水稻纹枯病菌菌核存活力及地下侵染的研究

不同生境下菌核萌发率和影响因子的作用,以及菌核的地下侵染试验结果表明：菌核的萌发率随温度升高而增加,分别组建了菌核萌发率与温度的定量关系式;菌核可多次萌发,室内保存１１年的浪渣菌核仍有１２％的萌发率。首次报道了不同生境下菌能在土层下侵染水稻表现典型病斑。菌核多次萌发特性和地下侵染能力使防治增加困难。     

新疆短命植物小拟南芥(Arabidopsis pumila)种子萌发特性及其生态适应性

通过显微结构及不同处理条件下种子萌发率的观察,对早春短命植物小拟南芥(Arabidopsis pumila)种子萌发特性及影响因素进行了研究,并对其生态适应性进行了讨论。结果表明:(1)温度和光照变化对自然生境和温室收获种子的萌发率影响均不显著,说明此种群在前期萌发阶段对光、温不敏感;(2)自然生境中采收的小拟南芥种子萌发率显著低于温室收获种子,说明环境条件的变化对短命植物种子的发育具有重要作用,可显著改变种子的萌发行为;(3)赤霉素使自然生境收获种子胚活性增强从而对萌发有较大促进作用,可使萌发率增加50%以上;(4)对种皮进行各种机械损伤处理使得种皮松弛或透气,可以显著提高自然生境种子的萌发率(超过70%);(5)盐和干旱胁迫对种子萌发均具有明显的抑制作用,但复水后部分被抑制种子可重新萌发,显示盐和干旱胁迫可导致种子产生浅度休眠。结合小拟南芥自然生存环境及本研究的结果,显示其种子萌发特性与生境具有高度适应性。     

桑椹肥大性菌核病病原菌生物学特性及流行性

【目的】对桑椹灾害性真菌病害——桑椹肥大性菌核病病原菌,即桑实杯盘菌(Ciboria shiraiana)的生物学特性进行研究,分析其流行性。【方法】采用人工接种、调查等研究方法,对C.shiraiana在无性生长阶段中菌丝侵染能力,菌核的休眠期,有性生长阶段中子囊孢子的结构、释放、数目以及萌发等进行研究,并对菌核萌发的物候期进行调查。【结果】C.shiraiana菌丝对桑雌花没有侵染能力;C.shiraiana菌核具有休眠期,低温处理6周以上的菌核才能萌发形成子囊盘;1个菌核可萌发1–15个子囊盘,直径为1.5 cm的子囊盘能产生高达(5.6–6.3)×10~7个子囊孢子;C.shiraiana子囊孢子在酸性环境中的萌发率明显高于在中性和碱性环境中的萌发率;C.shiraiana菌核萌发形成子囊盘产生子囊孢子的物候期,从1月下旬开始到4月中旬结束,其中在3月中旬萌发子囊盘的数目达到最高值。【结论】桑椹肥大性菌核病属于典型的流行性侵染病,在果桑栽培上容易造成毁灭性危害,生产上必须高度重视该病的防控。     

温度对青藏高原高寒草地植物种子萌发与病原真菌侵染关系的影响

自然条件下,病原真菌侵染是导致种子死亡的重要因素。气候变化背景下,种子特性(如休眠和发芽速率)与真菌侵染之间的关系仍不清楚。本研究以青藏高原高寒草地的17种草本植物种子为对象,设置不同温度(10、15、20和25℃)发芽实验,研究不同温度条件下种子病原真菌侵染和死亡与种子发芽速率和休眠特性之间的关系。结果表明：在各温度条件下,种子病原真菌侵染率、死亡率与种子休眠率均呈显著负相关(P<0.001),但在25℃条件下相关性最强：仅在25℃条件下,种子真菌侵染率、死亡率与种子平均发芽时间呈显著正相关(P<0.05);种子休眠在不同温度条件下均能有效抵御病原真菌的侵染;种子通过快速萌发有效逃避病原真菌的侵染,但其与病原真菌的关系受温度影响较大。     

雪腐核盘菌菌核的萌发条件与致死温度

菌核是核盘菌Sclerotinia spp.在土壤中的主要存活形式和菌核病的主要初侵染源,在土壤中可存活8年以上,其数量和存活状况直接影响着菌核病的发生和危害程度。本研究以雪腐核盘菌Sclerotinia nivalis菌株SS-TB为材料,分析了菌核萌发的影响因素、致死温度以及土壤温度对菌核存活的影响。结果表明,未成熟菌核较成熟菌核更容易萌发;菌核萌发的最佳温度为20-25℃、pH为3.0-4.0、土壤含水量为20%-45%。菌核长时间浸泡水中对其存活不利,浸泡30d以后,存活率开始急剧下降,至47d时存活率为0。雪腐核盘菌菌核具有较强的耐高温特性,随着温度和处理时间的增加,菌核萌发率呈下降趋势。菌核在水浴中85℃ 5min、80℃ 10min、75℃ 10min、70℃ 30min、65℃ 120min、60℃ 180min时全部丧失活力。在土壤温度30℃和35℃处理5周、40℃和45℃处理4周时菌核全部失去活力。该研究结果为通过水旱轮作和土壤高温处理来防治西洋参菌核病提供了理论基础。     

大丽轮枝菌微菌核的萌发条件及致死温度

微菌核是大丽轮枝菌在土壤中的主要存活结构和初侵染源,在土壤中可存活14年之久,其数量及存活状况直接影响着大丽轮枝菌型黄萎病的发生为害程度。以棉花黄萎病菌Verticillium dahliae XJ2008菌株为试材,研究了微菌核萌发的最佳条件、致死温度及土壤温度对微菌核存活的影响。结果表明,20℃、pH8.0是微菌核萌发的最佳条件。大丽轮枝菌微菌核具有很强的耐高温特性,随着处理时间的延长,微菌核的萌发率呈下降趋势,在55℃及以上处理时其萌发率下降迅速,而在50℃及以下处理时其萌发率下降相对较慢,在55℃处理360min可使微菌核完全致死,而在40℃、45℃和50℃处理1,440min,仍然有少量的微菌核存活,但其萌发率随着时间的推移呈下降趋势。土壤微菌核模拟试验结果表明,土壤温度对微菌核有很强的致死作用,40℃条件下处理4d后土壤中的微菌核已全部死亡。该研究结果为通过覆膜增温防治作物黄萎病提供了理论依据。     

丛枝真菌对互花米草和芦苇氮磷吸收的影响

互花米草(Spartina alterniflora Loisel.)是我国海滨盐沼的入侵植物,与土著种芦苇(Phragmites australis)形成了广泛的竞争;已知丛枝菌根(AMF)对不同植物的生长存在差异性影响;但其对互花米草与芦苇之间的种间关系,是否对互花米草入侵芦苇群体产生作用值得探讨.研究对两物种进行了丛枝菌根接种处理,种植模式处理和盐度处理的三因素实验.结果表明:盐度增加使得单种时芦苇、混种时互花米草的AMF侵染率显著下降(p<0.05),而混种时芦苇和单种时的互花米草AMF侵染率受盐度影响不显著(p>0.05).混种时,两种植物的丛枝菌根形成均受对方影响,并且盐度升高使两种植物之间对AMF侵染率的影响发生变化,在淡水生境下混种时,芦苇的AMF侵染率比单种时降低40.5%,互花米草的AMF侵染率比单种时提高了86.9%,均差异显著(p<0.05);在低盐度下混种时芦苇的AMF侵染率比单种时降低24.7%,差异显著(p<0.05),而对互花米草的影响不显著;在高盐度下混种对芦苇的AMF侵染率影响不显著,而使互花米草的AMF侵染率显著降低,降低率比例达78.7%.在淡水生境下,丛枝菌根对芦苇和互花米草的N、P吸收均有显著的促进作用;但是在咸水生境下生长时芦苇的N、P含量主要受盐度的显著影响(p<0.05),随盐度增加而增加;虽然在咸水生境下丛枝菌根仍旧促进芦苇的N、P吸收,但其影响远小于盐度的影响,并且促进效果受到盐度的抑制;但互花米草的N、P含量不受盐度影响.由此可见,接种AMF对这两种植物的氮磷吸收有着不同程度的促进,其作用大小与侵染程度有关,且受到盐度和种植模式的影响.     

VdToxD1和VdToxD3调控大丽轮枝菌微菌核的萌发

大丽轮枝菌Verticillium dahliae是一种土传性植物病原真菌,可侵染660多种植物,引发黄萎病。微菌核是大丽轮枝菌在侵染后期形成的特殊休眠结构,可在土壤中存活14年,是黄萎病的主要初侵染来源。本研究在前期大丽轮枝菌萌发与休眠微菌核转录组分析的基础上,选择微菌核休眠状态高表达的VdToxD1和VdToxD3基因进行功能研究。结果发现,VdToxD1和VdToxD3敲除突变体菌株的微菌核萌发率分别为87.3%和86.0%,显著高于野生型菌株的64.0%;负调控微菌核萌发的转录因子VdCrz1与VdToxD1上游的-937 bp到-349 bp中的特定基序结合,与VdToxD3上游的-752 bp到-496 bp中的特定基序结合,结合位点均位于2个基因的启动子区。     

储藏和萌发温度对青藏高原东缘12种灌木种子萌发的影响

研究了青藏高原东缘2个储藏条件下的12种灌木种子在10、15、20、25℃恒温培养下和5/25℃变温培养下的萌发特性及其与种子大小和生境的关系。结果表明:12种灌木室内干储种子在5/25℃变温培养下种子平均萌发率最高、萌发速率最快,室外埋藏种子10℃、5/25℃下种子平均萌发率相近且最高,但萌发速率5/25℃最快,10℃下最慢,4个恒温下的室内干储和室外埋藏种子的萌发速率均随温度升高而变快;10、15、20和25℃恒温培养下的室外埋藏种子平均萌发率、平均萌发速率均高于室内储藏,而5/25℃变温下则是室外埋藏种子平均萌发率、平均萌发速率均低于室内储藏;室内干储的12种灌木种子在5/25℃变温下的萌发率、萌发速率与种子大小呈显著负相关,而室外埋藏的种子在10℃以及5/25℃变温下的萌发率、萌发速率与种子大小均呈显著负相关,20℃下,只有萌发速率与种子大小呈显著负相关;其他储藏和温度下的萌发率、萌发速率与种子大小均没有显著相关;无论室内干储还是室外埋藏,阳坡灌丛物种在5个温度下的萌发率、萌发速率均显著高于阴坡灌丛物种,阴坡灌丛种子萌发率随温度升高而降低;变温有利于种子萌发,贮藏条件对种子的萌发特性的影响具有变温依赖性,种子的萌发特性与种子大小以及生境的关系具有明显的培养温度和储存条件依赖性。     

紫茎泽兰种子种群动态及萌发特性

在紫茎泽兰的入侵地四川省德昌县, 选择撂荒地、农田和马尾松林3个不同的生境, 从种子雨、种子库角度研究了紫茎泽兰种子种群动态规律,及其种子在不同光照和土壤基质条件下的萌发特性. 结果表明,3个生境下紫茎泽兰种子种群仅存在于当年3～6月,于4月底达到年高峰值. 其年降种子雨量在撂荒地中高达2.4×10⁵粒·m^-2,并均分布于2 cm土层以上, 且在撂荒地生境下紫茎泽兰种子的千粒重和活力均显著高于另外两个生境. 到7月上旬, 3个生境下土壤中均未发现有活力的种子. 在实验的光照条件下, 全光照对紫茎泽兰的种子萌发有抑制作用,而在28%光照条件下萌发率最高;砂壤土较适宜紫茎泽兰种子的萌发,生红土中其萌发速度及萌发率均最低.     

猪苓菌核结构性质的研究

利用光学显微镜和电子显微镜对猪苓菌核的结构及其发育进行了研究。组成猪苓菌核的菌丝与平板培养或发酵培养的猪苓菌丝比较,具有多分枝、融合频率高、菌丝形态不规则等特点。猪苓菌核表现了高度的结构分化,有表皮、表皮下层、疏松菌丝层和结构菌丝之分,结构菌丝是组成菌核的主要成分,疏松菌丝层类似一般菌核的髓,但大小、位置在菌核中变化较大。菌核的个体繁殖是由母体菌核的一束或几柬菌丝突破表皮而萌发产生新的菌核;较系统的观察了猪苓菌核细胞分裂及其菌丝内部结构的变化。     

Factors affecting the survival of sclerotia of Sclerotium cepivorum in the Fraser Valley of British Columbia

Sclerotia of Sclerotium cepivorum buried in muck soil in the Fraser Valley decayed with time. The rate of decay of sclerotia was influenced by local environmental conditions. A mixture of soil with sclerotia increased their survival but there was no difference in the rates of decay in three different soils. The decay was greatest during winter when Fraser Valley fields are often flooded. Sclerotial decay was also affected by pretreatment of the sclerotia. Dried sclerotia decayed significantly (P < 0.05) faster than sclerotia which had not been dried, a phenomenon which is apparently due to changes in micro-organisms on the sclerotia. Dried sclerotia which had been incubated in moist soil had fewer bacteria and more fungi than sclerotia which had been incubated in soil without being dried. The increase in fungi on the dried sclerotia was due to a dramatic increase in Trichoderma spp.     

Use of Coniothyrium minitans and other microorganisms for reducing Sclerotinia sclerotiorum

Biological control agents (BCAs) Bacillus subtilis QST 713, Coniothyrium minitans CON/M/91-08, Streptomyces lydicus WYEC 108, and Trichoderma harzianum T-22 were evaluated for their efficacy in the reduction of survival of sclerotia and production of apothecia of Sclerotinia sclerotiorum under controlled environments. A growth chamber assay was conducted where 25 sclerotia were buried in pots containing potting soil, and BCAs were drenched into the soil at various concentrations, and five soybean seeds were planted in each pot. The presence and number of S. sclerotiorum apothecia were recorded daily. Sclerotinia sclerotiorum sclerotia were retrieved six weeks after seeding and viability was assessed on water agar plates. All BCAs were effective in reducing S. sclerotiorum inoculum at various efficacies. In general, efficacy was positively correlated with the rate of application. At the rate of application when the efficacy did not change significantly by increasing the rate, the BCAs had various reductions of apothecia and sclerotia. B. subtilis reduced apothecia and sclerotia by 91.2 and 29.6%, respectively; C. minitans reduced apothecia and sclerotia by 81.2 and 50%, respectively; Streptomyces lydicus reduced apothecia and sclerotia by 100 and 29.6%, respectively; Trichoderma harzianum reduced apothecia and sclerotia by 80.5 and 31.7%, respectively. In addition, the commercial strain of C. minitans CON/M/91-08, and a wild Michigan strain of C. minitans W09 were compared for their growth and sclerotial reduction. W09 had faster growth rate than the commercial strain, indicating potential diversities of biological control strains to be studied.     

The respiration of sclerotia of Sclerotium rolfsii

Summary The respiration of sclerotia ofS. rolfsii was investigated using the Warburg constant-volume respirometer to measure oxygen uptake. The effects of age of sclerotia, pH, and temperature were studied. Sclerotia produced on prune agar were ideal for respirometric studies, being uniformly round and of approximately equal size. On a dry weight basis, the respiration rates of sclerotia were considerably less than those of vegetative mycelium. Sclerotia showed a decrease in respiration with increasing age. This was accompanied by morphological changes in the outer hyphal rind of the sclerotium during maturation. The respiration rate of sclerotia was approximately the same at 30° and 40° C, but was significantly lower at 45° C. Respiration of sclerotia was not markedly affected by normally encountered hydrogen-ion concentrations. However, a pH of 8.0 markedly repressed oxygen uptake. Sclerotia produced in rye grain cultures were chemically analyzed. The nitrogen content was 4.7 %, the petroleum-ether-soluble lipid content was 0.7 %, and the crude glycogen content was 14.2 % of the oven dry weight of the sclerotia.Contribution No. 345 from The Department of Botany. Portion of a thesis presented by the senior author in partial fullfillment for the M.S. degree.     

Germination of sclerotia of Botrytis tulipae, the cause of tulip fire

Sclerotia of Botrytis tulipae (Lib) Lind. buried in field soil germinated mainly in winter and early spring to produce conidiophores and conidia and then decayed. Except when buried very late in the year sclerotia germinated and decayed in the season following burial. In the laboratory, sclerotia from pure culture germinated in two ways. On sterile water-agar they formed colourless mycelium but no conidiophores; the rate of germination was greatest at 25 d?C. On unsterile filter paper and on soil they produced mainly conidiophores and conidia; the rate of germination was greatest at 5 d?C and was enhanced by previous cold treatment. It was unaffected by soil-moisture or pH. Primary infections of tulips arose from sclerotia placed in the soil but only when they were close to the shoot tip or developing stem. It is suggested that, because of their limited survival, soil-borne sclerotia are of importance only when tulips are planted in annual succession.     

激光诱变青霉PT95原生质体选育类胡萝卜素高产菌株

采用激光对青霉PT95菌株的原生质体进行了诱变处理,选育到一株菌核生物量和类胡萝卜素含量均有显提高的突变菌株L05。与出发菌株相比,L05菌株的菌核生物量提高了98.6%,菌核中的类胡萝卜素含量提高了28.3%,在查氏平板上的类胡萝卜素产率提高了154.0%。所选育的L05菌株经3次传代培养,菌落没有发生扇形变异,菌核生物量和类胡萝卜素含量没有明显改变,说明该菌株具有良好的遗传稳定性。     

Antifungal effects of essential oils from oregano and fennel on Sclerotinia sclerotiorum

AIMS: The antifungal effects of essential oils of oregano (Origanum syriacum var. bevanii) and fennel (Foeniculum vulgare) were evaluated against Sclerotinia sclerotiorum. Effects of the essential oils on morphological structures of hyphae and sclerotia were studied under light and scanning electron microscopes (SEM). METHODS AND RESULTS: Inhibitory effects of volatile and contact phases of the essential oils used were determined on hyphae and sclerotia. Both essential oils have a marked antifungal effect against S. sclerotiorum. Soil amendment with essential oils has significant effect on reducing sclerotial viability. Both essential oils significantly inhibited the fungal growth in soil, thereby increasing the number of surviving tomato seedling by 69.8% and 53.3%, respectively. Light and SEM observations on pathogen hyphae and sclerotia revealed considerable morphological alterations in hyphae and sclerotia. CONCLUSIONS: The significant reduction in the mycelial growth and germination of sclerotia would greatly reduce the pathogen inoculum source. This may influence the rate of disease development in soil. SIGNIFICANCE AND IMPACT OF THE STUDY: Considering the reduction in the number of diseased plants in infested soil amended with essential oils, we concluded that oregano and fennel essential oils could be used as possible bio fungicides alternative to synthetic fungicides against phytopathogenic fungi.     

Study on pectinase and sclerotium producing abilities of two kinds ofAspergillus flavus isolates from Zhejiang

Pectinase and sclerotium production by strains ofAspergillus flavus were determined with a pectinase culture plate assay and a Cz 3% NaNO₃ medium plate assay. In theA. flavus population, 51% of isolates produced sclerotia, the toxigenic strains showing a tendency to have smaller sclerotia. Strains producing both abundant small sclerotia and a large quantity of aflatoxin were not found. There was no linear correlation between the amount of aflatoxin produced and the number of sclerotia. Levels of pectinase produced by the toxigenic strains were higher than that of the non-toxigenic strains, and this character was more obvious in the sclerotium-producing strains than in the non-sclerotium-prodcing strains. In theA. flavus population from Zhejiang in which the toxigenic strain rate was low, toxigenic strains may require higher levels of pectinase to compete with the non-toxigenic strains when infecting foodstuffs.     

A new method to induce sclerotial differentiation in Polyporus umbellatus by split-plate culture

Polyporus umbellatus is one of the most valuable medicinal fungi, and its sclerotium has been used as a diuretic agent and an antidote in traditional Chinese medicine. In nature, Polyporus umbellatus has almost been depleted because of over-exploitation and lack of natural habitats. Thus, artificial sclerotia production has increased. This study aimed at finding an effective method to induce sclerotia, and selected the split-plate culture method. One side contained fructose agar medium (FAM), while the other side contained nutrient-limited medium. It was observed that sclerotia were only formed on the nutrient-limited medium side but scarcely emerged on the FAM side, even when the fructose concentration on both sides were the same. The sclerotial differentiation rate was 100% and the sclerotial yield was 106% higher than in the conventional way. In conclusion, the split-plate culture method is an effective way to induce P. umbellatus sclerotia in the laboratory.