我国玉米新病害顶腐病的研究初报

 本文报道了我国玉米上的一种新病害玉米顶腐病,是由串珠镰孢亚粘团变种(Fusarium moniliforme var.subglutinans Wr.&Reink)侵染所致。人工接种玉米后表现与田间自然发病症状一致,除侵染玉米外,尚能侵染高粱、苏丹草、谷子、小麦、水稻、珍珠粟等禾本科作物引起顶腐病,并可侵染狗尾草和马唐草等植物。病菌生长的适宜温度25~30℃,最适为28℃;大、小2型分生孢子萌发适宜温度均为25~30℃。木糖、葡萄糖、蔗糖、乳糖、半乳糖和菊糖均是病菌生长的良好碳源。适宜病菌生长的培养基为Richard's、PDA、PSA、玉米粉和燕麦片培养基。田间发病程度因地势而异,低洼易涝地和园田地发病重、坡地和高岗地发病轻。     

山东玉米茎基腐病病原菌的初步研究

 1979~1983年,从山东省主要病区采集的玉米茎基腐病病株分离得到的菌种有腐霉菌、禾谷镰刀菌、串珠镰刀菌、尖孢镰刀菌以及其它真菌。这些菌种经室内、外多次土壤接种试验表明,只有瓜果腐霉菌Pythium aphanidermatum(Edson) Fitzpatrick和禾谷镰刀菌Fusarium graminearum Schw.两种,对玉米苗期和成株期具有较高的致病力。如两种菌混合接种,则有加重发病的趋势。因此,可以初步认为玉米茎基腐病是以瓜果腐霉菌为主,与禾谷镰刀菌复合侵染而引起的玉米病害。     

湿度调控对番茄灰霉病菌侵染的影响

 番茄灰霉病菌(Botrytes cinerea)的分生孢子萌发需要高湿的环境,一般要求相对湿度在80%以上或水滴中萌发最好。在适温下,随着湿度的增加,病菌致病性增强,孢子在相对湿度85%以上、菌丝在相对湿度80%以上的高湿环境能够发生侵染,并形成危害性的软腐斑。在一天中高湿的时间直接影响番茄灰霉病的发生,高湿(相对湿度超过85%)时间8h以上病菌才能够连续侵染。     

寄生玉米的6种腐霉及其致病性研究

 从国内12省、自治区、直辖市玉米植株上分离出腐霉菌菌株,依据形态特征、培养性状、生长抑制温度,以及产生的有性与无性器官,鉴别出6个腐霉种:棘腐霉(Pythium acanthicum Drechsler),瓜果腐霉(P.aphanidermatum(Edson)Fitzpatrick),强雄腐霉(P. arrhenomanes Drechsler),禾生腐霉(P.graminicola Subramaniam),肿囊腐霉(P.inflatum Matthews),寡雄腐霉(P.oligandrum Drechsler),其中肿囊腐霉出现频率高,分布广泛。回接玉米表明,腐霉能够侵染玉米并引起病害,肿囊腐霉、禾生腐霉、强雄腐霉、棘腐霉是玉米青枯病的重要致病菌;瓜果腐霉能够引起玉米中部茎节腐烂;寡雄腐霉虽寄生玉米,但对玉米成株无致病力。     

环境与寄主条件对玉米灰斑病菌侵染寄主的影响

利用玉米灰斑病菌株20-47、感病玉米品种(掖单13)和抗病玉米品种(沈单10号),在人工气候室和自然条件下对影响玉米灰斑病菌侵染的环境条件和寄主生育期进行了研究。结果表明:玉米灰斑病是属偏高温高湿类型的病害,在温湿度条件不能得到满足时,病害就难以完成侵染发病;病菌接种侵入的最佳温度为25℃左右,水滴条件下侵染最容易;土壤条件特别是氮、磷肥如果施用不均匀、不足或过多,也都可以对结果产生影响,在通常情况下,增施氮、磷肥能提高玉米对灰斑病的抗性;在一定光照强度范围内,光对鉴定结果的影响不明显,但光暗交替更有利于寄主发病;寄主不同生育期对病原菌侵染寄主的影响不同,11～12叶期(喇叭口期)接种,病菌较易侵染。     

基底硬度对玉米大斑病菌主要侵染结构和黑色素沉积的影响

 基底硬度是调控植物病原真菌侵染结构形成的重要物理信号。为探讨基底硬度对玉米大斑病菌(Setosphaeria turcica)侵染能力的影响,本研究利用不同硬度的PDA培养基进行模拟试验,并在不同叶龄的玉米叶片上进一步验证,结果表明,基底硬度越大,气生菌丝越少,菌丝分枝越多;硬基底上,病菌的分生孢子产量高,是软基底和适中硬度基底上的29.93和6.82倍,且硬基底上病菌附着胞形成率显著高于软基底。研究发现,在硬基底上生长的大斑病菌菌落颜色较深,菌丝中黑色素含量高。利用实时荧光定量PCR技术分析病菌黑色素合成途径中相关基因的表达情况,发现在硬基底上StMR1、StPKS、St4HNR、StSCD、St3HNR、StLAC1、StLAC2和StLAC4基因的相对表达量均高于软基底。上述结果说明,基底硬度影响了病菌形态结构的发育,导致了与侵染相关的黑色素含量的变化和侵染结构的形成,研究结果为探究植物病原真菌的侵染机制和病害防控提供了理论依据。     

土壤温湿度及播种期对玉米丝黑穗病发生的影响

主要研究土壤温度、湿度及播种期与玉米丝黑穗病发生的关系。试验结果表明,土壤温度为21℃,玉米丝黑穗的发病率最高为31.3%,17℃低温下发病率为10.9%~16.7%,温度在24℃时,发病率为3.7%~4.8%;土壤含水量与病害侵染发病有较明显的关系,土壤湿度为15%时利于孢子萌发与侵染,发病率达为31.1%,湿度10%、20%时发病率仅为3.7%~8.8%,干旱和高湿不利于病菌孢子萌发,湿度是决定发病程度的主导因素。早播病害重,晚播病害轻但玉米产量低。     

玉米黑束病的初步研究

 1984年秋,甘肃省种植引进南斯拉夫玉米自交系母本773,穗期田间发生大面积枯死.病菌侵染玉米茎部维管束,致使植株叶片从上到下枯萎而死,病情发展迅速,造成严重为害.经调查发病率为66~98.9%.根据病原菌形态、培养性状和致病性试验,鉴定为直枝顶孢霉菌Acremonium strictum W.Gams (=CePhalas porium acremoninm Cda)侵染而引致的玉米黑束病,该病在我国引进玉米上大发生还是第一次.种子检验发现南斯拉夫玉米杂交组合的种子,均不同程度带有病原菌,带菌率为1.25~13%.经研究明确,南斯拉夫玉米自交系母本773对直枝顶孢霉菌高度感病,而当地品种中单二号和户单一号等表现抗病.田间大面积发病的菌源主要来自土壤.     

杨浦链霉菌WLU210的筛选、鉴定及其对苦瓜枯萎病的生防作用研究

本研究从河南黄河湿地采集土壤样品,采用梯度稀释涂布平板法分离和平板对峙培养法筛选获得一株对苦瓜枯萎病菌具有稳定拮抗活性的链霉菌WLU210。在形态学鉴定和生理生化特征测定的基础上,对菌株WLU210的16S rRNA基因序列进行比对分析,将WLU210鉴定为杨浦链霉菌Streptomyces yangpuensis;拮抗谱测定结果表明,杨浦链霉菌WLU210对苦瓜枯萎病菌、苹果轮纹病菌、小麦茎基腐病菌、辣椒疫霉病菌、西瓜炭疽病菌、小麦全蚀病菌和玉米大斑病菌等7种植物病原菌均具有一定的拮抗活性;盆栽试验和田间试验结果表明,杨浦链霉菌WLU210发酵液具有有效防治苦瓜枯萎病和促进苦瓜生长的作用,田间防治效果达68.89%。由此可见,杨浦链霉菌WLU210具有作为防治苦瓜枯萎病生防菌剂研发的潜力。     

短密木霉菌株GAS1-1的分离鉴定、拮抗作用及其生物学特性

为了解短密木霉Trichoderma brevicompactum对植物病害的生防作用及其生物学特性,利用稀释平板分离法从甘肃省景泰县马铃薯连作田植株根际土壤中分离获得1株木霉菌株GAS1-1,经形态观察、rDNA-ITS和EF-1α序列分析明确其分类地位;用生物学方法研究该菌的营养生长和产孢条件;采用对峙培养法测定该菌株对5种植物病原真菌的抑制作用。结果表明,基于形态学特征和基因序列分析结果,菌株GAS1-1被鉴定为短密木霉Trichoderma brevicompactum,为甘肃省木霉新记录种。该菌株对玉米镰孢茎腐病菌Fusarium graminearum、玉米穗腐病菌F. verticillioides、棉花枯萎病菌F. oxysporum、玉米腐霉茎腐病菌Pythium inflatum和灰葡萄孢霉Botrytis cinerea均具有较好的拮抗效果,尤其对玉米腐霉茎腐病菌的抑制作用最好,抑菌率达100.00%。该菌株营养生长和产孢的最适碳源和氮源分别为葡萄糖和酵母膏;其在15～35℃均可生长,菌丝最适生长温度为30℃,最佳产孢温度为25℃;在pH 5～12的培养基上菌丝均可生长,菌丝最适生长和产孢的pH均为5;24 h黑暗条件下菌丝营养生长最快,12 h光暗交替条件有利于产孢;孢子致死温度为69℃,10 min。表明短密木霉菌株GAS1-1具有较好的生防应用潜力。     

Critical factors driving aphanomyces damping‐off and root disease in clover revealed and explained using linear and generalized linear models and boosted regression trees

Subterranean clover (Trifolium subterraneum) is an important forage legume in Mediterranean regions worldwide. Aphanomyces damping‐off and root disease (Aphanomyces trifolii) poses significant threat to its persistence and productivity. Studies were conducted to define how environmental explanatory variables (temperature, soil type, moisture, nutrition) and variety influence disease severity and consequent forage productivity and persistence. Relationships were modelled using linear and generalized linear models and boosted regression trees. Linear modelling highlighted complex relationships between environmental variables and each dependent variable (emergence, tap and lateral root disease, dry shoot and root weight). All environmental variables produced significant interaction and/or main effects within each dependent variable. Boosted regression trees supported the complex nature of relationships in linear models, with temperature and either soil or variety most, and nutrition least, influential. Heat maps showed more disease for low temperatures. Least tap root disease was under high temperatures, while least lateral root disease was under medium or high temperatures, low moisture, and in sand‐based soil. These are the first studies using modelling approaches to reveal the complexities of how fluctuating soil temperature, moisture and nutrition conditions, and soil type and variety, determine aphanomyces damping‐off and root disease severity and resultant adverse impacts on forage legume productivity and persistence. Outcomes are widely applicable across soilborne oomycete pathogens of forage legumes. Studies highlighted how warming temperatures and drying climate associated with climate change should reduce future impact and importance of this and other soilborne oomycete diseases of forage legumes favoured by cold temperatures and wet and waterlogged conditions.     

Severity of phytophthora root rot and pre‐emergence damping‐off in subterranean clover influenced by moisture,temperature, nutrition,soil type,cultivar and their interactions

Studies were carried out in controlled environment rooms reflecting field situations. In the presence of the devastating soilborne pathogen Phytophthora clandestina, subterranean clover (Trifolium subterraneum) seedling emergence was significantly affected by moisture, soil type, temperature and cultivar. The level of rotting of tap and lateral roots was significantly affected by nutrition, soil type, temperature and cultivar. There were significant interactions involving temperature, moisture, soil type and cultivar; cultivar resistance, high moisture, high or medium temperature, high nutrition and sand soil all contributed towards less pre‐emergence damping‐off and tap and lateral root disease and to greater clover productivity. Host resistance of subterranean clover cultivars was critical for reducing disease severity and increasing productivity, even when favourable environmental conditions for severe disease occurred. In the presence of P. clandestina, the most resistant cultivar, Seaton Park, performed best under a high temperature, high nutrition and high moisture combination, but showed lower productivity under conditions of low nutrition or lower temperature, even when moisture level was high. In contrast, less resistant cultivars Riverina and Meteora had less disease and greater productivity under low moisture conditions. Findings reflect field observations that pre‐emergence damping‐off and root disease from P. clandestina in subterranean clover is particularly severe under colder conditions and in nutritionally impoverished sandy soils, and demonstrate how variations in soil type, nutrition, moisture, temperature and cultivar have profound effects on the expression and severity of phytophthora pre‐emergence damping‐off and root disease and the productivity of subterranean clover forages.     

果树根腐病的研究Ⅰ.病原鉴定与病菌侵染规律初步探讨

 此病分布于河北省24个县、市,山东、四川、江苏亦有发生。病原鉴定为发光假密环菌[Armillariella tabescens(Scop.ex Fr.) Singer],并非Armillariella mellea菌所致。
在土壤及朽根上均未发现菌索,在人工培养基上,菌索生长茂盛。用子实体、病土及已无菌丝膜腐朽病根接种不能传病,病根紧接健根全能发病,否则不能发病。病、健根接触是病害传播的主要方式。
据田间调查,土湿即使很高(20%),但地温较低(10℃),病菌不能活动;若土温在15℃左右,土湿在12%以上,病菌开始活动;当土温在25°~30℃,土湿愈大病菌发展愈速;如土湿长期在5%以下,菌即死亡。
病区开沟封锁,能防止病害扩散蔓延。     

Influence of salinity and moisture on the threshold shear velocity of saline sand in the Qarhan Desert,Qaidam Basin of China: A wind tunnel experiment

Determination of the threshold shear velocity is essential for predicting sand transport, dust release and desertification. In this study, a wind tunnel experiment was conducted to evaluate the influence of salinity and moisture on the threshold shear velocity of saline sand. Saline sand samples (mean particle size of 164.50-186.08 μm and the total silt, clay and salt content of 0.80%-8.25%) were collected from three saline sand dunes (one barchan dune and two linear dunes) in the Qarhan Desert, Qaidam Basin of China. Original saline sand samples were placed in two experimental trays for wet and dry processing to simulate deliquescence and desiccation, respectively. Surface moisture content ranging from 0.30% to 1.90% was generated by the steam method so that the saline sand can absorb water in a saturated water vapor environment. The motion of sand particles was determined by the observers with a solid laser. The laser sheet (0.80 cm thick), which was emitted by the solid laser, horizontally covered the sand surface and was bound to the sand. Results show that the cohesion of saline sand results from a combination of salt and water. The threshold shear velocity increases exponentially with the increase in crust thickness for the linear sand dunes. There is a positive linear correlation between the original moisture content and relative threshold shear velocity. The threshold shear velocity of dewatered sand is greater than that of wet sand with the same original moisture content. Our results will provide valuable information about the sand transport of highly saline soil in the desert.     

Overwintering of alternaria macrospora in Cotton Debris

An epidemic ofAlternaria macrospore in cotton started 1 month earlier, and developed faster in plots contaminated withA. macrospora-infected cotton debris than in debris-free plots. Overwintering of the pathogen in debris was associated with survival of the debris itself. With the exception of debris in dry soil, overwintering was better in debris located on the soil surface than in that buried beneath the surface. Under all conditions it was better in dry than in wet soil and in sterilized than in unsterilized soil. Survival was associated with micTobial activity in the soil, was highest in pure sand and decreased progressively in sandy loam, heavy soil and peat. The survival in debris was highest in soil kept at 10°C and decreased progressively at 20, 30 and 40°C. Increasing the soil moisture content reduced survival. Overwintering was better in a cotton field that was not cropped during the winter than in a field sown with wheat between the cotton seasons. The rate of transfer of disease to seedlings from debris buried in soil was low except when debris was in contact with the seed. The main means of disease transfer was by airborne spores produced on debris located on the soil surface. These spores had low infectivity and caused few lesions, but the second generation of spores formed on these lesions was highly infectious.     

Factors Influencing Transmission of Didymella rabiei (Ascochyta Blight) from Inoculated Seed of Chickpea Under Controlled Conditions

Ascochyta blight of chickpea (Cicer arietinum), caused by the fungus Didymella rabiei, has the potential to cause 100% crop loss in severe epiphytotics. Management of this disease often involves reducing sources of inoculum. The influence of sowing depth, host resistance, seed infection level and soil temperature on disease transmission was investigated in a series of glasshouse and growth room trials using seed artificially inoculated with D. rabiei. A positive correlation (R²=0.9992) was observed between rate of seed infection and the incidence of disease on seedlings. Disease transmission to seedlings was not significantly influenced by sowing depth (1, 3 and 6 cm) in separate trials on two cultivars. Susceptibility of the host showed no obvious influence on the frequency of disease transmission in two trials conducted using four cultivars ranging from highly susceptible to moderately susceptible/moderately resistant. Trials conducted in controlled conditions showed that there was no obvious relationship between soil temperature (5, 9, 14 and 19 °C) and the incidence of disease on seedlings.     

土壤环境因子对氯胺嘧草醚除草活性的影响

采用常规室内生物测定法,研究了土壤环境因子对氯胺嘧草醚[开发代号ZJ1835,化学名称为N-(2-氯-6-(4,6-二甲氧基嘧啶-2-氧基)苄基)苯胺]除草活性的影响。结果表明:土壤质地、p H值、有机质含量、土壤湿度和温度对其除草活性均能产生一定影响。氯胺嘧草醚在砂土和黏土中的活性高于壤土,其除草活性随土壤有机质含量、p H值和土壤湿度的升高而升高,而温度偏高或偏低均不利于其药效发挥,在15~25℃环境条件下除草活性最佳。     

陇东黄土塬区土壤包气带水分水势特征研究

选取陇东黄土包气带为研究对象,综合运用数理统计与对比分析相结合的方法,研究黄土地区包气带土壤水分、水势变化特征和土水势构成结构,结果发现,在陇东黄土塬区,坡头荒地等较干旱、沙质土壤中,包气带水分变化呈对数分布特征,而耕作土壤其水分含量特征则不满足这种类型.在土水势构成方面,溶质势所占比例平均约为20%,其中坡头荒地约占...     

科尔沁沙地坨甸交错区土壤水分的空间变异规律

科尔沁沙地沙丘-草甸相间地区,地貌形态多样、土地利用类型众多,从而导致土壤水分空间分布的复杂性。通过对科尔沁沙地典型沙丘-草甸相间地区的调查取样与试验分析,运用统计学理论和方法,研究土壤水分的空间变异性及其空间分布规律。结果表明：水平方向上,土壤水分总体表现为草甸地大于沙丘地,过渡带介于两者之间。就草甸地而言,植物生长越好,其土壤水分越高,保水持水性能也越好;沙丘地则与之相反,植被最稀疏的流动沙丘,其土壤含水量大于半流动半固定沙丘与固定沙丘,且有良好的储水条件。垂向上,高覆盖草甸、低覆盖草甸和农田（草甸）土壤含水量在地表下0～40 cm波动最大,40～160 cm随深度增加而递增;流动沙丘、半流动沙丘和固定沙丘土壤含水量随深度增加呈微弱加大趋势。林地、撂荒地、农田（沙丘）变化程度居中。从空间分布看,研究区中东部土壤水分偏大,且向南北两侧区域递减。