Allelopathic effect of common weeds on soybean growth and soybean-Bradyrhizobium symbiosis

Water extracts of shoot of common lambsquarters (Chenopodium album), yellow nutsedge (Cyperus esculentus) and sunflower (Helianthus annuus) at 1% level significantly reduced soybean seed germination. Soybean seedlings inoculated with broth culture of nodule bacterium were grown for 25 days in N-free nutrient solution amended with cold water extracts of weed residues at 1 and 2% levels. At both levels extracts from residues of all weeds except that of lambsquarters enhanced growth of soybean. Nodulation was generally stimulated by the extracts of five weeds at 1% level except that of lambsquarters. Extracts from lambsquarters at 2% level completely suppressed and at 1% level reduced nodulation by 60%. Extracts from green foxtail (Setaria viridis), Pennsylvania smartweed (Polygonium pensylvanicum) and sunflower at 2% level reduced and at 1% level enhanced nodulation. The residues of lambsquarters shoot incorporated with soil at 0.5 and 1% levels caused 85 and 96% reduction respectively in seed germination and those of Pennsylvania smartweed and sunflower at 1% reduced seed germination by 40–70% but not at 0.5% level. The residues of foxtail and smartweed at both levels enhanced growth and nodulation. Under similar conditions nutsedge at 1% level stimulated nodulation but not growth. The residues of lambsquarters at both levels were inhibitory to nodulation but stimulated growth at 0.5% level.     

Biological and genetic characterisation of Phoma macrostoma isolates with bioherbicidal activity

The fungus Phoma macrostoma Mont. isolate 94-44B was registered as a bioherbicide for control of broadleaved weeds in Canada and the USA in 2011 and 2012, respectively. To obtain the registrations, the fungus had to be characterised both biologically and genetically. The objectives of this study were to demonstrate that bioherbicidal activity was associated with specific genetic markers and to determine whether bioherbicidal activity was a general trait of the species or only selected isolates. A collection of 64 isolates of P. macrostoma was established. A greenhouse bioassay and bioherbicidal-specific primers were used to determine bioherbicidal activity of all isolates. Only isolates originating from Canada thistle demonstrated the ability to reduce dandelion seedlings and display the 853 bp amplicon for the bioherbicidal-specific primer. Bioherbicidal isolates were consistently differentiated from all other isolates with two main genotypic groupings (I and II) arising from internal transcribed spacer (ITS) and amplified fragment length polymorphisms (AFLP) sequence analyses. Using AFLP, two biotypes of bioherbicidal isolates were also differentiated by the presence or absence of an AFLP marker at a single polymorphic locus. The genetic divergence among the bioherbicidal and nonbioherbicidal isolates of P. macrostoma was only 2.21% which was lower than that reported for other related Phoma sp. Other than the bioherbicidal trait, there was no apparent affiliation of the genetics with known varietal types, host or geographic origin. ITS sequence analysis and AFLP fingerprinting may be used as tools to detect bioherbicidal isolates of P. macrostoma.     

Antifungal efficacy of some ethyl acetate extract fractions of Cyperus rotundus rhizomes against spore germination of some fungi

Plant products play an important role as safe and ecofriendly method in controlling various plant diseases. Ethyl acetate fractions of Cyperus rotundus rhizomes have been found highly effective against some species of Alternaria (A. alternata, A. brassicola, A. solani, Alternaria chearanthi), Colletotrichum (C. musae, Colletotrichum sp.), Curvularia (C. lunata, C. maculans, C. pallescens, C. pennisetti), Helminthosporium (H. pennissetti, H. spiciferum, H. echinoclova and Heterosporium colocasiae) in vitro. A. brassisicola was highly sensitive to all the fractions at all the concentrations. Fractions 4–7 inhibited complete spore germination at 2000 and 3000 μg/ml as compared to control. However, 100% spore germination inhibition was found in Colletotrichum species in all the fractions at 2000 and 3000 μg/ml but at lower concentrations 50–60% spore germination and 90% reduction of germ tube elongation were observed. Curvularia species was highly sensitive to all concentrations of all the fractions as 50–100% spore germination inhibition was recorded at 500 μg/ml dose. Some species of Helminthosporium were sensitive at 3000 μg/ml in some fractions but other test fractions showed least efficacy. Fractions 4–7 were 100% inhibitory for H. colocasiae. Germ tube elongation was also affected by 60–90%. The germ tube branching and their elongation were affected in almost all species at 30 to 95%. The high efficacy of ethyl acetate fractions of rhizomes of C. rotundus against some fungi indicates that they can be very well tried under field conditions against some important plant diseases as an ecofriendly method of plant disease control.     

苹果树腐烂病菌拮抗放线菌的筛选、鉴定及防效

以苹果树腐烂病菌为靶标菌,通过对峙法和生长速率法对分离自苹果树根际土壤的放线菌进行筛选,对筛选出的拮抗菌株通过形态学和分子生物学特征进行鉴定,并测定了拮抗菌ZZ-9发酵滤液对苹果树腐烂病菌孢子萌发和菌丝生长的影响及离体枝条防效.结果表明: 经对峙初筛,15株放线菌对苹果树腐烂病菌具有抑菌作用,占所分离株数的18.8%,其中抑制率>50%的有8株.复筛结果表明,ZZ-9对腐烂病菌抑制率最高,达96.4%,显著高于其他菌株;通过培养特征、生理生化特性及16S rDNA序列分析将菌株ZZ-9初步鉴定为娄彻氏链霉菌,其在GenBank上的序列登录号为KT986228;不同稀释倍数的ZZ-9发酵滤液对腐烂病孢子萌发及菌丝生长均有明显的抑制作用,其中50倍发酵滤液对孢子萌发抑制率和菌丝生长抑制率均达80%以上,且受抑制菌丝颜色加深,分支增多,末端膨大、畸形,出现原生质浓缩与释放现象;离体枝条防效试验表明,菌株ZZ-9发酵原液对苹果树腐烂病防效可达75%以上,表明该菌株可作为防治苹果树腐烂病的生防菌株.     

Isolation,structural identification and herbicidal activity of N-phenylpropanamide from Streptomyces sp. KA1-3

The secondary metabolites produced by Streptomyces sp. KA₁-3, cultured on starch casein broth, was extracted by ethyl acetate and concentrated. Purification of the compound by thin layer chromatography lead to isolation of N-phenylpropanamide from one polar fraction. The structure of the herbicidal compound was elucidated on the basis of UV, FT-IR, mass and H¹ NMR spectroscopy. The herbicidal activity of the isolate was tested against the weeds Cassia occidentalis L. and rhizome Cyperus rotundus L. by moist chamber technique and rolled towel paper assay method. Herbicidal activity of the bioactive compound N-phenylpropanamide was further evaluated under in vitro condition. The herbicidal compound showed 80% of seed germination inhibition in C. occidentalis L. and rhizome C. rotundus L. weed. The actinobacterium can be used as a source for bioherbicidal agent.     

Allelopathic effect of lantana on some agronomic crops and weeds

Summary The allelopathic effects of dried lantana shoot residues was examined on wheat, corn, soybean, Virginia pepperweed and velvetleaf on growth over a 30-day period. Significant differences in the growth of the test species were observed. Corn was the most sensitive and wheat was least affected by lantana residues. The other three species were intermediate in their growth response to lantana. Shoot lengths were affected in corn and velvetleaf while root length was reduced in all species except wheat. The shoot dry weights of wheat and soybean were not reduced by lantana residues. In the other three species there was a significant reduction of shoot dry weight due to lantana. The root dry weights of all the five species were reduced by lantana residue. The results demonstrated an overall rate dependent response of the plant species to lantana shoot residue concentrations. Florida Agricultural Experiment Station Journal Series No. 7166. Research Associate and Associate Professor, respectively.     

Production of L-leucine aminopeptidase by selected Streptomyces isolates

Aims: To screen various Streptomyces cultures producing l ‐leucine aminopeptidase (LAP). Methods and Results: Twenty‐one Streptomyces strains were screened for LAP production. The best three producers were found to be Streptomyces mobaraensis NRRL B‐3729, Streptomyces gedanensis IFO 13427, and Streptomyces platensis NRRL 2364. pH optima of the three enzymes were in the range of 8·0–8·5 and the temperature optima varied between 50 and 65°C. LAP of S. mobaraensis was stable at 60°C and pH 8·5 for 60 min. Metal ion salts, CoCl₂.6H₂O and ZnSO₄.7H₂O in 0·7 mmol l^?1 concentration enhanced the relative enzyme activity in all three enzymes. Molecular mass of LAP of S. mobaraensis was found to be approx. 37 kDa. Conclusions: Streptomyces mobaraensis NRRL B‐3729, S. gedanensis IFO 13427, and S. platensis NRRL 2364 were found to be good producers of extracellular LAP. The approx. 37 kDa enzyme of S. mobaraensis is considerably thermostable. Significance and Impact of the Study: A good number of Streptomyces were screened and the ability of the aminopeptidases to release a particular N‐terminal amino acid along with its good thermal stability makes them interesting for controlling the degree of hydrolysis and flavour development for a wide range of substrate.     

番茄（Lycopersicon）的化感作用研究

采用室内生测、室外盆栽和水培相结合的研究方法,以多种受体品种来探讨番茄 的化感作用．结果表明,番茄植物不仅具有自毒作用,番茄植株的水提液对黄瓜、萝卜、生 菜、白菜、包心菜的幼苗生长均有显著的抑制作用;番茄植株的挥发物对黄瓜的生长具有 明显的抑制作用,但对绿豆、白菜、生菜及番茄自身的幼苗生长则无明显的影响;番茄移苗 后４０ ｄ之内,其根分泌物对黄瓜生长有明显抑制作用,但对生菜作用不明显认为自毒作 用是造成番茄连作障碍的原因之一,指出番茄种植应采用轮作方式,水培或大棚种植番茄 时,应避免与黄瓜间种．     

外来杂草反枝苋对农作物的化感作用及其风险评价

利用改进的差时播种共培法,以麦田伴生恶性杂草播娘蒿为对照,在实验室条件下研究反枝苋根系分泌物及其不同浓度残枝浸提液对小麦、玉米、油菜种子萌发及生长的影响.结果显示:(1)反枝苋幼苗的根系分泌物能够显著抑制作物根长和苗高的生长;(2)反枝苋不同浓度浸提液均能抑制作物种子的萌发,其抑制作用随浓度的增加而增强;(3)除0.025 g·mL-1处理对小麦根长和苗高、玉米苗高有促进作用外,其余各浓度反枝苋浸提液对作物幼苗的根长和苗高有不同程度的抑制,且对根长的抑制作用更强;(4)反枝苋对作物幼苗的抑制作用强于恶性杂草播娘蒿,风险评估定量分析结果认定反枝苋为陕西省高度危险性植物.     

Field Note: Phytoremediation of Petroleum Sludge Contaminated Field Using Sedge Species,Cyperus Rotundus (Linn.) and Cyperus Brevifolius (Rottb.) Hassk

The aim of this study was to degrade total petroleum hydrocarbon (TPH) in a petroleum sludge contaminated site (initial TPH concentration of 65,000–75,000 mg.kg^–1) with two native sedge species namely Cyperus rotundus (Linn.) and Cyperus brevifolius (Rottb.) Hassk. Fertilized and unfertilized treatments were maintained separately to record the influence of fertilizer in TPH degradation. The average biomass production (twenty plants from each treatment) of C. rotundus was 345.5 g and that of C. brevifolius was 250.6 g in fertilized soil during 360 days. Decrease in soil TPH concentration was higher in fertilized soil (75% for C. rotundus and 64% for C. brevifolius) than in unfertilized soil (36% for C. rotundus and 32% for C. brevifolius). In unvegetated treatments, decrease in soil TPH concentration in fertilized (12%) and unfertilized soil (8%) can be attributed to natural attenuation and microbial degradation. TPH accumulation in roots and shoots was significantly higher in fertilized soil in comparison to unfertilized soils (p < 0.05). Most probable number (MPN) in planted treatments was significantly higher than in unplanted treatments (p < 0.05).     

香附子块茎试管苗繁殖

以香附子块茎为材料,用组织培养的方法,进行试管苗繁殖研究。结果表明,1/3MS+炉灰渣培养基是块茎生长芽培养的适宜培养基;1/2MS+ZT 0.6 mg/L+NAA 0.1 mg/L是生长芽分化和继代分化繁殖培养的适宜培养基;1/2MS+ABT 2号6 mg/L+IAA 0.4 mg/L是生根和试管苗微型块茎培养的适宜培养基。培养30 d试管苗移栽成活率96%;培养60 d试管苗移栽成活率89.7%;种植的块茎发芽率99.8%;试管苗和微型块茎定植的成活率在99%以上;定植试管苗保持了香附子的植物学特征。     

几丁质酶产生菌的筛选及产酶条件的研究*

从301株几丁质降解菌包括细菌、放线菌和真菌中,筛选出一株产几丁质酶活力较高的链霉菌A048(Streptomycessp．A048)。其产酶的适宜条件是,培养温度30℃,培养基pH7．0～7．5,碳源几丁质,氮源NH4NO3,体积溶氧系数kd值为1．56×10-6mol／(mL·min·atm),振荡培养120h,产酶可达15．1U／mL。     

Bioherbicidal effect of fumonisin B1, a phytotoxic metabolite naturally produced by Fusarium nygamai, on parasitic weeds of the genus Striga

Fusarium nygamai has been isolated and identified from diseased Striga hermonthica plants collected from sorghum fields in the Sudan. Fumonisin B₁, produced by this fungus, was isolated and purified. In in vitro experiments, the bioherbicidal potential of this mycotoxin was evaluated against S. hermonthica and S. asiatica. Different concentrations (250, 500 and 1000 μg L^-1 of water) of fumonisin B₁, applied during the conditioning phase of the Striga seeds significantly reduced the germination of both species in a range of 19.8-32.2 and 34.5-47.6%, respectively. In addition, the length of the germ tubes was reduced and the germ tubes became brownish. Fumonisin B₁ slightly delayed the emergence of Striga when 250 mg fumonisin B₁ dissolved in 1 L of water were applied into the soil per pot before sowing sorghum. By the way of contrast, fumonisin B₁ was very phytotoxic when Striga seedlings (leaves and stems) of different heights and ages were sprayed with a concentration series of 250, 500 and 1000 μg fumonisin B₁ mL^-1 until run-off, or when plants were injured with a scalpel before fumonisin B₁ was applied into the injury at concentrations of 250 and 500 μg mL^-1. One day after application, the plants showed symptoms of wilting, first at the top and then moving downwards. Leaves turned black and stems desiccated at the point of injuries. Within 4 days after the application, 55% of the plants tested were completely destroyed. In total, at the end of the experiment, 40 days after the treatment, 85% of the treated plants were killed by fumonisin B_1, regardless of the concentration applied and the application technique used.     

海洋链霉菌Streptomyces sp. SCSIO 1672及其代谢产物水杨酸的分离鉴定

从南海海洋沉积物中分离得到1株海洋放线菌,鉴定为链霉菌Streptomyces sp. SCSIO 1672。通过优化发酵条件,采用海虾生物致死活性和高效液相色谱追踪,利用有机溶剂萃取、正相硅胶、反相硅胶等各种色谱层析方法分离出活性化合物,通过波谱数据解析出海洋放线菌SCSIO 1672次级代谢产物中的该活性化合物为水杨酸。     

Influence of senescence and of carbohydrate levels on the pattern of leaf proteases in purple nutsedge (Cyperus rotundus)

Cyperus rotundus L. is a monocotyledonous perennial weed, which forms large numbers of tubers during its vegetative growth. Since these tubers represent major sinks, source/sink interactions are more complex, and leaf senescence and proteolytic processes in this species may be different from the situation in the well‐investigated annual crop plants characterized by monocarpic senescence. Judged by native PAGE and by inhibitor studies, three different aminopeptidases, one iminopeptidase, two or more carboxypeptidases and two or more different endopeptidases were present in mature green leaves. Exo‐ and endoproteolytic activities increased during the senescence of excised leaf segments. A marked change was observed in the endopeptidase pattern, since a cysteine proteinase activity was strongly induced during senescence of the segments. This endopeptidase was also found in naturally senescing leaves and may, therefore, participate in nitrogen salvage from these organs. An increase of different protease activities was demonstrated in leaf segments of C. rotundus in the presence of high carbohydrate levels. The mechanisms involved, and the importance of this phenomenon for the interaction between source/sink relations and senescence, remain to be demonstrated.     

Discrepancies between MIC and MLC values of amphotericin B against isolates ofAspergillus species

There is little information addressing the phenomena of discrepancy between minimal inhibitory concentrations (MIC) and minimal lethal concentrations (MLC) values of amphotericin B (AMB) to clinical isolates of fungi. This study assessed in vitro activity of AMB against 70 clinical isolates of aspergilli: 30 strains ofAspergillus fumigatus, 20 strains ofAspergillus flavus and 20 strains ofAspergillus niger. Susceptibility tests were accomplished using a macro broth dilution procedure, with special emphasis on ascertainment of MLCs. AMB exhibited low MIC values against all clinical isolates. While we did not identify any AMB resistant isolates among 70Aspergillus spp. studied as judged by MIC levels, analysis of the data demonstrated a clear discrepancy between the MIC and MLC levels of AMB obtained against clinical isolates ofAspergillus spp. The MLC values of AMB were significantly higher than the MIC values with MIC 50 and MIC 90 of 0.29 and 0.5 µg/ml, respectively, at the second reading time, and MLC 50 and MLC 90 of 2.31 and 9.24 µg/ml, respectively (p<0.001). Additionally, minimal lethal concentrations in 36/70 (51%) of aspergillal isolates studied produced drug concentrations above those which can usually be sustained in patient plasma or tissue.     

Comparative study on removal of enteric pathogens from domestic wastewater using Typha latifolia and Cyperus rotundus along with different substrates

A comparative study was carried out to evaluate the efficiency of different substrate materials along with macrophytes Typha latifolia and Cyperus rotundus in treating domestic wastewater intended for reuse in agriculture. The study was conducted over a period of 6 months with different retention times, and observations were taken twice per month. One-way analysis of variance and Tukey's Honest Significant Difference (HSD) tests were used to determine statistical significant differences between experimental columns. Treatment with T. latifolia planted in sand and mix substrate with 4-day retention time remarkably reduced the concentration of all bacterial pathogens. Log reductions observed were approximately 5.01 and 4.82 for total coliform (TC), 4.46 and 3.93 for Escherichia coli, and 5.52 and 5.48 for Shigella, respectively. Moreover, these treatments were also efficient in completely removing fecal coliform (FC) and Salmonella.Maximum parasites were removed by the treatment having sand alone as a substrate containing C. rotundus, but the difference was not significant from those planted with T. latifolia in the same substrate. The results suggest that T. latifolia aids in bacterial pathogens removal, while C. rotundus aids in parasites removal. Thus, wastewater treatment through constructed wetland having mix plantation of these species along with sand can eliminate some of the major enteric pathogens.     

Noxious floating weeds of Malaysia

After ten years of field surveys on various water bodies ranging from stagnant water ponds, pools and man-made lakes to flowing waters such as rivers, streams and canals, there is a clear evidence of four problematic weeds in Malaysia. These species are Eichhornia crassipes, Salvinia molesta, Lemna perpusilla, and Pistia stratiotes. Among these weeds, E. crassipes and S. molesta are widely distributed througout Malaysia. E. crassipes generally dominates canals and rivers although, recently, this species has spread to man-made lakes. The favourable tropical climate and conducive environmental factors help to trigger the massive growth of these weeds. The high nutrient concentrations, notably phosphate which has a soluble reactive concentration greater than 0.1 mg l^–1, initiate a high productivity. Manual control methods are generally used and several herbicides including 2,4-D and glyphosate are frequently employed to eradicate these weeds.     

红薯叶片浸提液对5种主要农田杂草种子萌发及幼苗生长的化感作用

以发芽率、发芽势、根长、茎长和鲜重变化为种子萌发和幼苗生长参数,研究了作物红薯叶片水浸液对云南省农田5种恶性杂草牛膝菊、藿香蓟、鬼针草、马唐和稗草的化感作用。结果表明,红薯叶片水浸液对5种受体杂草种子发芽率的影响不明显,但对发芽势有显著抑制作用。牛膝菊、藿香蓟、鬼针草和马唐的根长和生物量随红薯叶片水浸液浓度增加而显著降低,其中对马唐的抑制最强,高浓度0.1 g/m L时对根长和生物量抑制率分别为92.04%和73.33%,而低浓度0.0125 g/m L时分别为40.99%和46.67%;其次为鬼针草、藿香蓟、牛膝菊;最差的是稗草,随浓度的变化趋势均不明显。随红薯叶片水浸液浓度增加牛膝菊、鬼针草和马唐的茎长显著地降低,其中对马唐的抑制最强,高浓度0.1 g/m L和低浓度0.0125 g/m L时分别为86.85%和70.64%;其次为鬼针草和牛膝菊;相反藿香蓟和稗草的茎长随浓度增加而显著增加,高浓度0.1 g/m L和低浓度0.0125 g/m L时对藿香蓟的促进率分别为86.97%和16.03%。红薯叶片水浸液低浓度0.0125 g/m L时对牛膝菊的茎长和生物量有促进作用(低促高抑)。从化感作用响应指数和综合效应指数的综合对比来看,红薯对牛膝菊、藿香蓟、鬼针草、马唐具有显著的化感抑制作用,随浓度增加其抑制能力显著增加;其中对马唐的为最强,其次为鬼针草、牛膝菊和藿香蓟,相反对稗草具有促进作用(除了浓度0.1 g/m L)。所有这些表明,红薯叶片水浸液对5种杂草化感作用的敏感性趋势总体为:马唐鬼针草牛膝菊藿香蓟,最不敏感或者具有促进作用的是稗草。