几种杀菌剂防治甜菜褐斑病效果分析

[目的]筛选出防治甜菜褐斑病(Cercoapora belicola Sacc.)效果较好的杀菌剂为该病的有效防治提供理论依据.[方法]选择5种杀菌剂,进行防治甜菜褐斑病的田间小区试验.[结果]筛选出防治效果较好的杀菌剂是福星5000倍液和氟硅唑·多菌灵(12.5;·27.5;)悬浮剂,防效分别为60.80;和58.37;.与其他杀菌剂有显著性差异.5种杀菌剂防治时应连续喷药,间隔期7d,连续施药2次.I结论]5种杀菌剂均对甜菜褐斑病有一定的防治效果,防效最高的杀菌剂是福星、氟硅唑·多菌灵,可在生产上推广应用.     

Association between resistance to Cercospora and yield in commercial sugarbeet hybrids

This report documents the difficulty breeders have experienced in combining resistance to Cercospora leaf spot (causal agent Cercospora beticola Sacc.) with high yield in sugarbeet (Beta vulgaris L.). Forty commercial hybrids, all recommended for Cercospora-threat areas, were grown in a Cercospora-free and a diseased (inoculated) environment in 1991 and 1992. A 2.9 Mg/ha decrease in root yield associated with each increment increase in susceptibility confirmed that under a severe epiphytotic (1991) Cercospora resistance provided substantial protection. Under less-severe disease conditions (1992) there was no apparent relationship between yield and resistance, suggesting that the benefits of resistance were similar to the yield potential sacrificed to obtain the resistance. In the absence of the disease, root yields increased 2.7 Mg/ha for each increment of increased susceptibility. There was no evidence of association between sucrose concentration and resistance in the Cercospora-free environment. Despite the limited efforts and/or success in developing resistant commercial hybrids, the demonstrated ability of Cercospora to produce fungicide-resistant strains and the possibility that effective fungicides will not be available provide incentives to seek genetic resistance through breeding efforts.     

吉林省玉米灰斑病重要流行环节的初步研究Ⅰ孢子萌发、病斑潜育扩展和寄主抗侵染

对玉米灰斑病的重要流行环节——孢子萌发、病斑潜育扩展和寄主抗侵染进行了研究。结果表明:分生孢子在清水中就能够萌发,但未见附着胞形成;花粉和叶面物质对孢子萌发有促进作用。孢子抗干燥能力较强,萌发孢子须经3~4 d干燥才完全丧失存活能力。对灰斑病菌孢子萌发抑制作用较强的杀菌剂有百菌清、甲基托布津、大生、多菌灵等。病害潜育期较长,潜育期随玉米生育期推进而增长,在不同品种上潜育期为11~18 d。病斑长度(y)和病斑日龄(x)的关系大体为对数曲线,回归方程为y=0.263 5 5.163 ln(x 1)。随着玉米生育期的推进,抗侵染力逐渐增强。施用氮、磷、钾肥可在一定程度上增强玉米的抗侵染力。     

吉林省玉米灰斑病重要流行环节的初步研究Ⅱ.病斑产孢和孢子飞散

对玉米灰斑病在吉林省的重要流行环节——病斑产孢、孢子飞散进行了研究。结果表明:玉米灰斑病菌在吉林省能够顺利越冬。病斑在直射光下不能产孢,产孢在散射光下多于黑暗条件下。保湿时间越长,病斑产孢越多,保湿时间(t)与产孢量(y)关系的回归方程为y=exp[-14.59exp(-0.2t)]。病斑在20-30℃均可产孢,25℃最适合产孢,温度(x)与产孢量(y)关系的回归方程为y=sin(-1.685 7x 0.252 2x2-1.63×10-3x3)。病斑长度(x)与病斑产孢潜能(y)的关系曲线为单峰曲线,病斑长度在15-22 mm时产孢潜能较高。玉米施用氮、磷、钾肥可降低灰斑病病斑产孢。灰斑病菌孢子主要在夜间释放飞散。     

感染大豆灰斑病菌后不同抗性的大豆品种叶绿素动态变化的研究

本文采用了抗性不同的大豆品种，在3～4叶期接种，并于接种后1～10天内连续取样，然后测定其接种后内叶绿素的含量。试验结果表明：无论是抗病品种，还是感病品种，在病菌侵入的初期，叶绿素a、b的含量都有所下降：在病菌侵染后7～10天时，感病品种叶片内叶绿素a、b含量比未接种对照低，而抗病品种叶片内叶绿素a、b含量均明显高于未接种对照；另外，致病力不同的生理小种对叶绿素a、b含量变化的影响不同，7号生理小种对叶绿体的破坏能力最强，其次为6号生理小种，而4号生理小种则最弱，其中1号，2号生理小种居中。抗病品种叶片内叶绿素a/b的比值明显高于感病品种，初步认为叶绿素a/b的比值可作为大豆品种对灰斑病抗性鉴定的一种生化指标。     

Potential for Incorporation of Early and Late Leafspot Resistance in Peanut*

A detached leaf technique was used to evaluate components of resistance to both early and late leafspot caused by Cercospora arachidicola Hori and Cercosporidium personatum (Berk, and Curt.) Deighton, respectively, for F₂ plants of two peanut (Arachis hypogaea L.) crosses (FESR 5-P2-B1 /PI 269685 and PI 35068Q/GP-NC 343), No negative correlations were obtained when comparing components of resistance to early leafspot with components of resistance to late leafspot, indicating that the resistances are inherited independently. A small number of F₂ plants had greater partial resistance to both leafspots than their parents when evaluated by an index including percent necrotic area, latent period and sporulation. Broad sense heritabilities of resistance components were moderate to high (0.4 to 0.8) for the F₂ populations. A visual sporulation rating scale was significantly correlated (0.8 to 0.9) with conidia per lesion and conidia per necrotic area. The data suggest that peanut cultivars resistant to both leafspots can be developed.     

Spatial distribution of purple seed stain of soybean caused by <Emphasis Type="Italic">Cercospora kikuchii</Emphasis> in fields

To investigate the frequency distribution of purple seed stain of soybean caused by Cercospora kikuchii in two experimental fields in 2004, we set up rows 75 cm apart and sowed two asymptomatic seeds at each of positions 20 cm apart in each row. We sowed purple-stained seeds infected with the pathogen as inocula at four points instead of asymptomatic seeds in each field. We assessed disease incidence in harvested seeds by counting the numbers of purple-stained and asymptomatic seeds. To determine the spatial distribution of the disease, we grouped the field points into analytical units of several sizes. Beta-binomial and binomial distributions described the distribution patterns of purple-stained seeds. The smallest value of α, a beta-binomial parameter, occurred with analytical units that contained three or nine points next to each other within a single row, suggesting that these units showed the most aggregated distribution of the disease, each of the patches of seeds infected with C. kikuchii could be defined approximately by the area covered by three or nine points (75 × 60 or 75 × 180 cm), and the disease tended to infect plants next to each other within rows.     

水葫芦生防菌Cercospora piaropi的病理学特性

尾孢菌属的Cercospora piaropi是一种有潜力开发成为防除水葫芦的生物除草剂的真菌。水葫芦原生叶片从被C．piaropi感染到完全死亡，需要约6周时间。C．piaropi接种水葫芦的适宜孢子浓度为10^5CFU/ml，适宜保湿时间为24h。30℃时C．piaropi感染水葫芦的原生叶片病害严重度最高。除水葫芦和鸭舌草外，cpiaropi对其他被测农作物和杂草均不产生病理作用，表现出较强的专一性。     

大豆紫斑病菌（Cercospora kikuchii）生物学特性研究

大豆紫斑病菌在ＰＤＡ培养基上生长速率最快，在大豆叶葡萄糖琼脂培养基和番茄培养基瞳孢量经在ＰＤＡ上高２倍，比病菌生长发育最适温度为２５－２８℃，低于１５℃或高于３７℃均不适宜，在连续黑暗条件下有利于生长，ＰＨ４－９之间，均能生长和产孢以ＰＨ－＝７生长最适，ＰＨ＝７－８产孢最多，分生孢子在葡萄糖液中萌发最好，在１５－４０℃之间均能萌发，最适温度为３０－３３℃，ＰＨ＝３－９之间均能萌发，ＰＨ＝７－８萌发     

细胞壁糖蛋白与大豆灰斑病抗性关系的研究

利用电镜细胞化学方法，对大豆灰斑病抗、感品种在受到病菌侵害时，大豆叶片细胞壁糖蛋白的变化进行了观察。随着病变程度的加深，糖蛋白在细胞壁表面的积累，均呈现由薄到厚最终大部分的脱落这一有规律的变化。在抗病品种中糖蛋白在细胞壁表面的积累，较感病品种更为显著，菌丝侵染点周围的糖蛋白有成团聚增现象，形成凝固的团状，当细胞受到较严重损害时，糖蛋白呈块状的脱落于细胞间隙。而在感病品种中糖蛋白多呈现出絮状，常在病菌侵染的初期从细胞壁的表面脱落，此时细胞器大都完好。这一现象表明细胞壁表面糖蛋白的变化与大豆灰斑病的抗病性存在有密切的关系，并且在抗病品种中它的抗性作用更加明显。