云南省烟植地青枯菌RS-22的分离及其拮抗菌的筛选和鉴定

【背景】由青枯劳尔氏菌(Ralstonia solanacearum)引起的烟草青枯病是一种重要土传病害,在我国南方烟区普遍发生。生物防控是针对烟草青枯病的一种有效防治措施,但是相关的研究报道还较少。【目的】分离云南省烟植地的青枯病原菌,筛选其拮抗菌并对其抑菌效果进行鉴定。【方法】采用平板稀释法从云南感病烟草中分离获得青枯菌,采用平板对峙法筛选青枯菌拮抗菌,筛选得到的拮抗菌通过16SrRNA基因测序比对确定菌种类型,并在实验室和大田鉴定其对青枯病的防治效果。【结果】从感病烟草茎中分离出一株强致病性青枯菌小种RS-22,该菌能侵染烟草和番茄并最终使植物死亡;筛选出12株RS-22拮抗菌,其中拮抗作用最强的是Y4;Y4被鉴定为一株解淀粉芽孢杆菌(Bacillus amyloliquefaciens),其菌体和分泌物都能抑制RS-22生长;Y4根部灌根处理能显著提高烟草和番茄对青枯菌RS-22的抗性,Y4处理能使感病烟草部分恢复正常,在云南文山州烟草种植大田施加Y4菌剂和菌剂有机肥混合物也能显著降低烟草青枯病的感病率。【结论】青枯菌RS-22具有广谱的致病性,筛选的拮抗菌Y4能显著抑制青枯菌生长,而且对青枯菌侵染植物有很好的防治效果。研究结果为进一步研究烟草青枯病的生物防控提供了新的理论依据。     

Copper uptake and translocation in chicory (Cichorium intybus L. cv Grasslands Puna) and tomato (Lycopersicon esculentum Mill. cv Rondy) plants grown in NFT system. II. The role of nicotianamine and histidine in xylem sap copper transport

The effect of rooting media Cu concentration (0.05–20 mg Cu L^-1) on amino acid concentrations and copper speciation in the xylem sap of chicory and tomato plants was measured using 6 week old plants grown in a nutrient film technique system (NFT). Irrespective of the Cu concentration in the nutrient solutions, more than 99.68% and 99.74% of total Cu in tomato and chicory xylem sap was in a bound form. When exposed to high Cu concentrations in the rooting media, amino acid concentrations in the sap increased. Relative to other amino acids, the concentrations of glutamine (Gln), histidine (His), asparagine (Asn), valine (Val), nicotianamine (NA) and proline (Pro) in tomato xylem saps, and His, γ-aminobutyric acid (Gaba), glutamic acid (Glu), leucine (Leu), NA and phenylalanine (Phe) in chicory xylem saps showed the greatest increases. The data indicate that induced synthesis of some free amino acids as a specific and proportional response to Cu treatment. For a single complexation amino acid, the solution Cu²⁺concentration vs pH titration curve for NA at 0.06–0.07 mM was most similar, closely followed by His at 0.5–0.6 mM, to the solution Cu²⁺concentration behaviour in both tomato and chicory xylem sap. It is concluded that increased Cu concentrations in the rooting media induced selective synthesis of certain amino acid which include NA, His, Asn and Gln which have high stability constants with Cu. NA and His have the highest binding constants for Cu and the concentrations of NA and His in chicory and tomato xylem saps can account for all the bound Cu carried in the sap. This revised version was published online in June 2006 with corrections to the Cover Date.     

禾谷镰孢菌高产毒菌株的构建*

为研究禾谷镰孢菌Fusarium graminearum Schw.单端孢霉烯族毒素生物合成基因（产毒基因）在寄主体内的表达,作者构建了带报告基因GUS（(-葡糖苷酸酶基因）的质粒pGUSTRI6P5,并通过对野生型菌株的转化获得禾谷镰孢高产毒菌株。该质粒含有由TRI5（禾谷镰孢单端孢霉二烯合酶基因）启动子（TRI5 Prom）驱动的GUS基因编码区、潮霉素B抗性基因和拟枝孢镰孢F. sporotrichioides的产毒调控基因TRI6（FSTRI6）。用pGUSTRI6P5转化野生型菌株GZ3639后,在含潮霉素 B的培养基上选取抗性菌落,单孢分离获单孢菌株（转化子）。在GYEP（葡萄糖-酵母粉-蛋白胨）液体培养基上,转化子B4-1和B16-1的GUS比活力强,15-AcDON（15-乙酰脱氧雪腐镰刀菌烯醇）产量高,且两者呈正相关（相关系数（r）分别为0.9839和0.9523）。B4-1和B16-1两个转化子可作为研究禾谷镰孢与其寄主相互作用的工具菌株。     

Identification of a novel genetically controlled step in mycorrhizal colonization: plant resistance to infection by fungal spores but not extra-radical hyphae

Vesicular arbuscular mycorrhizal fungi infect plants by means of both spores and vegetative hyphae at early stages of symbiosis. Using 2500 M2 fast-neutron-mutagenized seeds of the miniature tomato (Lycopersicon esculentum) cultivar, Micro-Tom, we isolated a mutant, M161, that is able to resist colonization in the presence of Glomus intraradices spores. The myc(-) phenotype of the mutant was stable for nine generations, and found to segregate as a single Mendelian recessive locus. The mutant exhibited morphological and growth-pattern characteristics similar to those of wild-type plants. Alterations of light intensity and day/night temperatures did not eliminate the myc(-) characteristic. Resistance to mycorrhizal fungal infection and colonization was also evident following inoculation with the fungi Glomus mosseae and Gigaspora margarita. Normal colonization of M161 was evident when mutant plants were grown together with arbuscular mycorrhizal-inoculated wild-type plants in the same growth medium. During evaluation of the pre-infection stages in the mutant rhizosphere, spore germination and appressoria formation of G. intraradices were lower by 45 and 70%, respectively, than the rates obtained with wild-type plants. These results reveal a novel, genetically controlled step in the arbuscular mycorrhizal colonization process, governed by at least one gene, which significantly reduces key steps in pre-mycorrhizal infection stages.     

Efficacy of Fluensulfone in a Tomato–Cucumber Double Cropping System

Vegetable crops in the southeastern United States are commonly grown on plastic mulch with two crop cycles produced on a single mulch application. Field trials were conducted in 2013 and 2014 in two locations to evaluate the efficacy of fluensulfone for controlling Meloidogyne spp. when applied through drip irrigation to cucumber in a tomato–cucumber double-cropping system. In the spring tomato crop, 1,3-dichloropropene (1,3-D), fluensulfone, and a resistant cultivar significantly decreased root galling by 91%, 73%, and 97%, respectively, compared to the untreated control. Tomato plots from the spring were divided into split plots for the fall where the main plots were the spring treatment and the subplots were cucumber either treated with fluensulfone (3.0 kg a.i./ha. via drip irrigation) or left untreated. The fall application of fluensulfone improved cucumber vigor and reduced gall ratings compared to untreated subplots. Fluensulfone reduced damage from root-knot nematodes when applied to the first crop as well as provided additional protection to the second crop when it was applied through a drip system.     

陆地棉品种和骨干品系黄萎病抗性鉴定

选育和推广抗病品种是防治陆地棉黄萎病的主要措施,为了早日实现多类型、多区域大面积抗病品种的应用,本研究选取107份遗传背景差异较大的种质,利用河北省农林科学院棉花研究所小安舍试验站黄萎病病圃进行了3年黄萎病抗性重复鉴定。鉴定得到抗病品系8个,占7.5%;耐病品种(系)20个,占18.7%。本研究表明,当前被作为育种亲本的抗病品系还太少,需要深入开展抗病遗传机制,以及与其他经济性状协同改良的关系,为陆地棉抗病育种提供理论指导;达到抗病或接近抗病水平的大部分品种(系)来自于海陆野远缘后代,具有外源基因血统,证明了远缘杂交是陆地棉黄萎病抗性改良的有效手段。     

控制性分根交替灌溉下氮形态对番茄生长、果实产量及品质的影响

以高产大果型西红柿品种中研988为材料,采用分根培养的方法,研究了控制性分根交替灌溉(APRI)条件下,不同氮素形态(硝态氮、铵态氮)对番茄生长、产量及果实品质的影响.结果表明: 同一灌溉方式或下限处理下,铵态氮对番茄植株前期生长有利,而硝态氮促进番茄植株后期生长,并促进果实产量增加.在APRI同一灌水下限下,硝态氮处理可提高果实维生素C含量及糖酸比,提高营养品质.同一氮素形态供应下,APRI番茄的株高和叶面积均小于正常灌溉(CK),但灌水下限为60%田间持水量(θ_f)的APRI处理番茄茎粗在生长后期有所增加.在同一氮素形态下,与CK相比,APRI各处理的产量均下降,其中灌水下限在40%θ_f的APRI处理产量下降了22.4%～26.3%;而灌水下限在60% θ_f的APRI处理仅下降了5.3%～5.4%,下降幅度相对较小,而品质显著提高,并具有明显的节水效果.因此,控制灌水下限在60%θ_f、供应硝态氮的APRI处理为番茄高产、优质、节水的最佳处理.
     

Allelopathic impact of artificially applied coumarin on <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f.sp. <Emphasis Type="Italic">niveum</Emphasis>

Watermelon production is threatened by fusarium wilt caused by Fusarium oxysporum f.sp. niveum (FON) in continuous cultivation system. Some elements, mainly allelochemicals, released from living roots or decayed plants might be associated with the disease. The purpose of this work was to evaluate the possible impact of coumarin, one kind of watermelon allelochemical, on FON. Furthermore, possible new mechanisms might be investigated during the ecological interactions of plant-microbe. Results showed that coumarin strongly inhibited growth of FON leading to a decrease in its biomass, dry weight of mycelia of FON in a liquid culture. The dry weight was decreased by 62.9% compared with control. The hyphal growth of FON on plates was stopped at high (>400 mg l⁻¹) concentrations of coumarin. At 320 mg l⁻¹, sporulation and enzyme activities of FON were also severely suppressed by coumarin. The yield of conidia, and the activities of proteinase, cellulase, and amylase were reduced by 98.9%, 79.7%, 29.8% and 15.9% respectively. However, conidial germination and mycotoxin (MT) production of FON were greatly stimulated, being increased by 55.7% and 14.9 fold at 320 mg l⁻¹ respectively. We conclude that coumarin acted as an allelochemical substance to inhibit growth and pathogenic enzyme activities of FON but to stimulate mycotoxin production and conidial germination. It was suggested that coumarin acted as a signal transduction element bridging plant and pathogen in the process of plant-microbe interactions.     

Detection and Investigation of Soil Biological Activity against Meloidogyne incognita

Greenhouse experiments with two susceptible hosts of Meloidogyne incognita, a dwarf tomato and wheat, led to the identification of a soil in which the root-knot nematode population was reduced 5- to 16-fold compared to identical but pasteurized soil two months after infestation with 280 M. incognita J2/100 cm³ soil. This suppressive soil was subjected to various temperature, fumigation and dilution treatments, planted with tomato, and infested with 1,000 eggs of M. incognita/100 cm³ soil. Eight weeks after nematode infestation, distinct differences in nematode population densities were observed among the soil treatments, suggesting the suppressiveness had a biological nature. A fungal rRNA gene analysis (OFRG) performed on M. incognita egg masses collected at the end of the greenhouse experiments identified 11 fungal phylotypes, several of which exhibited associations with one or more of the nematode population density measurements (egg masses, eggs or J2). The phylotype containing rRNA genes with high sequence identity to Pochonia chlamydosporia exhibited the strongest negative associations. The negative correlation between the densities of the P. chlamydosporia genes and the nematodes was corroborated by an analysis using a P. chlamydosporia-selective qPCR assay.