Use of survival analysis to assess management options for ray blight in Australian pyrethrum fields

The effects of fungicide, cultivar and plant density on the time‐to‐death of pyrethrum flowers affected by ray blight (caused by Phoma ligulicola var. inoxydablis) in Australia were analysed using nonparametric Kaplan–Meier (KM) estimates and accelerated failure time (AFT) models with a Weibull probability distribution. Analyses using KM estimates and AFT models yielded similar results. The median survival time (T) for all flowers in the fungicide trial was estimated at 53 days [95% confidence interval (CI) = 43–53] in 2000 and 60 days (CI = 51–60) in 2001. In both years, all fungicides tested except copper oxychloride significantly (P ≤ 0·0495) increased the duration of flower survival compared with nontreated plots. Significant variation (P < 0·0001) was noted between years and among four cultivars in terms of flower survival, with T values for different cultivars ranging from 41 to 81 days, and averaging 69 days (CI = 60–69) in 2005 and 64 days (CI = 56–64) in 2006 for all cultivars. Planting at a quarter the density currently recommended increased flower survival by 41·8% (χ² = 29·19; P < 0·0001), but did not increase yield. Linear regression indicated that defoliation severity accounted for at least 94% of variation in median survival time. Improved management may be achieved via an integrated strategy incorporating these factors.     

Tan spot: a new disease of pyrethrum caused by Microsphaeropsis tanaceti sp. nov.

The isolation frequency of Microsphaeropsis sp. in spring in association with necrotic lesions on leaves in Tasmanian pyrethrum (Tanacetum cinerariifolium) fields has increased substantially since first identification in 2001. Examination of morphological features and sequencing of the internal transcribed spacer region (ITS) resulted in the identification of a new species, herein described as Microsphaeropsis tanaceti sp. nov. The pathogenicity of three M. tanaceti isolates to two pyrethrum cultivars was confirmed by inoculating glasshouse‐grown plants in three experiments. No significant differences in the susceptibility of the two cultivars to infection by M. tanaceti were found. Symptoms were tan‐coloured spots which coalesced around the margins of the leaves. Therefore, the name ‘tan spot’ is proposed for this new disease of pyrethrum. The sensitivity of seven M. tanaceti isolates to difenoconazole and azoxystrobin, commonly used fungicides for the management of foliar diseases in spring, was assessed under in vitro conditions. Sensitivity testing for difenoconazole was conducted using a mycelial growth assay on potato dextrose agar, whilst testing for sensitivity to azoxystrobin used a conidial germination assay on water agar. Microsphaeropsis tanaceti was found to be more sensitive to azoxystrobin than difenoconazole, with complete inhibition of conidial germination at concentrations above 0·625 µg a.i. mL^?1. By comparison, concentrations of 50 µg a.i. difenoconazole mL^?1 or greater were required for significant inhibition of mycelial growth. It therefore appears likely that there is currently some control of tan spot as a result of the use of azoxystrobin and to a lesser extent, difenoconazole, for the control of other diseases.     

Infection process of Stagonosporopsis tanaceti in pyrethrum seed and seedlings

Ray blight disease of pyrethrum (Tanacetum cinerariifolium) is caused by Stagonosporopsis tanaceti, with infected seed being a major means of transmission of this fungal pathogen. The infection process of S. tanaceti in pyrethrum seed and seedlings was determined. Infection hyphae only infected the outer and inner layers of the seed coat and not the embryo of naturally infected pyrethrum seed. During the process of germination of infected seed, S. tanaceti from the seed coat infected the developing embryo and cotyledon, resulting in pre‐ and post‐emergence death, depending on the level of infection in the seed coat. Pre‐emergence death occurred due to disintegration of the infected embryo, which was replaced by hyphae and extracellular anthocyanin‐like material (EAM) at 7 days after incubation (dai). Post‐emergence death occurred after both epidermal and cortical tissues of infected cotyledons at the crown/hypocotyl region disintegrated due to colonization by hyphae. Moreover, most of the tissues of the vascular bundles and cortical tissues contained heavy depositions of EAM at 10–14 dai. In 6‐week‐old infected seedlings, hyphae were confined to the epidermis and the cortical tissues at the crown/hypocotyl regions; the vascular bundles of both infected and uninfected regions, and cortical tissues of the uninfected regions of the seedlings were completely free from infection hyphae and EAM. These findings provide a better understanding of the early stages of the disease cycle of S. tanaceti and will lead to improved control measures for seedborne infection using seed treatments.     

Xanthomonas arboricola disease of hazelnut: current status and future perspectives for its management

This review presents an overview of bacterial blight, the predominant and emerging hazelnut disease worldwide. Here, disease symptomatologies, disease cycle, epidemiology, detection and identification methods are thoroughly discussed. It also focuses on plant health regulations and control strategies. The information reported throughout the review could help to give a better understanding of the hazelnut–bacterial blight pathosystem. A thorough knowledge of this pathosystem is important for the effective management of bacterial blight across the hazelnut orchards of the world.     

Dynamics of the ascospore dispersal of Stagonosporopsis citrulli,a causal agent of gummy stem blight of cucurbits

Sexually reproduced, airborne ascospores of Stagonosporopsis citrulli may play a role in its dispersal. S. citrulli causes gummy stem blight (GSB), one of the most important foliar diseases of cucurbits. Four studies were conducted with S. citrulli to investigate for how long ascospores are released and how far they can be dispersed from a source field. In the first study, colonized watermelon debris was sampled during three seasons and samples were assayed for ascospore release. Ascospores were detected 292, 313, and 306 days after inoculation of the source. In the second study, the active release of ascospores from pseudothecia in a Petri dish was monitored for 7 days. The release of ascospores decreased by ≤90% from 1 day after the start of the assay until 7 days after. In the third study, trap plant assays were conducted to measure the dispersal gradient of ascospores up to 366 m from the source. Generally, frequency of pathogen recovery from trap plants decreased with increasing distance from the source. The ascospore dispersal data fitted the exponential model better than the power law model. In the final study, dispersal experiments were conducted under controlled conditions. The incidence of GSB decreased with increasing distance, up to 55 m, from the source. It was concluded that ascospores of S. citrulli can serve as primary inoculum for epidemics and could easily spread among fields. Debris from cucurbit crops can be the source of ascospores for up to 10 months and should be cleared expeditiously.     

花生白绢病互作研究进展

花生白绢病是由齐整小核菌Sclerotium rolfsii Sacc.引起的发生在花生茎基部的真菌病害,严重制约花生的品质与产量。本研究利用稀释涂布法从怀牛膝根际土壤中分离纯化了116株放线菌,并从中筛选鉴定了能够防控花生白绢病的菌株。通过平板对峙试验筛选得到两株抑菌活性较好且稳定的菌株Soil-1-5和Soil-3-28,它们对齐整小核菌的抑制率分别为80.43%和92.34%。根据形态学观察、生理生化试验及16S rRNA基因序列分析鉴定,两株菌分别被鉴定为疮痂链霉菌Streptomyces scabiei和藤黄灰链霉菌Streptomyces luteogriseus。采用菌丝生长速率法测定了拮抗菌株无菌发酵滤液对植物病原菌的抑制作用。结果表明,菌株Soil-1-5和Soil-3-28的无菌发酵滤液稀释5倍后对齐整小核菌的抑制率分别为73.67%和57.11%,且对禾谷镰孢菌等6种植物病原菌均有不同程度的抑制作用。此外,两菌株的无菌发酵滤液对齐整小核菌菌核萌发和菌核形成也有较好拮抗作用。盆栽试验结果表明,菌株Soil-1-5和Soil-3-28对花生白绢病的防治效果分别为51.92%和31.74%,其中菌株Soil-3-28对花生生长有促进作用。综上,菌株Soil-1-5和Soil-3-28对花生白绢病有较好的防治效果,具有潜在应用价值。

     

广西苦瓜蔓枯病的病原分离与鉴定

正苦瓜(Momordica charantia L.),为葫芦科苦瓜属蔓生草本植物,既可作为蔬菜食用,也可以作为药材~([1-2]),还是我国"南菜北运"的重要瓜类蔬菜。随着苦瓜栽培面积的不断扩大,特别是设施大棚栽培面积的扩大,苦瓜蔓枯病的发生为害日趋严重。近年来,广西部分设施大棚中苦瓜植株蔓枯病发病率超过80%,造成严重的经济损失。蔓枯病     

新疆库尔勒香梨火疫病的发生特点及防控建议

梨火疫病(fire blight)是由解淀粉欧文氏菌Erwinia amylovora引起的蔷薇科果树毁灭性病害。2017年首次在新疆巴音郭楞蒙古自治州发生,对库尔勒香梨产业造成严重危害和经济损失。本文总结5年来库尔勒香梨火疫病发生危害特点,详细描述了病害的田间症状表现,提出了防治建议,并对当前库尔勒香梨火疫病防治中存在的问题进行了讨论。     

鸡骨草叶枯病调查及其病原鉴定

在广西鸡骨草种植基地,发现一种发生严重的叶枯病,植株自下部叶片开始枯黄,然后向上蔓延,严重时整株枯死。经田间调查、标本采集、病原菌分离、形态学鉴定及致病性测定,明确该病害由丝核菌属（Rhizoctonia）引起。该病害在田间的发病率为69%～88%,病情指数为17.4～34.6。     

云南魔芋新病害—疫病病原菌的鉴定

<正>魔芋为天南星科(Araceae)魔芋属(Amorphophallus Blume)植物,是富含葡甘露聚糖的经济作物。随着人们对魔芋葡甘露聚糖的进一步研究和深度开发利用,魔芋的生产越来越受到重视,种植方式也由传统的半野生零星种植转向规模化大面积种植。云南是魔芋的起源中心之一[1],其气候环境非常适宜魔芋的生长和种植,但由于规模化种植程度的扩大以及芋农较为粗放的栽培管理方式,魔芋病害日趋严重,新病害亦不断出现。20世纪90年代初,我国魔芋有3种主要病害,现已增至11种。最近在云南省魔芋不同生育期的叶片及茎杆上又发现一种新病害——魔芋疫病。该病水渍状的黑     

稻糠与浮萍控制稻田杂草和稻纹枯病初步研究

温室盆栽和田间小区试验研究了稻糠、稻草糠、浮萍和满江红对稻田主要杂草和水稻纹枯病的控制作用,以及对水稻生长及产量的影响。结果表明,单独施用稻糠、稻草糠、浮萍和满江红对水稻分蘖、株高、生物量和产量无显著影响,但可明显抑制稗草的萌发、降低其生物产量;对移栽的莎草、鸭舌草、牛毛毡的株高、鲜重控制效果不一。稻糠加浮萍可显著提高对主要杂草和水稻纹枯病的控制效果,且对水稻无明显影响。     

珠海非洲菊疫病的鉴定和防治

１９９６年,珠海非洲菊生产基地非洲菊出现萎蔫症状,大量植株死亡,感病品种年发病率达４０％～５０％。经病情调查和病原菌分离鉴定明确,该病由ＰｈｙｔｏｐｈｔｈｏｒａｃｒｙｐｔｏｇｅａＰｅｔｈｙｂｒｉｄｇｅ＆Ｌａｆｅｒｔｙ和Ｐ．ｃａｃｔｏｒｕｍＳｃｈｒｏｔｅｒ所致,前者为主要病原。发病程度与温度、田间湿度及品种抗病性密切相关。室内药剂筛选试验表明,甲霜灵－锰锌抑菌效果最好;杀毒矾次之。田间选种抗病品种、作高畦、改喷灌为滴灌、拔除病株、药剂防治等措施,防效较好。     

辽宁轮叶党参斑枯病发生初报

本文首次报道了辽宁省药用植物轮叶党参斑枯病的发生危害、症状描述及病原菌的形态特征,并进行了病原菌的分离和纯化。分离得到的菌株按照柯赫氏法则进行了致病性测定。初步研究结果表明,轮叶党参斑枯病是由真菌党参壳针孢(Septoria codonopsidis Ziling)侵染所致。针对此病害的发生特点,本文初步提出了相应的防治建议。     

Phytophthora infestans: a review of past and current studies on potato late blight

Phytophthora infestans is the causal agent of potato late blight. Genotypes of Japanese populations of P. infestans have been classified as US-1, JP-1, JP-2, JP-3, and JP-4 based on analyses of DNA polymorphisms. These populations may have been introduced to Japan by the migration of P. infestans from other countries and by domestic changes produced through sexual and asexual propagation. Resistance to late blight has been an ongoing desire of potato farmers in Japan and elsewhere. Recurrent backcrossing of Solanum demissum to varieties of S. tuberosum has been used to transfer late blight resistance. Many varieties carry the R1 gene, whereas others carry R2, R3, and/or R4. However, R genes provided only transient resistance to late blight. New races rapidly overcome R-gene-mediated resistance. The R genes of potato generally encode receptors that recognize secretory effector (Avr) proteins produced by P. infestans. These effector proteins induce robust resistance in potato varieties containing R genes, while they suppress resistance in potato varieties lacking R genes. Conserved molecules from Phytophthora species such as fatty acids, glucans, and elicitins also act as elicitors in Solanaceae species. These P. infestans-derived elicitors induce defensive reactions, including the accumulation of phytoalexins and hypersensitive cell death. A future challenge will be to combine our accumulated knowledge with that from other scientific fields to develop a disease management approach for late blight.     

水稻纹枯病生防细菌筛选及其与病原菌侵染垫形成的关系

为筛选对立枯丝核菌Rhizoctonia solani具有拮抗作用的生防细菌,利用稀释涂布平板法,从吉林省水稻纹枯病样中分离筛选出对立枯丝核菌AG-1A具有高拮抗活性的生防菌株,通过gyrB基因序列分析鉴定其分类地位,并采用离体侵染试验和温室防治试验测定筛选生防菌株对水稻纹枯病的防效,在显微镜下观察生防菌株预处理后接种病原菌的水稻叶片表面的菌丝生长情况,分析其生防机理。结果显示,从水稻纹枯病样中共分离获得35株菌株,其中菌株ND11对立枯丝核菌AG-1A的抑制率和抑菌圈直径最大,分别为74.12%和31.50 mm。基于gyrB基因序列分析最终将菌株ND11鉴定为短小芽胞杆菌Bacillus pumilus;该菌株能够减缓立枯丝核菌AG-1A的侵染速度,抑制其侵染垫的形成,对水稻纹枯病的温室防效达70.69%以上。表明短小芽胞杆菌菌株ND11能够通过抑制立枯丝核菌侵染垫的形成来防治水稻纹枯病,且防效较好,具有开发为生防菌剂的潜力。     

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。     

生物炭对小麦赤霉病的防治效果及产量的影响

为探索生物炭对小麦赤霉病的防治效果和对产量的影响,设置小麦播种前、返青拔节期单施或两个时期均施生物炭处理,在小麦分蘖期人工接种病麦粒,在抽穗扬花期采用孢子捕捉器对穗层空气中的赤霉病菌孢子数量进行动态监测,并在乳熟期调查各处理的病穗率和病情指数,成熟期测定各处理的理论产量、实际产量和籽粒中脱氧镰刀菌烯醇(deoxynivalenol,DON)毒素的含量。结果表明,施用生物炭后穗层赤霉病菌孢子的数量显著降低,赤霉病病情指数降低,且以基施和返青拔节期追施13 500 kg/hm~2生物炭的处理最优;施用生物炭后小麦千粒重和株高均显著增加(P0.05),其中基施和追施13 500 kg/hm~2生物炭的处理较对照处理增产29.5%(P0.05)。     

Breeding approaches for bacterial leaf blight resistance in rice (Oryza sativa L.), current status and future directions

Bacterial leaf blight (BLB) is one of the most serious threats to the rice crop in irrigated and rainfed areas of the world. It is caused by Xanthomonas oryzae pv. oryzae and has been known for more than a century. Through rigorous screening and selection, a number of resistant cultivars have been produced and utilized, but resistance was overcome by the development of mutant strains of pathogen and by the dynamic change in Xoo populations. About 38 resistance genes have been reported in rice against the disease and a few have been cloned. The pyramiding of several resistance genes through marker assisted selection has been a quite effective strategy for combating the disease. However, new powerful tools such as transgenics have been introduced to make a significant impact. The purpose of this mini-review is to consolidate the existing knowledge about bacterial leaf blight in rice and the progress made both in conventional as well as in molecular dimensions of breeding together with potential findings and constraints.     

7种杀菌剂对水稻白叶枯病防效评价

为科学合理选用防治白叶枯病的杀菌剂,本研究采用田间人工剪叶接种方法,开展了7种杀菌剂对白叶枯病防效评价。测试的杀菌剂对白叶枯病的田间防效和病斑抑制率均差异显著,其中20%噻唑锌SC防效最好,其次是20%噻菌铜SC,其他药剂防效和病斑抑制效果均较差。20%噻唑锌SC 450.00 mL/hm~2喷施2次处理的防效达62.84%、病斑抑制率为73.11%;20%噻菌铜SC 450.00 mL/hm~2防效为43.15%,病斑抑制率为54.84%。高效药剂的合理选用对提高病害防效具有显著作用。20%噻唑锌SC和20%噻菌铜SC是目前防治白叶枯病的较好药剂,建议轮换使用。     

半夏疫病病原鉴定和防治研究

为了明确甘肃清水半夏疫病的病原及其防治药剂,对该病病原菌进行了分离鉴定,并筛选防治该病的药剂。结果表明:半夏疫病的病原为寄生疫霉(Phytophthora parasitica Dast.),寄生疫霉菌丝生长最适pH、温度分别为6.8与27.3℃;室内药效比较表明,58%甲霜灵.锰锌可湿性粉剂和70%甲基硫菌灵可湿性粉剂药效最好,1 200倍抑菌率均为100%;田间药效试验表明,58%甲霜灵.锰锌可湿性粉剂500倍液药效最好,施药2次防效为97.4%,70%甲基硫菌灵可湿性粉剂500倍液施药2次后防效仅达71.5%。