Effect of planting density of maize on the progress and spread of northern leaf blight fromExserohilum turcicum infested residue source

Effect of plant density (37,037, 44,444 and 55,555 plants/ha) on the increase of northern leaf blight in time and space on two maize cultivars planted at spacings of 90, 75 and 60 between rows and 30 cm within rows was investigated.Exserohilum turcicum infested maize residue was used as an inoculum source. Maize density did not significantly affect the disease indices, but significantly influenced the grain yield of the two cultivars. In contrast, the two cultivars differed significantly (P0.01) in disease severity, but not grain yield. Higher disease severities and grain yields were associated with higher plant densities, whereas the apparent infection rate was lower in higher plant density. Distance from the maize residue (inoculum source) significantly influenced disease severity. The percentage leaf area blighted, area under disease progress curve and disease progress curve intercept decreased with distance from the maize residue area, but the apparent infection rate on EV8429-SR appeared to increase with distance. Disease gradients (b) were higher in closely planted maize and flattened with time in one location only.     

2012年玉米大斑病重发原因和控制对策

玉米大斑病是由真菌引起的世界性玉米病害,常给生产造成严重损失。2012年玉米大斑病在东北、华北地区大流行,本文归纳了玉米大斑病全国发生概况、区域分布和各地病情。总结了2012年玉米大斑病发病时间早,流行速度快,品种间和地区间发病程度差异大等发生特点,分析了适宜天气条件、主栽品种不抗病、栽培管理措施不合理是导致大斑病重发的主要原因。并针对性地提出了重视玉米病害的预测预报、推荐种植抗病品种、加强病害综合防治的对策建议,旨在对今后进一步做好玉米大斑病测报工作,指导玉米病害防治、有效控制其危害、保障玉米生产有所裨益。     

玉米小斑病研究进展

玉米作为重要的粮、饲、工兼用作物, 是重要的战略资源, 在国民经济中具有举足轻重的作用。但在实际生产过程中, 玉米受多种病虫害的威胁, 其中由玉蜀黍平脐蠕孢Bipolaris maydis引起的玉米小斑病严重影响玉米产量与品质, 是制约玉米高产与稳产的重要因素之一。近些年该病害的发病频率与严重程度均呈快速增长的态势, 对我国玉米安全生产构成巨大的潜在威胁。本文综述了玉米小斑病发生概况, 包括发生时期和引起的主要症状; 概括了玉米小斑病菌的侵染过程和相关功能基因的致病机制; 总结了抗玉米抗小斑病基因的定位、克隆与功能分析方面的研究进展, 玉米小斑病的防治措施等, 并对未来研究提出了一些建议和展望, 以期为玉米小斑病可持续治理提供理论参考和研究思路。     

Maize resistance to northern corn leaf blight is potentiated by nickel

Northern corn leaf blight (NCLB), caused by Exserohilum turcicum, is one of the most devastating diseases affecting maize yield worldwide. A foliar spray of nickel (Ni) to potentiate maize resistance against NCLB was investigated by examining alterations in the photosynthetic apparatus (leaf gas exchange and chlorophyll [Chl] a fluorescence parameters), production of ethylene and reactive oxygen species as well as activities of defence and antioxidant enzymes. Mycelial growth of E. turcicum was inhibited by Ni in vitro. Inoculated plants sprayed with Ni exhibited higher foliar Ni concentration, reduced NCLB symptoms, and lower concentrations of malondialdehyde and hydrogen peroxide. In inoculated leaves of plants not sprayed with Ni, concentrations of Chl a, Chl b, and carotenoids were lower and the photosynthetic apparatus was impaired at the biochemical level due to high NCLB severity. The activities of antioxidant enzymes were not affected by Ni, except an increase in glutathione reductase activity for noninoculated plants sprayed with Ni. High lipoxygenase and polyphenoloxidase activities, lower ethylene production, as well as elevated production of phenolics and lignin helped decrease NCLB severity in the leaves of Ni-sprayed plants.     

玉米三种叶斑病混发时的流行过程及产量损失研究

 通过2年的田间小区人工接种试验,观察比较了玉米大斑病、弯孢叶斑病和灰斑病单独及混合发生时的流行过程及对玉米产量损失的影响。结果表明,在病害混发初期,病害间无明显的负相关性,随着病情的发展,病害间的负相关性逐渐增大并达到显著水平,说明病害间有明显的抑制作用。病害混发时造成产量损失并不完全等于各病害单独造成损失之和,其中大斑病和弯孢叶斑病、弯孢叶斑病和灰斑病混合发生所造成的损失约为各病害单独造成损失之和的76%～88%,大斑病和灰斑病混合发生所造成的损失可近似看作两种病害各自引起产量损失之和,3种病害同时发生时最终损失率约为各自造成损失之和的67%～72%。     

Influence of rate of soil fertilization on alternaria leaf blight (Alternaria dauci) in carrots

The possibility of suppressingAlternaria dauci (Kühn) Groves & Skolko, the causal agent of Alternaria leaf blight in carrot, by excess application of fertilizer was examined in greenhouse and field experiments. Reducing the rate of fertilization by one half from the optimal rate (100 ppm N, 19 ppm P and 74 ppm K) resulted in a 23–30% increase in the severity of Alternaria leaf blight. However, doubling the rate of fertilization resulted in only a 10–15% decrease in disease severity. Inoculating with different concentrations ofA. dauci spores (10³ or 10⁴ spores/ml) did not alter the response of the plants to the fertilization rate, although significantly higher disease severity was observed in plants inoculated with the higher spore concentration. These results were corroborated in the field, where neither disease severity nor harvested yield was significantly affected by tripling the amount of soil fertilization. Application of foliar fungicides, on the other hand, had substantial effects on both disease and yield. Therefore, it was concluded that carrot crops should be fertilized and maintained for optimum yield, and thatA. dauci should be managed by properly timed applications of fungicides during the growing season. Contribution no. 533/99 from the Inst. of Plant Protection, Agricultural Research Organization.     

云南省荞麦叶枯病病原菌鉴定及其生物学特性

为明确云南省荞麦叶枯病病原菌种类,采用常规组织分离法获得病原菌菌株LW2015.3,通过形态学特征及分子生物学技术对菌株LW2015.3进行鉴定,并研究其生物学特性。结果表明,荞麦叶枯病病原菌的分生孢子呈倒棍棒状或倒梨状,褐色,具3～8个横隔膜,0～4个纵斜隔膜,大小为16.5～45.0μm×5.0～13.5μm,厚垣孢子呈球形,直径为6.0～12.0μm;该菌株ITS序列系统发育进化分析结果表明,菌株LW2015.3与链格孢Alternaria alternata(登录号:MG195995.1)的同源性为100%,结合形态学特征与分子鉴定结果确定云南省荞麦叶枯病病原菌为链格孢A. alternata(登录号:KT362732.1)。该病原菌菌丝生长适宜温度为20～30℃,25℃为最适温度;当p H为6～9时菌丝生长速率加快,pH 7最适菌丝生长;PDA培养基和PSA培养基最适菌丝生长;该病原菌对以麦芽糖为碳源和以硝酸钠为氮源时的利用率最高;菌丝的致死温度为50℃,10 min;不同光照条件对菌丝生长的影响有显著差异,连续光照最有利于菌丝生长。     

Evaluation of entomopathogenic nematodes for biocontrol of the european corn borer,Ostrinia nubilalis, on sweet corn in Israel

The potential of entomopathogenic nematodes for biological control of the European corn borer (ECB),Ostrinia nubilalis (Hübner), was evaluated under laboratory, screenhouse and field conditions. The ‘All’ and ‘Mexican’ strains ofSteinernema carpocapsae (Weiser) and the ‘HP88’ strain ofHeterorhabditis bacteriophora Poinar were compared in both dose response assays (5, 50 and 500 infective juveniles [IJ] per petri dish containing five 5th-instar ECB eggs; 72 h of incubation) and exposure time assays (3, 6 and 9 h of incubation). In the dose response assays the highest rates of ECB killing resulted from infestation with the Mexican strain ofS. carpocapsae. In the exposure time assays there were no significant differences between the killing rates of the three nematode strains. Sweet corn plants(Zea mays var.saccharata) grown in a screenhouse, were infested with ECB neonates and 4 days later sprayed with a suspension of the Mexican strain ofS. carpocapsae (50,000 IJ per plant). The number of ECB larvae found on treated corn plants after one week was significantly (P=0.05) lower (3- to 5-fold) than the number found on untreated plants. Similar treatment in the field significantly reduced the rate of economic ear damage from 20% to 5%. Contribution from the Agricultural Research Organization. No. 2260-E, 1997 series     

杭白菊叶枯病病原菌鉴定及其对多菌灵的抗性机制

为明确浙江省桐乡市发生的杭白菊叶枯病的病原菌,采用传统组织分离法对采集的病样进行病原菌分离,在测定其致病性的同时,结合形态学特征及基于核糖体内部转录间隔区(ITS)、nrDNA大亚基(LSU)和β-微管蛋白基因(TUB2)的联合系统发育分析对该病原菌进行鉴定,并测定其对多菌灵的抗性。结果表明,从杭白菊叶枯病病样中共分离到35株菌株,在回接试验中杭白菊表现出的症状与田间自然发病症状一致,证明分离到的菌株为引起杭白菊叶枯病的病原菌。该病原菌菌丝生长初期为淡黄色,后为灰白色;培养25 d后菌落上的黑色球形分生孢子器产生大量液体状的淡粉色分生孢子堆;分生孢子为单胞、无色、长椭圆形,大小(n=200)为2.8～4.9μm×1.2～3.0μm,初步判断该病原菌是茎点霉属Phoma真菌P. bellidis。基于ITS、LSU、TUB2联合系统发育分析的分子鉴定结果与形态学鉴定结果一致,确定引起该病害的病原菌为P. bellidis。该病原菌对多菌灵的抗性频率为94.3%,且全部为高水平抗性菌株,抗药性机制为其TUB2的E198A突变,即TUB2的第198位密码子从GAG突变为GCG,导致第198位氨基酸从谷氨酸(Glu)突变为丙氨酸(Ala)。     

玉米大斑病菌毒素对玉米叶肉细胞脂氧合酶活性的影响

 玉米大斑病菌2号小种粗毒素(HT-C)和标准毒素(5-羟甲基-2-呋喃甲醛,HT-I)处理玉米叶片,都能诱导3种供试基因型玉米叶片中脂氧合酶活性增高,但是不同基因型玉米对HT-C和HT-I的反应不同,HT-I对含有Ht1基因的品系诱导时间早,水平高,HT-C对于不带Ht基因的品系LOX的影响略高于HT-I;不同浓度的HT-I在OH43和OH43Ht1玉米叶片中诱导的LOX酶活性不同,高浓度HT-I和HT-C对LOX酶活诱导时间早,水平高,浓度降低诱导水平降低;外源H₂O₂对HT-I和HT-C在OH43叶片中LOX酶活性诱导作用的影响不同。     

五味子叶枯病病原菌鉴定

 The pathogen causing leaf blight on Schisandra chinensis (Turcz.) Baill. was isolated from diseased leaf. Based on morphological characteristics and pathogenicity test, the pathogen was identified as Alternaria tenuissima (Fr.) Wiltshire. This is the first report of this fungus infecting S. chinensis.     

闽南地区薏米叶斑病菌对吡唑醚菌酯的敏感性及吡唑醚菌酯的盆栽防治效果

采用菌丝生长速率法测定了闽南地区4个薏米产区72株薏米叶斑病菌对吡唑醚菌酯的敏感性,并通过室内盆栽试验测试了吡唑醚菌酯对薏米叶斑病的防治效果。结果表明:吡唑醚菌酯对供试菌株的EC₅₀值范围为1.11~5.06 μg/mL,平均值为 (3.44 ± 0.98) μg/mL,且其EC₅₀值频率分布为连续单峰曲线,符合正态分布,因此可将该EC₅₀平均值作为闽南地区薏米叶斑病菌对吡唑醚菌酯的敏感基线。盆栽防效结果表明,喷施有效剂量为250 μg/mL的25%吡唑醚菌酯乳油对薏米叶斑病的防治效果 (78.2%~79.7%) 较好,与喷施有效剂量为500 μg/mL的50%异菌脲悬浮剂的防治效果相当,显著高于喷施有效剂量为800 μg/mL的80%代森锰锌可湿性粉剂的防治效果。本研究结果为薏米叶斑病化学防治有效药剂的选择与合理使用提供了依据。     

Molecular marker analysis of European Setosphaeria turcica populations

Setosphaeria turcica is the causal agent of northern corn leaf blight, a foliar maize disease of worldwide economic importance. In Europe, its severity increases. To investigate the pathogen's population-genetic structure in central Europe, a total of 80 isolates was sampled in Germany, Switzerland, France, Austria, and Hungary and investigated with 52 random amplified polymorphic DNA (RAPD) markers. The mating type of the isolates was determined in testcrosses. Among the 73 isolates from maize there were 26 different RAPD haplotypes. All isolates with identical haplotype are considered clonemates. The haplotype shared by most members was represented by 22 isolates from Germany, Switzerland, and France, indicating high fitness and substantial migration. Only a single clone had members in both southeastern Austria and southwestern Switzerland, suggesting that the Alps constitute a major barrier for this pathogen. Several haplotypes differed by only one or two RAPD bands from the predominant haplotype and may have arisen by mutation. Few other clonal lineages were detected. The evolution of some haplotypes could not be explained by mutation alone. Sexual recombination may rarely occur. In population samples from Germany, Switzerland, and France, mating type MAT2 was predominating, while most isolates from Austria and Hungary had MAT1. Seven isolates from Johnson grass (Sorghum halepense), an alternative host of S. turcica, were clonemates and very different in RAPD haplotypes from all isolates collected from maize.     

银杏叶枯病的发生影响因子与防治技术研究

通过对湘南银杏叶枯病的症状、发生规律、影响发病的原因等进行观察和分析,并通过田间防治试验,初步筛选提出了防治药剂和方法,为大田防治提供了技术保证。     

桃蛀螟为害夏玉米果穗对产量的影响

为明确桃蛀螟Conogethes punctiferalis(Guenée)为害夏玉米果穗对产量的影响,于2012—2013年通过人工接种法将桃蛀螟初孵幼虫接到吐丝期玉米果穗上调查果穗被害程度,分析接虫密度对产量构成因素、穗腐病发生及产量损失的影响。结果表明,桃蛀螟主要通过降低百粒重、缩短果穗长度和减少行粒数等影响产量;当接虫密度每穗为1、3、5和10头时,不同处理的百粒重均比对照显著降低0.65、1.03、1.07和1.60 g;当接虫密度为每穗5和10头时,果穗长度比对照分别显著缩短9.66 mm和13.17 mm,行粒数减少5.15和5.45粒;桃蛀螟为害可诱发穗腐病的发生,主要病原菌为轮枝镰孢菌、青霉菌和禾谷镰孢菌,引起穗腐病的发生率分别为84.91%、54.45%和40.97%;接虫密度为每穗1、3、5和10头时,平均单穗产量损失率分别为0.73%、4.19%、11.65%和17.71%。研究表明,桃蛀螟为害不仅直接造成产量损失,还可加重穗腐病发生,影响玉米的质量。     

狗牙花叶枯病病原菌分离鉴定

狗牙花叶枯病是江西农业大学花圃重要病害之一。本文按照柯赫氏法则对狗牙花叶枯病病原进行了分离鉴定，鉴定结果为胶孢炭疽菌（Colletotrichum gloeosporioides(Penz.)Sacc.).     

Influence of host resistance and phenology on South American leaf blight of the rubber tree with special consideration of temporal dynamics

South American leaf blight (SALB), the most dangerous disease of the rubber tree, is responsible for the lack of significant natural rubber production in South America and is a major threat to rubber tree plantations in Asia and Africa. Although the selection of resistant clones is the preferred disease control method, greater knowledge is required of the relationship between host and pathogen, in order to construct more durable resistance. Based on small-scale trials, this study set out to compare the dynamics of SALB on two highly susceptible and one moderately susceptible clone and to analyse the effect of host phenology on disease severity, at leaflet and flush scales. Clonal resistance was found to have a noticeable effect on disease severity, asexual sporulation and stromatal density at both leaflet and flush levels, and on disease dynamics at a leaflet level; time for symptom and sporulation appearance were longer on the moderately susceptible clone than on the susceptible clones. On the moderately susceptible clone, the stromatal density was largely dependent on disease severity. The phenology did not differ among the three clones and could not be considered as a factor in genetic resistance to SALB. However, for the three clones, the position of the leaflet in the flush affected the duration of the immature stages and the disease: the shorter the duration of leaflet development, the lower the disease severity, the sporulation intensity and the stromatal density.     

黄淮海夏玉米区草地贪夜蛾为害籽粒玉米的产量损失与防治阈值

为确定我国草地贪夜蛾 Spodoptera frugiperda重点防范区——黄淮海夏玉米区该虫为害籽粒玉米的防治阈值,于2020—2021年分别在籽粒玉米小喇叭口期（6~8叶）、大喇叭口期（8~10叶）和抽雄吐丝期 （12~14叶）,通过人工接草地贪夜蛾2龄幼虫进行田间试验,分析不同虫口密度和为害株率下玉米的产量损失,并确定相应防治阈值。结果显示,草地贪夜蛾2龄幼虫密度为2~12头/株时,小喇叭口期、大喇叭口期和抽雄吐丝期的玉米产量损失率分别为16.78%~31.91%、 10.45%~25.14%和15.71%~29.17%,在3个玉米生育期对草地贪夜蛾的防治阈值分别为2龄幼虫55~67头/百株、 97~118头/百株和59~71头/百株;当草地贪夜蛾2龄幼虫为害株率为5%~60%时,小喇叭口期、大喇叭口期和抽雄吐丝期的玉米产量损失率分别为8.81%~22.43%、 4.83%~17.75%和8.16%~20.43%,在3个玉米生育期对草地贪夜蛾的防治阈值为害株率分别为4.24%~5.22%、 7.61%~9.49%和4.46%~5.55%。表明黄淮海夏玉米区草地贪夜蛾在不同生育期为害籽粒玉米的产量损失和防治阈值不同。     

南瓜叶枯病病原菌生物学特性研究

本文对南瓜叶枯病病原菌瓜链格孢（Alternaria cucumerina）进行了生物学特性研究,结果表明：温度、pH、光照对其生长和产孢都有一定的影响。该病原菌菌丝生长、产孢和萌发的适宜温度为28 ℃,pH为7时菌丝生长最快,pH为8时最易产孢。25 ℃下连续黑暗培养产孢最多。碳、氮源对菌丝生长和产孢量有一定的影响,碳源中甘露醇组菌丝生长最快,山梨醇处理产孢量最多。氮源中牛肉浸膏最适宜菌丝生长和产孢,硫酸铵最差。该菌致死温度为50 ℃。     

河南小麦叶枯类病害春季流行的时间动态规律研究

1997～1998年的研究结果表明:小麦叶枯病害在河南麦田春季的流行曲线基本呈S型曲线。始发期一般在3月20日～4月10日,指数增长期大约10～20d,该期流行速率最高;4月10～20日以后该病进入逻辑斯蒂增长期,可持续30～40d,流行速率比指数增长期稍低,没有明显的衰退期;影响小麦叶枯类病害始发期的气象因子为3月份的日照、降水量和气温,4月份的气温、日照、降水日数、相对湿度与发生程度关系密切。河南主栽小麦品种中没有对叶枯类病害免疫的品种,70%以上的主栽小麦品种为感叶枯病品种。