Studies on the Isolation of Endophytic Bacteria from Tomato Plants and Their Growth-promoting Activities

[Objective] The study aimed to investigate the growth-promoting activities of endophytic bacteria from tomato plants.[Method]The endophytic bacteria isolated from different tissues of tomato plants were analyzed for the effects of their growth-promoting activities on the germination and growth of tomato plants.The bacteria with growth-promoting activity were preliminarily identified.[Result]Totally 59 endophytic bacterial strains were isolated from roots and stems of tomatoes,of which 4 showed significantly growth-promoting activity to germination and growth of tomato.The results suggest that these strains are endowed with the potential capability of growth-promoting.[Conclusion]The endophytic bacteria with growth-promoting activity were found among the isolates from tomato plants.This provided a good foundation for utilization of these bacteria with growth-promoting activity.

Determination of Growth-promoting and Antagonistic Action of Endophytic Bacteria Strains Itb57 and Itb295 of Tobacco

[ Objective ] The paper was to study the growth-promoting and antagonistic action of endophytic bacteria strains Itb57 and Itb295 of tobacco to explore their functions in biological control. [ Method] The growth-promoting effects of bacterial suspension ~ff endophytic bacteria Itb57 and Itb295 on tobacco seedling un- der different treatment modes were studied using potting method in greenhouse. The antagonistic action of bacterial suspension of endophytic bacteria Itb57 and Itb295 on Phytophthora nicotianae, Alternaria alternata and Botrytis cinerea were measured by duel culture method. [ Result] Bacterial suspensions of enduphytic bacteria Itb57 and Itb295 had certain growth-promoting effects on tobacco seedling, which could significantly increase the fresh weight and dry weight in aerial part; the growth-promoting effect of soaking ＋ spraying and irrigating treatment was the best. Itb57 strain had good antagonistic action against P. nicotianae. A. alterna- ta and B. cinerea, while Itb295 strain only had good antifungal effect against P. nicotianae. [ Conclusion] The results provided basis for the study and application of tobacco endophytic bacteria strains Itb57 and Itb295 in biocontrol of tobacco diseases.

Endophytic bacteria associated with endangered plant Ferula sinkiangensis K. M. Shen in an arid land： diversity and plant growth-promoting traits

Ferula spp. are traditional medicinal plants found in arid land. Large-scale excavation for extracting bioactive compounds from the plants in arid regions of Xinjiang over the last few years has, however, significandy decreased their distributions. Due to the urgent need for preservation of these plant resources, along with the need of searching for alternative source of the useful metabolites, it is important to screen the endophytic microbial resources associated with the plant Ferula sinkiangensis K. M. Shen. In the study, a total of 125 endophytic bacteria belonging to 3 phyla, 13 orders, 23 families, and 29 genera were isolated based on 16S rRNA gene sequencing data. Among the different isolates, three strains isolated from roots were potential novel species of the genera Porphyrobacter, Paracoccus and draycofatopsis. In this study, 79.4% and 57.1% of the total isolates were capable of producing indole-3-acetic acid （IAA） and siderophore, respectively. And, 40.6% of the strains inhibit the growth of fungal pathogen Afternaria alternata, 17.2% and 20.2% strains were positive for antagonism against Vertidllium dahlia 991 and V. dahlia 7, respectively. These results demonstrated that E sinkiangensis is a rich reservoir of endophytic bacterial resources with potential for production of biologically important functions such as plant growth-promoting factors.

Endophytic Bacteria Promote the Growth of Suaeda glauca in Saline-Alkali Stress:Regulation of Osmotic Pressure and Antioxidative Defense System

Endophytic bacteria are promising bacterial fertilizers to improve plant growth under adverse environment.For ecological remediation of coastal wetlands,it was necessary to investigate the effect and interaction of endophytes on halophytes under saline-alkali stress.In this study,an endophytic bacterium strain HK1 isolated from halophytes was selected to infect Suaeda glauca under pH(7 and 8)and salinity gradient(150,300 and 450mmolL^(-1)).Strain HK1 was identified as Pantoea ananatis and it had ability to fix nitrogen,dissolve inorganic phosphorus and produce indole-3-aceticacid(IAA).The results showed that strain HK1 could promote the growth of S.glauca seedings when the salinity was less than 300mmolL^(-1),in view of longer shoot length and heavier fresh weight.The infected plants could produce more proline to decrease the permeability of cells,which content increased by 26.2%–61.1%compared to the non-infected group.Moreover,the oxidative stress of infected plants was relieved with the malondialdehyde(MDA)content decreased by 16.8%–32.9%,and the peroxidase(POD)activity and catalase(CAT)activity increased by 100%–500%and 6.2%–71.4%,respectively.Statistical analysis revealed that increasing proline content and enhancing CAT and POD activities were the main pathways to alleviate saline-alkali stress by strain HK1 infection,and the latter might be more important.This study illustrated that endophytic bacteria could promote the growth of halophytes by regulation of osmotic substances and strengthening antioxidant activities.This finding would be helpful for the bioremediation of coastal soil.

Identification of Growth-promoting Bacteria from Rhizosphere of Pastures and Their Effects on Growth of Lotus corniculatus L.

[Objectives] This study was conducted to explore the interaction between nitrogen-fixing and phosphate-solubilizing strains and the optimal combination of different functional strains,in order to provide a theoretical basis for the development of PGPR compound fertilizers suitable for local environment.[Methods] In this study,16S rDNA gene sequence analysis was used to identify fast-growing and competitive strains from pasture nodules and rhizosphere soils in Guizhou Province,and three representative Rhizobia and phosphorus-solubilizing bacteria were chosen for the test of bacterial combination when reducing 50% of nitrogen and 30% of phosphorus.The effects of different strain combinations on the plant height,root length,aboveground and underground biomass of Lotus corniculatus L.were investigated,and the total nitrogen and total phosphorus contents of the plants were determined.[Results] The mixed bacterial agents could promote the increase of root biomass,and the effects of A1,A3,B3 and C3 were the most obvious.The fresh weight and dry weight of the roots of L.corniculatus increased by 30.35%-168.45% and 26.43%-180.00%,respectively,and A3,B3,B2 and C3 had the best effects.The total phosphorus content of the plants increased by 12.79%-55.25% compared with the CK2;and most of the bacterial agents with significant growth-promoting effects showed decreased total nitrogen contents,while those with non-significant growth-promoting effects showed significantly-increased total nitrogen contents,which were not as much as the CK1.Comprehensively,the most productive combination was C3,namely R27-2 Rhinohizobium fredii and P33-3 Stenotrophomonas rhizophila.[Conclusions] This study can provide a theoretical basis for the production and promotion of bacterial fertilizers.

Antimicrobial and plant growth-promoting activities of bacterial endophytes isolated from Calotropis procera(Ait.)W.T.Aiton

Bacterial endophytes are beneficial to their hosts as they can fix nitrogen in the soil and make it available to the host.Endophytic bacteria also secrete plant growth-promoting hormones to support their host plants under normal as well as stress conditions.The current study aimed to isolate endophytic bacteria from different parts of Calotropis procera,i.e.,roots,stem and leaves of Calotropis procera(Ait.)W.T.Aiton.Plants were collected from the Lundkhwar,district Mardan.A total of 12 bacterial strains,i.e.,six from roots,three from the stem and three from the leaves were isolated.The strains were screened for their growth-promoting activity in rice plants because rice shows a quick and easy response to the bioactive compounds present in the culture filtrate(CF)of the potent endophytic strains.The rice plants were cultivated in pots containing 30 mL of 0.8%w/v water-agar medium.The pots were placed in a growth chamber,operated at 28±0.3℃ for 14 h(day);and 25±0.3℃ for 10 h(night),at 70%relative-humidity.Among the isolated strains,R1,S1,S3,L1,R5 and R6 showed visible growth promotion in rice plants.The biochemical analysis revealed that the strains were able to produce indole acetic acid(IAA)and flavonoids in higher quantities.Moreover,the strains also produced bioactive compounds that inhibited the growth of Escherichia coli and Aspergillus flavus using the well diffusion method.From the results,it was concluded that these strains can secrete potent compounds that can promote the host plant growth and inhibit the growth of pathogenic microorganisms and,therefore,can be used as bio-fertilizer and bio-control agents.

Selection,Identification and Growth Promotion of Inorganic Phosphorus-dissolving Bacterial Strains in Rhizosphere of Trifolium repens

[Objective] The aim was to select and identify inorganic phosphorus-dissolving bacteria in rhizosphere of Trifolium repens,and to research related effects of growth promotion.[Method] Phosphate solubilizing bacteria in rhizosphere of Trifolium repens in Guizhou Province were separated and selected to determine its ability of phosphate solubilizing and IAA secretion,and growth promotion effect.[Result] Phosphate solubilizing bacteria were multiple and varied in rhizosphere of Trifolium repens;solubilizing quantities of phosphorus from calcium phosphate by RW2,RW6 and RW18 were 337.39,447.45 and 462.03 μg/ml;solubilizing quantity was none of linear relation with organic acid;RW2 proved the one secreted most IAA at 12.69 μg/ml,followed by RW18 at 12.34 μg/ml;the three strains were all of Leclercia sp.,but were of none pathogenicity for seedlings of Trifolium repens,instead,a kind of growth promotion was found.Detailedly,RW18 was most effective in growth promotion for Trifolium repens and plant height,root length and weight,and aboveground biomass increased by 110.98%,9.17%,46.17% and 2% respectively.Hence,RW18 is of great potential.[Conclusion] The research provides scientific references for developing phosphate solubilizing bacteria and compound inoculation and develops a novel way to relieve barren soils,save phosphorus resource,reduce environment pollution,and guarantee sustainable development of agriculture and animal husbandry.

不同促生菌配合生长调节剂处理对滩涂稻田盐分变化、水稻产量及品质的影响

为了探明促生菌和生长调节剂对滩涂稻田盐分变化、水稻产量及稻米品质的影响,于2020年6—11月,在江苏南通沿海滩涂地区布置水稻种植试验,采用双因素裂区设计,主区为促生菌浸种处理,包括清水(CK)、如东促生菌(RD)和宁波促生菌(NB)浸种,副区为生长调节剂喷施处理,包括喷施清水(W)、碧护(0.136%赤·吲乙·芸苔)(T1)和复硝酚钠(T2)。结果表明,种稻过程中灌溉水盐度变化幅度为0.78~1.12 g·kg^(-1),CK、RD和NB处理水稻生长期间土壤盐分变化幅度为1.11~1.87 g·kg^(-1)。水稻产量在RD和NB下较CK分别增加了4.65%和1.83%;在T1和T2下较W分别增加了5.50%和1.05%;RD-T1下水稻产量较CK-W增加效果最好,达到11.66%(P<0.05),且每穗粒数和实粒数分别增加了13.45%和13.85%(P<0.05)。与CK相比,RD稻米糙米率、直链淀粉和蛋白质含量均显著降低,其他品质指标无显著差异。双因素分析结果表明,生长调节剂对穗长、每穗粒数、实粒数和产量均具有显著影响,促生菌对水稻千粒重具有显著影响,生长调节剂和促生菌仅对水稻千粒重具有显著互作效应。可见,促生菌结合生长调节剂处理对滩涂水稻增产具有明显效果,且生长调节剂主要提高了每穗粒数和实粒数,促生菌主要改善了滩涂水稻千粒重。本研究结果为探索适宜的农艺管理措施以达到滩涂水稻增产目的提供了技术参考。

PGPR调控植物响应逆境胁迫的作用机制

盐碱、干旱等非生物胁迫是限制植物生长和产量的重要环境因子。植物根际促生菌(PGPR)是一类定殖于植物根系的有益微生物,利用其生物学功能制成的生物菌剂具有低成本、高效和环保等优点,不仅可促进植物生长与作物产量,还能提高植物对非生物胁迫的耐受性。本研究对PGPR定义和种类、生物学功能及其在植物响应盐碱、干旱、高低温及重金属等非生物胁迫中的作用加以综述,并对其未来研究方向进行展望,以期为今后PGPR介导植物抗逆性的研究与生物菌剂的开发和应用提供理论支撑。

一株旱稻联合固氮菌株的分离鉴定及促生作用

[目的]旱稻是一种重要的种质资源,对成熟期旱稻根系内生固氮菌进行筛选与鉴定,以获得对旱稻有较好促生作用的菌株。[方法]采用联合固氮固体培养基培养方法,从成熟期旱稻根系中分离出内生固氮菌,通过扩增固氮酶nifH基因和16S rRNA基因进行分子鉴定和系统进化分析生化指标测定和形态学鉴定;采用透明圈法进行溶磷、产铁载体能力验证;以褐球固氮菌为阳性对照,利用ELISA测定试剂盒测定菌株分泌固氮酶活性、1-氨基环丙烷-1-羧酸(ACC)脱氨酶,采用Salkowski比色法测定生长素(IAA)含量,并研究其生长特征。将分离的固氮菌株以1%浓度(约8×10~7CFU/mL)浸泡旱稻谷种进行催芽,研究其促生效果。[结果]分离的菌株URR45为固氮菌,属于嗜温型微生物,最适生长温度为32~50℃,最适pH为6.0~6.5,不耐盐。其分泌的固氮酶含量为220.15 U/L,ACC含量为898.69 ng/mL,生长素含量为14.91 mg/L,固氮酶含量和ACC含量显著高于对照组褐球固氮菌。该菌株能够利用葡萄糖、麦芽糖等碳源,属于发酵型细菌,具有水解明胶、溶磷和产铁载体特性。该菌株经16S rRNA基因测序后通过NCBI BLAST比对,鉴定为Herbaspirillum seropedicae,隶属于Pseudomonadota门、Betaproteobacteria纲、Burkholderiale目、Oxalobacteraceae科、Herbaspirillum属,革兰氏染色呈阴性。促生试验结果表明,在主根长度、侧根长度以及测根数方面均显著高于对照组。[结论]该菌株对旱稻幼苗具有一定的促生作用,在农业上产上可作为功能性内生固氮菌开发利用。

生物法修复盐渍化土壤研究进展

我国盐渍化土壤面积大,已严重制约了农业的发展和土壤的循环利用,修复盐渍化土壤有利于增加我国耕地面积、提高粮食产量。盐渍化土壤通常采用物理、化学和生物3种方法进行修复。相比于化学和物理修复法,生物修复法利用生物的生命代谢活动降低土壤的盐分,更经济、环保和高效,因此已在盐渍化土壤修复中得到广泛应用。文章总结了土地盐渍化危害及我国土地盐渍化现状,论述了植物、微生物和微生物-植物联合修复盐渍化土壤的机制和研究现状,并展望了生物法修复盐渍化土壤的应用前景。

花生白绢病菌拮抗细菌的分离鉴定及其温室抑菌促生效果

由齐整小核菌Sclerotium rolfsii Sacc.侵染引起的土传真菌性病害——花生白绢病,严重威胁花生的生产。为挖掘对花生白绢病有较好防治效果的拮抗细菌,利用稀释涂布法从感染S.rolfsii的植株根际土壤中分离得到570株细菌,采用平板对峙法筛选出32株S.rolfsii拮抗细菌,结合16S rRNA基因序列、形态学及生理生化特征,确定细菌的分类学地位。通过S.rolfsii与拮抗细菌的发酵液共培养和盆栽试验结果表明:在所筛选的32株拮抗细菌中,4株细菌HNZZ23、HNKF5、HNXX14和HNXX169对S.rolfsii的抑制时间长,抑制效果好,其发酵液对S.rolfsii菌丝生长的抑制率分别为85.30%、85.88%、85.16%和91.00%,对S.rolfsii菌核萌发的最大抑制率分别为100%、85.33%、82.67%和93.33%。菌株HNZZ23和HNXX14的发酵液对盆栽花生白绢病的防治效果分别为30.50%和25.73%,且菌株HNZZ23对花生植株的生长具有显著的促进作用。经分类学鉴定,菌株HNZZ23、HNKF5、HNXX14和HNXX169分别为萎缩芽孢杆菌Bacillus atrophaeuse、短小芽孢杆菌B.pumilus、铜绿假单胞菌Pseudomonas aeruginosa和枯草芽孢杆菌B.subtilis。本研究结果表明,感病花生根际细菌HNZZ23、HNKF5、HNXX14和HNXX169对花生白绢病原菌S.rolfsii具有良好的拮抗作用和生防潜力,可为花生白绢病的生物防治提供优质菌种资源。

醉鱼草内生细菌ZJ1的生物学特性及防病促生效果

为推动生物防治技术在实践中的应用,本研究采用稀释涂布平板法对菌株ZJ1的致死温度和酸碱度进行测定,结果表明,菌株ZJ1的致死温度为96℃、可存活20 min;致死pH为≤4或≥14。而生物膜能够吸附土壤中的金属离子改善植物生长环境,帮助生防菌株更好地定殖在植物表面,发挥生防功能。采用菌膜检测法观察几种常见金属离子对菌株ZJ1生物膜形成的影响,结果表明,0.3%的Zn2+、Mn2+、Cu2+和Fe2+会抑制菌株ZJ1产生生物膜,但同浓度的Mg2+、K+均可促进菌株ZJ1生物膜的产生;进一步采用96微孔板定量法对菌株ZJ1生物膜形成能力进行了测定,结果表明,菌株ZJ1为强生物膜形成株。室内盆栽试验结果表明,菌株ZJ1发酵液10×稀释液对番茄早疫病的保护效果最高,达到95.54%,菌株ZJ1发酵液200×稀释液对番茄灰霉病的治疗效果最高达,到91.99%。综合考虑菌株ZJ1对两种病害的治疗和保护效果,菌株ZJ1发酵液稀释200×防治效果最好。且菌株ZJ1发酵液10~200×均具有促生效果。因此,菌株ZJ1是一株具有生防潜力的微生物菌株。

2株青贮玉米根际固氮菌的筛选鉴定及促生作用研究

为了获得优良的固氮菌,并评价其对青贮玉米的促生效果,本研究采用稀释涂布平板法,利用阿须贝氏固体培养基从青贮玉米根际土壤中分离筛选到10株固氮菌,对其固氮能力进行分析,结果表明,菌株ZL-2和ZL^(-1)3的固氮能力较强,菌株ZL-2的固氮量为1.07μg·mL^(-1),ZL^(-1)3的固氮量为0.95μg·mL^(-1)。通过细菌形态学、16S rDNA序列分析和生理生化特征,确定菌株ZL-2为生癌肠杆菌和ZL^(-1)3为成团泛菌。对2株固氮菌的促生特性进行分析,结果表明,2个菌株具有泌铵能力、溶磷能力、产嗜铁素能力和合成吲哚-3-乙酸(IAA)的能力。盆栽试验结果表明,接种固氮菌ZL-2和ZL^(-1)3能够显著提高青贮玉米的株高、根长、地上和地下干、鲜重(P<0.05)。田间试验结果表明,2株固氮菌单接种和双接种均能提高青贮玉米的株高、茎粗、产量、粗蛋白含量和全磷含量(P<0.05)。接种2株固氮菌的青贮玉米,其氮代谢和氨同化相关基因(ZmAMT-4、ZmAMTB、ZmGOGAT2和ZmGS1-3)的表达量显著提高(P<0.05)。因此,2株固氮菌具有较好的促生特性,在提高青贮玉米的产量和品质方面发挥了重要作用,是开发微生物菌剂的优质菌种资源。

棉花黄萎病生防菌筛选鉴定及根瘤菌DG3-1对棉花生长的影响

本研究旨在发掘南疆棉花内生菌种质资源来防治棉花黄萎病,探究根瘤菌对棉花生长的影响。采用常规组织分离法分离棉花不同组织内生细菌;平板对峙法筛选拮抗棉花黄萎病菌的内生菌,并对其进行分子鉴定;通过盆栽试验研究根瘤菌对棉花生长的影响。结果显示,棉花不同组织内生细菌的数量具有一定差异,根部最多,其次是叶和茎;在分离获得的31株内生菌中,有11株对棉花黄萎病菌具有拮抗活性,抑菌率在35.99%~68.28%之间,经鉴定,9株为芽孢杆菌,2株为根瘤菌,其中,根瘤菌DG3-1对棉花黄萎病菌的抑制率为(56.63±1.82)%;盆栽试验结果表明,菌株DG3-1处理后棉株的地上鲜重、地上干重、地下鲜重、地下干重、叶绿素含量分别比对照增加2.12、2.09、1.05、0.75、1.75倍。菌株DG3-1对棉花黄萎病菌有较好的抑制作用,并且对棉花的生长有一定的促生作用,是防治棉花黄萎病的潜力菌株,可为微生物菌剂的研发提供菌种资源。

香蕉抗枯萎病株系内生菌的分离鉴定及抑菌促生效果

【目的】筛选和鉴定从威廉斯香蕉抗枯萎病株系根、球茎及假茎分离得到的可抑制香蕉枯萎病菌(Fusarium oxysporum f.sp.cubense,Foc)内生菌,研究其抑菌促生效果。【方法】通过16S rRNA基因序列测定和生理生化试验,对香蕉抗枯萎病株系内生菌进行种类鉴定和系统发育分析;通过平板对峙试验检测各菌株的抑菌能力,探究拮抗菌分泌抑菌相关活性物质的种类;采用盆栽试验对香蕉抗枯萎病株系内生菌进行生防功能和促生功能的分析,筛选出生防性能优良且兼具促生效果的内生菌,并在大田试验中验证。【结果】分离获得13株代表菌株,其中8株对枯萎病1号生理小种(Foc 1)具有抑菌活性,7株对枯萎病4号生理小种(Foc 4)具有抑菌活性;综合盆栽试验和大田试验中代表菌株的防治效果及促生能力,筛选出贝莱斯芽孢杆菌XG1028、变栖克雷伯氏菌XQJ0301和暹罗芽孢杆菌XG0103共3株具备高抑菌活性以及促生能力的生防菌株。【结论】本研究筛选出的3株菌株丰富了抗香蕉枯萎病微生物种质资源,为防治香蕉枯萎病寻找安全、环保的新型生物防治剂提供参考。

青海野生中国沙棘根际解钾菌的分离、鉴定及其促生能力比较

【目的】从青海野生中国沙棘(Hippophae rhamnoides subsp.sinensis)根际土中筛选出具有解钾能力的菌株,并比较其促生能力,为高原地区高效生物菌肥的研发提供依据。【方法】利用纯化培养方法从中国沙棘根际土中分离解钾菌;通过形态观察、生理生化检测及16S rDNA序列比对鉴定菌株;对解钾菌的解有机磷、解无机磷、解钾、降解纤维素的能力进行测定;将解钾菌接种于空心菜幼苗以验证其促生效果。【结果】K15、K50和K65三株解钾菌均为乙酸钙不动杆菌(Acinetobacter calcoaceticus)。培养3 d后,3株解钾菌溶解有机磷的浑浊圈直径为3.75~7.13 mm,解有机磷菌液中磷的质量浓度为5.12~11.33μg·mL^(-1);溶解无机磷的透明圈直径为3.25~5.31 mm,解无机磷菌液中磷的质量浓度为3.39~6.63μg·mL^(-1);解钾的黄色光圈直径为17.53~25.17 mm,解钾菌液中K^(+)质量浓度为4.87~7.15μg·mL^(-1);降解纤维素的透明圈直径为8.37~12.07 mm。3株解钾菌均可提高空心菜种子的萌芽率(表现为K65>K50>K15)。施用解钾菌菌液可提高空心菜幼苗的生长发育速度(表现为K65>K50>K15)。其中,K65对幼苗的促生作用最显著,K65处理的幼苗鲜质量达到0.24 g,比CK提高33.3%。【结论】3株解钾菌均具有解有机磷、解无机磷、解钾、降解纤维素的能力;施用解钾菌菌液后空心菜幼苗的生长状况均得到一定程度的改善,种子发芽率显著提高,其中,K50和K65的促生效果均比K15好。

耐盐碱根际促生细菌对盐碱胁迫下紫花苜蓿生长和根系生理特性的影响

通过室外盆栽试验,以紫花苜蓿为对象,并选择实验室前期筛选得到的耐盐碱且具有促生能力的根际促生细菌嗜麦芽寡养单胞菌(JT4)和普城沙雷氏菌(JG1)作为供试菌株,试验设置了盐碱胁迫处理以探究两种根际促生细菌对紫花苜蓿生长和根系生理特性的影响,发现在盐碱胁迫条件下,与CK相比,紫花苜蓿接种JT4和JG1后,增加了株高、根长、茎粗、根鲜重和根干重等;同时接种降低了丙二醛含量、脯氨酸含量、过氧化氢酶活性和抗坏血酸过氧化物酶活性,提高了根系活力、可溶性蛋白含量和可溶性糖含量。表明耐盐碱根际促生细菌JT4和JG1能有效缓解盐碱胁迫对紫花苜蓿根系的损伤,为耐盐碱根际促生细菌JT4和JG1在植物抗盐碱材料的筛选和盐碱地改良中的应用提供了理论依据。

中国沙棘根际固氮菌的分离、鉴定及促生能力比较

【目的】对青海野生中国沙棘根际固氮菌进行分离、鉴定及促生能力比较,为挖掘具有潜在应用价值的根际促生菌提供依据。【方法】利用纯化培养方法从中国沙棘根际土中分离固氮菌;通过形态观察、生理生化检测和16S rDNA序列比对鉴定菌株;对固氮菌的解有机磷、解无机磷、解钾、固氮、种子萌发的能力进行测定;将固氮菌接种空心菜幼苗以验证其促生效果。【结果】鉴定出1株哈夫尼菌(N5)、1株不动杆菌(N6)、4株沙雷氏菌(N1、N2、N3、N4)。培养7 d后,6株固氮菌固氮透明圈直径与菌落直径的比值(D/d)为1.23~1.83,N3的D/d最大,较N5提高48.8%;培养3 d后,6株固氮菌溶解有机磷圈直径为6.43~9.65 mm,溶解无机磷圈直径为3.13~5.50 mm,解钾圈直径为8.18~22.17 mm。平板促生试验结果表明,固氮菌可提高空心菜种子萌芽率,并且可显著促进空心菜生长发育。其中,菌株N3和N6促生效果显著,其鲜质量分别为0.24 g和0.26 g,较对照组(CK)增加了33.3%和44.4%。【结论】固氮菌N3和N6分别为沙雷氏菌和不动杆菌,具有较强的解磷、解钾、固氮能力,且均能提高空心菜种子发芽率,促进空心菜幼苗生长发育。

解淀粉芽孢杆菌SQ-2对水稻的促生作用

【目的】对实验室分离筛选得到的一株解淀粉芽孢杆菌SQ-2进行促生特性研究,确定该菌株对水稻促生的浓度范围与作用机制,并分析接种菌株前后的土壤菌群结构。【方法】利用钼蓝比色法与固氮酶试剂盒对菌株SQ-2的溶磷能力及固氮酶活性进行检测。将10^(2)、10^(4)、10^(6)、10^(8)和3×10^(8)CFU/mL的菌悬液接种至水培与土培水稻中,分别培养14 d和20 d后测定其水培、土培水稻的根茎干鲜重、茎长与茎粗。采用苯酚-次氯酸钠比色法、茚三酮检测法与3,5-二硝基水杨酸比色法测定土培水稻土壤中脲酶、蛋白酶与蔗糖酶的活性。利用pH计电位法检测土壤pH值,用对应试剂盒检测土壤速效氮磷钾含量及酸性磷酸酶活性,并对接种3×10^(8)CFU/mL组的土培水稻土壤进行根际细菌群落结构分析。【结果】菌株SQ-2对磷酸三钙的溶解量为229.63 mg/L,固氮酶活性为55.07 U/L。与对照相比,接种菌悬液浓度在10^(4)CFU/mL时,水培水稻根的干、鲜重增长最为显著;在接种浓度为3×10^(8)CFU/mL时,土培水稻根茎的干、鲜重增长最为显著。随着接种菌悬液浓度的升高,上述土壤酶活性与速效氮磷钾浓度都有着不同程度的增加,而接种菌株3×10^(8)CFU/mL的土壤pH值则由原来的7.83降至7.26。接种菌株SQ-2改变了水稻根际土壤中的菌落构成,显著提高了土壤α多样性的Ace、Chao、Sobs与Shannon指数。【结论】解淀粉芽孢杆菌SQ-2对土培、水培水稻均有不同程度的促生效果。在土培实验中,能够通过提高土壤酶活性、速效氮磷钾水平及改变土壤菌群结构来起到促生作用,为细菌菌肥的研发提供了新的菌株资源。