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 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.

Phosphate-Solubilizing and -Mineralizing Abilities of Bacteria Isolated from Soils

Microorganisms capable of solubilizing and mineralizing phosphorus （P） pools in soils are considered vital in promoting P bioavallability. The study was conducted to screen and isolate inorganic P-solubilizing bacteria （IPSB） and organic P-mineralizing bacteria （OPMB） in soils taken from subtropical flooded and temperate non-flooded soils, and to compare inorganic P-solubilizing and organic P-solubilizing abilities between IPSB and OPMB. Ten OPMB strains were isolated and identified as Bacillus cereus and Bacillus megaterium, and five IPSB strains as B. megaterium, Burkholderia caryophyUi, Pseudomonas cichorii, and Pseudomonas syringae. P-solubilizing and -mineralizing abilities of the strains were measured using the methods taking cellular P into account. The IPSB strains exhibited inorganic P-solubilizing abilities ranging between 25.4-41.7 μg P mL^-1 and organic P-mineralizing abilities between 8.2-17.8μg P mL^-1. Each of the OPMB strains also exhibited both solubilizing and mineralizing abilities varying from 4.4 to 26.5 μg P mL^-1 and from 13.8 to 62.8 μg P mL^-1, respectively. For both IPSB and OPMB strains, most of the P mineralized from the organic P source was incorporated into the bacterial cells as cellular P. A significantly negative linear correlation （P 〈 0.05） was found between culture pH and P solubilized from inorganic P by OPMB strains. The results suggested that P solubilization and mineralization could coexist in the same bacterial strain.

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.

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 of Rhizosphere Phosphate-solubilizing Bacteria of Perennial Ryegrass

The research isolated phosphorus-soluble bacteria from different parts of ryegrasses and selected 7 bacteria performing better in solbilizing capacity. The test results showed that the capacity of phosphorus-solubilizing tended to be volatile in the range from 135.27 to 187.87 μg/ml and the secreting capacity of IAA was in3.47-24.27 μg/ml. It is believed that Lp59, Lp61, Lp65, Lp69, Lp70 and Lp72 are potential for further development.

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.

Species of Inorganic Phosphate Solubilizing Bacteria in Red Soil and the Mechanism of Solubilization

INTRODUCTION The insoluble phosphates which can not be directly absorbed by plants are the mai forms of inorganic phosphate in soil. These kinds of phosphates can be solubilized by several species of bacteria which are widely spread in soil especially in rhizosphere where70% of the bacteria are capable of solubilizing inorganic phosphate. Many researchers re-

Testing of Bacterial Endophytes from Non-Host Sources as Potential Antagonistic Agents against Tomato Wilt Pathogen <i>Ralstonia solanacearum</i>

The study was taken up with the objective of testing whether the endophytic organisms isolated from crops that are normally non-hosts to the bacterial wilt pathogen Ralstonia solanacearum possessed pathogen-antagonistic activity and to evaluate the selected isolates for the alleviation of wilt disease in the target tomato crop through horizontal movement of promising organisms. Sixteen endophytic bacteria (EB) isolated from the micropropagated cultures of grape, watermelon and papaya were tested for potential antagonistic effects against R. solanacearum tomato isolate “NH-01” through agar-well diffusion assay. Enterobacter cloacae from papaya (EB-11) displayed the maximum antagonistic effect followed by Bacillus subtilis (EB-06) and B. flexus (EB-07) from watermelon and B. pumilus (EB-02) from grape. Testing the above organisms for crop protection through seed fortification of susceptible tomato cv. Arka Vikas at sowing in R. solanacearum inoculated (Ral+) organic cocopeat showed EB-02 and EB-11 promising (33% and 32% survival, respectively, four weeks after sowing against 15% in Ral+ control). A second trial showed 37%, 28%, 21% and 55% seedling survival 6 weeks after sowing for EB-02, EB-06, EB-07 and EB-11 respectively, compared to 2.5% in non-treated control. Assessing the four endophytes for crop protection in Ral+ sick-soil through seedling fortification at transplanting indicated less disease incidence in treated sets (40%, 40%, 20% and 20% survival, respectively, six weeks after transplanting) over non-fortified control (5%). Endophytic fortification of seedlings through hypocotyl inoculation showed some systemic resistance induction upon seedling transplanting to sick soil but not with petiole fortification. Seedling growth was enhanced by the isolates EB-06 and EB-07. The study thus identifies four endophytic organisms from crops unrelated to tomato possessing potential antagonistic activity against the wilt pathogen and prospects for exploitation as biocontrol agents coupled with seedling growth promotion effects.

Plant Growth-Prompting Bacteria Influenced Metabolites of <i>Zea mays var. amylacea </i>and <i>Pennisetum americanum p. </i>in a Species-Specific Manner

Poor soil is one of the agricultural world’s principal challenges, inciting the use of chemical fertilizer’s to improve overall soil quality. However, the use of chemical fertilizer has significant and cascading environmental consequences. Therefore, the use of beneficial microbes’ inoculation in treating poor soil is a considerably ecofriendly sustainable solution. In the current study, we supplemented nutrient-deprived soil with plant growth promoting bacteria (PGPB), Pseudomonas fluorescens. The bacterial inoculations of Pseudomonas fluorescenswere added to the poor soil following two days post-sowing of Zea mays var. amylacea and Pennisetumamericanum p. seedlings. Metabolite analyses were conducted two months after treatment for both shoots and roots using nuclear magnetic resonance method (NMR). The data indicated significant changes in 19 metabolites relative to control in both plants shoot and roots. Among these metabolites, 7 were upregulated in roots of Zea mays var. amylacea, and 9 metabolites were upregulated in roots of Pennisetum americanum p. The PGPB enhanced sugars (fructose, glucose, sucrose) and amino acids (glutamate, alanine and succinate) in roots, while down regulating in shoots of Pennisetum americanum p. The Pseudomonas fluorescens induced, predominantly,Aminoacyl-tRNA related metabolite, and Alanine, aspartate and glutamate metabolite biosynthesis in Zea mays var. amylacea), whereas PGPB induced metabolites in Pennisetum americanum p., dominated by up regulated carbohydrate related (starch and sucrose) metabolites. The difference in some metabolic response between the two plants indicated that PGPB influence has a species-specific manner.

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。

Effect of Inoculation with Three Phytohormone Producers Phytobacteria with ACC Deaminase Activity on Root Length of Lens esculenta Seedlings

Plant-associated bacteria that inhabit the rhizosphere may influence the plant growth by their contribution to the endogenous pool of phytohormones and by the activity of ACC deaminase to decrease the ethylene concentration. The aim of this study was to analyse the root length growth by the promoting effect of indole acetic acid producers phytobacteria with ACC deaminase activity, on inoculated seeds of Lens esculenta as synergistic effect on root elongation. In this study, although the roots of L. esculenta seedlings do not show a significant promotion, these phytobacteria could be recommended to treat plants analyzing their added inoculum to increase plant biomass and retard the effect of ethylene on cultures supplied with Tryptophan and ACC.

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。

盐胁迫下植物促生菌和2,4-表油菜素内酯对月季幼苗光合生理及离子转运的影响

以月季品种巴西诺幼苗为试验材料,采用室内盆栽试验,探究不同盐质量分数(0、0.3%、0.6%、0.9%)胁迫下根际施用2,4-表油菜素内酯(EBR,1μmol/L)、接种植物促生菌(PGPB)普罗维登斯菌(Providencia vermicola,1×10^(7)cfu/mL)及其复合处理对月季幼苗生长、光合和叶绿素荧光参数、离子转运及抗氧化系统的影响,以探明两者缓解月季盐胁迫的机制。结果表明,不同质量分数盐胁迫下月季幼苗生长受到抑制,株高、叶片厚度以及地上部和根系生物量等显著下降,施用EBR或者PGPB可以缓解月季受到的生长抑制程度。0.9%盐胁迫下,与对照(不喷施EBR,不接种PGPB)相比,EBR+PGPB处理的叶绿素a、叶绿素b含量分别增加13.1%和32.3%;叶绿素荧光参数中PSⅡ最大光化学效率(Fv/Fm)与对照无显著差异,PSⅡ潜在活性(Fv/Fo)增加8.8%,净光合速率(Pn)增加53.7%,蒸腾速率(Tr)和气孔导度(Gs)与对照相比无显著变化,胞间二氧化碳浓度(Ci)降低6.0%。0.9%盐胁迫下,与对照相比,EBR+PGPB处理后月季地上部和根系Na+含量分别降低21.1%和26.6%,地上部和根系K^(+)含量则分别增加73.7%和70.4%,地上部和根系中K^(+)/Na^(+)值分别增加116.7%和135.1%;同时EBR+PGPB处理能够激活超氧化物岐化酶(SOD)、过氧化氢酶(CAT)活性,降低超氧阴离子自由基产生速率和H_(2)O_(2)累积,与对照差异显著。综上,添加EBR、接种PGPB或者EBR+PGPB处理均可以不同程度地提高月季叶绿素含量,保护叶绿素荧光系统,维持植物Na^(+)和K^(+)的平衡,激活SOD、CAT等抗氧化酶活性以及降低细胞膜脂过氧化和H2O2累积,以减轻盐胁迫对月季幼苗的伤害程度,促进月季生长,其中以EBR+PGPB处理下月季幼苗的抗盐性效果更佳。

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。

2株有效抑制剑麻斑马纹病菌的生防细菌鉴定

剑麻斑马纹病是一种由烟草疫霉(Phytophthoranicotianae)引起的传染性病害,导致剑麻出现叶斑、茎腐和轴腐的症状,对剑麻纤维的产量和质量造成严重影响。目前,剑麻斑马纹病的防治主要采取以农业栽培措施为主,抗病育种和化学药剂防治相结合的综合防治策略,但是农业防治人工成本高,工人操作技术参差不齐;抗病育种难度大,周期长;化学防治受剑麻叶片表面带有蜡质层的影响,存在药液不易吸附的问题,而且大量施药也容易造成病原抗药性提高和环境污染。因此,开发防治剑麻斑马纹病的生防菌资源,探索综合防控新途径显得尤为重要。本研究以烟草疫霉菌为靶标菌,通过五点对峙法筛选,获得2株生防菌PpHyHNCJ2和PpHyHNCJ5,其菌丝生长抑制率分别为85.92%和83.10%。通过对烟草疫霉菌菌丝显微结构进行观察发现,菌株PpHyHNCJ2和PpHyHNCJ5均抑制了烟草疫霉菌菌丝的生长,生防菌对峙的烟草疫霉菌出现菌丝体膨大增粗、分枝畸形、缠绕等现象。基于细胞形态、生理生化反应以及16S rDNA基因序列比对分析,菌株PpHyHNCJ2和PpHyHNCJ5鉴定为多粘类芽孢杆菌(Paenibacillus polymyxa)。进一步研究显示菌株PpHyHNCJ2和PpHyHNCJ5均具有广谱拮抗作用,能够很好地抑制辣椒疫霉菌(Phytophthora capsica)、大豆疫霉菌(P.sojae)、瓜疫霉菌(P.melonis)、棕榈疫霉菌(P.palmivora)、豇豆疫霉菌(P.vignae)、尖孢镰刀菌(Fusarium oxysporum)、黑曲霉菌(Aspergillus niger)、暹罗刺盘孢菌(Colletotrichum siamense)等11种病原菌的生长。此外,菌株PpHyHNCJ2和PpHyHNCJ5具有解有机磷能力、解无机磷能力、解钾能力、固氮能力和产铁能力,可为作物的良好生长提供条件。结果表明,菌株PpHyHNCJ2和PpHyHNCJ5对剑麻斑马纹病的防治具有良好的潜力,可为剑麻斑马纹病的生物防治提供基础材料。