木霉菌REMI变异株对部分生态因子的影响

采用常规微生物分离和植物生物量测定等方法,将木霉菌REMI变异菌株的孢子进行种子接菌、土壤接菌、水中接菌,研究木霉菌REMI变异菌株对农作物甜瓜和玉米及杂草等生长性状、甜瓜根际土壤微生物和鱼苗生长以及在水中存活等的影响,检测其生物安全性。结果表明,除Ttrm53外,其余木霉菌变异株和出发菌株T21对甜瓜和玉米种子安全,并且能够显著提高种子的出苗率、增加须根数和促进幼苗生长;部分变异菌株对杂草具有抑制作用;供试木霉菌变异株对甜瓜根际土壤真菌有抑制作用,对细菌和放线菌群体数量无显著影响;木霉菌孢子在河水及自来水中均不能萌发,分生孢子在水中存活约12～18天,厚垣孢子约18～27天,菌体自行消解;对鱼苗生长没有不良影响。     

树舌灵芝发酵液醇溶物对杂草植物生长的影响

以夏至草、稗草和反枝苋为受体杂草植物,采用琼脂混粉法研究了不同浓度树舌灵芝发酵液醇溶物对杂草植物生长的影响.结果表明:树舌灵芝发酵液醇溶物对稗草的胚根、胚轴具有明显的抑制作用;对夏至革和反枝苋胚根的抑制作用较弱,而对它们的胚轴具有促进生长的作用,且对反枝苋的促进作用尤其明显.     

禾长蠕孢菌和尖角突脐孢菌防治稗草的研究

 病原真菌禾长蠕孢菌稗草专化型(Helminthosporium gramineum Rabenh f.sp.echinochloae,HGE)和尖角突脐孢菌(Exserohilum monoceras,EM)在稗汁葡萄糖中的发酵滤液对稗草种子的发芽有明显的抑制效果,发芽抑制率分别为30.9%和13.5%.HGE菌在改良Fries、稗汁葡萄糖,EM菌在改良Fries中的发酵滤液对稗草根和芽的生长有明显抑制作用.HGE菌发酵滤液与其孢子混合使用比单独使用对稗草的防效明显提高,稗草感病株率、致死率分别达86.3%和69.5%,病情指数为78.7;发酵滤液与孢子结合(先后喷雾)使用后稗草的感病株率、致死率分别为83.9%和67.9%,病情指数为72.8.HGE与弯孢菌(Curvularia lunata)孢子混合喷雾接种对稗草防效明显高于2种菌孢子单独使用.     

水稻对无芒稗的异株克生研究初报

稗草与水稻竞争后降低水稻产量和质量。不同株型水稻与稗草的竞争力存在显著差异 ,高秆大冠层株型水稻可以明显减少产量损失[1,2 ] 。与生态竞争研究相关的水稻异株克生研究近年来日趋活跃 ,埃及科学家Ｈａｓｓａｎ[3,4] 于 1 993～ 1 996年开展了水稻与稗草的异株克生关系的研究 ,发现约有 30份材料可以控制田间稗草 5 0 %～ 90 %的生长。Ｏｌｏｆｓｄｏｔｔｅｒ[5 ] 等在菲律宾国际水稻所进行了水稻异株克生研究 ,发现有 1 1份材料在旱季可以使稗草的干重减少 5 0 %以上 ,2 1份使稗草干重减少 40 %～ 5 0 % ;有 2 1个品种在雨季抑制稗草在…     

玉林市早稻稗草发生为害较重

玉林市2004年早稻稗草为害较重,是多年来未见过的。据在水稻后期组织各地普查后推算。全市稗草发生面积5．46万hm^2。占种植面积40．91％,为害面积1．66万hm^2,占种植面积12．45％;其中为害较重的(有稗草20株／m^2以上)面积0．31万hm^2。为害重的田块有稗草53～88株／m^2;一般有5～20株／m^2,一些不及时除稗的田块损失产量达5％～100局。由于稗草发生较重,杀稗王、灭稗净等二氯喹啉酸的除草剂销售好,并曾一度出现脱销现象。     

稻蝗肠道真菌的除草活性筛选及菌株DH03的鉴定

利用涂布平板法从中华稻蝗肠道中分离得到6株真菌,活性筛选试验表明菌株DH03具有较好的除草活性。当供试质量浓度为100 μg/mL时,该菌株发酵液的乙酸乙酯提取物对稗草和反枝苋根生长的抑制率均大于80%,比阳性对照2,4-二氯苯氧乙酸的活性好;进一步研究表明发酵液活性物质主要集中在中等极性部分;该菌株的发酵液对盆栽稗草幼苗生长表现出较强的抑制作用,当喷施发酵液原液时,稗草的受害率和均株高分别为36.1%和9.78 cm。经形态学观察和ITS序列分析确定该菌株为Cladosporium oxysporum。DH03作为微生物源除草剂值得进一步研究。     

拮抗性木霉菌株抗逆性筛选评价标准与方法

本研究旨在为高效筛选耐受高温胁迫、低温胁迫、盐胁迫及干燥（干旱）胁迫拮抗性木霉菌株提供筛选阈值。根据5种、20株拮抗尖孢镰孢菌效果较好的木霉菌对上述逆境因子的反应差异,建立每种逆境因子在不同水平下的木霉菌株生长和酶活变化检测阈值和标准化评价方式;分析木霉菌在不同胁迫条件下发育相关生化因子与菌株生长变化之间的关系,及相应胁迫下的孢子萌发率与菌落直径之间的相关性。通过正态性检验获得供试木霉菌株生长响应胁迫的阈值为：1 mol/L NaCl（盐胁迫阈值）,36℃（高温胁迫阈值）,14℃（低温胁迫阈值）,400 g/L PEG-6000（干旱胁迫阈值）。相应胁迫下的菌落直径与孢子萌发率明显正相关。菌株在大部分胁迫下的抗坏血酸过氧化物酶（APX）及过氧化氢酶（CAT）酶活与菌丝干重有明显的相关性。本研究为科学评价生物防治木霉菌资源的抗逆性提供了依据。     

突脐蠕孢与弯孢原生质的双亲灭活融合

采用灭活原生质体方法,对致病力强、产孢量低的突脐蠕孢EM菌株和致病力较弱、但产孢量高的弯孢CL菌株两株稗草致病菌进行原生质体融合,通过观察形态、生物学及抑草活性等特性筛选融合子。结果表明,2%溶壁酶+2%蜗牛酶处理获得两亲株的原生质体释放数量最高,CL和EM分别达1.25×106个/ml和1.21×106个/ml;再生培养基○c处理的CL和EM原生质体再生率分别达14.7%和13.2%。EM利用热灭活55℃5min;CL利用紫外灭活30s,距离20cm,照射时间4min;聚乙二醇促融,获得3个融合子。融合子在孢子形态上与亲株存在明显差异,其菌丝生长速度、孢子产量、对稗草根生长的抑制作用等也与双亲菌株有差异。     

哈茨木霉菌T21转化体生物学特性研究

本研究表明,木霉菌转化体孢子萌发率有的高于野生菌株,如菌株Ttrm3,有的低于野生菌株,如菌株Ttrm47和Ttrm94;菌株Ttrm34产孢能力极显著高于野生菌株T21,而菌株Ttrm94和Ttrm111极显著低于野生菌株T21,菌株Ttrm111根本不产孢;对高温的适应能力也存在差异,其中菌株Ttrm31、Ttrm34、Ttrm47和Ttrm76比较耐高温,而菌株Ttrm55、Ttrm94和Ttrm111较差,短时间高温处理能够促进木霉菌转化体生长。不同木霉菌对低温(15℃)的适应也不同,菌株Ttrm76、Ttrm31和Ttrm55生长速度快于野生菌株T21,而菌株Ttrm94和Ttrm111生长明显慢于T21;在20~30℃范围内,菌株Ttrm31、T21、Ttrm34和Ttrm55生长速度基本一致,生长较快,菌株Ttrm94生长却很慢;超过30℃,菌株Ttrm76、Ttrm111和Ttrm47生长比较快,生长速度大于T21。不同pH条件下,木霉菌转化体培养形态和产孢方式均有变化。木霉菌转化体利用氮源较好的是蛋白质和天冬氨酸,碳源较好的是麦芽糖和葡萄糖。不同木霉菌转化体培养性状也不同,如菌株Ttrm111不产孢;菌株Ttrm94产孢少,两者培养颜色为黄色,而其他菌株为绿色。     

营养元素对木霉菌防治甜瓜枯萎病效果的影响

为明确各种营养元素在木霉菌防治甜瓜枯萎病生防体系中的作用,研究了9种营养元素铜、锌、铁、硼、钼、钙、锰、镁及钾对甜瓜枯萎病菌菌丝生长、木霉菌T23菌丝生长及产孢量、甜瓜种子萌发及根系生长的影响.结果表明:10～1000μg/mL的硫酸铜、硫酸锌、硫酸亚铁及硼酸对镰孢菌菌丝生长有较强的抑制作用,而对木霉菌的抑制作用远小于镰孢菌.适量加入钼酸铵、硫酸亚铁、硫酸钙及磷酸二氢钾有利于木霉菌菌丝生长及孢子形成,对甜瓜种子萌发及胚根生长也有较强的刺激作用.木霉菌结合钼酸铵、硫酸锰和硫酸钙处理土壤能显著降低甜瓜枯萎病的病情指数,相对防效分别为73.95%、73.77%和71.36%.     

稻田稗属杂草致病菌的分离与鉴定

稗草Echinochloa crus-galli作为稻田难以防除的恶性杂草,严重影响水稻产量。为发掘具有防治稻田稗草潜力的生防菌,本研究从江苏、广西、贵州三省采集感病稗草,采用组织分离法获得10株对稗草致病性较强的优势菌株。通过观察优势病原菌的形态特征,结合rDNA-ITS、GAPDH、EF-1α基因片段序列分析确定10株菌分别为新月弯孢Culvularia lunata、尖角突脐蠕孢Exserohilum monoceras、禾长蠕孢菌Setosphaeria rostrata、稻平脐蠕孢Bipolaris oryzae、梭形突脐蠕孢Exserohilum fusiforme、澳大利亚弯孢Curvularia australiensis、双色平脐蠕孢Bipolaris bicolor、高粱附球菌Epicoccum sorghinum、亚隔孢壳属Didymella americana和亚隔孢壳属Didymella pinodella。该研究丰富了稗草病原菌生物资源,为进一步开发稻田生物除草剂提供了新材料。     

Effects of glycerol ethers on monocotyledon nucleic acid and protein biosynthesis

The growth of the root systems of 2-day-old wheat seedlings was more sensitive to the experimental herbicide WL 29226 than was the growth of the shoots. Inhibition of root growth was observed after 12 hr of exposure to the herbicide. The nuclear activity in these root systems, as estimated by RNA and DNA synthesis, was significantly inhibited before this time, ～30% after 4 hr increasing to ～55% after 8 hr. Nuclear activity was inhibited by ～80% after 24 hr and showed little increase in inhibition with any further increase in exposure to the herbicide. Protein synthesis was initially less inhibited, ～6% after 4 hr, rapidly increasing to ～40% after 8 hr. DNA polymerase activity was monitored as an indication of the nucleic acid biosynthetic capacity of herbicide-treated maize and barnyard grass chromatin. In both plants, the herbicide induced an inherent modification of this activity. In maize this was reflected by an inhibition of activity and in barnyard grass by a stimulation. The effect on barnyard grass chromatin is likely to be more complex than in maize because of the presence of a chromatin-bound DNase in the chromatin from control plants. There is no evidence for such an enzyme in the chromatin from either maize or glycerol ether-treated barnyard grass. The apparent stimulation of DNA polymerase activity may in some way be associated with the loss of this nuclease activity. In order to obtain an inhibition of chromatin DNA polymerase, the plants must be pretreated with the herbicide prior to chromatin extraction. The failure of the herbicide to induce an inhibition in vitro on isolated chromatin does not support a direct interaction between the herbicide and chromatin. The results suggest that, following herbicide application to the plant, chromatin integrity has been altered.     

Behavior of pyriftalid in soil and its phytotoxic activity on Echinochloa oryzoides seedlings emerging from various soil depths

The phytotoxic activity of pyriftalid ([RS]‐7‐[4,6‐dimethoxypyrimidin‐2‐ylthio]‐3‐methyl‐2‐benzofuran‐1[3H]‐one) on barnyard grass (Echinochloa oryzoides) seedlings emerging from various depths in the soil was investigated in relation to its behavior in the soil. The growth of the barnyard grass seedlings in the soil mixed with pyriftalid was inhibited, depending on the concentration of the herbicide in the soil water but not on the amount in the total soil. A topmost pyriftalid‐treated layer was formed by applying the herbicide to the soil surface under water‐leakage conditions. The concentration of pyriftalid in the soil water and the amount that was adsorbed on the soil solid decreased with time, but the decrease was more marked in the pyriftalid concentration in the soil water than in the amount that was adsorbed on the soil solid. The emergence time of barnyard grass in the soil was faster in the seeds that were located in the shallower soil layer, compared to the deeper soil layer. The growth inhibition of the barnyard grass seedlings emerging from the shallower soil layer was greater than that of the barnyard grass seedlings emerging from the deeper soil layer after the soil surface application of pyriftalid. It is suggested that the emergence timing from the different soil depths is an important factor affecting the herbicidal activity of pyriftalid when it is applied to the soil surface under paddy field conditions.     

水稻田除草剂三唑磺草酮的作用特性

为了明确水稻田除草剂三唑磺草酮(QYR301)的最佳施药条件,以稗草Echinochloa crus-galli和水稻Oryza sativa作为测试靶标,采用温室盆栽法研究了其施药适期、耐雨水冲刷性、温度和光照强度对其除草活性的影响。结果显示:三唑磺草酮对不同叶龄水稻具有较高的安全性,在有效成分360 g/hm^2的剂量下,对2叶期以后的水稻干重抑制率为0%;其除草活性与稗草的叶龄显著相关,其中2~3叶期的稗草最为敏感,有效成分30 g/hm^2的三唑磺草酮对其干重抑制率为95%~98%;三唑磺草酮具有一定的耐雨水冲刷能力,药后降雨间隔达到8 h以上,其除草活性与药后降雨间隔时间无显著相关性,在有效成分30~120 g/hm^2的剂量下,对稗草的干重抑制率为75%~93%;在20~35℃区间,三唑磺草酮药效稳定,对稗草的GR50值在44.6~51.4 g/hm^2之间;相较于中度光照(45%)和低光照(4%),高光照(100%)条件下三唑磺草酮对稗草的干重抑制率显著增加。分析表明杂草叶龄、降雨、温度和光照会显著影响三唑磺草酮除草活性,为使其发挥最大药效,应选择在水稻2叶期以后至稗草2~4叶期,天气晴朗,气温高于20℃的情况下施药;如药后8 h以内遇降雨天气,则需进行补喷。     

Potential of barnyard grass to remediate arsenic‐contaminated soil

The present study investigated the arsenic (As) remediation potential of barnyard grass (Echinochloa crus‐galli L. Beauv. var. formosensis Ohwi), with a special focus on the behavior of As in the soil in comparison with rice (Oryza sativa L. cv. Nipponbare). For both plants, very little growth inhibition was observed in the As‐contaminated soil. The amount of As in the soil was reduced by the plant's uptake and the level of As in the soil water from the rice‐growing pots was remarkably lower than that in the plant‐free soil water. In the soil with the barnyard grass, the amount of As in the soil water was higher than that in the plant‐free soil water, but the amount of As in the soil and the amount of As that was adsorbed on the soil solid were reduced by the plant's uptake. At the highest As level in the soil (100 mg kg^?1), 249.60 and 101.26 µg As pot^?1 were taken up by the rice shoot and barnyard grass shoot, respectively, and total amounts of 1468.65 and 1060.57 µg As pot^?1 were taken up by the barnyard grass and rice seedlings, respectively. At the same As level in the soil, the As concentrations were 14.99 and 37.76 µg g^?1 in the shoot of barnyard grass and rice, respectively, and 486.61 and 339.32 µg g^?1 in the root of barnyard grass and rice, respectively. Barnyard grass took up more As than rice, but the As concentration in the shoot of barnyard grass was lower than that in the shoot of rice. A considerable amount of As was taken up by both barnyard grass and rice, suggesting that the plant species have the potential to remediate As‐contaminated soil.     

稗草对二氯喹啉酸抗性研究进展

生长素类除草剂二氯喹啉酸在我国使用了20多年,目前,稻田稗草对二氯喹啉酸产生了抗性,抗二氯喹啉酸稗草逐渐成为我国南北稻区的防除难题。稗草抗二氯喹啉酸机理比较复杂,从稗草感知二氯喹啉酸到产生氰化物的过程是通过生长素信号通路到乙烯信号通路传导的,期间发生了复杂的基因调控和相关酶的从头合成。最新研究认为,稗草主要通过提高氰化物解毒酶——氰丙氨酸合成酶(β-CAS)的活性和控制有毒氰化物的产量产生抗药性。本文综述了二氯喹啉酸的除草机理与稗草对二氯喹啉酸抗性这两个密切相关问题的研究进展。     

Influence of thiobencarb on nitrate reductase, nitrite reductase and DCPIP photoreduction in rice and Echinochloa crus-galli (L.) (barnyardgrass)

Summary. The influence of thiobencarb at 1500 ppm on levels of nitrate reductase, nitrite reductase and on 2,6-dichlorophenolindophenol (DCPIP) photoreduction was studied in rice ( Oryza sativa L.) and Echinochloa crus-galli (L.) (barnyardgrass) to understand the different sensitivities of these two plants to the herbicide. The herbicide treatment did not cause appreciable inhibition of nitrate reductase and nitrite reductase in rice leaf sections. In barnyard grass, the treatment strongly lowered nitrite reductase activity. DCPIP photoreduction by isolated chloroplasts of the treated rice leaves was not greatly affected. On the other hand DCPIP photoreduction by both mesophyll and bundle sheath chloroplasts from treated barnyardgrass was inhibited by 70%. Herbicide caused accumulation of nitrite in treated barnyard grass leaves when compared to rice. Thiobencarb phytotoxicity to barnyard grass may be due to impairment of the Hill reaction that in turn caused accumulation of nitrite in the leaf tissue.     

Potential allelopathic rice lines for weed management in Cambodian rice production

In Cambodia, the planting of rice lines with a competitive and/or allelopathic ability would be a very useful way to supplement weed management in the rain‐fed, low‐input production systems. The present study examines a wide range of rice germplasm, mainly from Cambodia, and uses a series of bioassay techniques to identify those that might have a weed growth‐suppressing, allelopathic trait. A laboratory bioassay study that involved 359 rice lines showed that there were 15 that could significantly reduce the growth of awnless barnyard grass seedlings. In a second laboratory bioassay, involving the best 96 rice lines that were identified in the first study, 14 were shown to suppress the shoot growth of awnless barnyard grass, 11 could suppress the shoot growth of barnyard grass, six could suppress the shoot growth of small umbrella sedge, four could suppress the shoot growth of two‐leaf fimbristylis, four could suppress the shoot growth of water primrose, and three could suppress the shoot growth of gooseweed. Of the 13 rice lines that were able to suppress the growth of at least two weed species, there were three lines that could suppress the growth of three weed species, one line that could suppress the growth of four weed species, and one line that could suppress the growth of five weed species. In a third soil‐based, pot bioassay that studied the 18 best lines coming from the second laboratory bioassay, all showed a significant weed growth‐suppressive ability. A linear regression analysis showed that there was no correlation between their weed growth‐suppressive ability and their physical seedling size, supporting the idea that the growth suppression was allelopathic in nature and not a physical competition effect. In summary, the results indicate that an allelopathic trait does exist in some Cambodian rice lines and that this trait is effective in the growth suppression of a number of major rice weeds.     

Oregano green manure for weed suppression in sustainable cotton and corn fields

A 2 year field experiment was conducted in northern Greece to study the biomass effects of four oregano (Origanum vulgare) biotypes, used as incorporated green manure, on the emergence and growth of barnyard grass (Echinochloa crus‐galli), bristly foxtail (Setaria verticillata), common purslane (Portulaca oleracea), cotton (Gossypium hirsutum), and corn (Zea mays). The oregano biotypes were selected on the basis of their high phenolic content. The phytotoxic potential of the oregano biotype extracts also was determined in the laboratory by using a perlite‐based bioassay with cotton, corn, and barnyard grass. The bioassays indicated that the germination, root elongation, and fresh weight of cotton, corn, and barnyard grass were reduced by the oregano biotype extracts. In the field, the emergence of common purslane, barnyard grass, and bristly foxtail was reduced by 0–55%, 38–52%, and 43–86%, respectively, in the oregano green manure treatments, as compared with the oregano green manure‐free treatments (the controls). At harvest, the cotton lint and corn grain yields in the oregano green manure treatments were 24–88% and 5–16%, respectively, greater than those in the corresponding green manure‐free, weedy treatments. These results indicated that when the biomass of the oregano biotypes with a high phenolic content were incorporated into the soil as green manure, they could be used to suppress barnyard grass, bristly foxtail, and common purslane in cotton and corn and consequently to minimize herbicide usage.     

东北地区四种常见禾本科杂草病原真菌资源调查及其致病性测定

为了解我国东北地区常见禾本科杂草病原真菌资源状况,于禾草生长季节对东北三省19个县市的稗草、狗尾草、马唐和虎尾草的发病情况进行了调查和采样。对病害样品用组织分离法分离获得186个真菌菌株,经形态学观察和rDNA ITS序列比对分析,鉴定到10个属的真菌。对其中分离率较高具代表性的或来自发病严重样品的31个菌株用人工接种法进行了致病性测定,明确了新月弯孢(Curvularia lunata)对稗草、狗尾草、马唐和虎尾草均有较强致病性,梭形凸脐蠕孢(Exserohilum fusiforme)和尖角凸脐蠕孢(E. monoceras)对稗草具有较强致病性,麦根腐平脐蠕孢(Bipolaris sorokiniana)、狗尾草平脐蠕孢(B. setariae)、嘴突凸脐蠕孢(E. rostratum)和链格孢(Alternaria spp.)对狗尾草具有较强致病性。不同菌株致病性有差异,一般来讲,对原寄主的致病性强于对其他寄主的致病性。研究结果丰富了禾草的病菌资源和信息,为真菌除草剂的研发奠定了基础。