生菜软腐和菌核病拮抗菌贝莱斯芽胞杆菌BPC6鉴定与防效

软腐病和菌核病是生菜生产中两大毁灭性病害。为有效控制这2种病害，利用平板稀释和对峙法，从生菜根际土壤中分离到一株拮抗菌BPC6，其菌悬液、无菌滤液对软腐病菌Pectobacterium carotovorum和菌核病菌Sclerotinia sclerotiorum的生长均具有抑制效果，该菌株也能抑制其他14种植物病原菌的生长。形态学、16S rDNA及基因组序列分析将其鉴定为贝莱斯芽胞杆菌Bacillus velezensis。BPC6能产生纤维素酶和蛋白酶，不能产生几丁质酶和嗜铁素。比浊法分析的生长曲线显示，BPC6能在1%～10% NaCl及pH 5.0～9.0条件下生长。通过分析不同浓度BPC6对软腐病菌和菌核病菌侵染生菜离体叶片的影响，明确了菌株BPC6适宜用量为1.4×10⁹～2.8×10⁹ CFU/mL。菌株BPC6对生菜软腐病和菌核病盆栽防效分别为44.09%和53.58%，对菌核病大田防效为77.41%。本研究表明BPC6是一株对生菜软腐病和菌核病具有拮抗作用的潜在生防菌。     

Aluminum concentrations in sclerotia from a buried humic horizon of volcanic ash soils in Mt. Myoko,Central Japan

The morphology and chemical composition of fungal sclerotium-like grains collected from the buried humic horizon of volcanic ash soil in Mt. Myoko were examined using a scanning electron microscope (SEM), energy dispersion xray micro-analyzer (EDX), and electron probe micro-analyzer (EPMA). A high C content, low level of Si and high concentration of Al characterized the grains considered to correspond to the sclerotia of Cenoccocum graniforme. The ²⁷Al MAS NMR spectrum of the sclerotia showed the existence of 6- and 4-coordinated Al. X-ray diffraction analyses supported the presence of amorphous Al (ex. Al-humus complex) in the sclerotia.     

Method for Estimating the Content of the Chloroform-Extractable Green Fraction (CEGF) in HCl-DMSO Extract of Soils

Chloroform-extractable green fraction (CEGF) was detected in the supernatant obtained by alkali precipitation from the HCI-dimethylsulfoxide (DMSO) extract of Pg-rich soil. In the alkaline solution, the color of CEGF was green and CEGF showed strong Pg-like absorption bands. Ultraviolet and visible (UV-VIS) spectral analysis and gel chromatography on Sephadex G-50 were performed to compare several properties between CEGF and Pg. CEGF, which was purified by gel chromatography on Bio-Beads SX-1, displayed strong absorption bands at 609, 562, 445 and 280 inn in the alkaline solution. These absorption bands were almost similar to those of Pg. Furthermore, the UV-VIS spectrum of CEGF in the organic solvents showed a similar characteristic pattern of 4,9-dihydroxyperylene-3,10-quinone (DHPQ), which was considered to be a chromophore of Pg. Based on the results of gel chromatography on Sephadex G-50, CEGF mainly consisted of two fractions, corresponding to the G₂ and G₃ fractions of Pg. These results indicated that the method for extracting CEGF from Pg-rich soil in the present study was easy and selective and that CEGF was one of the components of, or a closely related substance to Pg. A colorimetric method for the estimation of the CEGF content in soils was developed. The calibration curve of CEGF was linear over a wide range of contents from 2.75 to 220 mg L⁻¹. The CEGF content in twelve samples of various soils was examined. CEGF was detected in all the soil sampled (5 orders) including three samples (3 orders) where Pg was not detected, and the content ranged from 0.07 to 1.66 g kg⁻¹ (dry soil). Therefore, the method for estimating the CEGF content in soils developed in the present study was found to be suitable for various soil orders and it was assumed that CEGF occurred in various soil orders.     

山东省不同地区蔬菜菌核病菌对四霉素的敏感性

采用菌丝生长速率法测定了四霉素对采自山东省不同地区不同蔬菜作物的151株菌核病菌的毒力作用,同时比较了其对蔬菜菌核病菌不同生育阶段的抑制活性,并通过离体叶片法评价了四霉素对蔬菜菌核病的防治效果。结果表明:菌核病菌对四霉素比较敏感,敏感性频率呈单峰正态分布,151株病菌菌丝生长的平均EC₅₀值为 (0.29 ± 0.01) μg/mL,该值可作为蔬菜菌核病菌对四霉素的敏感基线。此外,经四霉素处理后,该病菌的菌核数量以及干重明显降低,菌核明显变小;2 μg/mL的处理对菌核萌发的抑制率达到100.00%。 离体黄瓜叶片接种试验表明,四霉素对菌核病具有较好的保护和治疗效果,且保护作用较为显著。在质量浓度为20 μg/mL时,四霉素对该病的防效显著高于对照药剂多菌灵和异菌脲。因此,四霉素具有防治蔬菜菌核病的潜在价值,可进一步通过田间试验验证其应用效果。     

稻曲病菌成灾机制与防控技术研究进展

过去数十年来我国稻曲病的发生一直呈不断加重趋势,并逐渐由一个水稻次要病害发展成为一个水稻主要病害。最近不断强化的针对稻曲病成灾机制和防控技术的研究有了新发现和新观点。稻曲病菌主要侵染水稻花期的花丝等细胞壁相对疏松的组织,细胞外扩展。我国长江中下游地区稻曲病的加重与稻曲病菌菌核生成密切相关,菌核在其生活史中发挥了重要作用,可能是其主要的初侵染源。目前水稻孕穗初期使用杀菌剂是最为有效的稻曲病防控措施。未来对其生活史深入持续的研究是稻曲病发生流行中长期预测预警的重要前提。     

Integrated control of Allium white rot with Trichoderma viride, tebuconazole and composted onion waste

Two isolates of Trichoderma viride (L4 and S17A) were assessed for biological control of Allium white rot (AWR) with different onion accessions and cultivars, alone and in combination with a tebuconazole-based seed treatment or composted onion waste. In glasshouse tests, 23 new bulb-onion accessions from previous work to detect resistance to Sclerotium cepivorum showed no differences in susceptibility to AWR but, when combined with S17A, disease was reduced by up to two-thirds over all accessions. Trichoderma viride L4 and S17A also reduced the proportion of infected plants for five commercial bulb-onion cultivars and one advanced breeding line by at least one-third. Further glasshouse tests using a salad-onion cultivar showed that L4, S17A, tebuconazole or composted onion waste controlled AWR and at least halved the proportion of diseased plants. Combination treatments of T. viride with either tebuconazole or compost enhanced control and, in some treatments, disease was almost eliminated. In field trials, control of AWR by S17A was significant for 17 out of 18 individual or mixed bulb-onion accessions, with disease reduced overall by more than half. In another field experiment, S17A failed significantly to reduce AWR for two out of three commercial bulb-onion cultivars, while tebuconazole reduced the final proportion of AWR-infected plants over all cultivars from 0·47 to 0·09. Combining S17A and tebuconazole resulted in a similar level of AWR to using tebuconazole alone. The use of T. viride in an integrated strategy with other treatments to enhance control of S. cepivorum is discussed.     

Relationships between aflatoxin production and sclerotia formation among isolates of <Emphasis Type="Italic">Aspergillus</Emphasis> section <Emphasis Type="Italic">Flavi</Emphasis> from the Mississippi Delta

Aspergillus section Flavi isolates, predominately A. flavus, from different crops and soils differed significantly in production of aflatoxin and sclerotia. About 50% of the isolates from corn, soil and peanut produced large sclerotia, while only 20% of the rice isolates produced large sclerotia. There was a higher frequency of small sclerotia-producing isolates from rice compared to the other sources and isolates that did not produce sclerotia were significantly less likely to be toxigenic than strains that produced large sclerotia.     

Investigations on the effect of haulm destruction and additional root cutting on black scurf on potato tubers

In greenhouse experiments factors which are involved in the stimulation of sclerotia formation byRhizoctonia solani Kühn on potato tubers after haulm destruction were investigated. Cutting off the shoot stimulated the production of sclerotia as much as chemical haulm destruction. This was also observed when potato tubers were grown away from the roots in a separate compartment filled with steamed perlite. Fewer sclerotia were produced when roots were cut in addition to haulm destruction compared to haulm destruction alone. Cutting off the roots alone often stimulated sclerotia production. The data indicate that sclerotia production was directly affected by the tuber and probably due to physiological changes in the tuber caused by elimination of the shoot.Samenvatting In kasproeven werd onderzocht welke factoren betrokken zijn bij de stimulering van de produktie van sclerotiën op aardappel doorRhizoctonia solani Kühn als gevolg van loofvernietiging. Afknippen van het loof stimuleerde de vorming van sclerotiën evenzeer als chemische vernietiging. Na afknippen van het loof trad de stimulering ook op bij knollen, die zich ruimtelijk gescheiden van de wortels in gestoomd vochtig perliet konden ontwikkelen. Doodspuiten plus doorsnijden van de wortels resulteerde in minder lakschurft dan doodspuiten alleen. Wanneer alleen de wortels werden doorgesneden resulteerde dat vaak in meer lakschurft. De vorming van sclerotiën wordt dus direct door de knol beïnvloed. Dit effect lijkt voort te komen uit fysiologische veranderingen in de knol.     

In vitro Variability of a number of characteristics ofSclerotinia sclerotiorum

Studies were made of the variability ofSclerotinia sclerotiorum (Lib.) de Bary: (i) growth rate when cultivated on potato-dextrose agar (PDA); (ii) thein vitro resistance of this organism to the fungicides benomyl, vinclozolin and procymidone; and (iii) the size and number of sclerotia formed on PDA. The isolates used were collected from eggplants, French beans and tomatoes cultivated in the same locality, but although marked differences were observed among them, especially in growth rate and formation of sclerotia, it was not possible to establish groups or categories among the isolates studied, or to relate the observed variability to their origins. Temperature was a decisive factor for formation of sclerotia on PDA. No correlation was found between size and number of sclerotia, and growth rate. The ED₅₀ level for both vinclozolin and procymidonein vitro was 2 mg l⁻¹, whereas that for benomyl was below the minimum level used, and therefore could not be established.     

Nutritional requirements of the mycoparasitic fungus Verticillium biguttatum

Verticillium biguttatum was able to grow axenically in a synthetic liquid medium with a compound containing ammonium or amino group as nitrogen source, glucose as carbon source and biotin as growth factor. Among various carbon and nitrogen compounds tested, highest mycelial production was achieved with mannitol and with two ammonium salts and glutamine; sporulation reached highest values with galactose and glutamine. Highest yields of mycelium and conidia were obtained at pH 4.3 and 5.1, respectively. Although neutral and alkaline conditions were growth-limiting in the synthetic medium some growth ofV.biguttatum occurred on solid media at pH 7.0 and on sclerotia ofRhizoctonia solani in natural soil at pH 7.2–7.3.Samenvatting Een synthetisch vloeibaar medium met glucose als koolstofbron, een ammonium- of aminogroep bevattende verbinding als stikstofbron en biotine als groeifactor voldeed aan de voedingseisen vanVerticillium biguttatum. Van de verschillende koolstof- en stikstofbronnen leverden mannitol en twee ammoniumzouten en glutamine de hoogste opbrengsten aan mycelium; de opbrengst aan conidiën was het hoogst met galactose en glutamine. De hoogste opbrengsten aan mycelium en conidiën werden bereikt bij respectievelijk pH 4,3 en 5.1. Ofschoon neutrale en alkalische omstandigheden de groei vanV. biguttatum in het synthetische medium beperkten, werd enige groei vanV. biguttatum waargenomen op vaste voedingsbodems bij pH 7,0 en op sclerotia vanR. solani in natuurlijke grond bij pH 7,2–7,3.