蛇床子素对植物病原真菌抑制机制的初步研究

天然化合物蛇床子素(osthol)对草坪纹枯病菌Rhizoctonia solani、芒果炭疽病菌Colletotrichum musae、苹果叶枯病菌Rhizoctonia solani、辣椒疫霉病菌Phytophora capsici、辣椒炭疽(红)病菌Collectotrum gloesporioides、番茄灰霉病菌Botrytis cinerea Pers、油菜菌核病菌Sclerotinia sclerotiorum、小麦赤霉病菌Fusarium graminearum、苹果轮纹病菌Macrophoma kawatsukai、水稻稻瘟病菌Pyricularia grisea、西瓜枯萎病菌Fusarium oxysporum f.sp.niveum、棉花枯萎病菌Fusarium oxysporum f.sp.vasinfectum、棉花黄萎病菌Verticillium dahliae等有不同的抑制活性,对大多数病菌其抑制中浓度(EC50值)在21.15~61.62 μg/mL之间。以小麦赤霉病菌为研究对象,结果表明50 μg/mL蛇床子素对其孢子萌发有显著的抑制作用;100 μg/mL蛇床子素处理24 h后,菌丝大量断裂,可溶性蛋白含量增加,菌体葡萄糖含量呈"V"型变化,几丁质水解酶活性和几丁糖含量均高于对照。     

天然产物对植物病毒的抑制作用

本文简要介绍了自然界中含有病毒抑制剂的植物和微生物,以及天然产物对植物病毒产生抑制作用的有效成发和作用机理。     

新疆阿克苏地区种稻改良盐渍土问题

通过新疆阿克苏地区的定点观测试验,以及阿克苏地区种稻改良盐渍土对塔里木河的影响的分析,提出当地通过种稻改良盐渍土的作法是不合理的。阿克苏地区改良盐渍土的根本途径应是完善排水系统,降低地下水位。     

20%高渗乙蒜素乳油在水稻植株、稻米、稻壳、稻田水及土壤中的残留检测及消解动态

研究了20%高渗乙蒜素乳油在水稻植株、稻米、稻壳、稻田水和土壤中的残留分析方法及消解动态。样品采用二氯甲烷提取,液液分配净化,气相色谱(GC-ECD)测定。结果表明:乙蒜素在稻田水样中的平均添加回收率为85.3% ~89.1%,相对标准偏差(RSD)为4.3% ~6.3%;在植株中的平均添加回收率为87.0% ~90.3%,相对标准偏差为2.6% ~4.9%;在土壤中的平均添加回收率为90.3% ~95.4%,相对标准偏差为3.0% ~7.4%。乙蒜素的最小检出量为2.0 ×10-11 g,水样、土样、植株(以及稻米和稻壳) 中乙蒜素的最低检测浓度分别为0.002、0.01、0.02 mg/kg。湖南、天津、浙江、湖北 4地 的残留消解动态试验结果表明: 20%高渗乙蒜素乳油在稻田水样和水稻植株中的半衰期分别是 0.3 ~1.1 d和1.4~2.1 d。至水稻收获时,在稻田土壤、稻米和稻壳中均未检出乙蒜素残留,建议我国对乙蒜素在水稻中的最大允许残留限量(MRL)值可暂定为0.05 mg/kg。     

Defense induced by a bis-aryl methanone compound leads to resistance in potato against Phytophthora infestans

Plants recognize certain microbial compounds as elicitors of their active defense mechanisms. In the present study, NUBS-4190, a synthetic bis-aryl-methanone compound elicited NO and ROS generation in potato suspension cultured cells and intact potato leaves. Hypersensitive cell death was found in these cultured cells and in potato leaves without the accumulation of phytoalexins in the tubers. Defense-related genes such as StrbohB, StrbohC, StNR1, StNR5, Sthsr203J and StPR1 were expressed in potato suspension cultured cells treated with NUBS-4190. Resistance against Phytophthora infestans also increased in NUBS-4190-treated potato leaves.     

南繁区转基因水稻田杂草种类调查

为了弄清南繁区转基因水稻田、非转基因水稻田和空白对照田杂草种类及发生情况,采取5点取样法,对3种田的田间杂草种类及危害情况进行了调查。结果表明：转基因水稻田有杂草19种,隶属11科,优势杂草为空心菜、牛毛毡、水莎草、莲子草、水苋菜、千金子,相对多度分别为37．58％、28．51％、26．24％、21．70％、21.62％、20．84％;非转基因水稻田主要杂草包括17种,隶属10科,优势杂草为空心菜、水莎草、牛毛毡、莲子草、水苋菜,相对多度分别为40．14％、29．83％、29．83％、24．11％、21．70％;空白对照田主要杂草包括12种,隶属8科,优势杂草为空心菜、水莎草、水苋菜、碎米莎草、莲子草、鳢肠,相对多度分别为60．28％、36．76％、34．98％、33.80％、29．11％、23．25％;水稻田（转基因水稻和非转基因水稻）中各优势杂草的危害程度明显低于空白对照;除了千金子,转基因水稻田中的优势杂草（空心菜、牛毛毡、水莎草、莲子草、水苋菜、碎米莎草、鳢肠）的危害程度均略低于对应的非转基因水稻。     

Rice seedbeds as a source of primary infection by Rice yellow mottle virus

The effect of contamination of rice seedlings by Rice yellow mottle virus (RYMV) in seedbeds on the onset and spread of rice yellow mottle in the field was investigated. Rice seedlings were artificially contaminated in seedbeds at different rates (0.1, 0.5, and 2.5%) and pooled in bundles before transplantation, as done by farmers. RYMV was successfully transmitted through contaminated hands and bundling healthy and diseased seedlings together. Hand contamination was responsible for 4.5% infection. Disease incidence in the field after secondary spread reached 32% for 2.5% seedbed contamination rate but remained limited (less than 10%) for all other rates. Eradicating infected plants from seedbeds lessened disease incidence in the field. This technique may be used in conjunction with other prophylactic measures to efficiently control rice yellow mottle disease.     

Effects of SSF-126, a novel alkoxyiminoacetamide blasticide, on mycelial growth and oxygen consumption of Pyricularia oryzae

SSF-126, ( E )-2-methoxyimino-N-methyl-2- (2-phenoxyphenyl)acetamide, inhibited mycelial growth (IC₅₀ 7·7 μM) of Pyricularia oryzae. The inhibited mycelium, which was incubated for 30 h in the presence of SSF-126, grew vigorously after transfer to a fungicide-free medium, indicating that SSF-126 is a fungistatic compound. SSF-126 strongly inhibited oxygen consumption by P. oryzae at low concentrations (IC₅₀ 0·8 μM). However, the initial inhibition of oxygen consumption was followed by normal mycelial respiration that was insensitive to SSF-126. These results suggest that SSF-126 has a new type of antifungal action.     

Physiological and Cytological Studies on the Inhibition of Striga Seed Germination by the Plant Growth-promoting Bacterium Azospirillum brasilense

Striga hermonthica (Del.) Benth. is an obligate parasitic weed of tropical cereals whose rhizosphere can also be colonised by bacteria of the genus Azospirillum. A previous study demonstrated that the two organisms (Azospirillum and striga) interacted during cerealroot colonisation. Two strains of A. brasilense isolated from an African sorghum rhizosphere prevented the germination of striga seeds although they were stimulated to germinate by the presence of sorghum roots. Azospirillum cells suspended in a synthetic germination stimulant (GR24) did not inhibit striga seed germination, but did block radicle elongation. Those radicles had an abnormal morphology, and contained no vacuolated cells in the root elongation zone. Lipophilic compounds extracted from the medium of bacteria in the log and stationary growth phases prevented the germination of striga seeds.     

Inhibition of acetyl-coenzyme a carboxylase by coenzyme a conjugates of grass-selective herbicides

A total of 146 samples of different kinds of cheeses produced in Spain were analysed in order to ascertain the specific contamination pattern. The organochlorine compounds studied were those most commonly investigated in previous surveys: α-HCH, β-HCH, γ-HCH (lindane), γ-HCH, chlordane, aldrin, dieldrin, endrin, heptachlor, heptachlor epoxide, and the isomers and metabolites of DDT. α-HCH, β-HCH, γ-HCH, chlordane, p,p′, DDT, and p,p′-DDE were found in more than 76% of samples; p,p′-DDE and γ-HCH were the most frequently detected, with frequencies of 100 and 97.9% respectively. γ-HCH, aldrin, dieldrin, heptachlor, heptachlor epoxide, o,p′-DDT, p,p′-DDD and o,p′-DDD were observed at lower frequencies. No residues of endrin were detected in any sample. Insecticides exceeding the maximum residue limits (MRLs) were chlordane, β-HCH, α-HCH and γ-HCH, with 42, 20, eight and six samples respectively. Mean residues of organochlorines found were as follows (μ kg^?1 butterfat): α-HCH = 46.3; β-HCH = 46.5; γ-HCH = 54.2; δ-HCH = 16.9; aldrin = 16.7; dieldrin = 9.7; heptachlor = 15.9; heptachlor epoxide = 14.8; chlordane = 50.2; o,p′-DDT = 5.1; p,p′-DDT = 12.4; o,p′-DDT = 19.6; p,p′-DDD = 46.7; o,p′-DDE = 6.9; p,p′-DDE = 40.7 (.DDT = 55.0). Estimated dietary intakes (EDIs) from cheese consumption were compared to acceptable daily intakes (ADIs) for the pesticides where residues exceeded the MRL. EDIs calculated were in all cases below ADIs, and, therefore, based on the ADIs, there is no health risk involved in the consumption of cheese from Spain arising from organochlorine residues.     

Sequence Analysis Shows that a Dwarfing Disease on Rice, Wheat and Maize in China is Caused by Rice Black-streaked Dwarf Virus

Isolates of plant reoviruses causing severe stunting and dark leaf symptoms on wheat in Hebei province, on maize in Hubei province and on rice in Zhejiang province, China have been characterized. Four of the ten genome segments corresponding to Rice black-streaked dwarf virus (RBSDV) S7, S8, S9, S10 were amplified by RT-PCR from the Hebei and Zhejiang isolates and sequenced. Sequences of S9 and S10 were also obtained from the Hubei isolate. Sequences of corresponding segments of the Chinese isolates were very similar to each other (94.0–99.0% identical nucleotides and 96.3–100% identical amino acids) and were closer to those of a previously reported Japanese RBSDV isolate (90.0–94.9% identical nucleotides and 91.1–98.6% identical amino acids) than to those of an Italian Maize rough dwarf virus isolate (85.1–88.1% identical nucleotides and 85.5–94.3% identical amino acids). The Chinese isolates should be classified as RBSDV.     

Inhibition of appressorial adhesion of Pyricularia oryzae to barley leaves by fungicides

The effects of rice blast fungicides known to inhibit melanisation or penetration on the adhesion of Pyricularia oryzae to the leaf surface of barley were investigated. Adhering appressoria were counted after shaking inoculated leaves vigorously with water. On untreated leaves, appressoria began to adhere at the time when appressorial melanisation was initiated. The number of adhering appressoria then increased gradually, and most were melanised. On chlobenthiazone-treated leaves, appressoria were not melanised and were easily detached from the surface. Similar results were obtained with tricyclazole. However, after treatment with tetrachlorophthalide or pentachlorobenzyl alcohol, which are also known to prevent penetration of P. oryzae, melanised appressoria still remained after shaking in water. It is suggested that appressorial melanisation in P. oryzae is involved in appressorial adhesion. The antipenetrant action of the melanin biosynthesis inhibitors chlobenthiazone and tricyclazole may be ascribed to the lack of adhesive intensity necessary to support the mechanical shearing of the cuticle of rice plants.     

认清形势振奋精神努力开创植物检疫工作的新局面--农业部党组成员、种植业管理司司长崔世安在全国植物检疫工作会议上的讲话摘要

同志们 :我们这次全国植物检疫工作会议是在我国即将加入世界贸易组织 (ＷＴＯ)的背景下召开的。目的是研究如何适应中国加入ＷＴＯ的新形势 ,加强农业植物检疫的意见和措施。下面我结合植物检疫工作的实际讲四个方面的问题。1　认识功能 ,明确地位目前植物检疫工作面临的形势发生了变化 ,面对新的形势我们有必要重新认识植物检疫的功能。概括地说 ,植物检疫具有以下三个方面的功能 :一是保护把关的功能。植物检疫工作事关农业生产的安全 ,特别是随着市场经济的建立 ,植物及其产品调进调出量加大 ,因危险性病虫危害对农业造成损失的例子是很…     

Mechanism of disease development caused by a multihost plant bacterium, Pseudomonas cichorii, and its virulence diversity

Pseudomonas cichorii causes rot on lettuce leaves, distinct from the necrotic spots of infected eggplant leaves. On lettuce leaves, P. cichorii invades intercellular spaces through stomata and grows vigorously, causing rot on the leaves. Surprisingly, P. cichorii does not produce pectate lyase, the most important enzyme for degrading plant cell walls. Alternatively, infection with P. cichorii causes heterochromatin condensation and DNA laddering in lettuce cells, followed by induced cell death, which results in disease symptoms. Thus, apoptotic programmed cell death (PCD) is associated with the symptoms on lettuce leaves. Although PCD in P. cichorii-infected eggplant leaves is also associated with necrotic spots caused by the bacteria, there are differences in the responses of the two hosts. P. cichorii harbors the N-acetyltransferase family gene (pat) and the hrp genes (hrp) encoding a type III secretion system, adjacent to an aldehyde dehydrogenase gene (aldH). The virulence of P. cichorii is hrp-dependent in eggplant, but not in lettuce. Furthermore, hrp, pat and aldH are implicated in the diversity of P. cichorii virulence on susceptible Asteraceae species. The involvement of hrp, aldH and pat in bacterial virulence on the respective species has no relationship with the phylogeny of the plants species. When these results are considered together, P. cichorii has multiple virulence determinants. The involvement of not only hrp but also aldH and pat in P. cichorii virulence arose after species diversification of host plants. Host responses implicated in symptom development have been responsible for the development of virulence determinants of P. cichorii.     

植物免疫蛋白制剂阿泰灵诱导小麦抗病增产效果及作用机制

阿泰灵是我国自主研发的植物免疫蛋白制剂,能诱导多种植物的广谱抗性,并能促进植物生长、提高产量,但在小麦生产中尚未开展相关研究。2016年作者分别在山东省和河南省开展了阿泰灵对小麦抗病和促生长的田间试验,并初步研究了阿泰灵诱导小麦抗病的作用机制。研究结果表明,用400倍阿泰灵稀释液拌种,并分别在返青期、拔节期和扬花期进行1000倍喷雾使用,能显著提高小麦叶片的叶绿素含量、须根数和根系活力;对小麦纹枯病、白粉病和叶锈病3种病害的诱抗效果达到29.3%~64.9%;穗长、穗粒数和千粒重也显著提高,产量增加15%以上。阿泰灵喷雾处理小麦6叶期幼苗后12~24 h,POD、SOD和CAT防御酶活性提高45%,抗病相关基因PR-1、PR-2和PR-5也比未处理小麦转录表达提高10倍。以上研究结果表明,阿泰灵能有效促进小麦生长,并提高小麦抗病性;防御酶活性提高和抗病基因上调表达是阿泰灵诱导小麦抗病增产的重要作用机制之一。     

Inhibition of juvenile hormone biosynthesis in the tobacco hornworm, Manduca sexta, by a bisthiolcarbamate juvenoid and related compounds

Biosynthesis of juvenile hormone in the tobacco hornworm, Manduca sexta, is inhibited by the bisthiolcarbamate juvenoid N-ethyl-1,2-bis(isobutylthiolcarbamoyl)ethane both in vitro and in vivo. In vitro an extremely steep dose-response curve was obtained with an ID₅₀ value of 6 × 10^?6M. However, in vivo topical treatment with the compound resulted in mild JH antagonistic symptoms, suggesting rapid metabolism of the compound. In agreement with results from metabolic studies performed on plants and in mammals, sulfoxidation of the thiocarbamate S-(4-chlorobenzyl)N,N-diethylthiocarbamate resulted in an enhanced inhibitory effect on JH biosynthesis in vitro. This suggests that the corresponding thiocarbamate sulfoxides may act as intermediates in carbomylating critical thiol sites important in the terpenoid biosynthesis pathway. Furthermore, this study shows that these prototype compounds are interesting tools for further investigation of chemical inhibition of JH biosynthesis in insects.