Molybdenum reserves of seed,and growth and N2 fixation by Phaseolus vulgaris L.

Summary Plants grown from seed with high (1.5–7.3 g Mo seed^-1) and low (0.07–1.4 g Mo seed^-1) Mo contents were grown in the presence and absence of Mo in growth media (perlite) or in a flowing-solution culture, in a controlled environment. Neither the high (1.5 g Mo seed^-1) nor the low (0.1 g Mo seed^-1) Mo content in seed from a small-seeded genotype (BAT 1297) was able to prevent Mo deficiency (reduced shoot, root and nodule dry weight, N₂ fixation and seed production) in growth media without an external supply of Mo, whereas both the high (7.3 g Mo seed^-1) and the low (0.07 g Mo seed^-1) contents in seed were able to prevent Mo deficiency in a large-seeded genotype (Canadian Wonder). Responses to Mo treatment by the Two genotypes were inconsistent between the growth media and solution culture experiments. Seed with a large Mo content (3.5 g Mo seed^-1) from the Canadian Wonder genotype was unable to prevent Mo deficiency (reduced shoot and nodule dry weight and N₂-fixation) in a solution culture without an external source of Mo, whereas both the large (1.7 g Mo seed^-1) and the small (0.13 g Mo seed^-1) contents in seed prevented a deficiency in BAT 1297. Growing plants from seed with a small Mo content, without additional Mo, reduced the seed Mo content by 83–85% and seed production by up to 38% in both genotypes. Changes in seed size and increases in shoot, root and nodule dry weight occurred, but varied with the genotype and growth conditions. These effects were also observed in some cases where plants were grown with additional Mo, demonstrating that the amount of Mo in the seed sown can influence plant nutrition irrespective of the external Mo supply. Nodule dry weight, total N content of shoots and seed production were improved by using seed with a small Mo content (1.64–3.57 g Mo seed^-1) on acid tropical soils in Northern Zambia. Plants of both the large- and small-seeded genotypes grown from seed with a small Mo content (<1.41 g Mo seed^-1) had a smaller nodule weight, accumulated less N and produced less seed. The viability of seed with a small Mo content was lower (germination up to 50% less) than that of seed with a large Mo content.     

Estimation of associative nitrogen fixation in relation to water regime and plant nutrition in a long-term pot experiment with rice (Oryza sativa L.)

Summary The contribution of associative N₂ fixation to the N nutrition of lowland rice was estimated in a long-term pot experiment with ten consecutive crops of rice. The experiment comprised two N and two K levels with wet (WF) and dry fallow (DF) between the cropping seasons. Growth of N₂-fixing cyanobacteria was prevented. Greatest yields were obtained in the high NK fertilizer treatment, but with continuation of the experiment yields responsed more to DF than to WF. Nitrogenase activity, however, was favoured by WF. Higher K application increased and higher N application decreased nitrogenase activity. Under WF treatments the organic C and total N contents of the soil remained unchanged during the experimental period, but alternate drying and flooding in DF treatments caused a decline. Lower N fertilizer rates in the second five-crop period did not affect yields, but increased the ratio of N removed to N applied. For the ten-crop period the estimated N balance was positive in the low-N and negative in the high-N treatments. N balances were also established separately for both the first and the second halves of the ten-crop period. In the first period N losses were higher, and the N balance was mostly negative. In the second period only high-N combined with low-K fertilization resulted in a negative N balance. DF favoured N losses in the first but not in the second period. The highest N gain in the second period was found in the DF treatment with low-N and high-K application. In this treatment, nearly one-quarter of the N taken up by the above-ground parts of the plants could be ascribed to associative N₂ fixation. In the corresponding treatment with the higher N level and a 49% higher yield, the contribution of fixed N declined to less than 5%. When harvested straw contained more than 10 mg N g^–1, the N balance was mostly negative, while at N contents less than 10 mg N g^–1, the N balance was generally positive.     

Effect of high temperature on growth,nitrogen fixation,and chlorophyll content of five species of Azolla Anabaena symbiosis

Summary Cultures of Azolla sp. ST-SI, A. microphylla BR-GI, A. mexicana BR-GL, A. caroliniana WT-V, and A. filiculoides BR -H were grown in N-free International Rice Research Institute growth medium in the glasshouse at 38±1 °C (day) and 25±1 °C (night) under a light intensity of 350 Em²s^–1 for 27 days. Biomass, chlorophyll contents and nitrogenase activity (acetylene reduction assay) were recorded on the 19th and 27th day. For comparison the same parameters were studied in Azolla spp. under normal growth conditions at 26±1 °C (day) and 19±1 °C (night). Azolla sp. STSI and A. microphylla BR-GI had produced a larger biomass by the 19th and the 27th day of incubation than A. caroliniana WTV and A. filiculoides which showed poor growth. Under normal growth conditions A. caroliniana WTV and A. filiculoides BRH produced less biomass than the other Azolla spp. cultures tested. A. mexicana BR-GL had a higher total chlorophyll content in both incubation periods than A. caroliniana WT-V and A. filiculoides BR-H. The N content was high in Azolla sp. ST-SI, A. microphylla BR-GI, and A. mexicana BR-GL compared with the low N content of A. filiculoides BR-H and A. caroliniana WT-V. At the higher temperature (38±1 °C/25±1 °C) Azolla sp. ST-SI and A. microphylla BR-GI consistently showed a higher growth rate than A. filiculoides BR-H and A. caroliniana WTV, while the growth rate of A. mexicana BR-GL was intermediate.The study was carried out at C.F. Kettering Research Laboratory, Yellowsprings, OH - 45387, USA     

5种蒿属植物提取物对马铃薯晚疫病的抑菌活性研究

以牛尾蒿、黑蒿、艾蒿、青蒿及茵陈蒿5种蒿属植物的乙醇提取物为供试药剂,采用带毒平板法测定蒿属植物的乙醇提取物对马铃薯晚疫病pn5502和pn7604菌株的抑菌活性,采用硅胶柱层析法对牛尾蒿的乙醇提取物的抑菌活性成分进行追踪,筛选抑制马铃薯晚疫病菌活性成分。结果表明：当各粗提物浓度为1 mg/mL时,对供试菌株均有一定的抑菌活性,其中牛尾蒿粗提物的抑菌活性最强,对菌株pn5502和pn7604的抑菌率分别为89.04%和71.38%。其中,馏分Fr₁浓度为0.5 mg/mL时,对2株菌的抑制活性高达100%。馏分Fr₁对pn5502的EC₅₀为7.4733 μg/mL,对pn7604的EC₅₀为9.4634 μg/mL。因此,5种蒿属植物的乙醇提取物对2株马铃薯晚疫病均有一定的抑菌活性,其中牛尾蒿馏分Fr1抑制作用最强,抑菌活性高于阳性对照药剂霜脲·锰锌,其抑菌活性成分值得进一步研究。     

The in vitro motility response to various anthelmintics of third-stage larvae of Oesophagostomum spp. from pigs

The in vitro activities of thiabendazole, levamisole, pyrantel, morantel and ivermectin against Oesophagostomum spp., the nodular worm of pigs, were determined and compared. The study was carried out using isolates of O. dentatum and O. quadrispinulatum, which had been defined in vivo. Infective larvae were exposed to the anthelmintics for 24 h and then placed in a micromotility meter. All the treatments significantly reduced the motility of the ensheathed L₃ larvae, but the micromotility meter was not able to differentiate between anthelmintic resistant and anthelmintic susceptible isolates.     

高寒地区燕麦根际联合固氮菌研究 Ι固氮菌分离及鉴定

结合气相色谱仪,利用乙炔还原等方法对高寒地区重要饲用植物——燕麦(Avenasativa)根际联合固氮菌进行了分离和鉴定。结果表明,该地区燕麦根际联合固氮菌株较少(8株),菌株分布以根系表面(RP)最多,根表土壤(RS)次之,距根系较远的土壤(NRS)和根内(HP)最少,即:RP>RS>NRS≥HP;菌株固氮酶活性相差较大(C2H4112.5～1147.9nmol/mL·h),具有较高固氮酶活性的菌株较少(C2H4大于500nmol/mL·h只有2株);菌株均为革兰氏阴性菌,经鉴定分属Azotobacter(3株)、Pseudomonas(3株)和Azospirillus(2株)3个属。相对于其它生境和植物,高寒地区燕麦根际联合固氮菌种类较为单一。     

一株鸭源禽流感病毒（H9N2）全基因序列分析及其排毒规律的研究

为研究一株鸭源H9N2亚型禽流感病毒(JN1株)全基因组的分子特征和遗传进化情况以及感染雏鸭后的排毒规律,对其生物学特性、全基因组序列以及遗传进化进行了分析,通过点眼滴鼻方式感染3周龄健康雏鸭,利用建立的实时荧光定量PCR(RT-PCR)检测鸭的排毒规律,并测定血清抗体效价。JNI株的鸡胚半数感染量为10~(-7.54)/0.2mL,鸡胚最小致死量的平均死亡时间为72h,静脉致病指数为0.266,抗原相关系数为0.47。系统发育分析表明,JN1株的HA与CK/HK/G9/97和DK/HK/Y280/97在同一分支上,NA、M、NP、PA、PB1、PB2基因与SH/F/98同源性较高,NS基因则与H5N1亚型禽流感病毒进化关系较近。HA的裂解位点为PSRSSR↓GL,存在6个潜在糖基化位点,在234位的氨基酸残基为L,NA基因颈部存在缺失。雏鸭在感染该病毒后,饮食正常,精神良好,3~17d均有排毒,咽拭子和泄殖腔棉拭子排毒规律基本一致,分别在第3天和第13天出现排毒高峰。该H9N2亚型禽流感病毒属欧亚大陆分支,为低致病性禽流感,病毒可通过呼吸道和泄殖腔向外界排毒,排毒时间较长。     

Application of time-resolved fluorometry to immunoassays for bovine reproductive hormones

The principle of time‐resolved fluorometry with lanthanide chelates was established in the 1980s, but in the field of animal sciences it has not been widely applied to immunoassays. However, immunoassays that utilize time‐resolved fluorometry are possible alternatives to radioimmunoassays, since they can attain high sensitivity without safety risks. In this short review, we introduce the development of time‐resolved immunoassays for inhibin A, inhibin B and follicle‐stimulating hormone (FSH), and describe their application to the investigation of FSH regulation in male and female cattle. The results obtained using these newly developed immunoassays indicate that inhibin A acts as a feedback regulator for FSH secretion in female cattle, whereas inhibin A, and probably inhibin B, do so in male cattle.     

A novel enzyme-linked immunosorbent assay for the detection of Wx-B1 null wheat lines using a monoclonal antibody and its application for the detection of marker heterogeneity within commercial cultivars

A monoclonal antibody was raised with specificity for the granule bound starch synthase (GBSS1) Wx-B1 homeoallele of wheat (Triticum aestivum L.) using a synthetic peptide immunogen. This was used to develop a simplified enzyme-linked immunosorbent assay (ELISA) for the discrimination of Wx-B1a and Wx-B1b alleles which differ in the starch properties they confer. Discrimination of these alleles is important for the selection of wheat lines for Udon-style noodle production. The simplified ELISA worked in a single antibody (indirect) format and gave improved ease of use, discrimination of alleles and resolution relative to a previously developed 2-antibody (sandwich) ELISA. When the test was validated using breeders seed of a panel of commercial cultivars, heterogeneity of Wx-B1 alleles was observed for a significant proportion of the cultivars tested and this was confirmed using PCR analysis of the Wx-B1 and Wx-A1 genes. This observation has implications for cultivar wheat quality assessment, the application of molecular markers for variety identification purposes and the establishment of mapping populations from commercial cultivars.