Prof. Nantakorn Boonkerd

Year	Title	Journal
1993	Serological grouping of indigenous Bradyrhizobium sp. (Arachis) isolated from various soils of Thailand Kishinevsky B.D., Gurfel D., Boonkerd N., Nemas C.	World Journal of Microbiology & Biotechnology
Abstract: ELISA and antibody adsorption tests were applied to determine the minimal somatic antigen constitution of 243 strains of Bradyrhizobium sp. (Arachis) using 12 antisera. The 243 indigenous bradyrhizobial isolates were from 15 sites in four regions of Thailand. A total of 29 serogroups were identified. Most (80%) of the isolates tested had at least one heat-stable antigen in common with strain 280A, forming a so-called 280A serocluster. At 11 of 15 sites tested, 53 to 100% of the isolates fell into one or two predominant serogroups. The serological properties of the indigenous bradyrhizobia were not related to the cropping history of the cultivated fields from which they were isolated. © 1993 Rapid Communications of Oxford Ltd. Keyword: Antigens; antisera; Arachis; Bradyrhizobium; ELISA; peanut; serological groups Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250081724&doi=10.1007%2fBF00369570&partnerID=40&md5=a081cdb9e4bc4f6cfd9d78f19d519364 DOI: 10.1007/BF00369570
1993	Natural abundance of 15N in tropical plants with emphasis on tree legumes Yoneyama T., Muraoka T., Murakami T., Boonkerd N.	Plant and Soil
Abstract: Natural abundance of 15N (δ 15N) of leaves harvested from tropical plants in Brazil and Thailand was analyzed. The δ 15N values of non-N2-fixing trees in Brazil were +4.5±1.9, which is lower than those of soil nitrogen (+8.0±2.2‰). In contrast, mimosa and kudzu had very low δ 15N values (-1.4≈+0.5‰). The δ 15N values of Panicum maximum and leguminous trees, except Leucaena leucocephala, were similar to those of non-N2-fixing trees, suggesting that the contribution of fixed N in these plants is negligible. The δ 15N values of non-N2-fixing trees in Thailand were +4.9±2.0‰. Leucaena leucocephala, Sesbania grandiflora, Casuarina spp. and Cycas spp. had low δ 15N values, close to the value of atmospheric N2 (0‰), pointing to a major contribution of N2 fixation in these plants. Cassia spp. and Tamarindus indica had high δ 15N values, which confirms that these species are non-nodulating legumes. The δ 15N values of Acacia spp. and Gliricidia sepium and other potentially nodulating tree legumes were, on average, slightly lower than those of non-N2-fixing trees, indicating a small contribution of N2 fixation in these legumes. © 1993 Kluwer Academic Publishers. Keyword: N2 fixation; natural 15N abundance; Panicum maximum; tree legumes; tropical ecosystem Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027846347&doi=10.1007%2fBF00013003&partnerID=40&md5=e436d8d78339397898247b51cab46048 DOI: 10.1007/BF00013003
1993	Population size and N2-fixing activity of native peanut rhizobia in soils of Thailand Boonkerd N., Wadisirisuk P., Meromi G., Kishinevsky B.D.	Biology and Fertility of Soils
Abstract: The objective of this study was to assess the number and effectiveness of peanut rhizobia in soils of the major peanut-growing areas of Thailand. Three cropping areas, (1) continuously cropped with peanuts, (2) continuously cropped with non-legumes, and (3) non-cultivated fields, were chosen in each region. Peanut rhizobia were found in the soil at 38 to 55 sites sampled. Cultivated fields with a peanut cultivation history contained (as estimated by most probable numbers) an average of 1.6×103 cells g-1 of soil. The numbers of peanut rhizobia in most of the fallow fields and some of the noncultivated shrub or forest locations were much the same as at the sites where Arachis hypogaea was cultivated. In contrast, there were no or few (28-46 cells g-1 soil) peanut rhizobia in the majority of fields continuously cultivated with sugarcane, cassava, corn, and pineapple. It appears that in these areas the indigenous peanut rhizobial populations are not adequate in number for a maximal nodulation of peanuts. A total of 343 Bradyrhizobium isolates were tested for effectiveness and were found to vary widely in their ability to fix N2. In some areas the majority of rhizobia were quite effective while in others they were less effective than the inoculum strain THA 205 recommended in Thailand. © 1993 Springer-Verlag. Keyword: Arachis hypogaea; Bradyrhizobium spp.; Continuous cropping; Effectiveness of rhizobia; Nitrogen fixation; Peanuts Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027881990&doi=10.1007%2fBF00337212&partnerID=40&md5=9990acde43c167d6955c1eb6f89b7a1d DOI: 10.1007/BF00337212
1990	Natural 15N abundance in shrub and tree legumes, Casuarina, and non N2 fixing plants in Thailand Yoneyama T., Murakami T., Boonkerd N., Wadisirisuk P., Siripin S., Kouno K.	Plant and Soil
Abstract: The leaves and nodules from the shrub and tree legumes, particularly, Aeschynomene spp., Sesbania spp., Mimosa spp. and Leucaena spp., and Casuarina spp. and the leaves from neighbouring non-fixing plants were analyzed for their natural abundances of 15N (δ 15N). The δ 15N in the leaves of non-fixing plants was +5.9% on average, whereas those from shrub legumes and Casuarina spp. were lower and close to the values of atmospheric N2, suggesting the large contribution of N2 fixation as the N source in these plants. The δ 15N values of the leaves from tree legumes except for Leucaena spp. were between the shrub legumes and non-fixing plants, which suggests that the fractional contribution of fixed N2 in tree legumes may be smaller than that in the shrub legumes. Casuarina spp. was highly dependent on N2 fixation. The δ 15N values of the nodules from most of the shrub legumes investigated were higher than those of the leaves. © 1990 Kluwer Academic Publishers. Keyword: δ 15N; Aeschynomene spp.; Casuarina spp.; Mimosa spp.; N2 fixation; Sesbania spp.; tree legumes Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-0025629063&doi=10.1007%2fBF00011121&partnerID=40&md5=b0745ab29ce29510cad647bd33cef549 DOI: 10.1007/BF00011121
1989	Nitrogen fixation (N‐15 dilution) with soybeans under Thai field conditions. IV. Effect of N addition and Bradyrhizobium japonicum inoculation in soils with indigenous B. japonicum populations Kucey R.M.N., Chaiwanakupt P., Boonkerd N., Snitwongse P., Siripaibool C., Wadisirisuk P., Arayangkool T.	Journal of Applied Bacteriology
Abstract: The effects of Bradyrhizobium japonicum inoculation and pre‐plant additions of N fertilizer on soybean (Glycine max L. Merrill) yields and levels of N2 fixation were studied under field conditions at two sites in Thailand. Bacterial inoculants were composed of B. japonicum strains selected for high N2 fixation levels in Thai soils. Nitrogen fertilizer addition rates used were from 0 to 250 kg N/ha in 50 kg N/ha increments. At the Chiang Mai site in northern Thailand, bacterial inoculation increased nodule weights on plants receiving 100 kg N/ha or less. Increases in nodule parameters due to inoculation were evident at 45 d after planting (DAP) but disappeared by 60 DAP. Addition of N fertilizers decreased the incidence of nodulation and sap ureide contents and decreased the contribution of N2 fixation to the N content of plants at maturity as measured by N‐15 isotope dilution methods. At the Kampang Saen site in central Thailand, bacterial inoculation had significant positive effects on nodule numbers and weights, ARA, sap ureide contents and levels of N2 fixed as measured by N‐15 isotope dilution methods. Addition of N fertilizers at this site also reduced the effectiveness of N2‐fixing symbioses. It was concluded that small additions of N fertilizer added before planting did not significantly decrease N2 fixation levels, but did have a significant positive effect on plant growth. Larger N additions would reduce N2 fixation levels in excess of the benefits of adding more N in chemical form. Copyright © 1989, Wiley Blackwell. All rights reserved Keyword: Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-0024309656&doi=10.1111%2fj.1365-2672.1989.tb03388.x&partnerID=40&md5=8927691f8884e97a482f8de8facddf57 DOI: 10.1111/j.1365-2672.1989.tb03388.x
1988	N2 fixation in Thai soybeans: Effect of tillage and inoculation on15N-determined N2 fixation in recommended cultivars and advanced breeding lines Rennie R.J., Rennie D.A., Siripaibool C., Chaiwanakupt P., Boonkerd N., Snitwongse P.	Plant and Soil
Abstract: The practice of seeding soybeans following paddy rice in Thailand has encountered difficulties in seedling germination, nodulation and crop establishment. This research project evaluated the choice of a non-fixing control to quantify N2 fixation by15N isotope dilution, and the effect of tillage regime, soybean cultivar, strain of Bradyrhizobium japonicum and P fertilization on yield and N2 fixation after paddy rice in northern and central Thailand. Japanese non-nodulating lines Tol-0 and A62-2 were the most appropriate control plants for15N isotope dilution for Thai soybeans in these soils which contained indigenous rhizobia. Cereals such as maize, sorghum and barley were also appropriate controls at some sites. The choice of the appropriate non-fixing control plant for the15N isotope dilution technique remains a dilemma and no alternative exists other than to use several possible controls with each experiment. Acetylene reduction assay (ARA) proved of little value for screening varieties on their N2 fixing capacity. The recommended Thai soybean cultivars (SJ1, 2, 4, 5) and an advanced line 16-4 differed little in their ability to support N2 fixation or yield, possibly due to similar breeding ancestry. The ten AVRDC (ASET) lines showed considerable genotypic control in their ability to utilize their three available N sources (soil, fertilizer, atmosphere) and to translate them into yields. None of these lines were consistently superior to Thai cultivars SJ4 or SJ5 although ASET lines 129, 209 and 217 showed considerable promise. Neither recommended Thai or ASET cultivars were affected by tillage regime. Zero tillage resulted in superior N2 fixation and yield at two sites but conventional tillage was superior at another site. Soybean cultivars grown in Thailand were well adapted to zero tillage. Levels of N2 fixation were similar to world figures, averaging more than 100 kg N ha-1 and supplying over 50% of the plant's N yield. However, seed yields seldom exceeded 2 t ha-1, well below yields for temperately-grown soybeans. It is not clear why Thai soybeans support N2 fixation, but do not translate this into higher seed yields. © 1988 Kluwer Academic Publishers. Keyword: 15N isotope dilution; Bradyrhizobium japonicum; Glycine max Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-0000033961&doi=10.1007%2fBF02139994&partnerID=40&md5=50a8c05d24aca718e503f6a0ed3dbdb4 DOI: 10.1007/BF02139994
1988	Adaptation of exotic Azolla to tropical environment of Thailand Choonluchanon S., Boonkerd N., Sawatdee P.	Plant and Soil
Abstract: There are seven known species of Azolla, two of which have been used in cultivated systems, the tropical species A. pinnata, and the temperate species A. filiculoides. Only A. pinnata is indigenous in Thailand. In this study the two exotic species, A. caroliniana and A. microphylla, were evaluated under the various tropical field conditions in Thailand. When compared with seven selected strains of A. pinnata under three field conditions, A. caroliniana and A. microphylla were similar to the indigenous species, in terms of growth performance, N2 fixation, and yield. This study suggests that A. caroliniana and A. microphylla can be successfully cultivated as a nitrogen fixing green manure for rice production in the tropics. © 1988 Kluwer Academic Publishers. Keyword: Anabaena azollae; Azolla caroliniana; Azolla microphylla; nitrogen fixing symbiosis Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-34250095453&doi=10.1007%2fBF02370100&partnerID=40&md5=249b608eff27f9efc2d184546e126cc4 DOI: 10.1007/BF02370100
1988	Mineral constraints to nitrogen fixation O'hara G.W., Boonkerd N., Dilworth M.J.	Plant and Soil
Abstract: Mineral nturient defiencies are a major constraint limiting legume nitrogen fixation and yield. In this review general techniques for assessing nutrient involvement in symbiotic nitrogen fixation are described and specific methods are outlined for determining which developmental phase of the symbiosis is most sensitive to nutrient deficiency. The mineral nutrition of the Rhizobium component of the symbiosis is considered both as the free living organism in the soil and as bacteroids in root nodules. Rhizobial growth and survival in soils is not usually limited by nutrient availability. Multiplication of rhizobia in the legume rhizosphere is limited by low Ca availability. Nodule initiation is affected by severe Co deficiency through effects on rhizobia. Nodule development is limited by severe B deficiency via an effect on plant cell growth. Fe deficiency limits nodule development by affecting rhizobia and strains of rhizobia differ widely in their ability to acquire sufficient Fe for their symbiotic development. Nodule function requires more Mo than does the host plant, and in some symbioses nitrogen fixation may be specifically limited by low availability of Ca, Co, Cu and Fe. The importance of the peribacteriod membrane in determining nutrient availability to bacteroids is considered. It is concluded that the whole legume-Rhizobium symbiosis should be considered when improving legume growth and yield under nutrient stress conditions. Differences among rhizobial strains in their ability to obtain mineral nutrients from their environment may be agronomically important. © 1988 Kluwer Academic Publishers. Keyword: (Brady) Rhizobium; bacteroid; legume; nodulation; nutrient deficiency; symbiosis Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-0344472780&doi=10.1007%2fBF02370104&partnerID=40&md5=6c265ab61812a7c845694649d4644a47 DOI: 10.1007/BF02370104
1988	Nitrogen fixation (15N dilution) with soybeans under Thai field conditions - I. Developing protocols for screening Bradyrhizobium japonicum strains Kucey R.M.N., Snitwongse P., Chaiwanakupt P., Wadisirisuk P., Siripaibool C., Arayangkool T., Boonkerd N., Rennie R.J.	Plant and Soil
Abstract: Controlled environment and field studies were conducted to determine relationships between various measurements of N2 fixation using soybeans and to use these measures to evaluate a number of Bradyrhizobium japonicum strains for effectiveness in N2 fixation in Thai soils.15N dilution measurements of N2 fixation showed levels of fixation ranging from 32 to 161 kg N ha-1 depending on bacterial strain, host cultivar and location. Midseason measures of N2 fixation were correlated with each other, but not related measures taken at maturity. Ranking of B. japonicum strains based on performance under controlled conditions in N-free media were highly correlated with rankings based on soybean seed yields and N2 fixation under field conditions. This study showed that inoculation of soybeans with effective B. japonicum strains can result in significant increases in yield and uptake of N through fixation. The most effective strains tested for use in Thai conditions were those isolated from Thai soils; however, effective strains from other locations were also of benefit. © 1988 Kluwer Academic Publishers. Keyword: 15N dilution; Bradyrhizobium japonicum strain; N2 fixation; nodule; soybean Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-0343633366&doi=10.1007%2fBF02370097&partnerID=40&md5=fd6bc223dced44880d9b85edac0aca78 DOI: 10.1007/BF02370097
1988	Nitrogen fixation (15N dilution) with soybeans under Thai field conditions - II. Effect of herbicides and water application schedule Kucey R.M.N., Chaiwanakupt P., Arayangkool T., Snitwongse P., Siripaibool C., Wadisirisuk P., Boonkerd N.	Plant and Soil
Abstract: Field experiments were conducted in northern Thailand to evaluate the effect of five herbicides and three watering schedules on soybean yields and N2 fixation. The herbicides sethoxydim, alachlor, fluazifop butyl and metolachlor when added at recommended rates for weed control did not result in detrimental effects on seed yields or benefits of N2 fixation. Paraquat additions significantly reduced the amount of N2 fixed as measured by15N dilution methods. Inoculation of the soil with a mixed strain inoculum of Bradyrhizobium japonicum increased seed yields and measurements of N2 fixation. The application of water to soybeans only when water stress symptoms such as wilting were observed resulted in drastic reductions in both yield and N2 fixation of four cultivars of soybeans. Reducing the water application from weekly to biweekly did not seriously reduce yields or N2 fixation benefits. © 1988 Kluwer Academic Publishers. Keyword: 15N dilution; herbicides; irrigation; N2fixation; soybean Scopus Link: https://www.scopus.com/inward/record.uri?eid=2-s2.0-0011968310&doi=10.1007%2fBF02370103&partnerID=40&md5=29300b2aaec3544e5061c588e2517309 DOI: 10.1007/BF02370103