菌土接种法在香蕉枯萎病苗期抗性评价中的应用及效果

【目的】建立一套稳定可靠且更符合自然条件下发病的香蕉枯萎病苗期抗性鉴定方法,为香蕉枯萎病抗性种质的筛选评价提供参考。【方法】以尖孢镰刀菌古巴专化型4号生理小种(Fusarium oxysporum f. sp. cubense 4,Foc4)为供试病原菌,分别采用伤根淋菌接种法、浸根接种法及菌土接种法接种感病香蕉品种巴西蕉,比较分析不同处理种植基质中病原菌孢子浓度的动态变化及植株发病情况,优选最佳的接种方法。采用Foc4不同孢子浓度菌土接种抗、感种质材料,统计发病情况,比较抗性评价效果;应用菌土接种法对31份香蕉种质进行枯萎病苗期抗性鉴定,考察其评价效果。【结果】采用不同接种方法,巴西蕉杯苗种植基质中Foc4孢子浓度变化、发病率和病情指数存在较大差异,其中,采用菌土接种法,种植基质中Foc4孢子浓度稳定保持在原始接种浓度1.0×10^(6)~1.1×10^(6)个/g土;采用浸根接种法,种植基质中Foc4孢子浓度呈先升后降的变化趋势,并于21 d达最大值(1.0×10^(6)个/g土),28 d降至0.5×10^(6)个/g土,35 d后稳定在0.4×10^(6)个/g土;采用淋菌接种法,种植基质中Foc4孢子浓度在0~14 d内由1.5×10^(6)个/g土迅速下降至0.5×10^(6)个/g土,35 d后稳定在0.6×10^(6)个/g土。接种42 d后菌土接种法的蕉苗发病率及病情指数均最高,分别为98.9%和67.3,浸根接种法次之,分别为86.7%和51.6,淋菌接种法发病率及病情指数均最低,分别为76.7%和44.1。在Foc4孢子浓度为1.1×10^(4)、1.1×10^(5)、1.1×10^(6)个/g土条件下,采用菌土接种法的高感品种巴西蕉发病率均在80.0%以上,高抗种质GCTCV-119的发病率分别为16.7%、35.6%和54.4%。在孢子浓度为1.1×10^(4)个/g土条件下,巴西蕉及GCTCV-119外观发病症状均不明显;综合高感和高抗品种(系)的发病情况,菌土接种法Foc4孢子浓度宜在1.0×10^(5)~1.0×10^(6)个/g土。采用菌土接种法对31份香蕉种质进行抗性评价,其中有中抗种质11份、感病种质14份、高感种质6份。【结论】菌土接种法具有稳定、准确、高效、简便、可操作性强的特点,可作为香蕉枯萎病苗期抗性评价及抗性种质筛选的优选方法。

用菌土接种法鉴定云南省主要十字花科作物对根肿病的抗性

采用菌土接种法鉴定了云南地区110份十字花科作物对根肿病的抗性。结果表明:芜菁材料TS04病情指数仅为1.46,为高抗材料;H166、牛心莲花白、圆秆大青菜、建水青花、TS095份材料表现抗病,病情指数在14.44～19.57之间;尖叶花菜、春不老、东川黑二茵、TS114份材料表现耐病,病情指数在20.79～23.51之间;其余材料均表现为感病。

微型大白菜“娃娃菜”根肿病抗性遗传规律及分子标记辅助选择研究

以高抗根肿病大白菜材料CCR001、感病娃娃菜材料CM002以及后代材料F_1、F_2、BC_1为研究对象,分析娃娃菜根肿病抗性遗传规律,结果表明:符合孟德尔遗传规律,材料中根肿病抗性受显性单基因控制。采用分子标记辅助选择法与菌土法对F_1、F_2进行抗病性鉴定,印证了分子标记辅助选择根肿病抗性育种是可行的。

Effect of Arbuscular Mycorrhizal Inoculation on Plant Growth and Phthalic Ester Degradation in Two Contaminated Soils

A 60-day pot experiment was carried out using di-(2-ethylhexyl) phthalate (DEHP) as a typical organic pollutant phthalic ester and cowpea (Vigna sinensis) as the host plant to determine the effect of arbuscular mycorrhizal inoculation on plant growth and degradation of DEHP in two contaminated soils, a yellow-brown soil and a red soil. The air-dried soils were uniformly sprayed with different concentrations of DEHP, inoculated or left uninoculated with an arbuscular mycorrhizal (AM) fungus, and planted with…

Speciation of chromium in soil inoculated with Cr(Ⅵ)-reducing strain,Bacillus sp.XW-4

Cr(Ⅵ)-amended soil was inoculated with Cr(Ⅵ)-reducing strain,Bacillus sp.XW-4 and incubated at 28 ℃in an incubator. Cr(Ⅵ)reduction,available Cr and Cr fractionin soils were studied.The results show that addition of Bacillus sp.XW-4 can promote Cr(Ⅵ)reduction,but inoculation of this strain has a negative effect on the decrease of available Cr content in soil.In controls (without this strain)amended with 100 and 200 mg/kg of Cr(Ⅵ),Cr(Ⅵ)contents decrease to about 41 and 92 mg/kg respectively after incubation of 4 d,while in soil inoculated with XW-4,Cr(Ⅵ)contents decrease to about 18 and 60 mg/kg,respectively.The content of available Cr in soils with inoculation of XW-4 is higher than that in controls.Chromium is partitioned into water soluble Cr,exchangeable Cr,precipitated Cr,Cr bound to organics and residual Cr.The highest content of Cr is observed in residual form and water soluble Cr is not detected for all treatments after 42 d,but the soils inoculated with Bacillus sp.XW-4 contain higher content of exchangeable Cr and lower content of precipitated Cr than the soil without the inoculum.Inoculation of Bacillus sp.XW-4 can increase chromium activity in soils.

Response of Soil Phosphorus Required for Maximum Growth of Asparagus officinalis L. to Inoculation of Arbuscular Mycorrhizal Fungi

Fertilizer application efficiently increases crop yield, but may result in phosphorus(P) accumulation in soil, which increases the risk of aquatic eutrophication. Arbuscular mycorrhizal fungi(AMF) inoculation is a potential method to enhance P uptake by plant and to reduce fertilizer input requirements. However, there has been limited research on how much P application could be reduced by AMF inoculation. In this study, a pot experiment growing asparagus(Asparagus officinalis L.) was designed to investigate the effects of AMF inoculation and six levels of soil Olsen-P(10.4, 17.1, 30.9, 40.0, 62.1, and 95.5 mg kg-1for P0, P1, P2, P3, P4 and P5treatments, respectively) on root colonization, soil spore density, and the growth and P uptake of asparagus. The highest root colonization and soil spore density were both obtained in the P1treatment(76% and 26.3 spores g-1soil, respectively). Mycorrhizal dependency significantly(P < 0.05) decreased with increasing soil Olsen-P. A significant correlation(P < 0.01) was observed between mycorrhizal P uptake and root colonization, indicating that AMF contributed to increased P uptake and subsequent plant growth.The quadratic equations of shoot dry weight and soil Olsen-P showed that AMF decreased the P concentration of soil required for maximum plant growth by 14.5% from 67.9 to 59.3 mg Olsen-P kg-1. Our results suggested that AMF improved P efficiency via increased P uptake and optimal growth by adding AMF to the suitable P fertilization.

Exopolysaccharide-Producing Plant Growth-Promoting Rhizobacteria Under Salinity Condition

Salt-tolerant plant growth-promoting rhizobacteria （PGPR） can play an important role in alleviating soil salinity stress during plant growth and bacterial exopolysaccharide （EPS） can also help to mitigate salinity stress by reducing the content of Na＋ available for plant uptake. In this study, native bacterial strains of wheat rhizosphere in soils of Varanasi, India, were screened to identify the EPS-producing salt-tolerant rhizobacteria with plant growth-promoting traits. The various rhizobacteria strains were isolated and identified using 16S rDNA sequencing. The plant growth-promoting effect of inoculation of seedlings with these bacterial strains was evaluated under soil salinity conditions in a pot experiment. Eleven bacterial strains which initially showed tolerance up to 80 g L-1 NaC1 also exhibited an EPS-producing potential. The results suggested that the isolated bacterial strains demonstrated some of the plant growth-promoting traits such as phosphate solubilizing ability and production of auxin, proline, reducing sugars, and total soluble sugars. Furthermore, the inoculated wheat plants had an increased biomass compared to the unoinoculated plants.

Indigenous Microbial Community Structure in Rhizosphere of Chinese Kale as Afected by Plant Growth-Promoting Rhizobacteria Inoculation

Plant growth-promoting rhizobacteria （PGPR） have been widely recognized as an important agent, especially as a biofertilizer, in agricultural systems. The objectives of this study were to select effective PGPR for Chinese kale （Brassica oleracea var. alboglabra） cultivation and to investigate the effect of their inoculation on indigenous microbial community structure. The Bacillus sp. SUT1 and Pseudomonas sp. SUT19 were selected for determining the efficiency in promoting Chinese kale growth in both pot and field experiments. In the field experiment, PGPR amended with compost gave the highest yields among all treatments. The Chinese kale growth promotion may be directly affected by PGPR inoculation. The changes of microbial community structure in the rhizosphere of Chinese kale following PGPR inoculation were examined by denaturing gradient gel electrophoresis （DGGE） and principal coordinate analysis. The DGGE fingerprints of 16S rDNA amplified from total community DNA in the rhizosphere confirmed that our isolates were established in the rhizosphere throughout this study. The microbial community structures were slightly different among all the treatments, and the major changes depended on stages of plant growth. DNA sequencing of excised DGGE bands showed that the dominant species in microbial community structure in the rhizosphere were not mainly interfered by PGPR, but strongly influenced by plant development. The microbial diversity as revealed by diversity indices was not different between the PGPR-inoculated and uninoculated treatments. In addition, the rhizosphere soil had more influence on eubacterial diversity, whereas it did not affect archaebacterial and fungal diversities.

Effect of Rhizobacterium Rhodopseudomonas palustris Inoculation on Stevia rebaudiana Plant Growth and Soil Microbial Community

There is an increasing concern that the continuous use of chemical fertilizers might lead to harmful effects on soil ecosystem.Accordingly, a biocompatible approach involving inoculation of beneficial microorganisms is presented to promote plant growth and simultaneously minimize the negative effect of chemical fertilizers. In this study, Rhodopseudomonas palustris, a plant growth-promoting rhizobacterium(PGPR), was inoculated into both fertilized and unfertilized soils to assess its influence on Stevia rebaudiana plant growth and microbial community in rhizosphere soils in a 122-d field experiment. Soil enzyme assays(dehydrogenase, urease, invertase, and phosphomonoesterase), real-time quantitative polymerase chain reaction(RT-_qPCR), and a high-throughput sequencing technique were employed to determine the microbial activity and characterize the bacterial community. Results showed that the R.palustris inoculation did not significantly influence Stevia yields and root biomass in either the fertilized or unfertilized soil. Chemical fertilization had strong negative effects on soil bacterial community properties, especially on dehydrogenase and urease activities.However, R. palustris inoculation counteracted the effect of chemical fertilizer on dehydrogenase and urease activities, and increased the abundances of some bacterial lineages(including Bacteroidia, Nitrospirae, Planctomycetacia, Myxococcales, and Legionellales). In contrast, inoculation into the unfertilized soil did not significantly change the soil enzyme activities or the soil bacterial community structure. For both the fertilized and unfertilized soils, R. palustris inoculation decreased the relative abundances of some bacterial lineages possessing photosynthetic ability, such as Cyanobacteria, Rhodobacter, Sphingomonadales, and Burkholderiales. Taken together, our observations stress the potential utilization of R. palustris as PGPR in agriculture, which might further ameliorate the soil microbial properties in the long run.

Arbuscular Mycorrhizal Fungal Inoculation Enhances Suppression of Cucumber Fusarium Wilt in Greenhouse Soils

A pot experiment was conducted to study the plant growth and fruit yields of cucumber （Cucumis sativus L.） on a greenhouse soil with or without inoculation of arbuscular mycorrhizal fungi （AMFs） and Fusarium oxysporum f. sp, cucumerinum under unsterilized conditions. Two AMF inocula were tested： only one AMF strain Glomus caledonium 90036 and an AMF consortium mainly consisting of Glornus spp. and Acaulospora spp. There were four treatments including no inoculation （control）, inoculation with F. oxysporum but without mycorrhizae （FO）, inoculation with F. oxysporum and G. caledonium （FO＋M1）, and inoculation with F. oxysporum and the AMF consortium （FO＋M2）. Cucumber plants were harvested at weeks 3 and 9 after transplanting. Compared with the control, the FO treatment without AMF inoculation had less biomass both at weeks 3 and 9 （P 〈 0.05） and had higher incidence of Fusarium wilt and produced no cucumber fruit at week 9. Both FO＋M1 and FO＋M2 treatments had higher mycorrhizal colonization than the treatments which received no AMF inoculation at week 3 （P 〈 0.05）, but only the FO＋M2 treatment elevated plant biomass, decreased the incidence of Fusarium wilt, and improved cucumber yields to the same level as the control at week 9. The results indicated that the AMF consortium could suppress Fusarium wilt of cucumber and, therefore, showed potential as a biological control agent in greenhouse agroecosystems.

Improved Biodegradation of 1,2,4-Trichlorobenzene by Adapted Microorganisms in Agricultural Soil and in Soil Suspension Cultures

Inoculating soil with an adapted microbial community is a more effective bioaugmentation approach than inoculation with pure strains in bioremediation.However,information on the potential of different inocula from sites with varying contamination levels and pollution histories in soil remediation is lacking.The objective of the study was to investigate the potential of adapted microorganisms in soil inocula,with different contamination levels and pollution histories,to degrade 1,2,4-trichlorobenzene (1,2,4-TCB).Three different soils from chlorobenzene-contaminated sites were inoculated into agricultural soils and soil suspension cultures spiked with 1,2,4-TCB.The results showed that 36.52% of the initially applied 1,2,4-TCB was present in the non-inoculated soil,whereas about 19.00% of 1,2,4-TCB was present in the agricultural soils inoculated with contaminated soils after 28 days of incubation.The soils inoculated with adapted microbial biomass (in the soil inocula) showed higher respiration and lower 1,2,4-TCB volatilization than the non-inoculated soils,suggesting the existence of 1,2,4-TCB adapted degraders in the contaminated soils used for inoculation.It was further confirmed in the contaminated soil suspension cultures that the concentration of inorganic chloride ions increased continuously over the entire experimental period.Higher contamination of the inocula led not only to higher degradation potential but also to higher residue formation.However,even inocula of low-level contamination were effective in enhancing the degradation of 1,2,4-TCB.Therefore,applying adapted microorganisms in the form of soil inocula,especially with lower contamination levels,could be an effective and environment-friendly strategy for soil remediation.