Some Microbiological Aspects of Staphylococcal Mastitis

(1) Mannitol fermentation is a reasonably reliable method for the detection of coagulase positive staphylococci in milk. This reliability can be improved if mannitol fermentation is carried out under anaerobic conditions.

(2) Among hemolytic strains of staphylococci isolated from milk, beta hemolytic staphylococci predominate. Bovine and sheep blood agar plates give similar hemolytic patterns, but the hemolysis is more pronounced on sheep blood agar.

(3) Gelatin liquefaction cannot be relied upon for the selection of coagulase positive staphylococci in milk.

(4) Urease production is a feature of the majority of coagulase positive staphylococci isolated from milk.

(5) Tellurite Glycine agar medium is not satisfactory for the selection of coagulase positive staphylococci in milk.

     

Distribution and Biocontrol Potential of phlD(+) Pseudomonads in Corn and Soybean Fields

ABSTRACT The abundance and diversity of phlD(+) Pseudomonas spp. colonizing the rhizospheres of young, field-grown corn and soybean plants were assayed over a 3-year period. Populations of these bacteria were detected on the large majority of plants sampled in the state of Ohio, but colonization was greater on corn. Although significant variation in the incidence of rhizosphere colonization was observed from site to site and year to year on both crops, the magnitude of the variation was greatest for soybean. The D genotype was detected on plants collected from all 15 counties examined, and it represented the most abundant subpopulation on both crops. Additionally, six other genotypes (A, C, F, I, R, and S) were found to predominate in the rhizosphere of some plants. The most frequently observed of these were the A genotype and a newly discovered S genotype, both of which were found on corn and soybean roots obtained from multiple locations. Multiple isolates of the most abundant genotypes were recovered and characterized. The S genotype was found to be phylogenetically and phenotypically similar to the D genotype. In addition, the novel R genotype was found to be most similar to the A genotype. All of the isolates displayed significant capacities to inhibit the growth of an oomycete pathogen in vitro, but such phenotypes were highly dependent on media used. When tested against multiple oomycete pathogens isolated from soybean, the A genotype was significantly more inhibitory than the D genotype when incubated on 1/10x tryptic soy agar and 1/5x corn meal agar. Seed inoculation with different isolates of the A, D, and S genotypes indicated that significant root colonization, generally in excess of log 5 cells per gram of root, could be attained on both crops. Field trials of the A genotype isolate Wayne1R indicated the capacity of inoculant populations to supplement the activities of native populations so as to increase soybean stands and yields. The relevance of these findings to natural and augmentative biocontrol of root pathogens by these bacteria is discussed.     

Identification and Characterization of Novel Genetic Markers Associated with Biological Control Activities in Bacillus subtilis

ABSTRACT Suppressive subtractive hybridization (SSH) was used to identify genetic markers associated with biological control of plant pathogens by Bacillus subtilis. The genomes of two commercialized strains, GB03 and QST713, were compared with that of strain 168, which has no defined biocontrol capacities, to obtain a pool of DNA fragments unique to the two biocontrol strains. The sequences of 149 subtracted fragments were determined and compared with those present in GenBank, but only 80 were found to correspond to known Bacillus genes. Of these, 65 were similar to genes with a wide range of metabolic functions, including the biosynthesis of cell wall components, sporulation, and antibiotic biosynthesis. Sixteen subtracted fragments shared a high degree of similarity to sequences found in multiple B. subtilis strains with proven biocontrol capacities. Oligonucleotide primers specific to nine of these genes were developed. The targeted genes included five genes involved in antibiotic synthesis (bmyB, fenD, ituC,srfAA, and srfAB) and four additional genes (yndJ, yngG, bioA, and a hypothetical open reading frame) not previously associated with biological control. All nine markers were amplified from the commercialized B. subtilis strains GB03, QST713, and MBI600, with the exception of ituC, which was not detected in GB03. The markers also were amplified from four other B. subtilis isolates, but they were not amplified from other related Bacillus strains, including the plant growth-promoting rhizobacteria IN937a and IN937b. Sequencing of the amplified markers revealed that all seven of the isolates that scored positive for multiple markers were genotypically distinct strains. Interestingly, strains scored positive for the amplifiable markers generally were more effective at inhibiting the growth of Rhizoctonia solani and Pythium ultimum than other Bacillus isolates that lacked the markers. The potential utility of the defined genetic markers to further define the diversity, ecology, and biocontrol activities of B. subtilis are discussed.     

水稻外来入侵软体动物的治理

本文阐述了福寿螺[Pomacea canaliculata (Lamarck)]的原产地概况、生活习性、传播特性、入侵及其危害特点。并特别指出,由福寿螺入侵所引起的经济、健康和环境的问题是一个不可逆转的过程,不但治理所需的费用巨大,而且多数措施对环境有害。为此,本文提出了福寿螺综合治理的方法和治理新策略,强调治理与利用并举,利用其作为动物和人类的营养食品,也可利用它来防治杂草。     

Impact of Subsurface Drainage on Improvement of Crop Production and Farm Income in North-West India

The Indian Council of Agricultural research has given priority to control and manage salinity problems that have developed in north-west India. Multi-disciplinary taskforces have recommended installation of subsurface drainage for salinity control, based on design and management techniques developed by the Central Soil Salinity Research Institute (CSSRI), to rehabilitate lands with excess soil salinity. After small-scale studies, large-scale pilot projects were launched to install subsurface drainage in problem areas. One such attempt in was initiated in the north-west region of India where a large-scale drainage project was carried out with Dutch collaboration. We assessed the impact of investments in subsurface drainage in order to validate past funding on research of drainage in India. The important methods used for assessing the efficiency benefits of drainage investment were: to determine the impact of subsurface drainage in terms of net present value, internal rate of returns, consumers' surplus and producers' surplus; to assess the social welfare in terms of social equality and sustainability of the drainage system; and to examine the factors affecting the sustainability of the technology. The internal rate of return was computed to assess the efficiency parameter of subsurface drainage for salinity management. In order to measure the changes in inequality distribution of income, Gini concentration ratios were computed with and without installing sub surface drainage. The Radar Approach, a method based on a graphical display of differences between actual ideal performance, was used to quantify drainage sustainability in terms of optimizing gains and conserving, or improving the quality of soil and water resources. There were several farm-level benefits as a result of installing subsurface drainage: these included: (i) a substantial increase in farm income; (ii) cropping intensification and diversification toward high value crops; and (iii) generation employment. A high internal rate of return justified investment in subsurface drainage. Income inequalities across farms were reduced. The radar approach showed improvement in sustainability in terms of economic gains and resource conservation. Despite of these economic, social, and environmental benefits, the sustainability of subsurface drainage technology is questionable. The specific reasons include: (i) the nature of the technology; (ii) lukewarm collective action by the beneficiaries; (iii) conflicting objectives among beneficiaries; and (iv) growing numbers of free riders. To a large extent these were addressed in the study area by forming village committees. Without appropriate institutional arrangements, subsurface drainage may not yield the desired results, and in the long run may result in neglect of operation and maintenance needs and ultimately the abandonment of the technology.     

Seasonal pattern of total soil respiration in undisturbed and disturbed ecosystems of Central Himalaya

Summary The rates of CO₂ efflux were measured by an alkali absorption method (using 20 ml 0.5 N NaOH) from soils in four undisturbed sites [two evergreen oak forests, Quercus floribunda Lindl. (tilonj oak), Quercus leucotrichophora A Camus (banj oak), and two evergreen conifer forests, Cedrus deodara Loud. (deodar forest) and Pinus roxburghii Sarg. (chir pine forest)] and three disturbed sites. The sites were located between elevations of 1850 and 2360 m in the Central Himalaya. The seasonal pattern of soil respiration was similar in all the sites with a maximum during the rainy season, intermediate rates during the summer season and the lowest level of activity in winter. The rate of CO₂ efflux was higher in broadleaf than in conifer forests, and it was lowest in the disturbed sites. Among the edaphic conditions, soil moisture, N, organic C, pH, soil porosity, and root biomass positively affected total soil respiration. The proportion of root respiration to total soil respiration was higher in the disturbed sites than the undisturbed sites in winter. Conditions in the winter season were less favourable for microbial respiration than for root respiration.     

Helminthosporium leaf blight resistance and agronomic performance of wheat genotypes across warm regions of South Asia

Helminthosporium leaf blight (HLB) is the most important disease constraint to wheat (Triticum aestivum L.) cultivation in the eastern Gangetic Plains of South Asia. A Helminthosporium Monitoring Nursery (HMN) including potential adapted and exotic sources of HLB resistance was developed in Bangladesh, India and Nepal to assess the stability of genetic resistance across locations. The 8th, 9th and 10th HMN assessed the HLB resistance and agronomic traits of 17 wheat genotypes across 20 environments of Bangladesh, India and Nepal in the 1999‐2000, 2000‐2001 and 2001‐2002 cropping seasons, respectively. The area under the disease progress curve (AUDPC) for HLB, grain yield, thousand‐kernel weight (TKW), days to heading, days to maturity, and plant height were examined. The 17 genotypes showed a range of variability for disease and agronomic characters. Disease severity (AUDPC) differed in the 3 years and showed the highest values in 2002. The increase in AUDPC in 2002 caused the lowest grain yield, with an average 18% reduction due to HLB. A few genotypes (SW 89‐5422, Yangmai‐6 and Ning 8201) appeared to have stable HLB resistance across environments. However, most of the higher‐yielding genotypes, except BL 1883, were unstable. The results suggest that careful selection of HLB resistance with acceptable grain yield, TKW and plant height may be possible using the wheat genotypes included in the HMN.