尖角突脐孢菌与化学除草剂混用防治稻田稗草效果的研究

用平板表面萌发法测定化学除草剂对尖角突脐孢菌菌株X27分生孢子萌发的影响,在温室研究该菌分生孢子干粉与化学除草剂的相互作用,在田间评价其混剂的除稗效果.结果表明,二氯喹啉酸和苄嘧磺隆对分生孢子的萌发影响不明显,其它除草剂均有不同程度的影响.在温室条件下,菌X27干粉与二氯喹啉酸混用具有明显的增效作用,与敌稗混用具有加成作用;在水田条件下,单用菌X27干粉防除稗草效果差,防效只有60%,而与低量的二氯喹啉酸混用,防效明显提高,达90%以上.     

Germination and seedling growth under anaerobic conditions in Echinochloa crus-galli (barnyard grass)*

Abstract Although rice has long been recognized to be uniquely adapted for growth in low oxygen environments of flooded rice fields, rice weeds of the Echinochloa crus-galli complex appear to be at least as well specialized for germination and growth under such unusual biological conditions. Seeds of two varieties of E. crus-galli germinate and grow for prolonged periods in a totally oxygen-free environment. E. crus-galli germinates as well as rice (Oryza sativa) under a total nitrogen atmosphere and produces as large a seedling in spite of its much smaller seed size. Like rice, the seedlings of E. crus-galli are unpigmented, the primary leaves do not emerge from the coleoptile and no root growth occurs without oxygen. Of particular interest is the ultrastructure of mitochondria from anaerobically-grown seedlings. Mitochondrial profiles from the primary leaf of seedlings grown continuously in nitrogen are very similar to those grown aerobically. The size and shape of the mitochondria are similar and the cristae are numerous and normal in appearance. This is in sharp contrast to previous studies of other species which have reported that mitochondria were vesiculate and tended to lose their normal fine-structure after similar periods without oxygen. Finally, based on ultrastructure and ¹⁴C labeling studies, anaerobically-grown seedlings are highly active metabolically, which may explain, at least for E. crus-galli var. oryzicola, its ability to germinate and emerge from flooded rice fields.     

Variation of weed-suppressing potential of Vietnamese rice cultivars against barnyardgrass (Echinochloa crus-galli) in laboratory,greenhouse and field screenings

Abstract

A total of 73 different varietal groups and cultivars of Vietnamese rice (Oryza sativa L.) were evaluated for the allelopathic potential on barnyardgrass (Echinochloa crus-galli) in laboratory, greenhouse and field screenings. In a bioassay, Y1, U17, Nep Thom and Lua Huong, cultivars showed the highest weed-suppressing ability against the length of shoot and root of barnyardgrass. Y-1, Nhi Uu and Khau Van exerted significant inhibitory effects in greenhouse screening. In the field study, Phuc Tien obtained the highest weed-suppressing potential. The allelopathic activity of Vietnamese rice showed cultivar-dependence and varietal group-dependence, of which hybrid group cultivars (H) showed the highest inhibition, followed by the local non-sticky cultivars (LNS), foreign (F), traditional sticky (TS), and traditional upland sticky (TUS), while the least were the local upland non-sticky (LUNS) cultivars. The inhibition exerted in both bioassay and greenhouse was lower than the observed weed suppression in the field by 15–20%; however, rice cultivars against the growth of barnyardgrass in greenhouse screening showed more correlation to the results obtained in the field than that of the laboratory, but both laboratory and greenhouse screenings may arduously reflect the actual weed-suppressing ability of rice exhibited in the field. The obtained data might be useful for the enhancement of the weed-suppressing ability of rice in this country.     

A large-scale field study of transgene flow from cultivated rice (Oryza sativa) to common wild rice (O. rufipogon) and barnyard grass (Echinochloa crusgalli)

The introgression of transgenes into wild relatives or weeds through pollen-mediated gene flow is a major concern in environmental risk assessment of transgenic crops. A large-scale (1.3–1.8 ha) rice gene flow study was conducted using transgenic rice containing the bar gene as a pollen donor and Oryza rufipogon as a recipient. There was a high frequency of transgene flow (11%−18%) at 0–1 m, with a steep decline with increasing distance to a detection limit of 0.01% by 250 m. To our knowledge, this is the highest frequency and longest distance of gene flow from transgenic rice to O. rufipogon reported so far. On the basis of these data, an adequate isolation distance from both conventional and transgenic rice should be taken for in situ conservation of common wild rice. Meanwhile, there is no evidence of transgene introgression into barnyard grass, even when it has coexisted with transgenic rice containing the bar gene for five successive years. Thus, the environmental risk of gene flow to this weedy species is of little concern.     

Activity of the Pentose Phosphate and Glycolytic Pathways During Anaerobic Germination of Echinochloa crus-galli (barnyard grass) Seeds

Changes in the activity of key enzymes in glycolysis and theoxidative pentose phosphate pathway were studied in Echinochloacrus-galli (L.) Beauv. var. oryzicola seeds during germinationin air or nitrogen. In addition, the metabolism of specificallylabelled [^I4C]glucose was followed to evaluate the activityof both pathways during anaerobic germination. During the 7 d time period studied there was no difference betweenair and nitrogen in phosphofructokinase activity. Under anaerobicconditions, fructose-1, 6-bisphosphate aldolase increased morethan two-fold in 7 d; whereas in air, it decreased. The activityof the pentose phosphate pathway enzyme, glucose-6-phosphatedehydrogenase, increased under N₂ until day three, when it levelledoff, whilst it continued to increase up to day seven in air. Incubation of Echinochloa seedlings with specifically labelledglucose also resulted in differences between anaerobic- andair-grown seedlings. Labelling of phosphorylated sugars andlipids predominated under N₂; whereas in air, malate and fumaratewere the most heavily labelled compounds. In both air and N₂,there was a greater percentage of label in CO2 from [l-¹⁴C]glucose,while [6-14C] resulted in a greater percentage label in ethanol.These differences were more pronounced under N2, especiallyduring the first 24 h of imbibition, suggesting increased activityof the pentose phosphate pathway. Key words: Echinochloa, Anaerobic metabolism, Oxidative pentose phosphate pathway     

二氯喹啉酸诱导稗草EcDnaJ基因表达

DnaJ作为分子伴侣在植物抗逆中起重要作用. 但目前在二氯喹啉酸逆境下,其在抗药性稗草中表达特点却鲜有报道. 本研究采用RACE技术从抗二氯喹啉酸稗草中克隆了1个DnaJ基因, 命名为EcDnaJ1 (GenBank登录号：JX518598), 其cDNA全长为2 154 bp, 开放阅读框为1 350 bp,编码449 个氨基酸, 理论分子量为48.4 kD, 等电点为9.5. 该蛋白质氮端含有1个保守的J结构域, 中部含有4个模式为CxxCxGxG的锌指结构. Real-time PCR分别测定EcDnaJ1在二氯喹啉酸抗性和敏感的稗草生物型苗期叶、根及成株期根、茎、叶和种子中的表达, 在感、抗生物型的相对表达量分别是0.8～20.9和7.4～30.2, 其中在抗性稗草苗期叶片中相对表达量最高为30.2, 而在敏感稗草种子中最低为0.8, 抗性稗草是敏感稗草的1.4～9.2 倍. 受二氯喹啉酸诱导后, 其在感、抗稗草的相对表达量分别为35.8～72.5和84.9～261.9, 在抗性稗草苗期叶片中相对表达量最高为261.9, 而在敏感稗草的种子中相对表达量最低为35.8, 抗性稗草是敏感稗草的2.4～3.6 倍. 诱导前后, 无论是在苗期根和叶中还是成株期的根、茎、叶和种子中, EcDnaJ1表达量均是抗性稗草高于敏感稗草. 抗、感稗草生物型的EcDnaJ1在mRNA水平差异表达暗示,它可能参与了稗草对二氯喹啉酸的抗药性.     

Disulfide-stabilized helical hairpin structure and activity of a novel antifungal peptide EcAMP1 from seeds of barnyard grass (Echinochloa crus-galli)

This study presents purification, activity characterization, and (1)H NMR study of the novel antifungal peptide EcAMP1 from kernels of barnyard grass Echinochloa crus-galli. The peptide adopts a disulfide-stabilized α-helical hairpin structure in aqueous solution and thus represents a novel fold among naturally occurring antimicrobial peptides. Micromolar concentrations of EcAMP1 were shown to inhibit growth of several fungal phytopathogens. Confocal microscopy revealed intensive EcAMP1 binding to the surface of fungal conidia followed by internalization and accumulation in the cytoplasm without disturbance of membrane integrity. Close spatial structure similarity between EcAMP1, the trypsin inhibitor VhTI from seeds of Veronica hederifolia, and some scorpion and cone snail toxins suggests natural elaboration of different functions on a common fold.     

Effect of increased concentration of soil CO2 on intermittent flushes of seed germination in Echinochloa crus-galli var. crus-galli

Soil-buried seeds of barnyardgrass ( Echinochloa crus-galli var. crus-galli ) germinated from April to June in three intermittent flushes. The later two flushes of germination occurred after heavy rainfall. Carbon dioxide concentration in soil air transiently increased to 30 dm³ m^–3 after the rainfall, probably due to the increase in soil temperature and water potential. Germination of exhumed seeds was stimulated by exposure to CO₂ at 30 dm³ m^–3. Fluctuating temperature, light, water, ethylene, and nitrate are known to promote seed germination in many species. However, of these environmental factors, within ranges found in the field, only CO₂ was effective in enhancing the germination of barnyardgrass seeds. We conclude that soil CO₂ is responsible for causing intermittent flushes of germination. Detection of vegetation gaps may be explained by the responsiveness of buried seeds to CO₂.     

Plastid development in seedlings of Echinochloa crus-galli var. oryzicola under anoxic germination conditions

Plastid development in the primary leaf of Echinochloa crus-galli (L.) Beauv. var. oryzicola (Vasing.) Ohwi was followed during 5 d of anoxic germination and growth. Plastids develop slowly from simple spheroidal proplastids into larger pleomorphic plastids with several stromal membranes and many peripheral membrane vesicles. A small prolamellar body is present at 96 h with perforated (pro)thylakoids extending into the stroma. Changes in starch grains and plastoglobuli are evidence of carbohydrate and lipid metabolism. Plastid division is indicated by dumbbell plastid profiles after 4 d of anoxia. These results demonstrate that plastids not only maintain their integrity during anaerobic germination but also show developmental changes involving an increase in internal membrane complexity, although to a lesser extent than in etiolated shoots.Abbreviation PLB prolamellar body Scientific paper No. 6167. College of Agriculture, Washington State University, Pullman     

Efficacy of Beauveria bassiana (Hyphomycetes) for control of Russian wheat aphid (Homoptera: Aphididae) on resistant wheat under field conditions

The Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Homoptera: Aphididae) is considered the most important pest of wheat produced under dryland field conditions in South Africa. As part of an integrated pest management strategy, the entomopathogenic hyphomycete Beauveria bassiana (Balsamo) Vuillemin was evaluated in combination with antibiotic host plant resistance under dryland field conditions during 1998 and 1999. A commercial formulation, Mycotrol® ES, was applied at a rate of 2.4 L (5×10¹³ conidia) per hectare +0.1% organosilicone surfactant. During both years, two applications were administered, i.e., on growth stages 31 (first node detectable) and 39 (early flag leaf). An additional treatment, application at growth stage 39 only, was included during 1999. Over the duration of the 1998 trial, ca. 65% fewer aphids were observed on treated plots compared with controls. A similar level of population reduction was observed during the 1999 trial; however, treatment effects were only briefly evident due to a rapid field-wide decline in aphid populations caused by adverse (cool, wet) weather conditions. The early application (GS 31) resulted in some level of control only during 1998. It was hypothesized that this phenomenon was the result of greater exposure to the spray applications and/or greater secondary pick-up of fungal inoculum by the aphids due to the higher level of aphid activity observed on the cultivar employed during that year. In this regard, migration of D. noxia onto the flag leaves should be further investigated as a behavioural trait for possible exploitation when considering the use of a mycoinsecticide.     

特异性适应稻作系统的稗草种群生活史特性

长期进行除草剂药效试验可能会导致田间杂草种群发生适应性进化。本研究在安徽南陵县除草剂药效试验专用稻田中采集了1个稗草种群A,并以从常规稻田采集的3个稗草种群为对照,开展同质园栽培试验。结果表明: 与3个对照种群相比,A种群稗草植株的单株种子产量显著减少,种子千粒重显著增加,幼苗生长速率显著加快,结实分蘖数显著增多,生育期显著缩短;A种群稗草成株的株高、生物量及对除草剂五氟磺草胺的敏感性均显著降低。A种群稗草幼苗3～4叶期时经五氟磺草胺推荐剂量2倍量(有效成分60 g·hm^-2)处理后,其株高、生物量及成熟种子产量(平均每株1066粒)显著降低,而抽穗期、结实分蘖数、单个总状花序的种子数及种子千粒重无显著差异。因此,种子较重、生活史周期短、植株矮小、结实分蘖多及对除草剂五氟磺草胺具有抗药性,使得A种群稗草对稻作系统具有特异适应性,应防止此类种群扩散至常规稻田。     

水稻田稗草叶片光合作用对开放式空气CO2浓度增高(FACE)的适应

于分蘖、拔节和抽穗 3个时期在空气CO2 浓度 (380 μmol·mol-1)下测定稻田中稗草叶片的净光合速率 (Pn) ,发现在开放式CO2 浓度增高 (FACE)条件下生长的稗草叶片后 2个时期的Pn显著低于普通空气中生长的对照 ,比对照下降约 2 0 % ,说明FACE条件下稗草叶片光合作用对高CO2 浓度发生了明显的适应 .同时 ,叶片的气孔导度 (Gs)和胞间CO2 浓度 (Ci)的下降更为明显 .与对照相比 ,叶片可溶性蛋白含量明显降低 ,拔节期只有对照的 6 2 .4 % ;高CO2 浓度下生长的稗草叶片Rubisco含量也降低 ,分蘖期和拔节期分别为对照的 87%和 84 % ,但其差异未达到显著水平 .可以认为 ,长期生长在高CO2 浓度下的C4植物稗草叶片光合作用的适应是叶片气孔部分关闭和可溶性蛋白含量下降的结果 .     

从无芒稗花粉活力评价其与转基因抗除草剂水稻基因漂移的可能性

为给转基因抗除草剂水稻和稗草间的基因漂移研究提供必要的信息,探寻了无芒稗(Echinochloacrusgalli var.mitis)花粉活力及其测定的最佳方法,并利用该方法测定了无芒稗开花盛期后离体和活体条件下不同时间的花粉活力。结果表明无芒稗开花盛期取样离体条件下花粉活力下降较快,3 h后花粉活力只有5.41％,活体条件下花粉活力下降较慢,3 h后仍有17.31％的花粉有活力。这说明无芒稗花粉在水稻开花时仍有部分保持活力,因而存在潜在的基因漂移可能性。同时用最佳培养基法测定了不同条件处理下(紫外灯照射,反复冻融,黑暗放置)无芒稗花粉活力,结果表明无芒稗花粉在不利环境条件下活力难以保持。     

Interactions of Alcohols and Increased Air Pressure on Echinochloa crus-galli (L) Beauv. Seed Germination

In contrast to previous findings, where stimulation of E. crus-galliseed germination by n-propanol was reversed by simultaneoustreatment with 0.965 MPa air pressure, similar pressure wasunable to reverse stimulation by n-butanol. When pressure wasapplied up to 2 d prior to n-propanol, stimulation by n-propanolwas still prevented. Pressure appeared to exert its effect rapidly;only 15 min exposure gave the maximum effect. If temperatureduring treatment with pressure and n-propanol was 15 °C,rather than 35 °C, the inhibitory effect was not observed.The inhibitory action of pressure can persist but is not lethalsince drying the seeds after n-propanol and pressure treatmentrestored high levels of responsiveness to red irradiation. Theseseveral facts suggest that pressure may not simply prevent theaction of alcohols (anaesthetics) as previously thought, butmay have an action of its own, which may only be apparent uponinteraction with specific compounds, e.g. n-propanol. Phytochrome, anaesthesia, dormancy, membrane, Echinochloa crus-galli (L.) Beauv., barnyardgrass     

二氯喹啉酸对稗草生长发育及生长素含量的影响

通过外施二氯喹啉酸、生长素处理,研究二氯喹啉酸对稗草Echinochloa crusgalli生长特性、蛋白浓度、过氧化物酶及超氧化物歧化酶活性、生长素含量的影响。结果表明,800 g·hm-2二氯喹啉酸处理24 h未对S型稗草的生长产生明显抑制,而二氯喹啉酸单独处理及外施IAA的二氯喹啉酸处理均能显著增加R型稗草鲜重。在不施药、二氯喹啉酸单独处理、二氯喹啉酸与IAA共同处理的条件下,R型稗草比S型稗草的蛋白浓度分别提高23.5%、29.8%和64.0%,R型稗草表现出较高的抗逆境耐受能力。经二氯喹啉酸处理后,两种生物型稗草SOD活性上升,POD活性下降。施外源IAA能提高S型稗草POD活性,而对R型稗草SOD、POD活性影响不显著。提高生长素含量可显著促进R型稗草的生长。     

Bioherbicidal potential of a strain of Xanthomonas spp. for control of common cocklebur (Xanthium strumarium)

Several isolates of a previously unreported bacterial pathogen were discovered on common cocklebur seedlings in Chicot County, AR and Washington County, MS. Diseased plants in nature exhibited angular-shaped leaf spotting symptoms on leaf margins and central leaf areas. The isolates were cultured from diseased leaf tissue and tentatively identified as Xanthomonas spp., and their virulence on common cocklebur seedlings compared. The most virulent isolate (LVA987) was used in studies to define disease progression on cocklebur seedlings and to carry out a host range evaluation on various weeds and crop plants. High virulence was found on common cocklebur > marestail (Conyza canadensis) > giant ragweed (Ambrosia trifida) ≥ and common ragweed (Ambrosia artemisifolia). These results suggest this pathogen may be useful for the biological control of these important species of weeds. This is also highly relevant since all of these weeds have evolved resistance to one or more synthetic herbicides and are thus becoming more difficult to control with conventional herbicides.     

Candida spp. morphotype differentiation on Sabouraud-Triphenyltetrazolium-Agar (STTZ-Agar) under three different experimental conditions

One hundred and thirty-two strains of Candida spp. were cultured on STTZ-Agar at 37 degrees C for 6 days and at 25 degrees C for 6 and 21 days to determine the culture conditions that would ensure maximum reproducibility in the discrimination of the strains of the same species. Standardization is of utmost importance, as varying experimental conditions can alter the results of the tests. Further studies are needed also implementing molecular tests to establish possible relationships between morphotype, genotype and virulence.     

田埂留草控制稻飞虱效果及对捕食性天敌多样性影响

为探讨稻田田埂保留杂草控制稻飞虱的效果及对捕食性天敌多样性的影响,以稻田田埂周年性保留杂草为处理,以稻田田埂不保留杂草为对照,对处理区和对照区稻田稻飞虱成若虫、捕食性天敌种类和数量进行系统调查和分析。结果表明,在调查期内(6—10月),田埂留草稻田百丛稻株稻飞虱数量为(891.11±133.12)头,较非留草稻田减少35.31%;田埂留草稻田捕食性天敌隶属5目23科35种,而田埂非留草稻田隶属5目21科33种;田埂非留草稻田捕食性天敌优势种为食虫沟瘤蛛Ummeliata insecticepsBoes.etStr.、拟水狼蛛Pirata subpiraticus Boes.etStr.和黑肩绿盲蝽Cyrtorrhinus livdipennis Reuter,而田埂留草后优势种为食虫沟瘤蛛U.insecticeps、草间小黑蛛Erigonidium graminicolum(Sundevall)、拟水狼蛛和拟环纹狼蛛Lycosa pseudoamulata(Bose.etStr.);田埂留草稻田捕食性天敌的个体数量、丰富度、多样性指数分别为(128.89±13.52)、(33.67±0.50)、(4.53±0.04)头/百丛,较田埂非留草稻田分别增加31.96%、25.73%、5.59%,而优势度指数和均匀性指数没有显著变化。研究结果为发展稻田景观多样化控害提供依据。     

Isolation and characterization of microsatellites in Echinochloa (L.) Beauv. spp.

Five primer pairs were developed that amplify microsatellite loci in three agronomically important Echinochloa (L.) Beauv. species: E. colona (L.) Link, E. crus‐galli (L.) Beauv. and E. crus‐pavonis (Kunth) Schultes. The microsatellites were tested on 24 individuals representing three species collected in rice fields from different geographical regions and revealed 3–7 alleles per microsatellite. Gene diversity [1 ? Σp_ij²] for four polymorphic loci within E. crus‐galli ranged from 0.12 to 0.61. Alleles at a fifth locus were useful in discriminating the species. The microsatellites should provide useful markers for intraspecific diversity studies and aid classification of species within this complex genus.