The effect of plant age and soil amendments on severity of phytophthora root rot of pepper (Capsicum annuum L) in South Western Nigeria

The incidence and severity of pepper Capsicum annuum to phytophthora root rot caused by Phytophthora infestan in Southwestern Nigeria was investigated. Root rot incidence and severity was significantly reduced with increase in the plant age. The highest level of root rot, of 81.7% and 67.6% obtained in 4 and 6 weeks old pepper plants were reduced to 25% and 5% in 10 and 12 weeks old pepper plants respectively. The resistance of the pepper plant to root rot severity increased with age. The result also showed that amendments of the soil with chicken manure wood ash and neem leaf suppressed the root rot incidence and severity of disease in the pepper plant.     

Influence of P and K fertilization on Phytophthora root rot or excess soil water injury of alfalfa cultivars

Abstract

Phytophthora root rot (PRR) is an important disease of alfalfa (Medicago sativa L.) in wet soils. Excess soil water (ESW) stress is required for the successful infection and development of PRR. The effects of P at 0, 40, and 80 μg.g^‐1 soil and K at 0, 120, and 240 μg.g^‐1 soil (in factorial combinations) on the severity of PRR or ESW stress was investigated on a PRR‐susceptible (Iroquois) and a resistant (Oneida) alfalfa cultivar in a greenhouse trial. P and K applications significantly increased the dry weight of tops prior to imposition of PRR or ESW stress. However, plants subjected to PRR or ESW stress did not respond significantly to P or K and there was no significant effect of P or K on the severity of PRR or ESW injury. The plants subjected to PRR or ESW stress had lower tissue P concentration than those under stress‐free conditions. Increasing P additions resulted in a significant increase in P concentration of Iroquois plants, while in Oneida the response was non‐significant. The response of K concentration in the plant to increasing K additions was dependant on P levels.     

Effect of phosphonate on the rhizosphere microflora and the development of root rot (Phytophthora cinnamomi) in avocado (Persea americana) and pepper-corn (Schinus molle) tree seedlings

Summary Application to soil of 1 g (recommended rate) or 10 g l^-1 of phosphonate did not affect the numbers of bacteria and fungi nor the proportions of actinomycetes and fungi antagonistic to Phytophthora cinnamomi. Foliar phosphonate applications to avocado seedlings (Persea americana) did not affect microbial numbers or the proportions of microbes in the rhizosphere capable of antagonizing P. cinnamomi. Mycelium of P. cinnamomi and zoospores of P. palmivora did not appear to respond to diffusates from excised roots of phosphonate-treated avocado and pepper-corn tree (Schinus molle) seedlings, respectively. However, less extensive lesions were observed on the roots of fungicide-treated avocado and pepper-corn tree seedlings exposed to P. cinnamomi and P. palmivora, respectively. The reduction in P. cinnamomi infection on pepper-corn tree seedlings appears to be brought about by additive rather than interactive effects of the resident soil microflora and foliar-applied phosphonate.     

混合盐碱对紫花苜蓿苗期根系特征的影响

为研究紫花苜蓿根系对混合盐碱胁迫的响应,探索紫花苜蓿对混合盐碱的适应特点,为紫花苜蓿在盐碱地的栽培实践提供理论依据。本试验以"甘农三号"紫花苜蓿为试验材料,采用两种中性盐NaCl和Na2SO4及两种碱性盐NaHCO3和Na2CO3,按不同比例混合成为A(NaCl∶Na2SO4=1∶1)、B(NaCl∶NaHCO3=1∶1)、C(NaCl∶Na2SO4∶NaHCO3∶Na2CO3=1∶1∶1∶1)、D(Na2SO4∶Na2CO3=1∶1)、E(NaHCO3∶Na2CO3=1∶1)5种混合盐,分别以25 mmol.L 1、50 mmol.L 1、100 mmol.L 1、150 mmol.L 14种盐浓度,模拟出20种盐度和碱度各不相同的混合盐碱条件对紫花苜蓿幼苗进行处理,测定了根系总长度、根系平均直径、根表面积、根尖数等指标,以了解紫花苜蓿根系在混合盐碱胁迫下的生长特性。结果表明,盐浓度为影响紫花苜蓿根系生长的主要因素。混合盐碱对根尖数的影响表现出明显的负效应,对根系平均直径的影响并不明显。随着混合盐浓度的升高,根系总长度、根表面积呈现先增大后减小的趋势。A、B处理的根长分别在盐浓度为25 mmol.L 1和50 mmol.L 1时达到最大值,分别比对照(0 mmol.L 1)增加50.7%和37.9%,而且差异均达到显著水平(P<0.05);在盐浓度达到150 mmol.L 1时,A、B、C、D、E的根系总长度分别比对照减少26.6%、37.7%、51.6%、37.0%和55.7%,差异显著。A、C、D组处理下仅在25 mmol.L 1时,根表面积显著增加,分别比对照增加21.1%、43.4%和12.7%;在浓度为150 mmol.L 1时,E处理下根表面积显著减小,比对照减少49.6%。表明低浓度混合盐碱对紫花苜蓿根系的生长影响不显著或具有一定的促进作用,高浓度胁迫下抑制根系的生长;在高盐浓度下随着碱性盐比例的增加,对紫花苜蓿根系生长的抑制作用越明显。     

细菌性根腐病对三七光合特性的影响

根腐病是严重威胁三七生产的重要因素之一,常年发病率在5%～20%。其中,由假单胞杆菌(Pseudomon adaceae)引起的细菌性根腐病,因叶片出现缺水萎蔫症状时才能发现,目前尚无有效的预防措施。为探究细菌性根腐病对三七光合生理特性的影响,从而为三七病害生理学研究提供理论基础,本文以2年生三七为材料,设置2个处理[发病植株和健康对照植株(CK)],研究细菌性根腐病对三七形态结构、光合特性和光系统功能的影响。结果表明:1)根腐病导致三七的主根褐变腐烂,须根断损,茎基部腐烂中空,叶片萎蔫,各器官含水量比CK显著降低(P≤0.05);而株高、叶面积和叶片解剖结构(上表皮厚度、下表皮厚度、栅栏组织厚度和海绵组织厚度)在两处理间均无显著差异。2)发病植株叶片叶绿素含量、净光合速率(P_n)、气孔导度(G_s)、水分利用效率(WUE)和表观叶肉导度(AMC)显著低于CK(P≤0.05),且CK叶片胞间CO_2浓度(C_i)与P_n呈反比。3)发病植株叶片的光系统Ⅰ(PSⅠ)反应中心P700最大荧光信号(P_m)根腐病初期暂不受影响,而叶片暗适应下最大量子效率(F_v/F_m)、光系统Ⅱ(PSⅡ)电子传递速率[ETR(Ⅱ)]、PSⅡ实际光化学量子产量[Y(Ⅱ)]、PSⅠ电子传递速率[ETR(Ⅰ)]、PSⅠ周围的环式电子流(CEF)和PSⅠ实际光化学量子产量[Y(Ⅰ)]均显著低于CK(P≤0.05);参与调节性能量耗散的量子产量[Y(NO)]则显著高于CK(P≤0.05);发病植株的快速叶绿素荧光动力学曲线上出现K相,且显著高于CK(P≤0.05)。总的来看,细菌性根腐病对三七发病植株各器官的损伤严重程度为根茎叶,且根腐病导致发病植株叶片叶绿素降解, PSⅡ受到不可逆损伤, PSⅠ的电子传递被抑制,且叶肉细胞CO_2的同化能力降低,根腐病限制三七正常进行光合作用的条件。     

Variation of Pythium-induced cocoyam root rot severity in response to soil type

In Cameroon, andosols are suspected to be suppressive to cocoyam (Xanthosoma sagittifolium) root rot disease (CRRD) caused by the Oomycete pathogen Pythium myriotylum. To determine factors involved in disease suppressiveness, andosols were studied in comparison to ferralsols known to be disease-conducive. Soil samples were collected from six sites of which three were in andosols around Mount Cameroon (Boteva, Njonji, and Ekona) and the three others in ferralsols (Bakoa, Lapkwang, and Nko’o canane). Greenhouse plant experiments were used to assess soil suppressiveness. Soils were artificially infested with two levels of P. myriotylum inoculum (100 and 300 mycelia strands g⁻¹ soil) prior to planting cocoyam. Disease severity was significantly higher in ferralsols than in andosols. Andosols partly lost their suppressiveness as a result of autoclaving and could recover suppressiveness following recolonisation by their original microflora. Soil microbial groups implicated in the disease suppression were investigated by assessing the effect of fungicide, bactericide, and pasteurisation on andosol suppressiveness. Andosols suppressiveness was significantly reduced following pasteurisation and treatment with fungicide and bactericide. The possible influence of microbial biomass on andosol suppressiveness was investigated by comparing microbial populations of suppressive andosols to those in andosols that had lost suppressiveness. A comparative analysis of suppressive and conducive soil properties was performed to identify soil variables, which may contribute to soil suppressiveness. Soil chemical analysis results showed that organic matter content was higher in andosols than in ferralsols. In addition, the content of mineral nutrients such as Ca, K, Mg and N, was higher in andosols than in ferralsols. These soil variables negatively correlated with disease severity. By contrast, sand and clay, which were higher in ferralsols than in andosols, were positively related to disease severity. This study has confirmed the suppressive nature of andosols from Mount Cameroon to CRRD. The results suggest that high organic matter content is likely mediating P. myriotylum suppression in andosols by improving soil structure, increasing soil nutrient content and microbial biomass, and sustaining microbial activity.     

安徽省大豆疫病病原鉴定及生物学特性研究

自安徽蒙城大豆疫病病株上分离得到2个疫霉菌株,对其培养性状、形态特征、生理特性等方面进行了鉴定研究。结果表明,2个菌株均为同宗配合的,雄器绝大多数侧生,偶见围生;孢子囊无乳突,不具脱落性,内层出;最高生长温度35°C,最低生长温度高于7°C,对孔雀绿敏感;对大豆具有致病性。根据研究结果,参照主要疫霉分类检索表,将上述菌株鉴定为大雄疫霉大豆专化型(P hy tophthora m eg asp erm af.sp.g ly cinea)。据此初步认为大雄疫霉大豆专化型是引致安徽蒙城大豆疫病的病原菌。     

Use of soil solarization to control root rots in gerberas (Gerbera jamesonii)

Summary An investigation was conducted during the summer months of 1986–1987 and 1987–1988 in Western Australia to evaluate the effect of soil solarization on the control of root rot of gerbera an also on the microbial and nutrient status of the soil. Infested soil cores were sampled from a site where root-rot was a severe problem and were removed to a non-infested site where they were subjected to soil solarization or fumigation. Soil solarization resulted in reduced root rot (root disease index 28.6%) in comparison to the untreated control (52.0%) 8 months after planting. Plants in the fumigated plots had 15.8% less disease than those in solarized plots. Solarization increased the total numbers of bacteria and actinomycetes, and the proportion of bacteria and fungi antogonistic to Fusarium oxysporum, F. solani and Rhizoctonia solani. The proportion of actinomycetes antagonistic to these fungi, however, did not differ between solarized and control soil treatments. There was a significant reduction in disease in plants grown in infested fumigated soil to which a 10% concentration of solarized soil had been added, suggesting the development of microbial suppression in solarized soil. Phytophthora cryptogea was eradicated to 30 cm by solarization as well as by fumigation. Solarization eliminated R. solani but not F. oxysporum to a soil depth of 10 cm. Solarization increased the levels of NO _n3 ^– -N and NH₄ ⁺-N in soil, but did not affect the concentrations of PO₄ ^3–, K⁺, Fe²⁺, organic C and pH. Yield (as number of flowers per plant) was increased by soil solarization and by fumigation.Increased yields and decreased disease severity in the solarized plots could have been caused by (1) a reduction in the infectivity of the infested soils, (2) an increase in the suppressiveness of the soil, and (3) an increased available of plant nutrients.     

Variations in soil characteristics affecting the occurrence of Aphanomyces root rot of sugar beet - Risk evaluation and disease control

Damping off and chronic root rot of sugar beet caused by Aphanomyces cochlioides is a major constraint in cultivation of sugar beet, with occurrence of the disease in Sweden being concentrated to specific areas. This study examined soil factors that can be used for risk assessment of Aphanomyces root rot. Soils from 134 field plots were assessed over three years for Aphanomyces root rot potential in bioassays and analysed for easily measured soil factors such as soluble nutrients, pH and soil electrical conductivity (EC). Classification of the field plots into four groups with increasing disease severity index (DSI) according to the bioassay revealed that the group with the lowest DSI (<39) had an average soil calcium (Ca) content of 430 mg/100 g and a soil EC of 1.12 mS/cm, which were significantly higher than in the groups with DSI >40. From these results, we concluded that soil Ca concentration is an easily measured factor that can be used to identify soils with an increased risk of Aphanomyces root rot. We suggest that the Ca content should be above 250 mg Ca/100 g soil to avoid problems with Aphanomyces root rot in sugar beet. To gain a more thorough understanding of the geographical variation in Aphanomyces root rot and its connection to the geological origin of the soils, a number of other soil factors were analysed in the field plots, including clay mineralogy, CEC, and particle size distribution. Aphanomyces root rot was very rare in soils with a high proportion of smectite and vermiculite relative to illite and kaolin minerals, here predominantly calcareous soils developed on clay till in south-western Scania.     

Influence of biopores on root growth,water uptake and grain yield of wheat (Triticum aestivum) based on predictions from a computer model

Summary The use of vertical biopores by wheat (Triticum aestivum) seminal roots for easy access to the subsoil and the consequences for plant water supply and yield has been investigated by computer simulation. Parameters included were: biopore density and diameter, depth of cultivation and strength of the subsoil — all under a wide range of seasonal weather conditions. The model predicts that biopores add significantly to root penetration at depth, even at a density of 0.1% v/v of small, vertical pores, while 1.5% to 2.0% v/v can ensure maximum root penetration. When the growing season is shorter a larger number of biopores is needed to ensure timely root penetration to depth. With shallow tillage, biopores occur closer to the soil surface, and their importance is increased. Deeper root penetration invariably gives greater water uptake and transpiration, but may have a negative effect on grain yield, especially under the driest climatic conditions. An increase in early water use may result in less soil water being available during the grain-filling period. The effect of biopores on plant transpiration varies from year to year, depending on the amount of rain and its distribution in time, and on the amount of soil water stored at time of sowing.     

Influence of clipping and soil water status on vesicular-arbuscular mycorrhizae of two semi-arid tussock grasses

Summary Using two tussock grasses, Agropyron desertorum, a grazing-tolerant species, and A. spicatum, a grazing-sensitive species, we measured the responses of vesicular-arbuscular mycorhizae (VAM) to clipping and soil moisture status. The clipping was carried out over a 4-year period (1982–1985). For the soil moisture × clipping studies, a rainout shelter was used to create drought stress, and irrigation was used to create high moisture conditions over a 2-year period (1984 – 1985). No consistent patterns in VAM infection frequency and VAM fungal spore counts were observed, either between species or among treatments. Increased moisture tended to increase total root and total VAM length, but there were no consistent moisture × clipping effects. Nor did the phenology of the fungus follow consistent patterns: there were similar lengths of root containing vesicles and arbuscules in 1984, and predominantly vesicles in 1985. The greatest effect was a large difference in VAM activity between years regardless of treatment, despite our attempts to use extreme environmental conditions and a rigorous sampling design. The VAM of both plant species were highly correlated. We postulate that VAM are highly plastic and that they respond to environmental pressures that we do not yet understand.     

Effect of Azospirillum brasilense inoculation on root morphology and respiration in tomato seedlings

Summary The level of Azospirillum brasilense strain Cd colonization in the rhizosphere of some vegetables was 10⁴–10⁵ colony-forming units (CFU) per root of one plant in 2-week-old plants inoculated with 5 × 10⁸ Azospirillum cells. Significant increases in root length (35%) and in top (90%) and root (50%) dry weight and total leaf area (90%) were observed in 18-day-old inoculated tomato plants compared with non-inoculated controls. An inoculum concentration of 1 × 10⁸ to 5 × 10⁸ CFU/ml stimulated the appearance of root hairs. Large numbers of bacteria (1 × 10⁹ CFU/ml) caused asymmetrical growth of the root tip. In a petri dish system, Azospirillum (1 × 10⁸ CFU/ml) increased root dry weight (150%), protein content (20%), respiration rate per root (70%) and the specific activity of malate dehydrogenase (45%–65%) over non-inoculated controls. The specific respiration rate, expressed as micromol of O₂ per minute per milligram of dry weight of roots, was significantly lower in inoculated roots, suggesting that less energy was spent for accumulation of more dry material.     

不同根型苜蓿根系对低温胁迫的响应及其抗寒性评价

为了解不同根型苜蓿在越冬期根系对低温胁迫的响应特征及其抗寒性强弱, 本研究以根茎型“清水”紫花苜蓿 (Medicago sativa L. cv. “Qingshui”)、根蘖型“甘农2 号”杂花苜蓿(M. varia Martin. cv. “Gannong No. 2”)和直根型“陇东”紫花苜蓿(M. sativa L. cv. “Longdong”)为材料, 于2009 年9 月15 日、10 月15 日、12 月15 日, 2010 年1 月15 日、3 月15 日在甘肃天水、榆中和武威3 个生态区, 对自然降温、升温过程中苜蓿根系脯氨酸、可溶性蛋白质、可溶性糖和丙二醛(MDA)含量及过氧化氢酶(CAT)、超氧化物歧化酶(SOD)活性6 项生理指标的动态变化进行监测。结果表明, 在3 个生态区, 3 类根型苜蓿根系MDA 含量随气温的变化均呈先升高后降低再升高的变化趋势; 脯氨酸、可溶性糖含量和CAT 活性均随气温的下降而增加, 随气温升高而减少; 而可溶性蛋白质含量和SOD 活性在不同生态区的不同品种间随气温的变化规律不同。应用隶属函数法进行抗寒性综合评判, 不同根型苜蓿抗寒性强弱顺序为: 根茎型“清水”紫花苜蓿>根蘖型“甘农2 号”杂花苜蓿>直根型“陇东”紫花苜蓿; 同一品种在不同生态区抗寒性强弱顺序为: 榆中>武威>天水, 与所在地的海拔呈显著正相关。     

猪粪沼液防治辣椒疫病机理研究--沼液中铵与腐殖酸的作用

为探明猪粪沼液对作物土传病害的防治效果与机制,设纯化肥处理为对照,采用盆栽试验比较了猪粪沼液(ADP1)、外源添加铵沼液(ADP2)、除铵沼液(ADP3)、除腐殖酸沼液(ADP4)施用对辣椒疫病的防治效果。结果表明,猪粪沼液(ADP1)可以显著降低辣椒疫病的发病率(防效40.8%),去除沼液中的铵或腐殖酸后,对辣椒疫病的防治效果显著下降,其发病率与病原菌对照(PC)无显著差异。定量PCR检测结果表明,ADP2处理土壤疫霉数量最少(2.51×103copies.g 1),ADP3、ADP4沼液处理的辣椒根际疫霉数量较多,分别为8.19×103copies.g 1、1.38×104copies.g 1;土壤中辣椒疫霉菌的数量低于9.54×103copies.g 1时,辣椒疫病发病率与土壤中病原菌数量有较好的对应关系。不同沼液处理对细菌、真菌和放线菌数量的影响不同。病原菌存在下,ADP1处理的细菌、真菌、放线菌数量均最多,ADP2处理的真菌数量最少。孢子萌发试验表明,随着铵和腐殖酸处理浓度的增加,对疫霉菌游动孢子萌发的抑制率均逐渐增大。浓度为500 mg.L 1、1 000 mg.L 1、1 500 mg.L 1NH4+对疫霉菌孢子萌发的抑制率分别为77.6%、81.8%、95.4%。用浓度为25 mg(C).L 1、50 mg(C).L 1、75 mg(C).L 1、150mg(C).L 1的猪粪沼液腐殖酸处理疫霉菌游动孢子6 h,游动孢子萌发率分别比无菌水对照下降了27.8%、54.5%、70.0%、87.5%。研究表明铵和腐殖酸可能是沼液的主要抑菌因子,沼液作为土传病害抑制剂具有一定的应用前景。     

三七设施栽培根际微生物菌群变化及其与三七根腐病的相关性研究

本研究通过对三七免耕种植的定位研究,探讨三七根腐病发病过程中的菌群变化及其与三七根腐病的相关性。结果表明:设施栽培条件下三七根际土壤中各类微生物数量及种群结构均随着季节气温而变化,其消涨变化规律与三七根腐病高发期吻合,是诱发三七根腐病发生的根本原因。进一步的研究表明三七根腐病的发生,与土壤中厌氧细菌、真菌及放线菌数量的增加及其种群数量比例变化有密切的关联性,这三类菌群的数量及其比例变化是诱导三七根腐病害发生的主要原因;土壤温度与根腐发病率没有直接的关联作用,但是温度可改变土壤微生物种群变化并导致三七根腐病的发生发展;根际土壤中好氧细菌数与厌氧细菌数比例及真菌与细菌总数比值可作为三七根腐发病及病害防治的预期参考指标。     

Efficacy of root litter as a biofertiliser

The efficacy ofLeucaena leucocephala root litter as a natural biological fertiliser was assessed usingZea mays as a test plant. Up to 8% of the fine roots of the plants constituted root litter. This fine root litter was better than that ofTrigonella foenum-graecum at increasing the growth and productivity ofZea mays. The root litter increased the growth of maize shoots more than the growth of roots. This appears to be a general phenomenon when plant nutrients are insufficient, as in the present study.     

Potassium uptake of rye-grass (Lolium perenne) and red clover (Trifolium pratense) as related to root parameters

Summary Rye-grass (Lolium perenne) is known to be a strong competitor to red clover (Trifolium pratense) for soil K⁺ under conditions of low K availability in the soil. The objective of this study was to clarify whether this competitive behaviour of the two species can be explained by root morphology. Total K⁺ uptake ofL. perenne andT. pratense was studied under field conditions in relation to root fresh weight, root density, root cation exchange capacity, root surface and root length. The soil was an Alfisol, Udalf. All root parameters, when calculated per unit soil surface (M²), were higher inL. perenne than inT. pratense. In addition,L. perenne had longer root hairs and a denser root hair system thanT. pratense. The greatest difference in root morphology between species was root length, withL. perenne roots averaging 4–6 times longer than those ofT. pratense.Significant correlations were found between the total K⁺ uptake and all root parameters examined, with highest correlationsforroot fresh weight (r,0.92***T. pratense; 0.94***L. perenne) and root length (r, 0.91***T. pratense;r, 0.93***L. perenne). Potassium uptake per unit root fresh weight, root surface and root length were all significantly higher forT. pratense than for L. perenne. Differences in the rate of K⁺ uptake between species were particularly high when expressed per unit root length. Because of its greater root length and surface area,L. perenne can take up more soil K⁺ thanT. pratense, particularly where there is a low K^– supply in the soil. Under such conditionsL. perenne will be a particularly strong competitor toT. pratense.     

柴达木盆地灌区枸杞根系水分吸收来源研究

探讨柴达木盆地灌区作物水分利用特征,可为灌溉系统设计和水资源高效利用提供理论依据。以柴达木盆地怀头他拉灌区主要作物枸杞为对象,将枸杞潜在水源划分为浅层(0～20cm)、中层(20～60cm)和深层(60～100cm)土壤水,利用稳定氧同位素示踪技术以及MixSIAR模型定量研究不同田间管理模式下[平作裸地(CK)、平作覆膜(MF)和垄作覆膜(MR)]枸杞根系水分吸收特征。结果表明:萌芽展叶期浅层土壤水分环境相对较好,CK和MF处理枸杞主要吸收浅层土壤水分,利用比例分别为45.9%和37.7%,MR处理对浅层、中层和深层土壤水源的利用比例相当;开花坐果期各层土壤水分都有所提高,相比于CK, MF处理浅层土壤水分利用比例增加13.5%, MR处理浅层土壤水分利用比例减少11.1%;果熟期枸杞蒸腾耗水量增加,相比于CK, MF和MR处理对浅层土壤水分的利用比例分别增加11.7%和24.0%;落叶期浅层土壤含水量较低, 3个处理都主要吸收深层土壤水分。浅层土壤水源的利用比例与该层土壤水分呈正相关,枸杞对浅层土壤水分变化较敏感。3种管理模式下枸杞根系水分吸收来源差异明显。覆膜和垄作措施均提高了土壤含水量。相比于CK,MF和MR处理枸杞都增加了对浅层水源的利用。MR处理下土壤水分状况较好且枸杞根系水分吸收利用模式更加灵活,对柴达木盆地灌区是一种较优的田间水分管理模式。     

看麦娘根系对小麦根水提液化感作用的生理响应

为探讨小麦化感作用机理,以强化感小麦‘115/青海麦’、‘92L89’和弱化感小麦‘抗10103’材料,设置小麦根水提液浓度为0%、0.2%、1.0%和5.0%的水培试验,测定了看麦娘根系对小麦根水提液化感作用的生理响应。结果表明,小麦根水提液处理显著抑制了看麦娘根的生长,根鲜重抑制率随处理浓度的升高而增大,强化感小麦的抑制率高于弱化感小麦。当处理浓度达5.0%时,不同化感小麦间无显著差异。‘115/青海麦’、‘92L89’和‘抗10103’根水提液处理后,看麦娘的根系活力的抑制率分别为52.0%~59.6%、46.5%~55.0%和27.2%~44.7%,但前二者间无显著差异;看麦娘根系中可溶蛋白含量、SOD、POD、CAT活性及MDA含量显著升高;SOD和POD活性大小均表现为‘115/青海麦’‘92L89’≈‘抗10103’;CAT活性随处理浓度的升高显著增大,但不同品种小麦间无显著差异。‘115/青海麦’、‘92L89’和‘抗10103’根水提液处理的看麦娘根系MDA含量依次是对照的10.9~25.5倍、5.9~24.2倍和1.2~6.8倍。小麦化感作用引起看麦娘根系细胞膜脂氧化胁迫,并诱导看麦娘根系抗氧化物质类黄酮和总酚含量的合成。可见,降低根系活力、增强保护酶系统活性及抗氧化物质代谢是看麦娘应答小麦化感作用的生理响应。     

Possible influence of Rhizobium on VA mycorrhiza metabolic activity in double symbiosis of alfalfa plants (Medicago sativa L.) grown in a pot experiment

Summary Alfalfa (Medicago sativa, L. cv Aragón) plants were grown under greenhouse conditions in pots of inert sand and vermiculite. The plants were inoculated with Rhizobium meliloti strain 102F28, with Glomus fasciculatus or with a mixture of both microorganisms. Plants inoculated with both Rhizobium and Glomus had the highest shoot dry weight and the lowest root-to-shoot ratio. Roots from dually inoculated plants also had a higher oxygen uptake and nodule nitrogenase activity than those from plants inoculated with either of the two microsymbionts alone. However, the dry weight of the roots from only VAM-infected plants was higher than those from Rhizobium or from Rhizobium plus Glomus-inoculated ones. These differences did not correlate with succinate dehydrogenase activity, which was similar between treatments. Nutrient element concentrations were increased in dually infected plants in comparison with those of plants inoculated with only Rhizobium or Glomus. These data suggest that Rhizobium may affect fungal metabolism and that the effect is not achieved via the tricarboxylic acid pathway.