Relationships between Weather Variables, Airborne Spore Concentrations and Severity of Leaf Blight of Garlic Caused by Stemphylium vesicarium in Spain

Ascospores and conidia released into the air were recorded around plots on which garlic debris infected by Stemphylium vesicarium were fixed onto the soil surface. Symptoms in garlic trap plots located in the vicinity of infected debris, started in March and developed during April–May to reach disease incidence close to 100%, final disease severity values being lower in 1993 and 1995 than in 1994 and 1996. Whereas daily concentrations of ascospores were rather erratic, with 30% of captures between 0 and 6 h, conidia showed a daily periodicity with highest concentrations between 12 and 18 h, with a pronounced peak between 14 and 16 h, and lowest values at night. Ascospore release occurred mainly in February and March. It coincided with rainfall periods, 14 h with vapour pressure deficit 5 mb and solar radiation <145 W m^–2 on the current day of the capture. In contrast, greatest captures of conidia started in late April and were prevalent in May, and were associated with rainfall in days previous to the capture in which rather high temperature occurred and solar radiation was 109–345 W m^–2. Among the weather variables considered, rainfall appeared directly related to the aerial concentration of ascospores and conidia. The role of relative humidity seemed essential when rainfall did not occur. There was a relationship between conidia concentration in the air and number of hours with temperature in the range 12–21 °C. Ascospore production was not essential for infections to take place, since primary infection from conidia may occur and disease can develop from them readily.     

80%代森锰锌可湿性粉剂(美生)对番茄早疫病的防治效果

代森锰锌是防治蔬菜病害的保护性杀菌剂。研究结果表明，80％代森锰锌可湿性粉剂(美生)600～800倍，在番茄早疫病发生初期用药，间隔7天施药1次，能有效控制住番茄早疫病的危害。     

叶枯唑防治水稻白叶枯病的作用方式研究

叶枯唑具有诱导受体植物水稻产生抗病性的作用 ,能使水稻体内脂质过氧化程度加强 ,刺激水稻体内产生 O-2 ,阻止白叶枯病菌侵入。O-2 清除剂 (甘露醇、抗坏血酸 )处理水稻能显著降低叶枯唑的保护作用。叶枯唑也能直接作用于水稻白叶枯病菌 ,抑制菌体生长 ,表现出治疗作用。     

氨基寡糖素对番茄晚疫病的防治效果研究

2年的田间药效试验结果表明,氨基寡糖素0.5%水剂防治番茄晚疫病效果显著,能有效地增强番茄的抗病能力,使用剂量在14~18.8g a.i./hm2时,防效均在80%以上,优于生产上大面积推广的嘧菌酯250g/L悬浮剂。由于氨基寡糖是从海洋生物外壳提取而来的安全、无毒、无残留的多糖类天然产物,在化学农药对环境的污染和人类健康的威胁、抗药性等问题凸显的今天,氨基寡糖素是一个很有应用价值和发展前景的绿色环保型农药,可以作为无公害蔬菜生产的配套药剂进行大力推广应用。     

小麦真菌性叶枯病的发生特点与防治技术

小麦叶枯病是由病原真菌侵染小麦产生叶枯症状的一类病害的统称。据报道[1,3,6],我国较常见的叶枯病有20余种,鉴定出病原真菌10多种。20世纪80年代以来随着矮秆品种的推广,灌溉与施肥水平的提高及耕作栽培制度的改变,该病发生面积迅速扩大,为害逐渐加重。到20世纪90年代中...     

山麦冬叶枯病病原菌分离鉴定

山麦冬叶枯病是山麦冬叶的重要病害之一,本文按照柯赫氏法则对山麦冬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.）。     

Chemical Control of Alternaria sp. Causing Leaf Blight of Wheat

Abstract

A replicated fungicidal trial was conducted to control leaf blight of wheat caused by Alternaria sp. on Bijaga yellow. Out of the 5 fungicides used zineb and thiram were found to be most effective in controlling the disease.     

Typing of Tomato Yellow Leaf Curl Viruses in Europe

Tomato yellow leaf curl disease is spreading in southern Europe, where it has quickly become a serious problem. In recent years, several virus isolates have been characterised. Although with some genetic variability, all isolates found in Europe belong to one of two species Tomato yellow leaf curl-Sardinia (TYLCV-Sar) or Tomato yellow leaf curl-Israel (TYLCV-Is). Several methods were tested to identify and type TYLCV isolates from field samples: (1) RFLP of a DNA fragment amplified from the coat protein gene; (2) PAGE of a fragment amplified from the C2 gene; (3) dot-blot hybridisation. All methods enabled the detection of the TYLCVs and provided good indications for attributing them to one species or the other. However, for typing purposes, the RFLP method was the most reliable, due to the easily recognisable pattern produced by the two virus species present in Europe. Dot-blot hybridisation is less expensive for identifying TYLCVs in large numbers of samples, particularly when a mixture of two probes is used. PAGE of the C2 fragment is the fastest of the methods tested.     

阳春砂仁叶枯病药剂防治试验

室内药效测定以甲基托布津对砂仁叶枯菌的抑菌效果最好。田间小区防治试验以７０％甲基托布津１０００倍液效果最佳，２０％粉诱宁乳油１５００倍液和６４％杀毒矾Ｍ_８５００倍液对该病的的防治效果亦较好。     

薏苡叶枯病病原菌的分离鉴定与生物农药筛选

叶枯病是危害薏苡的主要病害之一,为明确引起薏苡叶枯病的病原菌种类,有效控制叶枯病的发生,本试验对病原菌进行了分离、纯化及形态学鉴定,选用常用的7种生物农药对病原菌进行毒力测定,并建立毒力回归方程,结果表明,通过分离鉴定明确该致病菌为平脐蠕孢属(Bipolaris);1%申嗪霉素悬浮剂和5%中生茵素对病原茵的抑制率较高,毒力较强,抑制率分别为100%、97.65%,EC_(50)分别为6.918 3和19.856 6μg/mL。     

Harpin xoo在水稻中表达提高对白叶枯病不同小种抗性

用剪叶接种法测定10个转hrf1基因水稻株系对15个水稻白叶枯病菌小种的抗性.所有的转基因系对JxOV和PXO79小种的抗性与受体对照相比显著提高,RT-PCR结果显示,在转化hrf1基因的抗病水稻中,信号传导基因npr1表达明显增强,表明转hrf1基因水稻可能通过激发水稻中信号传导基因的表达,提高对白叶枯病菌不同小种的抗性.     

神农架玉米大斑病暴发原因及防治对策

神农架地处鄂西北山区,气温偏凉而且多雨,年降水量900～1000mm。玉米是神农架主要粮食作物,常年种植玉米3333．33hm2以上。玉米大斑病是玉米生产上的常见的病害之一,历来由于发病较轻,没有引起足够重视,近几年来玉米大斑病发生趋重,2008年全区8个乡镇玉米大斑病普遍发生,局部暴发流行成灾,此病已成为影响神农架林区玉米高产的一个突出问题。为深入了解玉米大斑病发生的实际情况,正确分析病害发生原因,我们对发病较重的乡镇进行田间实地调查,向农民询问玉米品种、施肥等情况,提出本区相应的防治措施,以减少因大斑病造成的玉米产量损失,保证玉米生产安全。     

表达Harpin蛋白的芽孢杆菌工程菌防治水稻白叶枯病的研究

本文研究了生防促生芽孢杆菌OKB105、FZB42和以其为宿主菌的可外泌表达Harpin蛋白激发子的基因工程菌OKBHF、FZBHarpin对水稻白叶枯病的防治效果。菌株OKB105、FZB42、OKBHF和FZBHarpin温室防效分别为31.7%、23.6%、43.2%和56.7%;田间防效分别为29.8%、21.8%、40.4%和43.1%,表达Harpin蛋白的芽孢杆菌工程菌的防病效果显著高于出发菌株。两株生防芽孢杆菌及其工程菌对水稻均有良好的促生作用,特别是对水稻植株的生长促进明显,其中FZBHarpin使植株增高达15.86%。田间产量统计结果显示,OKBHF增产效果最显著,为14%,产量达8869 kg·hm^-2。工程菌比出发菌株显著提高水稻抗病性和促进植物生长,在农业生产上具有应用的潜力。     

Mitochondria and Cytoplasmic Male Sterility as Related to Southern Corn Leaf Blight

Abstract

The use of one source of cytoplasmic male steriity, leading to widespread uniformity of maize, coupled with the appearance of a new virulent race of Helminthosporium maydis made the Southern Corn Leaf Blight epidemic possible. The weather during 1970 was very suitable for the spread of the disease and thus the epidemic occurred. The possible role of cytoplasmic DNA, carried most probably by the mitochondria, in the susceptibility or resistance of various maize lines in discussed. The relationship of cytoplasmic male sterility and disease resistance or susceptibility is considered. The effects of the pathotoxin, produced by H. maydis, its uses as an experimental tool in research, and its potential uses in further investigations are described in detail.     

Tomato Breeding Lines Resistant and Tolerant to Tomato Yellow Leaf Curl Virus Issued from Lycopersicon hirsutum

ABSTRACT Two tomato yellow leaf curl virus (TYLCV)-resistant plants from accessions LA1777 and LA386 of the wild tomato species Lycopersicon hirsutum have been crossed. The resulting resistant F1 plants were crossed with the domesticated tomato L. esculentum, and a series of selfing was performed. At each generation, individuals were selected for resistance (no symptoms and undetectable viral DNA) and tolerance (no symptoms but with detectable viral DNA) following controlled massive and repeated inoculations with viruliferous whiteflies. A stable BC1F4 line (denominated 902) that does not segregate for resistance was obtained. This line does not support virus accumulation, even upon extensive whitefly-mediated inoculation of young seedlings, and does not need protection with nets or insecticides. Another stable BC1F4 line (denominated 908) was tolerant to the virus. Both lines have good horticultural characteristics and bear 80- to 120-g red fruits. Analysis of segregation of susceptibility, tolerance, and resistance during the BC1F1 to BC1F4 crosses indicated that tolerance is controlled by a dominant major gene and resistance by two to three additive recessive genes. The resistant and tolerant lines do not need to be protected by insecticides or nets.     

Effect of Film-forming Polymers on Control of Lily Leaf Blight Caused by Botrytis elliptica

The effectiveness of film-forming polyelectrolytes for the control of lily leaf blight caused by Botrytis elliptica was evaluated using laboratory a leaf disk assay, greenhouse tests and field trials. Among the six polyelectrolytes, 400ppm FO4240SH, FO4490SH and FO4550SH reduced the disease severity of lily leaf blight in leaf-disk tests. Both FO4240SH and FO4490SH also suppressed sporulation of the pathogen on leaf disks. In greenhouse tests, the number and size of lesions on leaves of Lilium oriental hybrid cv. Star Gazer were markedly reduced by FO4490SH and FO4550SH. Field trials showed that the effectiveness of FO4490SH was similar or better than that of procymidone on the reduction of lily leaf blight disease severity. The polymers had no harmful effects on the lily plants. The cationic polyelectrolytes FO4240SH, FO4490SH and FO4550SH reduced the percentage of conidial germination, inhibited germ-tube growth, and also suppressed the esterase production by germ tubes of B. elliptica. All the above evidence indicates that the disease control achieved with polyelectrolytes is due, at least in part, to the reduction of esterase secretion by B. elliptica.     

Photosynthetic performance of Hevea brasiliensis affected by South American Leaf Blight under field conditions

South American Leaf Blight (SALB), caused by the fungus Pseudocercospora ulei, is the principal rubber crop disease in Latin America. Several studies have focused on the genetics of resistance and the epidemiology of this disease, but few have analyzed the physiological alterations caused by SALB in Hevea brasiliensis. In addition, changes under field conditions are poorly understood. The present study aimed to analyze changes in gas exchange and chlorophyll a fluorescence traits in leaflets with different leaf stages and SALB severity levels from two H. brasiliensis clones with distinct susceptibility to disease in juvenile plants grown under field conditions (clonal garden). The photosynthetic performance was strongly limited in the high susceptibility clone (FX 3864), mainly in the young leaflets with maximum SALB severity (‘3’ and ‘4’), as compared to the low susceptibility clone (FX 4098). The principal alterations included a reduction in the photosynthetic rate (>?79%), stomatal conductance (>?85%), extrinsic water use efficiency (>?85%), and ability to capture, use and dissipate light energy in photosystem II, as compared to healthy leaflets. The damage was less intense in mature leaflets from both rubber tree clones. The favorable performance observed in clone FX 4098 means it is a potential candidate for commercial scale use under non-SALB escape conditions in the Amazon region.

     

Displacement of Tomato Yellow Leaf Curl Virus (TYLCV)-Sr by TYLCV-Is in Tomato Epidemics in Spain

ABSTRACT A progressive displacement of tomato yellow leaf curl virus (TYLCV)-Sr by TYLCV-Is was observed in tomato epidemics in southern Spain based on incidence data of both virus species obtained during surveys conducted between 1996 and 1998. Ecological factors that might be involved in such a displacement, such as competition of TYLCV-Sr and TYLCV-Is in tomato, transmission by local biotypes (B and Q) of Bemisia tabaci, and presence in weeds and alternate crops, have been analyzed. No selective advantage is observed for TYLCV-Sr or TYLCV-Is in tomato plants either infected via Agrobacterium tumefaciens or via B. tabaci. However, TYLCV-Is is more efficiently vectored by local biotypes of B. tabaci; and common bean, a bridge crop between tomato crops, is a host for TYLCV-Is but not TYLCV-Sr. Therefore, common bean acts as a reservoir for TYLCV-Is. These two factors are probably responsible for the displacement of TYLCV-Sr by TYLCV-Is as the causative agent of epidemics in tomato in southern Spain.     

番茄早疫病生防细菌B731的分离、鉴定及抑菌防病作用

利用对峙培养法,从分离自番茄根部土壤的细菌中筛选得1株对番茄早疫病菌具强拮抗活性的菌株B731.根据形态特征、生理生化反应及16S rDNA序列分析将其鉴定为枯草芽孢杆菌Bacillus subtilis.该菌在初始pH 7.0的NB培养液、装液量25 mL(250 mL锥形瓶)、28℃、120 r/min培养24～48 h抑菌能力最大,抑菌带宽达1.24 cm,且其在番茄植株及根际土壤中有很强的定殖能力.接种15d后,在番茄植株叶片或果实表面,其定殖量可保持在2×102 cfu/cm2以上;而在番茄根际土壤中,其定殖量可达104 cfu/g.菌株B731的代谢产物能有效抑制番茄早疫病菌分生孢子的萌发和菌丝生长,抑制率分别高达89.72％和82.62％.喷施于叶面,具有很好的防病效果,预防处理防效可高达81.83％.