Katsuki Adachi

Isolation of an Endophytic Diazotroph, Klebsiella oxytoca, from Sweet Potato Stems in Japan

Abstract The population density of endophytic bacteria in the stem of field-grown sweet potato cultivars (Beniotome [BO], Koganesengan [KS], and Shiroyutaka [SYD in Miyakonojo, Miyazaki, Japan, ranged from 102 to 104 cells g−1 fresh weight sample using a semi-solid nitrogen-free medium. Eleven strains were isolated from the stems and two isolates, BO-1 and BO-5, showed a positive reaction in the acetylene reduction activity (ARA) test. BO-1 and BO-5 were isolated from cv. Beniotome in September 1999 and 2000, respectively. Morpho-physiological characterization of these isolates revealed that BO-1 and BO-5 showed a similar colony color in potato sucrose agar slants, produced bubbles in a modified semi-solid medium, acidified the medium, and displayed similar characteristics using the API 20NE rapid diagnostic kit. Partial sequence analysis of 16S rRNA from BO-1 revealed a 100% similarity (491 bp) to that of Klebsiella oxytoca. The other 9 isolates showed a negative reaction in the ARA test, slightly acidified or did not acidify the medium. Partial sequence analysis of the 16S rRNA revealed that the isolate SY-2 corresponded to Methylobacterium sp. (99.3% similarity for 1,241 bp), BO-3 to Pantoea agglomerans (99.1% similarity for 469 bp), and BO-8 to Sphingomonas sanguinis (98.8% similarity for 419 bp).

Promotive and inhibitory effects of rice straw and cellulose application on rice plant growth in pot and field experiments

Abstract In a pot experiment, rice straw and cellulose were applied at the rates of 0.2 and 0.5% on a dry soil weight basis with two different incubation periods (2 months and 3 months) from their incorporation to rice transplanting. Seven treatments were designed as follows, T1, control; T2, straw 0.2%; T3, straw 0.5%; T4, cellulose 0.2%; T5, cellulose 0.5%; T6, straw 0.2%+inorganic N fertilizer; and T7, cellulose 0.2%+inorganic N fertilizer. T6 and T7 contained 50 mg N pot−1 of ammonium chloride (approximately 10 kg N ha−1) in addition to straw and cellulose, respectively. Promotive and inhibitory effects of straw and cellulose application were observed and both were closely related to the incubation period. Straw application at 0.5% increased plant dry matter yield and N uptake compared to T1 and the promotive effect was more appreciable in the 3-month-incubation period than in the 2-month one (hereafter referred to as 3i and 2i, respectively). Cellulose application at 0.5% inhibited rice plant growth ...

Isolation and some properties of methane-oxidizing bacteria from a subtropical paddy field

Abstract Methane is the second most important greenhouse gas which contributes to global warming. As an important source of methane, rice paddy fields contribute an estimated lO% to the global methane emissions (IPCe 1992). Land use and agricultural practices significantly affect atmospheric methane fluxes (Bouwman 1989; Hutsch et al. 1994). Microbial oxidation of atmospheric methane in terrestrial environments is the only known net biological methane sink and the process consumes the equivalent of 1–l0% of the total global emission (Adamsen and King 1993). Methane-oxidizing bacteria (MOB, methanotrophic bacteria) are considered to be obligately or facultatively aerobic respiratory bacteria that can utilize methane as the sole source of carbon and energy for growth (Hanson et al. 1992; Roslev and King 1994). As a result, they are important regulators of atmospheric methane fluxes in nature (Mancinelli 1995). MOB have been isolated from a variety of environments including freshwater lakes, wetlands, and th...

EFFECT OF APPLICATION OF GLUCOSE, CELLULOSE, AND RICE STRAW ON NITROGEN FIXATION (ACETYLENE REDUCTION AND SOIL-NITROGEN COMPONENTS) IN ANAEROBIC SOIL

The use of the plastic net bag method for the measurement of the decomposition rate of rice straw in the reduced layer enabled to demonstrate that the organic matter of rice straw consisted of at least two components, one rapidly decomposable (half-life, 17 days) and the other slowly decomposable (half-life, 58 days). Stimulation by rice straw of N2-fixation under anaerobic (under N2 gas) conditions was compared with that by cellulose and glucose. The peak of acetylene reduction activity (ARA) in the soil to which glucose had been added occurred on the 1st day of incubation. When cellulose or straw was added at 1%, the ARA peak occurred after 3 to 4 days. Peak height induced by cellulose was 3 times larger than that by straw. After 2 weeks of incubation, the activity was negligible. Addition of glucose and cellulose increased the number of colonies of anaerobic bacteria grown on nitrogen-free medium. The levels of hydrolyzable-N and α-amino acid-N increased by glucose or cellulose addition, presumably due...

EFFECT OF THE APPLICATION OF LIGNIN AND/OR CHITIN TO SOIL INOCULATED WITH Fusarium oxysporum ON THE VARIATION OF SOIL MICROFLORA AND PLANT GROWTH

Effect of the application of organic materials to soil inoculated with Fusarium oxysporum on the variation of soil microflora was studied during three years. Plant cucumber was cultivated five times and the growth was analyzed statistically. Lignin and/or chitin were applied to soil at concentrations of 2,000 and 1,000 ppm, respectively. Fusarium oxysporum f.sp. cucumerinum (F.o.c.) was inoculated to the soil at a level of 109 propagules/pot. After cucumber, the host plant, had been cultivated five times during three years, the following results were obtained: 1) Chitin application increased the populations of fungi and actinomycetes and decreased the population of F.o.c. in the soil. 2) Lignin application inhibited the multiplication of fungi, induced the growth of a peculiar fungal flora and promoted the survival of F.o.c. in the soil and also masked the useful effect of chitin application. 3) Increase of F.o.c. population by host plant cultivations was not observed. Populations of F.o.c. decreased in a...

Transplantation of Half-Cut Tuber Seedlings Provides Enhanced Yields Over Conventional Sprouted-Vine Planting in Sweet Potato Cultivar “Murasakimasari”

Abstract Seed tubers of sweet potato cultivar “Murasakimasari”, the weights of which range from 30 to 100 g, were cut in half at a right angle to the long axis of the tuber, and planted in cell trays (cell size: 55 mm×55 mm×height 62.5 mm, 50 cells in a 30 cm×60 cm tray) with commercial soil mixes. The planted half-cut tubers in cell trays were incubated at 25ºC under natural sunlight conditions in a glasshouse for 3 to 4 wk to raise half-cut tuber seedlings. Half-cut tuber seedlings were transplanted on 28 March (TST1) or on 24 April (TST2), whole seed tubers were directly planted on 26 March (DP), conventional sprouted vines were planted on 30 April (VP) in an experimental field. The highest tuber yield was obtained from TST1, followed by TST2 and VP, and DP in this order. Deformed tubers emerged from the TST1 and TST2 groups, at a rate of 3.0% and 6.7% of daughter tubers, respectively. A regional trial in a farmer’s field revealed that the tuber yields and numbers of tubers per plant were higher in TST (tuber seedling transplanting) than those in VP (vine planting). The statistical analysis of the 2 field experiments suggests that transplantation of half-cut tuber seedlings provides enhanced yields over conventional sprouted-vine planting.

Yield-enhancing and tuber-downsizing effects of transplantation cultivation method of case-held tuber seedlings in the sweet potato cultivar Beniharuka

Abstract We developed transplantation cultivation method of case-held tuber seedlings (CTS), which was derived from direct planting method of seed tubers, and applied this method to the sweet potato cultivar Beniharuka. A plastic case made of polypropylene was designed for cultivation of CTS. Seed tubers of cultivar Beniharuka in the range of 30–80 g were cut in half. The half-cut tubers were placed inside the plastic cases, and the cases were filled with a commercial soil mix. The case-held tubers were incubated under natural sunlight in a glass house. After 3–4 wk, the CTS were transplanted into a field. Mother tuber (seed tuber) enlargement was suppressed by the plastic confinement of the cases, and daughter tubers were formed above the case as vine-root-originated tubers. In the field experiments in 2012 and 2013, daughter tuber yields were increased 19% and 21% by case-held tuber seedling transplanting (CTST) over conventional vine-planting (VP), the number of daughter tubers per plant in CTST were 36 and 68% higher than in VP, and the mother tuber yields were limited to 2.1 and 4.3% of the total fresh yield of mother and daughter tubers, respectively in 2012 and 2013. Application of CTST method to cultivar Beniharuka enhanced tuber yield, increased the number of daughter tubers per plant, downsized daughter tubers compared to VP, and mother tuber enlargement was suppressed by case-holding. The CTST method is expected to produce more and smaller good in shape tubers of cultivar Beniharuka compared to VP.

Suppression of Mother Tuber Enlargement in the Sweet Potato Cultivar “Koganesengan” by Transplantation of Bottled Tuber Seedlings

Abstract Seed tubers of the sweet potato cultivar “Koganesengan” ranging from 40 to 70 g were cut in half at a right angle to the long axis. The half-cut tubers were planted in plastic wide-mouthed bottles, and the bottles were filled with a commercial soil mix. These bottled tubers were kept under natural sunlight in a glasshouse at 25°C, and watered regularly. After 3–4 wk, the bottled tuber seedlings were transplanted to a field, leaving the tubers in the plastic bottles. Mother tuber enlargement was suppressed in the bottle, but daughter tubers were formed above the bottle, and the mother tuber yield was 4.5% of the total fresh yield of mother and daughter tubers. In the cultivation of tuber seedlings without bottling, the mother tuber yield was 11.2% of the total yield.