Modes of action of the protective strain Fo47 in controlling verticillium wilt of pepper

The protective fungus Fusarium oxysporum Fo47 reduces the severity of wilt caused by the soilborne pathogen Verticillium dahliae in pepper. Modes of action responsible for the biocontrol activity were studied. Microscopic observations of fluorescent protein‐transformed strains colonizing the root surface show that the colonization patterns of Fo47 and V. dahliae were similar. Pixel counting of the images obtained by confocal microscopy showed that Fo47 reduces colonization of the root surface by V. dahliae, suggesting a possible role of competition for nutrients at the root surface. Besides these effects on surface colonization, the hormonal pathways activated during priming of plant defence responses were identified by measuring the amount of some phytohormones and their derivatives in roots and stems of pepper. Results showed an early, slight increase of jasmonyl isoleucine, followed by a transient increase of salicylic acid during the pre‐challenged phase of priming and an increase of 12‐oxo‐phytodienoic acid during the challenge phase of priming. The caffeic, ferulic and chlorogenic acids, known to play a role in plant defence reactions, showed a strong antimicrobial activity against V. dahliae in vitro. In pepper roots, Fo47 stimulated the biosynthesis of caffeic acid and primed that of chlorogenic acid. These results demonstrated that the effective control of V. dahliae provided by Fo47 is based on different but complementary mechanisms.     

绿针假单胞菌HL5-4对番茄灰霉菌的抑制活性及其定殖能力

为探讨绿针假单胞菌HL5-4对番茄灰霉病的生防潜力,通过对峙培养和孢子萌发试验测定其对灰葡萄孢菌的抑制活性;进行离体试验和苗期试验测定其对番茄灰霉病的防治效果;采用平板稀释法测定其在番茄果实和叶片的定殖能力;并根据形态特征、生理生化特性及16SrDNA序列同源性对其进行鉴定。结果表明:HL5-4显著抑制灰葡萄孢菌的菌丝生长和分生孢子萌发,萌发抑制率为70.74%;在离体试验中,对番茄果实和叶片灰霉病的防治效果分别达到72.36%和59.85%,在盆栽试验中,对番茄苗期灰霉病的防治效果为62.88%;HL5-4在番茄果实和叶片保持一定的定殖密度,处理7d时能保持10~4和10~3 cfu·g~(-1)以上;HL5-4菌株鉴定为绿针假单胞菌(Pseudomonas choloeaphtis)。     

生防菌株SC11的鉴定、定殖及对棉花枯萎病防治效果研究

 通过生物学特性观察和16S rDNA基因序列分析鉴定菌株SC11为壮观链霉菌(Streptomyces spectabilis)。该菌可在棉花根际土壤以及棉花根部长期定殖,30 d的定殖密度分别为1.38×10⁵ CFU/g和2.95×10³ CFU/g。2011年和2012年的大田防治试验显示,SC11菌粉对棉花枯萎病防效分别为42.51%和36.70%,与对照50%多菌灵(WP)的防效相比无显著差异,施用90~150 d的防效分别显著高于多菌灵(P<0.05)。与清水对照相比,田间施用SC11菌粉棉花倒三叶面积显著提高52.6%,籽棉和皮棉产量分别增加21.9%和23.0%(P<0.05)。研究结果表明,壮观链霉菌SC11是一株对棉花枯萎病具有应用前景的生防菌株。     

GFPuv标记猕猴桃溃疡病菌的生物学特性 及其在土壤、根系中的定殖

【目的】获得具有荧光标记的猕猴桃溃疡病菌（Pseudomonas syringae pv. actinidiae）菌株,为进一步揭示其侵染致病过程奠定基础。【方法】电击法对病菌进行GFPuv基因标记,应用荧光显微镜和平板稀释法研究标记菌株在土壤和根部的定殖情况。【结果】GFPuv标记的猕猴桃溃疡病菌菌株在荧光显微镜下发出强烈的绿色荧光,8株标记菌基因组DNA中均扩增出约700 bp的目的片段。标记菌株PSAmx7-GFPuv1的菌体形态、生长曲线、最适温度、最适pH、致病性均与野生型无显著差异,其绿色荧光可稳定遗传。标记菌在灭菌土壤中可存活3个月左右,在未灭菌土壤中也能存活3周;灌根1 d检测,根表、根内组织中可分离到目标菌落,随后标记菌株数量呈现“先增后降”的趋势。【结论】电击法成功地将GFPuv基因转入猕猴桃溃疡病菌;导入的GFPuv 基因对宿主菌的生物学特性没有影响;标记菌可在灭菌土壤中长期存活,并在根部定殖和增殖。     

Microbial Dynamics,Root Colonization,and Nutrient Availability as Influenced by Inoculation of Liquid Bioinoculants in Cultivars of Apple Seedlings

The present study investigates the performance of recommended doses of chemical fertilizer (RDF) and locally isolated strains of Azotobacter, Azospirillum, and arbuscular mycorrhizal fungi (AMF) inoculated either solely or in combination with seedlings of Red Delicious and Lal Ambri cultivars. The RDF (T₇) treatment recorded significantly greater vegetative growth and leaf nitrogen (N), phosphorus (P), and potassium (K) contents over multi-inoculation of Azotobacter + Azospirillum + AMF (T₆) but root colonization and microbial counts decreased significantly. Inoculation of Azotobacter + Azospirillum + AMF (T₆) was superior over sole and dual inoculation with respect to vegetative growth and nutrient contents in leaves and soil but had significant greater counts of Azotobacter, Azospirillum, and Pseudomonas than RDF. Greatest root colonization (34.0 and 35.1%) was recorded in Azotobacter + Azospirillum + AMF (T₆) followed by AMF (T₄) treatment (29.3 and 32.0%) in Red Delicious and Lal Ambri seedlings, respectively. Overall, it can be inferred that multiinoculation of synergistically interacting bioinoculants may be helpful in the establishment of healthy organic apple orchards.     

田菁茎瘤固氮根瘤菌在小麦体内的定殖及营养元素相关miRNA的表达

【目的】随着化肥过度使用引起的环境问题的出现,无公害农业的推广,以及新型肥料研究领域不断拓宽,微生物肥料,尤其是植物根际促生菌的研究成为近年来的热点。然而微生物肥料的增产机理还基本停留在作物农学性状的表观调查上,没有从分子水平进行研究。因此,本文用田菁茎瘤固氮根瘤菌（Azorhizobium caulinodans ORS571）侵染小麦,探索GFP-A.caulinodans在小麦幼苗组织中的分布与定殖规律以及营养元素相关miRNAs在小麦与A.caulinodans互作中的作用机制。【方法】使用A.caulinodans侵染小麦种子（品种为小偃22）,将接菌6 d后的小麦幼苗的根和接菌12 d后的叶制作玻片,利用激光共聚焦显微镜对样品进行逐层扫描,检测GFP-A.caulinodans在幼苗不同组织中的分布与定殖情况。同时,采集接菌后0 h、 6 h、 12 h、 24 h、 48 h、 72 h、 96 h的小麦幼根取样,用Trizol法提取总RNA。利用试剂盒进行加尾和反转录反应,将样品总RNA中的miRNA合成为cDNA,使用-tubulin作为内参基因,进行实时定量PCR反应,使用2-CT方法计算相对表达量。利用psRNATarget 在线软件,采用默认参数,对miRNA的靶基因进行预测。【结果】 1）激光共聚焦结果显示,GFP-A.caulinodans可定殖于根的表皮细胞、 细胞间隙、 根尖破损处和根毛,在根维管组织和叶片气孔部位,也发现有GFP-A.caulinodans存在。2）实时定量PCR分析结果表明,6条与营养元素代谢有关的miRNA表达发生变化,其中miR164、 miR167和miR827相对表达量呈现出先上调后下调的趋势,miR169 和miR398相对表达量也基本呈现出这一趋势。miR164、 miR167、 miR169和miR398的相对表达量在接菌12 h时上调至最高点,分别为对照的4.13、 2.84、 2.46和3.99倍; miR827相对表达量在接菌24 h时达到最高点,为对照的2.17倍。miR399相对表达量呈现出先下调后上调的趋势,在接菌24 h时降至最低点,为对照的0~21倍。3）通过靶基因预测,6条miRNA的靶基因分别编码了NAC1转录因子、 生长素响应因子、 HAP转录因子、 Cu/Zn 超氧化物歧化酶、 蛋白缀合酶PHO2和SPX-MFS亚家族蛋白。【结论】GFP-A.caulinodans能够从根毛和根尖破损处等部位进入小麦幼苗根部定殖,并可通过向上迁移到达叶片,在气孔处定殖。接种A.caulinodans可不同程度增加小麦根中响应氮素、 磷素、 微量元素的miRNAs相对表达量,增强小麦幼苗对营养元素的吸收和利用,促进小麦根的形态建成。     

山区玉米单株定植技术应用效果分析

文章结合不同种植方式试验和大面积推广实践,论述了玉米单株定植在黔西北山区玉米生产中的应用效果.试验证明,实行玉米单株定植可提高种植密度,改善田间通风透光条件,促进玉米根系发达、茎粗叶茂、穗大粒多产量高.     

Arbuscular mycorrhizal fungi are directly and indirectly affected by glyphosate application

Glyphosate is a systemic non-selective herbicide, the most widely used in the world. Alongside with its use in agricultural and forestry systems, this herbicide is used in grasslands in late summer with the aim of promoting winter species with the consequent increase in stocking rate. However, its effects on non-target organisms, such as arbuscular mycorrhizal fungi (AMF), are unclear. Arbuscular mycorrhizal fungi (AMF) colonize the root of more than 80% of terrestrial plants, improving their growth and survival, and therefore playing a key role in ecosystem structure and function. The aim of this work was to investigate the possible pathways through which glyphosate application affects AMF spores viability and root colonization in grassland communities. Our hypothesis is that glyphosate application can damage AMF directly (through contact with spores and external hyphae) or indirectly through the changes it generates on host plants. The experiment had a factorial array with three factors: (1) plant species, at two levels (Paspalum dilatatum and Lotus tenuis), (2) doses of glyphosate, at three levels (0 l ha⁻¹, 0.8 l ha⁻¹ and 3 l ha ⁻¹), and (3) application site, at two levels: soil (direct pathway) and plant foliage (indirect pathway). Spore viability was reduced even under the lowest glyphosate rate, but only when it was applied on the soil. Total root colonization for both species was similarly decreased when glyphosate was applied to plant foliage or on soil, with no difference between 0.8 and 3 l ha⁻¹. The number of arbuscules was 20% lower when glyphosate was applied on plant foliage, than when it was applied on the soil. Our findings illustrate that glyphosate application negatively affects AMF functionality in grasslands, due to different causes depending on the herbicide application site. While, under field conditions, the occurrence of direct and/or indirect pathways will depend on the plant cover at the time of glyphosate application, the consequences of this practice on the plant community structure will vary with the mycorrhizal dependence of the species composition regardless of the pathway involved.     

Survey of Mycorrhizal Colonization in Native,Open-Pollinated,and Introduced Hybrid Maize in Villages of Chiquimula,Guatemala

Replacing native plant types with introduced cultivars may have unexpected cropping system consequences. Native species and introduced cultivars may vary in their ability to form mycorrhizal symbioses with soil fungi and consequently affect phosphorus (P) nutrition. Low-input cropping systems often depend on mycorrhiza for adequate nutrition and growth, while high-input systems minimize the benefit of and need for colonization. Studies in wheat (Triticum aestivum L.) suggest that improving cultivars reduced the ability to form mycorrhiza. This study was conducted at six sites in the province of Chiquimula, Guatemala, to determine the difference in mycorrhizal infection rates between two maize (Zea mays L.) cultivars—‘Cushpeño,’ a native, open-pollinated variety, and ‘HB-83,’ an introduced, improved hybrid. The ‘HB-83’ was colonized at a significantly lower percentage (67%) than was ‘Cushpeño’ (72%; α = 0.0137). A strong negative correlation (r = ?0.953) existed between Mehlich-3 extractable soil P and differences in mycorrhizal colonization rates between the two genotypes. The full impact of lower colonization rates of the introduced hybrid on sustainability of the village agricultural system needs further investigation.     

内生菌-植物联合修复污染土壤研究进展

环境污染对生态系统及人类健康造成严重威胁。近年来,许多学者研究发现内生菌联合植物修复体系对修复自然环境中的重金属和有机物具有巨大的潜力。本文主要从内生菌联合植物进行污染修复的机理和应用两方面入手,介绍了内生菌接种宿主植物根、茎、叶部的几种方法及定殖的检测方法,总结了污染土壤中内生菌在植物组织内的定殖动态,以及内生菌-植物联合体系强化有机物污染和重金属污染修复效果的应用,并从内生菌调节生长因子、生物固氮和溶磷、在宿主植物体内的共代谢有机物、产生特异性酶降解有机物、提升植物对重金属抗性和降低重金属毒性几个方面解释了内生菌和植物的联合修复机理。最后指出,虽然已经有许多对于内生菌联合植物修复体系的研究,但是目前两者相互作用机理尚未完全清楚,对于多种内生菌组合体系以及处理水体和大气污染的研究并不完善,这些都将成为今后的研究重点。