草莓、辣椒枯萎病菌的分离、鉴定及化学防治

由尖孢镰刀菌引起的辣椒枯萎病及草莓枯萎病是为害辣椒和草莓的主要病害之一。为明确淮安地区辣椒、草莓枯萎病的病原菌种类及防治方法,采集辣椒、草莓根际土壤样品,对其病原菌进行了分离、纯化和鉴定。结果表明,该病原菌为尖孢镰刀菌辣椒专化型及尖孢镰刀菌草莓专化型。采用菌丝生长速率法对3种杀菌剂进行筛选,其中氟硅唑抑制作用较好,对尖孢镰刀菌辣椒专化型的EC_(50)为0.181 7～0.251 7 μg·mL~(-1),对尖孢镰刀菌草莓专化型的EC_(50)为0.076 0～0.212 8 μg·mL~(-1),且活体药效实验表明该药剂有效。     

pH胁迫下尖孢镰刀菌生长动力学模型

尖孢镰刀菌(Fusarium oxysporum)是兼性寄生真菌,引起农作物枯萎病,防治困难。研究来自不同寄主的尖孢镰刀菌在不同pH马铃薯蔗糖(PS)琼脂培养基上的生长情况,构建动力学模型,以了解培养基的初始pH差异对尖孢镰刀菌生长特性的影响。测定了尖孢镰刀菌菌株在不同pH培养基、25℃培养条件下的生长速度,构建生长动力学模型。供试6个尖孢镰刀菌菌株在pH为3~10的液体培养基中均有不同程度生长,不同菌株对培养基pH的影响规律相似,在不同pH的PS液体培养基中培养14 d后,液体培养基的pH均有靠近6~7的趋势。在pH为3~9的培养条件下,尖孢镰刀菌菌落可以分成4类:菌丝型、粘滑层型、菌丝粘滑层型和菌丝带粉状物,各菌株的菌丝和培养基色泽也有所差异。同一菌株在培养基不同pH下生长速度不同,其生长的最适pH为6~8,菌落平均直径最大(45~49 mm),亚适pH为4、5和9;而在pH为3、10和11时菌落直径明显变小(17~21 mm)。培养14 d后培养基pH对菌落形态、色泽有一定的影响,不同菌株在不同pH培养基培养下产孢量也存在差异。pH在4~8时其平均产孢量最大,达(223.8~273.3)×104cfu.mL 1,其中pH为6.38(自然pH)时产孢量最高,pH为11时产孢量最低。供试菌株在不同pH条件下的菌落生长速度和产孢量变化动力学模型均符合二次曲线方程。     

土壤环境因子对土壤中黄瓜枯萎病致病菌增殖的影响

通过实验室模拟试验,研究了连作土壤中p H值、相对含水率及施用不同类型氮肥等环境因子对土壤中黄瓜枯萎病致病菌(Fusarium oxysporum f.sp.cucumerinum)增殖的影响。研究结果表明,土壤p H值对致病菌的影响最显著,致病菌增殖速率在初始p H值为3.0和5.0时显著高于p H值为7.0和9.0;土壤相对含水率在10%~30%之间时,有利于尖孢镰刀菌的生长繁殖;施用不同形态氮肥对致病菌在土壤中的增殖均有促进作用,且随施用量的增加而增加,其中铵态氮更易导致致病菌快速增长。研究结果阐明了黄瓜枯萎病致病菌在不同土壤环境因子影响下的增殖规律,将有助于指导黄瓜枯萎病防治,提高防效。     

强还原土壤对尖孢镰刀菌的抑制及微生物区系的影响

强还原土壤灭菌(reductive soil disinfestation,RSD)是一种抑制土传病原菌的高效和环保的方法。本试验通过荧光定量PCR和变性梯度凝胶电泳研究RSD对土壤尖孢镰刀菌(Fusarium oxysporum)及微生物区系的影响。结果表明:处理15天后,较对照(CK)相比,除添加氨水处理(NH3)土壤p H上升外,以苜蓿粉和乙醇为有机碳源的RSD(Al-RSD和Et-RSD)处理土壤p H分别降低了0.54和1.16;NH3、Al-RSD和Et-RSD处理将尖孢镰刀菌数量分别降低了74%、98%和93%;Al-RSD显著增加了细菌的数量和多样性,Al-RSD和Et-RSD处理显著降低了土壤中真菌的数量,但增加了真菌的多样性。结果表明RSD与氨气熏蒸相比对于土壤微生物区系的改善具有更好的作用。     

强还原土壤灭菌处理对连作病土改良效果的影响因素

以西瓜和草莓连作病土为研究对象，设置不同处理时间(3、4、5、7周)、处理温度(10、20、30、40℃)、含水量(80%和100%田间最大持水量、淹水)以及物料类型(稻草、稻草+牛粪、稻草+铁粉)的强还原土壤灭菌(reductive soil disinfestation,RSD)处理，通过冗余分析和随机森林分析探讨RSD处理对不同土壤类型的改良效果及其共性影响因子。结果表明：与对照相比，RSD处理能显著降低两种土壤的电导率和提高土壤p H，且能有效减少土壤真菌/细菌比、尖孢镰刀菌数量及其在真菌中的占比。然而，各因素RSD处理间的土壤性状也呈显著差异，其中pH、电导率以及杀菌效果的整体变化幅度分别为6.48～8.64、0.15～0.22 mS/cm及0.6%～99.9%。RSD在处理温度高于10℃且处理时长为3周时可显著提高土壤pH；在淹水处理时土壤盐渍化去除效果最佳；在处理温度40℃条件下，尖孢镰刀菌的杀灭效果于两种土壤中均达99.7%以上。相关性分析进一步表明，处理温度与RSD处理后的土壤pH和微生物性质相关性最高，且各因素对RSD处理杀菌效果的重要性排序为：温度>时间&g...     

硝/铵营养对香蕉枯萎病尖孢镰刀菌生长的影响

通过室内平板培养,研究了不同硝/铵配比的氮源,以及不同的pH对香蕉枯萎病尖孢镰刀菌生长的影响。结果表明: 1）在所有不同硝/铵配比处理中,低pH（pH=4）均抑制尖孢镰刀菌的生长。在相同pH值条件下,100%铵态氮处理中尖孢镰刀菌的生长受到明显抑制,其菌落直径均小于4 cm; 2）在不同浓度铵处理后,尖孢镰刀菌的生长在铵态氮大于5 mmol/L时受到强烈的抑制; 3）通过模拟植物细胞壁被尖孢镰刀菌侵染并穿透的过程中发现,尖孢镰刀菌在100%铵态氮处理下不能穿透赛璐膜。本研究结果说明,铵态氮能够控制香蕉尖孢镰刀菌的生长,并抑制其侵染穿透寄主细胞壁。     

不同栽培条件下蔬菜塑料大棚土壤尖孢镰刀菌数量的变化

应用尖孢镰刀菌选择性培养基,调查了太湖地区不同蔬菜品种、不同栽培年限、不同栽培方式及不同土壤深度的蔬菜塑料大棚土壤中尖孢镰刀菌数量的变化情况。结果显示,栽种黄瓜的土壤中尖孢镰刀菌数量达1.6×104cfug-1干土,显著大于栽种芹菜和茄子的土壤。随着栽培年限的增加,土壤中尖孢镰刀菌数量有增加的趋势,连作4a土壤中尖孢镰刀菌数量比连作1a土壤增加了22%。与有土栽培相比,基质槽培土壤中尖孢镰刀菌数量较少,仅1.1×104cfug-1干土,基质栽培可能是国内今后蔬菜塑料大棚的发展方向之一。随着土层深度的增加,土壤中尖孢镰刀菌数量逐渐降低,尖孢镰刀菌很少从表层土向下迁移。这些结果为蔬菜塑料大棚土壤的可持续利用提供了一些初步的微生物学依据。     

香蕉根围土壤尖孢镰刀菌与养分特征及相关性

拟通过分析香蕉种植土壤中尖孢镰刀菌数量与养分含量,阐明香蕉枯萎病发生流行时土壤中尖孢镰刀菌与养分的特征及其相互关系,为香蕉枯萎病的防控提供一定的理论依据。在我国及老挝15块香蕉园中分别随机采集9个罹患枯萎病与9个未患病植株根围土壤样品,应用实时荧光定量PCR与土壤农化分析技术,测定了270个土壤样品中尖孢镰刀菌数量与养分含量。结果表明,患病香蕉根围土壤中尖孢镰刀菌的数量显著高于未患病土壤,每克干土中lg转化后的平均拷贝数为5.5;而患病与未患病植株土壤各养分指标之间几乎无显著差异。各养分指标在土壤中含量分布规律各不相同,其中仅有机质与全磷的含量呈正态分布,土壤pH、全氮及锌的含量呈偏正态分布。蒙特尔检验结果表明,土壤整体养分含量与尖孢镰刀菌数量显著相关。各养分与尖孢镰刀菌的斯皮尔曼相关性分析进一步发现,土壤pH、铁、锰、铜、锌的含量与土壤中尖孢镰刀菌的数量呈显著负相关关系。此外,不同酸性程度及不同有机质含量土壤中尖孢镰刀菌与各养分的相关性分析发现,在弱酸性蕉园土壤（pH > 6.0）中,土壤尖孢镰刀菌的数量与铁、锰、铜的含量显著负相关;而在有机质含量未严重缺乏（SOM > 1%）的土壤中,土壤尖孢镰刀菌的数量与土壤pH及铁、锰、铜、锌的含量呈现显著负相关关系。在我国及老挝香蕉产区蕉园土壤普遍呈现酸化趋势,患病香蕉植株根围土壤中尖孢镰刀菌数量上升,而尖孢镰刀菌与土壤pH及微量元素,尤其是铁、锰、铜、锌的含量呈负相关关系。     

枯草芽孢杆菌D9生物有机肥对连作芦蒿扦插苗枯萎病病害防控研究

芦蒿连作土壤中的枯萎病病原菌尖孢镰刀菌(Fusarium oxysporum)通过扦插茎秆的切口处侵染扦插苗,严重地降低扦插苗的成活率。实验通过分离生防菌株,开发生防生物有机肥防控扦插苗连作病害。研究结果显示,分离到的具有生防芦蒿枯萎病病原菌尖孢镰刀菌能力的菌株为枯草芽孢杆菌(Bacillus subtilis)D9。D9菌株的代谢物能够显著地抑制尖孢镰刀菌的孢子萌发和菌丝的伸长(P0.05)。芦蒿连作土壤扦插苗病害的防控实验结果表明,有机肥和D9生物有机肥的防病率分别达到77.3%和97.1%,同时能够显著地(P0.05)降低芦蒿扦插苗的茎内尖孢镰刀菌数量,而且D9生物有机肥能够显著(P0.05)降低扦插苗根际土壤中尖孢镰刀菌的数量。相较于对照处理,D9生物有机肥处理的根际土壤和茎内尖孢镰刀菌数量分别降低了35.7%和93.7%。有机肥没有提高芦蒿几丁质酶和β-1,3葡聚糖酶活力,而D9生物有机肥显著提高芦蒿几丁质酶和β-1,3葡聚糖酶的酶活(P0.05)。D9生物有机肥能够有效防治连作芦蒿扦插苗的病害,为芦蒿产业提供一条绿色、安全的栽种途径。     

一株抗药用白菊枯萎病生防菌的分离与生防效应研究

从生长健康的药菊根际土壤分离筛选获得一株对其连作土传枯萎病致病菌（尖孢镰刀菌菊专化型）具有较强拮抗作用的细菌a4,并通过盆钵和田间小区试验研究其生防效果。结果表明,拮抗菌a4对药菊枯萎病病原菌的抑制率达71%。盆栽试验,施用a4二次发酵的生物有机肥（CK+BOF1）,未发生药菊枯萎病,而对照植株则完全发病;对照植株根际土壤尖孢镰刀菌的数量为CK+BOF1处理的6.5倍。田间小区试验,苗床育苗和移栽时都施用BOF并加灌a4发酵液的处理（n+F+a4）,根际土和非根际土中病原菌的数量分别为2.0103和2.8103 cfu/g,而对照则分别为1.4104和1.2104 cfu/g。n+F+a4处理生长120 d的药菊生物量（干重）为对照的4.47倍,生防效果达93.2%。采用苗床育苗和移栽时都施用高效拮抗菌的方法,能有效防止枯萎病发生,促进药菊植株生长,提高产量。     

Earthworms disseminate a soil-borne plant pathogen,Fusarium oxysporum f. sp. raphani

Radish plants infested with a soil-borne plant pathogen, Fusarium oxysporum f. sp. raphani PEG-4, which is resistant to hygromycin B, were placed on the surface of a soil microcosm containing earthworms (Pheretima sp.). The earthworms ate the radish plants and scattered individual casts everywhere in the burrows. The fungal propagules were detected in the gut of the earthworms and in 26 out of 28 casts. These results suggested that the pathogen could survive passage through the alimentary canal of the earthworms and be disseminated anywhere earthworms wandered. The collected casts were incubated in a moist chamber at 28°C for 14 days, which resulted in a decline in the number of the propagules. The effects of the earthworms on the population dynamics of the pathogen were estimated. The earthworms seemed to cause a decline in total propagules of the pathogen in soil, although they expanded its distribution in soil.     

Screening of fungal strains responsible for strong fungistasis against Fusarium oxysporum f. sp. radicis-lycopersici in a coffee compost-amended soil

(pp. 817–824)
Disease incidence of crown and root rot of tomato, caused by Fusarium oxysporum f. sp. radicis-lycopersici J3 (FOL J3) was significantly lower in a soil (CC-soil) amended with coffee compost and chemical fertilizers (CF) than in a soil (CF-soil) amended with only CF. Germination of microconidia of various plant-pathogenic Fusarium oxysporum strains was consistently lower in the CC-soil than in the CF-soil, suggesting that the CC-soil possessed a higher degree of fungistasis. When the CC-soil was supplemented with rifampicin and kanamycin, germination of FOL J3 didn't increase, suggesting that the higher degree of fungistasis in the CC-soil may not be of bacterial origin. The substrate-induced respiration inhibition method demonstrated that the CC-soil possessed higher microbial activity and was dominated by fungi. PCR-DGGE analysis showed that the microbial community structure of the two soils was different. Fungal mycelia were isolated from the soils and the effect of the isolates on soil fungistasis was examined. Three isolates, all belonging to F. oxysporum out of 49 showed strongest suppressive effect on the germination of FOL J3 and two isolates suppressed Fusarium crown and root rot disease when they were inoculated into autoclaved CC-soil. These results might suggest that the isolates close to F. oxysporum were responsible for highly fungistatic capability in the CC-soil and were a possible source for disease suppression.     

Effect of elevated atmospheric CO2 and temperature on disease severity of Fusarium oxysporum f.sp. lactucae on lettuce plants

Climate change effects on Fusarium oxysporum f.sp. lactucae (FOL) on lettuce plants grown under simulated climate change were studied. An artificial growing substrate was infested with FOL to reach a final concentration of 1 × 10⁴ CFU g⁻¹ of substrate. A non infested tank was used as control.Subsequently, 32 pots (2 l each) were prepared from the infested tank and other 32 pots were prepared from the non infested tank (control). Lettuce plants were then transplanted into the pots and grown in phytotrons under four simulated environmental conditions: (1) 800 ppm CO₂, 22–26 °C; (2) 800 ppm CO₂, 18–22 °C; (3) 400 ppm CO₂, 22–26 °C and (4) 400 ppm CO₂, 18–22 °C. Substrate samples were collected from each phytotron at 7, 14, 21 and 28 days after transplanting. Plate counts, enzymatic assays, and polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) analyses were performed to evaluate the effect of climate change on the microbial population. The abundance of Fusarium spp. and the severity of Fusarium wilt of lettuce varied significantly as a consequence of increased temperature (22–26 °C). Increased CO₂ levels showed no effect on the severity of Fusarium wilt of lettuce and on the abundance of Fusarium spp. On the other hand, the total bacterial abundance was reduced at elevated CO₂ concentration (800 ppm). PCR-DGGE fingerprints of the ascomycete community obtained from DNA directly extracted from infested substrate samples did not change as a consequence of elevated temperature and CO₂.Enzymatic activities were not affected by the elevated CO₂ level. Our study indicates that the CO₂ concentration used in our experiment had no detectable impact on Fusarium wilt of lettuce. Only temperature influenced all observed parameters, but did not affect the fungal species diversity. Other factors, such as nutrient limitation and the effect of plant species needs further study.     

Combining ability of yield and yield components among Fusarium oxysporum f.sp. strigae-compatible and Striga-resistant sorghum genotypes

ABSTRACT

Use of sorghum [Sorghum bicolor (L.) Moench] cultivars with partial resistance to Striga spp. and Fusarium oxysporum f.sp. strigae (FOS) represents a novel strategy to control Striga. This study aimed to identify the nature of gene action controlling grain yield and yield components and to select promising sorghum crosses possessing both FOS compatibility and Striga resistance, along with good combining ability effects. One-hundred hybrids, developed from pairwise matings among 10 FOS compatible, high-yielding female lines and 10 Striga-resistant male lines, were evaluated with and without FOS inoculation. The F₁s were field evaluated at three locations in Tanzania known for their severe Striga infestation, using an alpha lattice design with two replications. General (GCA) and specific combining ability (SCA) variances were significant for grain yield per plant, hundred-seed weight, plant height, flowering time and the number of Striga plants. The study demonstrated FOS inoculation to be an effective means of controlling Striga. Families 675?×?672, AS435?×?3993 and 4643?×?AS436 displaying large SCA effects for grain yield, and 4567?×?AS429, 3424?×?AS430 and 3424?×?AS436 with small SCA effects for Striga counts should be useful genetic resources for breeding and integrated Striga management.     

枯萎病菌侵染后香蕉乙烯形成酶基因MaA CO及乙烯响应因子MaERF1表达水平分析

香蕉与枯萎病互作机理研究一直是近年来研究的热点,目前对枯萎病菌的致病机理及香蕉的感、抗病机理还不清楚。本文利用前期表达谱分析结果克隆了乙烯合成及调控途径中的关键酶基因乙烯形成酶基因（MaACO）和乙烯响应因子基因（MaERF1）,通过RT-PCR检测,对这两个基因在感、抗病香蕉种质中的表达水平进行研究。结果表明,MaACO和MaERF1基因对机械损伤非常敏感,尤其在损伤初期（3h）的表达水平远高于后期;对于枯萎病菌侵染处理的植株,尤其在感染初期（3h）MaACO和MaERF1的表达水平在抗性植株中的表达量均比感病植株中的低;抗性种质中乙烯途径可能受到抑制,香蕉的感病性可能与侵染初期对乙烯信号的敏感性相关。本研究为利用乙烯抑制剂进行香蕉抗枯萎病新方法的研究奠定了基础。     

Shifts in ascomycete community of bisolarizated substrate infested with Fusarium oxysporum f. sp. conglutinans and F. oxysporum f. sp. basilici by PCR-DGGE

Substrate samples were artificially infested with Fusarium oxysporum f. sp. conglutinans (FOC) and F. oxysporum f. sp. basilici (FOB) in order to evaluate the shift in fungal population by using culture dependent and culture independent methods. Solarization was carried out with transparent polyethylene film during a summer period on a greenhouse located in Northern Italy, in combination or not with Brassica carinata defatted seed meals and/or compost. Biosolarization treatment was carried out in a growth chamber by heating the substrate for 7 and 14 days at optimal (55–52 °C for 6 h, 50–48 °C for 8 h and 47–45 °C for 10 h/day) and sub-optimal (50–48 °C for 20 h, 45–43 °C for 8 h and 40–38 °C for 10 h/day) temperatures. Plate counts and polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) analyses were performed to evaluate the effect of biosolarization on the microbial population. The abundance of FOC and FOB were reduced as a consequence of biosolarization approach, while bacterial population (total aerobic mesophilic bacteria and Pseudomonas spp.) were higher compared to control samples during the experiment. PCR-DGGE fingerprints of the ascomycete community obtained from DNA directly extracted from infested substrate samples showed that the use of organic amendments increased the similarity of the fungal population.     

土壤厌氧还原消毒对尖孢镰刀菌的抑制研究

试验采用土壤淹水同时添加有机物料的方法创造土壤厌氧还原环境,抑制香蕉连作土壤中致病菌尖孢镰刀菌(Fusarium oxysporum,FOC)的数量。结果表明:土壤淹水同时添加玉米秸秆的处理显著增加了土壤p H,降低了土壤氧化还原电位和土壤中NO3–-N的浓度;土壤淹水同时添加玉米秸秆的处理过程中,土壤可培养细菌数量显著增加,土壤中可培养放线菌和真菌数量显著降低;土壤淹水同时添加石灰或玉米秸秆均显著降低了土壤中FOC的数量,其中每千克土添加20 g玉米秸秆的处理中FOC数量下降最多,仅为对照处理FOC数量的2.8%。田间试验结果表明:土壤淹水同时每千克土添加5 g玉米秸秆可以有效降低香蕉枯萎病的发生,防效为69.5%。因此,土壤淹水同时添加有机物料是一种可以防控香蕉枯萎病的高效和环保的方法。     

Potassium Selectivity in Transported Volcanic Soils (Sorribas) under Banana Cultivation in Relation to Banana-Wilt Expression Caused by Fusarium oxysporum f. sp. Cubense

The bases for the microbiological nature of certain soils to suppress plant diseases caused by soil pathogens are well established. However, the microbial origin of the suppressiveness does not exclude edaphic factors and soil-management strategies, which need to be studied under field conditions. With respect to abiotic factors, we investigated the importance of potassium (K) selectivity on soil conduciveness and suppressiveness to banana wilt (positive or negative disease expression) caused by soil fungus Fusarium oxysporum f. sp. cubense in Sorribas field plots (transported volcanic soils) from the Canary Islands that are naturally affected by Fusarium wilt. To facilitate comparison among sites, soil K variables were normalized using Z scores and tested by one-way analysis of variance within each soil sample type (soil areas where banana plants show positive or negative wilting symptoms characteristic of Panama disease), with the site as the block factor. Variations of Z scores within the same plot were explained mostly by the differences between soil K indices between areas with and without disease. In fact, soil conduciveness or suppressiveness to Fusarium wilt seemed to be substantially affected by changes in exchangeable and solution K indices. Potassium selectivity coefficients (K_G) were always greater in areas without disease than in those with disease. The differences between samples can be related to allophane composition and clay mineral distribution in disease and disease-free soils. The larger selectivity of suppressive soils for K can be partly attributed to the K-fixing capacity of silicon-rich allophane. Moreover, there was a clear separation between available iron (Fe) [extracted by diethylenetriaminepentaacetic acid (DTPA)] and the mass of stable aggregate in water (WSA) in conducive and suppressive soil samples by K_G. These results suggest that WSA and Fe-DTPA in soils of volcanic nature affected by F. oxysporum f. sp. cubense seem to depend on K selectivity characteristics associated with these soils.     

Fusarial wilt suppression and crop improvement through two rhizobacterial strains in chick pea growing in soils infested with Fusarium oxysporum f.sp. ciceris

 Bacterization of chick pea seeds with a siderophore-producing fluorescent Pseudomonas strain RBT13 and an antibiotic-producing Bacillus subtilis strain AF1, isolated from tomato rhizoplane and pigeon pea rhizosphere repectively, increased the shoot height, root length, fresh weight, dry weight and yield in soils infected with Fusarium oxysporum f.sp. ciceris. Seed bacterization also resulted in a significant reduction in chick pea wilt caused by the same pathogen. Addition of iron to the soil completely eliminated disease suppression by RBT13 but not by AF1. Dual drug-resistant mutant strains derived from the rhizobacteria were used to monitor and confirm root colonization. The results indicate the potential for development of both strains for the biological control of chick pea wilt. Received: 29 April 1998