Constancio A. Asis

Bio: Constancio A. Asis is an academic researcher from Philippine Rice Research Institute. The author has contributed to research in topics: Nitrogen fixation & Straw. The author has an hindex of 11, co-authored 23 publications receiving 568 citations. Previous affiliations of Constancio A. Asis include Ibaraki University & Benguet State University.

Methane emission from irrigated and intensively managed rice fields in Central Luzon (Philippines)

Abstract: Methane (CH4) emissions were measured with an automated system in Central Luzon, the major rice producing area of the Philippines. Emission records covered nine consecutive seasons from 1994 to 1998 and showed a distinct seasonal pattern: an early flush of CH4 before transplanting, an increasing mend in emission rates reaching maximum toward grain ripening, and a second flush after water is withdrawn prior to harvesting. The local practice of crop management, which consists of continuous flooding and urea application, resulted in 79-184 mg CH4 m’ d-’ in the dry season (DS) and 269–503 mg CH4 m-2 d-1 in the wet season (WS). The higher emissions in the WS may be attributed to more labile carbon accumulation during the dry fallow period before the WS cropping as shown by higher % organic C. incorporation of sulfate into the soil reduced CH4 emission rates. The use of ammonium sulfate as N fertilizer in place of urea resulted in a 25-36% reduction in CH4 emissions. Phosphogypsum reduced CH4 emissions by 72% when applied in combination with urea fertilizer. Midseason drainage reduced CH4 , emission by 43%, which can be explained by the influx of oxygen into the soil. The practice of direct seeding instead of transplanting resulted in a 16–54ik reduction in CH4 emission, but the mechanisms for the reducing effect are not clear. Addition of rice straw compost increased CH4 emission by only 23-30% as compared with the 162-250% increase in emissions with the use of fresh rice straw. Chicken manure combined with urea did not increase CH4 emission. Fresh rice straw has wider C/N (25 to 45) while rice straw compost has C/N = 6 to 10 and chicken manure has C/N = 5 (o 8. Modifications in inorganic and organic fertilizer management and water regime did not adversely affect grain yield and are therefore potential mitigation options. Direct seeding has a lower yield potential than transplanting but is getting increasingly popular among farmers due to labor savings. Combined with a package of technologies, CH4 emission can best be reduced by (1)the practice of midseason drainage instead of continuous flooding,(2) the use of sulfate-containing fertilizers such as ammonium sulfate and phosphogypsum combined with urea; (3) direct seeding crop establishment; and (4) use of low C/N organic fertilizer such as chicken manure and rice straw compost.

Isolation of endophytic diazotroph Pantoea agglomerans and nondiazotroph Enterobacter asburiae from sweetpotato stem in Japan

Abstract: Aims: To isolate and identify diazotrophic endophytes in the stem of Japanese sweetpotato cv. Koganesengan. Methods and Results: Surface-sterilized and thinly sliced (1–2 mm) sweetpotato stem samples were incubated in test tubes with semi-solid modified Rennie (MR) medium. The test tubes were assayed for acetylene reduction activity (ARA) 5 days after incubation at 30°C. Twelve isolates were obtained from MR plates inoculated with a loop of semi-solid MR medium from ARA+ tubes. However, ARA test showed that only nine isolates were diazotrophic and three were nondiazotrophic strains. Using the API 20E diagnostic kit, four diazotrophic isolates were identified as strains of Pantoea spp. and five isolates as Klebsiella spp. The nondiazotrophic bacteria were strains of Enterobacter spp. A diazotrophic isolate Pantoea sp. MY1 and nondiazotrophic isolate Enterobacter sp. MY2 were identified to the species level by full sequence analysis of 16S rRNA gene. The results showed that MY1 had 99·2% similarity to Pantoea agglomerans ATCC 27155 and MY2 had 99·5% similarity to Enterobacter asburiae ATCC 35953. Conclusion: The stem of sweetpotato cv. Koganesengan was colonized by diazotrophic endophyte P. agglomerans and nondiazotrophic endophyte E. asburiae. Significance and Impact of the Study: This study is an essential step toward understanding the ecology and interaction between endophytic bacteria and sweetpotato.

Production of growth-promoting substances and high colonization ability of rhizobacteria enhance the nitrogen fixation of soybean when coinoculated with Bradyrhizobium japonicum

Abstract: Understanding the interaction mechanisms between plant growth-promoting rhizobacteria (PGPR), leguminous crops, and rhizobia is necessary to effectively use PGPR in increasing the biological nitrogen fixation of legumes. We determined the coinoculation effects of Bradyrhizobium japonicum A1017 and a gusA-marked strain of Pseudomonas fluorescens 2137, P. fluorescens WCS365, Azomonas agilis 125, and Azospirillum lipoferum 137 on soybean [Glycine max (L.) Merr] cv. Enrei grown under axenic conditions. The gusA-marked rhizobacteria effectively colonized the root tips and surfaces near the roots tips with a colonization rate ranging from 7.50 to 8.62 log colony forming units (cfu) gfw–1. P. fluorescens 2137 had the highest colonization activity on soybean roots whether inoculated alone or coinoculated with B. japonicum A1017. Coinoculation of P. fluorescens 2137 and B. japonicum A1017 increased the colonization of B. japonicum A1017 on soybean roots, nodule number, and acetylene reduction activity (ARA) at 10 and 20 days after inoculation. Moreover, the addition of sterile spent medium of P. fluorescens 2137 increased the growth of B. japonicum A1017 in yeast mannitol broth (YMB), indicating that P. fluorescens 2137 may have released substances that increased the rhizobial population. The results of this study suggest that the enhanced nodulation and ARA of soybean due to the high colonization of P. fluorescens on soybean roots could depend on the production of growth-promoting substances that stimulate the growth of B. japonicum. However, coinoculation with P. fluorescens WCS365 decreased the nodule number and ARA, despite its slight stimulation of the growth of B. japonicum on the roots, indicating that coinoculation effects are strain dependent.

The use of GUS-reporter gene to study the effect of Azospirillum-Rhizobium coinoculation on nodulation of white clover

Abstract: The gusA-marked Azospirillum lipoferum T1371, constructed by inserting transposon mTn5SSgusA20 from Escherichia coli S17-1 λ-pir into the genome of Azospirillum lipoferum 137, was used to evaluate its effect on nodulation of white clover with and without Rhizobium inoculation. When inoculated alone, Azospirillum colonized the tap roots, secondary roots and root hairs. The combined inoculation of white clover with Rhizobium leguminosarum bv trifolii and A. lipoferum enhanced the number of nodules by 2–3 times from 5 to 20 days after inoculation (DAI). The combined inoculation also enhanced acetylene reduction activity by 2.3–2.7 times at 20 DAI. Moreover, Azospirillum was observed colonizing the tap root, root hairs and sites near or on the nodules. These results suggest that the formation of additional infection sites by A. lipoferum, with a combined inoculation, may be the mechanism that will enhance nodulation and nitrogen fixation of white clover.

Isolation and partial characterization of endophytic diazotrophs associated with Japanese sugarcane cultivar

Abstract: Endophytic bacteria were isolated from the juice of a 6 month-old sugarcane cv. NiF-8, which was collected from Miyako, Okinawa and planted in a field lysimeter in Tsukuba, Ibaraki, Japan. The most probable number of N2-fixing endophytes was 4.5 × 105 cells per gram of fresh weight sample and 21 isolates have a positive reaction for ARA in an N2-free semi-solid medium with 10% crystallized sugarcane sugar and 0.5% sugarcane juice. Analyses of some of the biochemical properties of the N2-fixing isolates indicated that 13 isolates were putative strains of Acetobacter diazotrophicus, 4 isolates showed similar characteristics to those of Herbaspirillum seropedicae, and 4 isolates consisted of Herbaspirillum rubribalbicans-like strains. This study confirmed the existence of N2-fixing endophytic bacteria in the Japanese sugarcane cv. NiF-8.

Climate change 2014 - Mitigation of climate change

Abstract: The talk with present the key results of the IPCC Working Group III 5th assessment report. Concluding four years of intense scientific collaboration by hundreds of authors from around the world, the report responds to the request of the world's governments for a comprehensive, objective and policy neutral assessment of the current scientific knowledge on mitigating climate change. The report has been extensively reviewed by experts and governments to ensure quality and comprehensiveness.

Sustainable biochar to mitigate global climate change

Abstract: Production of biochar (the carbon (C)-rich solid formed by pyrolysis of biomass) and its storage in soils have been suggested as a means of abating climate change by sequestering carbon, while simultaneously providing energy and increasing crop yields. Substantial uncertainties exist, however, regarding the impact, capacity and sustainability of biochar at the global level. In this paper we estimate the maximum sustainable technical potential of biochar to mitigate climate change. Annual net emissions of carbon dioxide (CO 2 ), methane and nitrous oxide could be reduced by a maximum of 1.8 Pg CO 2 -C equivalent (CO 2 -C e ) per year (12 % of current anthropogenic CO 2 -C e emissions; 1 Pg = 1 Gt), and total net emissions over the course of a century by 130 Pg CO 2 -C e , without endangering food security, habitat or soil conservation. Biochar has a larger climate-change mitigation potential than combustion of the same sustainably procured biomass for bioenergy, except when fertile soils are amended while coal is the fuel being offset.

Bacterial Endophytes and Their Interactions with Hosts

Abstract: Recent molecular studies on endophytic bacterial diversity have revealed a large richness of species. Endophytes promote plant growth and yield, suppress pathogens, may help to remove contaminants, solubilize phosphate, or contribute assimilable nitrogen to plants. Some endophytes are seed-borne, but others have mechanisms to colonize the plants that are being studied. Bacterial mutants unable to produce secreted proteins are impaired in the colonization process. Plant genes expressed in the presence of endophytes provide clues as to the effects of endophytes in plants. Molecular analysis showed that plant defense responses limit bacterial populations inside plants. Some human pathogens, such as Salmonella spp., have been found as endophytes, and these bacteria are not removed by disinfection procedures that eliminate superficially occurring bacteria. Delivery of endo-phytes to the environment or agricultural fields should be carefully evaluated to avoid introducing pathogens.

Microbial co-operation in the rhizosphere

Abstract: Soil microbial populations are immersed in a framework of interactions known to affect plant fitness and soil quality. They are involved in fundamental activities that ensure the stability and productivity of both agricultural systems and natural ecosystems. Strategic and applied research has demonstrated that certain co-operative microbial activities can be exploited, as a low-input biotechnology, to help sustainable, environmentally-friendly, agro-technological practices. Much research is addressed at improving understanding of the diversity, dynamics, and significance of rhizosphere microbial populations and their cooperative activities. An analysis of the co-operative microbial activities known to affect plant development is the general aim of this review. In particular, this article summarizes and discusses significant aspects of this general topic, including (i) the analysis of the key activities carried out by the diverse trophic and functional groups of micro-organisms involved in cooperative rhizosphere interactions; (ii) a critical discussion of the direct microbe–microbe interactions which results in processes benefiting sustainable agroecosystem development; and (iii) beneficial microbial interactions involving arbuscular mycorrhiza, the omnipresent fungus–plant beneficial symbiosis. The trends of this thematic area will be outlined, from molecular biology and ecophysiological issues to the biotechnological developments for integrated management, to indicate where research is needed in the future.