessed. Single isolates from each diazotrophic consortium were shown to be capable of both the inhibition and promotion of N2-fixation. Some isolates were closely related to Enterobacter dissolvens, Brevundimonas aurantiaca, Pantoea agglomerans, Pseudomonas spp., and Enterobacteriaceae. Carbon source utilization, and production of IAA, pectinase and cellulase indicated high diversity in the rice tissues. The presence of diazotrophic bacteria was detected in roots, stems and leaves on the basis of the GUS reporter gene. PCR-DGGE analysis conducted directly on rice tissue samples using 16S rDNA primers was used to elucidate the structure of the endophytic bacterial communities. Nested PCR-DGGE analysis with nifH primer demonstrated less diazotrophic bacterial diversity in the roots of rice cultivated in paddy soil amended with nitrogen fertilizer than in unfertilized and previously uncultivated soil. Plant tissue type was found to dictate the endophytic diazotrophic community structure rather than the type of soil or fertilizer amendment. In order to detect the nifH gene expression which implies the nitrogen fixing activities of the diazotrophic bacterial community, the RT-PCR approach was used. The results demonstrated that nifH gene expression could be differently detected in each part and growth stage of rice plants as well as being influenced by soil nitrogen status. The expression level of the nifH gene in all roots from plants grown in N-fertilized soil was the lowest among the treatments studied. The results confirm the complexity of the endophytic diazotrophic bacterial community, and indicate that the type of plant tissue seems to influence the community structure. © 2009 Elsevier B.V. All rights reserved. Keyword: Cultivated rice; Endophytic diazotrophic bacteria; Microbial community; nifH Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-67349253602&doi=10.1016%2fj.apsoil.2009.02.008&partnerID=40&md5=e7782155545f048ff2d17b3c5bc94a83 DOI: 10.1016/j.apsoil.2009.02.008
2009	Genetic transformation of a seedless grape cultivar 'autumn royal' (vitis vinifera L.) Jittayasothorn Y., Lu J., Xu X., Thipyapong P., Boonkerd N.	Acta Horticulturae
Abstract: Agrobacterium-mediated transformation was developed for 'Autumn Royal Seedless' with SPEMs or somatic embryo as the target materials. No transformed cells were obtained when we used SPEMs as target cells. GFP was very helpful to monitor transformed cells. Two months after transformation, some embryogenic calli and globular somatic embryos showed fluorescent signal on selection medium. The somatic embryos did not grow beyond the globular stage. Using this protocol with 'Autumn Royal Seedless', putative transgenic somatic embryos were produced in low transformation frequency. Keyword: Agrobacterium tumefaciens; GFP; Grape; Transformation; Vitis vinifera Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-70350096266&doi=10.17660%2fActaHortic.2009.827.69&partnerID=40&md5=902557a4613342955006ae4eacddd451 DOI: 10.17660/ActaHortic.2009.827.69
2009	The influences of steeping duration and temperature on the α- and β-amylase activities of six Thai rice malt cultivars (Oryza sativa L. Indica) Usansa U., Sompong N., Wanapu C., Boonkerd N., Teaumroong N.	Journal of the Institute of Brewing
Abstract: A preliminary study of malting conditions for six Thai rice cultivars was conducted. Three non-glutinous rice cultivars (KDML105, PT60, and WR) and three glutinous rice cultivars (SPT, RD6, and KND) were selected. The steeping durations (24, 48, and 72 h) and temperatures (20, 25 and 30°C) were investigated for their effect on α- and β-amylase, the key enzymes for malt quality evaluation. During steeping, the production of both enzymes was lower than at the germination process. The longer the steeping duration, the lower the maximum β-amylase activity obtained. The contradictory effect was observed for α-amylase activity, near the end of the germination time. Additionally, temperature influenced the water absorption content as well as the amylolytic enzyme activity. Particularly at 30°C, the maximum β-amylase activity (6.7 unit/mg protein) was found in KND malt steeped for 24 h, and maximum α-amylase activity (20 unit/mg protein) was found in PT60 malt steeped for 72 h. The amount of enzyme production depended on the variety rather than the amylose content in the rice. The optimal condition for malting rice regarding β-amylase activity and α-amylase activity was analyzed at 30°C, with steeping for 24 h and germination for 4-5 days. © 2009 The Institute of Brewing & Distilling. Keyword: Amylolytic activity; Rice; Steeping duration; Temperature Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-70349281995&doi=10.1002%2fj.2050-0416.2009.tb00359.x&partnerID=40&md5=01c84c67f5bd474f60377aa115fe886e DOI: 10.1002/j.2050-0416.2009.tb00359.x
2008	A simple and efficient protocol for high quality RNA extraction and cloning of chalcone synthase partial cds from muscadine grape cultivars (Vitis Rotundifolia michx.) Louime C., Vasanthaiah H.K.N., Jittayasothorn Y., Lu J., Basha S.M., Thipyapong P., Boonkerd N.	European Journal of Scientific Research
Abstract: Muscadine grapes (Vitis rotundifolia Michx.) possess one of the highest levels of reactive phenolic compounds among fruit crops. Compared to Vitis vinifera, they also contain much higher amounts of chlorophyll pigment within their photosynthetic tissue. These biochemical characteristics of the muscadine grapes make it very difficult to isolate RNA from its tissues. Here we report for the protocol for extraction of high quality RNA from leaves of muscadine grapes. The whole procedure consists mainly of three basic steps: 1) removal of proteins and phenolic compounds, 2) removal of remaining polysaccharides, chlorophyll and debris, and 3) precipitation of total RNA. DEPC or commercial RNase inhibitors were not required. Total RNA extracted with this protocol was successfully used to amplify chalcone synthase gene through reverse transcription-polymerase chain reaction. This method due to its simplicity and cost-efficiency could be useful for a variety of plants, especially for species with high levels of phenolic compounds and chlorophyll content. © EuroJournals Publishing, Inc. 2008. Keyword: Chalcone synthase; Muscadine grape; Reactive phenolic compounds; RNA extraction Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-55249108516&partnerID=40&md5=a5eec879ffae7cf6bd4cdf881782b856 DOI:
2008	Molecular and phenotypic characterization of potential plant growth-promoting Pseudomonas from rice and maize rhizospheres Lawongsa P., Boonkerd N., Wongkaew S., O'Gara F., Teaumroong N.	World Journal of Microbiology and Biotechnology
Abstract: In this study, Pseudomonas species were isolated from the rhizospheres of two plant hosts: rice (Oryza sativa cultivar Pathum Thani 1) and maize (Zea mays cultivar DK888). The genotypic diversity of isolates was determined on basis of amplified rDNA restriction analysis (ARDRA). This analysis showed that both plant varieties selected for two distinct populations of Pseudomonas. The actual biocontrol and plant promotion abilities of these strains was confirmed by bioassays on fungal (Verticillum sp., Rhizoctonia solani and Fusarium sp.) and bacterial (Ralstonia solanacearum and Bacillus subtilis) plant pathogens, as well as indole-3-acetic acid (IAA) production and carbon source utilization. There was a significant difference between isolates from rice and maize rhizosphere in terms of biological control against R. solanacearum and B. subtilis. Interestingly, none of the pseudomonads isolated from maize rhizosphere showed antagonistic activity against R. solanacearum. This study indicated that the percentage of pseudomonad isolates obtained from rice rhizosphere which showed the ability to produce fluorescent pigments was almost threefold higher than pseudomonad isolates obtained from maize rhizosphere. Furthermore, the biocontrol assay results indicated that pseudomonad isolated from rice showed a higher ability to control bacterial and fungal root pathogens than pseudomonad isolates obtained from maize. This work clearly identified a number of isolates with potential for use as plant growth-promoting and biocontrol agents on rice and maize. © 2008 Springer Science+Business Media B.V. Keyword: Amplified rDNA restriction analysis (ARDRA); Maize; Plant growth-promoting rhizobacteria (PGPR); Pseudomonas spp.; Rice Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-48349111396&doi=10.1007%2fs11274-008-9685-7&partnerID=40&md5=e4935ea28eb0175d8efbd6cade6f9416 DOI: 10.1007/s11274-008-9685-7
2007	Characterization and monitoring of selected rhizobial strains isolated from tree legumes in Thailand Manassila M., Nuntagij A., Kotepong S., Boonkerd N., Teaumroong N.	African Journal of Biotechnology
Abstract: Tree legume rhizobia were isolated from five tree legumes; Acacia auriculaformis Cunn., A. mangium Willd., Milletia leucantha Kurz., Pterocarpus indicus Willd., and Xylia xylocarpa Taub. grown in Thailand. Forty four highly effective rhizobial strains were selected on the basis of nitrogenase activity, number of nodules and plant biomass. The selected strains were characterized in both terms of physiology and genetics. Most of the strains are slow grower and able to nodulate cowpea rather than soybean. In addition, IAA production could be detected only from few strains. When almost complete 16S rRNA sequences were analysed, the results indicated that most of the selected strains most likely belong to Bradyrhizobium elkanii and Bradyrhizobium sp. except strains AA67 and PT59 which most likely belong to B. japonicum. The nodule occupancy of selected strains in forest soil condition was investigated by using GUS reporter gene. The nodule occupancy is in the range of 63 - 100%. This suggests the appropriate strains should be produced as inoculum for further application in reforestation programmes in Thailand. © 2007 Academic Journals. Keyword: Acacia auriculaformis; Acacia mangium; Milletia leucantha; Pterocarpus indicus; Tree legume rhizobia; Xylia xylocarpa Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-34347341768&partnerID=40&md5=00c5c2e09574252476a515557752a00c DOI:
2007	A simple and highly efficient protocol for somatic embryogenesis and plant regeneration from proembryonic mass suspension culture in 'Autumn Royal Seedless' Jittayasothorn Y., Lu J., Xu X., Thipyapong P., Boonkerd N.	Vitis - Journal of Grapevine Research
Abstract: [No abstract available] Keyword: Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-33846553073&partnerID=40&md5=b5224261dd7ddde4e22be6c76abb1a1f DOI: