Optimization of plant growth-promoting bacteria-assisted phytostabilization of mine tailings

Recent studies have indicated that plant growth-promoting bacteria (PGPB) can improve revegetation of arid mine tailings as measured by increased biomass production. The goals of the present study were first to evaluate how mode of application of known PGPB affects plant growth, and second to evaluate the effect of this inoculation on rhizosphere microbial community structure. PGPB application strategies investigated include preliminary surface sterilization of seeds (a common practice in phytoremediation trials) followed by a comparison of two application methods; immersion and alginate encapsulation. Results with two native desert plant species, Atriplex lentiformis and Buchloe dactyloides, suggest that seed surface sterilization prior to inoculation is not necessary to achieve beneficial effects of introduced PGPB. Both PGPB application techniques generally enhanced plant growth although results were both plant and PGPB specific. These results demonstrate that alginate encapsulation, which allows for long-term storage and easier application to seeds, is an effective way to inoculate PGPB. In addition, the influence of PGPB application on B. dactyloides rhizosphere community structure was evaluated using PCR-DGGE (denaturing gradient gel electrophoresis) analysis of bacterial DNA extracted from rhizosphere samples collected 75 d following planting. A comparative analysis of DGGE profiles was performed using canonical correspondence analysis (CCA). DGGE-CCA showed that rhizosphere community profiles from PGPB-inoculated treatments are significantly different from both uninoculated tailings rhizosphere profiles and profiles from the compost used to amend the tailings. Further, community profiles from B. dactyloides inoculated with the best performing PGPB (Arthro Mix) were significantly different from two other PGPB tested. These results suggest that introduced PGPB have the potential to influence the development of the rhizosphere community structure found in plants grown in mine tailings.     

Responses of native legume desert trees used for reforestation in the Sonoran Desert to plant growth-promoting microorganisms in screen house

Three slow-growing legume trees used for desert reforestation and urban gardening in the Sonoran Desert of Northwestern Mexico and the Southwestern USA were evaluated whether their growth can be promoted by inoculation with plant growth-promoting bacteria (Azospirillum brasilense and Bacillus pumilus), unidentified arbuscular mycorrhizal (AM) fungi (mainly Glomus sp.), and supplementation with common compost under regular screenhouse cultivation common to these trees in nurseries. Mesquite amargo (Prosopis articulata) and yellow palo verde (Parkinsonia microphylla) had different positive responses to several of the parameters tested while blue palo verde (Parkinsonia florida) did not respond. Survival of all tree species was over 80% and survival of mesquite was almost 100% after 10 months of cultivation. Inoculation with growth-promoting microorganisms induced significant effects on the leaf gas exchange of these trees, measured as transpiration and diffusive resistance, when these trees were cultivated without water restrictions.     

促进小麦生长的根围细菌的筛选及初步鉴定

为探明从植物根围土壤中筛选到具有高效促生作用的细菌菌株的分类地位和促生效果,并为进一步的应用奠定基础。从33个供试土样中分离得到1 700多个细菌菌株,在小麦上进行了促进生长的筛选。经过初筛、复筛,并对数据进行相关分析,最终得到2株具有良好促生效果的细菌菌株ZX-7和ZX-9,菌株ZX-7和ZX-9处理的小麦根重比对照分别增加38.8%和26.1%,鲜重比对照分别增加26.9%和19.3%、株高比对照分别增加7.4%和3.9%。通过对其16S rDNA序列分析,两菌株初步鉴定为芽孢杆菌属(Bacillus)细菌。     

植物根际促生菌的研究进展及其环境作用

具有固氮、溶磷、产生植物激素和分泌抗生素等功能的植物根际促生菌已成为新型生物肥料开发的研究热点.介绍了植物根际促生菌的定义、主要种类、作用机制、研究和应用现状.并提出绿色食品生产、资源再生利用要与植物根际促生菌生产相结合,促进绿色农业的发展,表明促生菌在经济与环境协调发展中具有重要的理论和现实意义.     

植物根际促生菌作用机理的研究进展

介绍了植物根际促生菌的种类,总结了近年来植物根际促生菌在作用机理方面的研究成果,指出了该研究领域存在的问题,并对今后的研究方向进行了展望。     

Effects of organic wastes,Glomus intraradices andPseudomonas putida on the growth of tomato and on the reproduction of the Root-knot nematodeMeloidogyne incognita

Effects of organic wastes (biosolids, horse manure, sawdust and neem leaf litter [NLL]), an arbuscular mycorrhizal (AM) fungusGlomus intraradices, and a plant growth-promoting rhizobacteriumPseudomonas putida, were studied on the growth of tomato and on the reproduction ofMeloidogvne incognita. Pseudomonas putida andG. intraradices promoted tomato growth in nematode-infected and nematode-free plants but growth promotion was higher in the infected ones. WhenP. putida andG. intraradices were applied together, the increase in tomato growth was greater than when either agent was applied alone. Of the organic wastes, NLL was better in improving tomato growth of nematode-infected plants followed by biosolids, horse manure and sawdust. Combined use of NLL withP. putida plusG. intraradices was best in improving growth of the infected plants. Root colonization byP. putida was increased more when inoculated withG. intraradices than when inoculated singly. Of the organic wastes, use of sawdust withP. putida caused a greater increase in root colonization by fluorescent pseudomonads followed by NLL, horse manure and biosolids. Nematode parasitism had an adverse effect on root colonization byP. putida. Inoculation ofP. putida and organic wastes increased the root colonization caused by the AM fungus.P. putida was better in reducing galling and nematode multiplication thanG. intraradices, whereas use of the two together was better than that of either of them alone. Among organic wastes, NLL was better in reducing galling and nematode multiplication followed by biosolids, horse manure and sawdust. Combined use of NLL withP. putida plusG. intraradices was better in reducing galling and nematode multiplication than any other treatment.     

饲用玉米根际促生菌资源筛选及其特性研究

为获得玉米根际促生菌(PGPR)菌株并明确其功能特性;以玉米根系及根际土壤为材料,利用选择性培养基分离筛选溶磷菌与固氮菌,测定所选菌株溶磷能力和固氮酶活性,并测定其产IAA的能力,从中筛选综合性能优良的菌株,在此基础上,运用生理生化鉴定和16SrDNA分子生物学鉴定相结合的方法鉴定优良菌株的种属。结果表明:玉米根际有大量PGPR菌,分布特征表现出根表(RP)根表土(RS)远根土(NRS)根内(HP)的数量分布规律,呈根际效应。最终获得262株PGPR菌,其中固氮菌48株,溶解无机磷细菌108株,溶解有机磷细菌106株,有分泌IAA能力的菌株15株。筛选出综合性能优良、有进一步开发应用潜力的菌株7株。经鉴定其中3株为Pseudomonas fluorescens;2株为Bacillus subtilis;Klebsiella oxytoca和Bacillus megaterium各1株。     

耐镉根际促生菌的筛选及其对一年生黑麦草镉吸收积累的影响

利用含不同镉(Cd)浓度的LB(Luria-Bertani)培养基,从植物根际土壤分离得到32株耐镉根际菌,测定了这些菌株产吲哚乙酸、ACC脱氨酶活性、溶磷能力并根据培养皿促生试验的复筛结果,选取A02,Oj06和Ps08作为供试菌株。以一年生黑麦草(Lolium multiflorum Lam.)为材料,开展了耐镉根际促生菌调控镉胁迫下幼苗生长的试验。当土壤中镉含量为20±0.33mg·kg-1时,分别接种A02,Oj06和Ps08菌株,结果表明:与未接种菌株相比,接种3种菌株后一年生黑麦草地上部生物量和镉积累量皆显著提高,叶片中膜脂过氧化水平(MDA含量)则显著降低(P0.05),土壤镉有效态含量增加,其中A02处理达显著水平(P0.05)。因此,接种耐镉根际促生菌株可显著促进镉胁迫下一年生黑麦草幼苗生长,并且能通过增加土壤中镉的有效态,促进植株对镉的吸收与积累。     

AMF+PGPR组合提高黄瓜抗枯萎病的作用机制

对黄瓜(Cucumis sativus)品种香翠16接种尖孢镰刀菌黄瓜专化型(Fusarium oxysporum f.sp.cucumerinum,Foc)、丛枝菌根真菌(AMF)Funneliformis mosseae(Fm)+Foc、丛枝菌根真菌Glomus versiforme(Gv)+Foc、根围促生细菌(PGPR)PS2-6+Foc、PS3-2+Foc、Fm+PS3-2+Foc以及Gv+PS2-6+Foc,以不接种处理作为对照。结果表明,接种Foc条件下,Fm+PS3-2和Gv+PS2-6组合处理的抗病效果显著优于单接种AMF或PGPR处理;镜检观测到靠近AMF菌丝的Foc菌丝纤细,生长不良。AMF菌丝能缠绕Foc菌丝,并阻挡其侵入根系;AMF侵染率与其防效均呈正相关(P0.05);Fm+PS3-2+Foc和Gv+PS2-6+Foc处理的根系活力是单接种Foc的4.6倍;与不接种对照相比,Fm+PS3-2+Foc和Gv+PS2-6+Foc处理的黄瓜叶片中吲哚乙酸(IAA)含量分别提高了205%和166%,赤霉素(GA3)提高了33%和22%,玉米素核甘(ZR)提高了100%和80%,JA平均提高了65%,ABA降低23%和17%;而与单接种Foc处理相比,IAA提高了667%和568%,GA3提高了223%和196%,ZR提高了254%和219%,茉莉酸(JA)含量平均提高了215%,而脱落酸(ABA)含量只有单接种Foc处理的53%;Fm+PS3-2+Foc和Gv+PS2-6+Foc处理显著提高了黄瓜叶内苯丙氨酸解氨酶(PAL)防御酶活性和PAL基因表达量。综上推断AMF+PGPR组合是通过拮抗病原物、促进合成抗病信号物质、上调防御基因表达、提高防御酶活性和降低植株体内有毒物质等机制降低病害和改善植物抗病性。     

苏云金芽胞杆菌——开放的基因组与多种功能

苏云金芽胞杆菌Bacillus thuringiensis(Bt)作为微生物杀虫剂,被广泛应用于农业、林业和卫生害虫的防治;而利用Bt杀虫基因研制的转基因植物,也在全球植物害虫防治中发挥了重要作用。近年来,随着科学技术的发展与社会需求的拓展,Bt新的功能被不断发掘出来。这些新的功能包括抗线虫、抗病杀菌、促进植物生长、环境修复等。本文从Bt的泛基因组结构及其遗传学特性分析入手,在详细介绍了近来Bt杀虫基因发掘进展的同时,分析了泛基因组与Bt新的功能之间可能存在的关系,旨在为我国Bt资源的研究与应用提供参考。