Factors Influencing Development of Root Rot on Ginseng Caused by Cylindrocarpon destructans

ABSTRACT The fungus Cylindrocarpon destructans (Zins) Scholten is the cause of root rot (disappearing root rot) in many ginseng production areas in Canada. A total of 80 isolates of C. destructans were recovered from diseased roots in a survey of ginseng gardens in British Columbia from 2002-2004. Among these isolates, 49% were classified as highly virulent (causing lesions on unwounded mature roots) and 51% were weakly virulent (causing lesions only on previously wounded roots). Pectinase and polyphenoloxidase enzymes were produced in vitro by C. destructans isolates when they were grown on pectin and phenol as a substrate, respectively. However, highly virulent isolates produced significantly (P < 0.001) higher enzyme levels compared with weakly virulent isolates. Histopathological studies of ginseng roots inoculated with a highly virulent isolate revealed direct hyphal penetration through the epidermis, followed by intracellular hyphal growth in the cortex. Subsequent cell disintegration and accumulation of phenolic compounds was observed. Radial growth of highly and weakly virulent isolates on potato dextrose agar was highest at 18 and 21 degrees C, respectively and there was no growth at 35 degrees C. Mycelial mass production was significantly (P 相似文献   

White rot of Panax quinquefolius caused by Sclerotinia nivalis

American ginseng (Panax quinquefolius), one of the most well-known araliaceous perennial herbs, suffered from root rots and mortality in 2020 in Taibai County, Shaanxi Province, China, leading to 40%–60% yield losses. The diseased plants initially showed unevenly yellowing foliage, and yellow-brownish, water-soaked roots with internal softening. Subsequently, white fluffy mycelia manifested on the surface of diseased P. quinquefolius roots, followed by the appearance of black irregular sclerotia-like bodies. In this study, a fungal isolate (SS-TB, GenBank no. MT830866) was obtained from the infected roots. Based on the culture morphology, pathogenicity tests and phylogenetic analysis of the internal transcribed spacer (ITS) region, this isolate was identified as Sclerotinia nivalis. The optimum temperature for mycelial growth and sclerotial production was 20 ℃ and 15 ℃, respectively; the optimum pH for mycelial growth and sclerotial production was pH 6.0. This isolate grew faster and produced more sclerotia on potato dextrose agar than on other media. It infected ginseng roots with or without wounds, but inoculation of wounded roots led to more severe disease. S. nivalis also infected 43 of the 48 plant species tested, including vegetables, fruits, oil crops, and flowering plants from Fabaceae, Asteraceae, Solanaceae, Cucurbitaceae, Brassicaceae, Apiaceae, Rosaceae, Liliaceae, Chenopodiaceae, and Orchidaceae. It was nonpathogenic on Triticum aestivum, Zea mays, Anemone vitifolia, Ipomoea batatas, and Vaccinium sp. This study is the first report of S. nivalis causing white rot on P. quinquefolius.     

Root Rot of Miniature Roses Caused by Pythium helicoides

Miniature roses growing in an ebb-and-flow watering system developed dieback during the summer growing season of 1996 in Gifu Prefecture. The main diagnostic symptoms were chlorosis of leaf followed by blight, and a brown, water-soaked root rot followed by dieback. Pythium isolates were recovered from the rotted root. The isolates form proliferous ellipsoidal papillate sporangia, spherical smooth oogonia, elongate antheridia, and aplerotic oospores. The optimum temperature for hyphal growth was 35°C with a growth rate of 34 mm/24 hr. Optimum temperature of zoospore formation (25-30°C) was lower than that of mycelial growth, and zoospores were produced even at 10°C. The isolates were identified as P. helicoides on the basis of these characteristics. In pathogenicity tests disease severity was highest at the highest tested temperature (35°C) at which the disease naturally occurred in summer. Four days after inoculation, the leaves turned yellow and the roots had a water-soaked rot, followed by leaf blight and root dieback after 7 days. The disease transmission test showed that diseased plants were found throughout the bench after 10 days. Received 4 July 2001/ Accepted in revised form 10 October 2001     

Root and Collar Rot of Milkwort Caused by Cylindrocladium pauciramosum, a New Record for Europe

A new disease of milkwort (Polygala myrtifolia) was observed on several commercial nurseries in southern Italy. Diseased plants showed wilting, stunting, chlorosis or loss of foliage, and rotting of the basal stem as well as the crown and roots. A Cylindrocladium species was consistently found associated with crown, basal stem, and root lesions. The etiology of this disease was proved on milkwort, by fulfilling Koch's postulates. Two hundred Cylindrocladium isolates were collected from the most important Sicilian and Calabrian ornamental production areas from different host plants. Isolates were identified as Cylindrocladium pauciramosum (teleomorph Calonectria pauciramosa) on the basis of their obpyriform to broadly ellipsoidal terminal vesicles, conidiophore branching pattern, conidium morphology, as well as mating type studies with tester strains of C. pauciramosum for selected isolates. This is the first record of this pathogen from Europe and it is the first report of C. pauciramosum on milkwort.     

Black Rot of Artichoke Leaves Caused by Two Phoma Species in Japan

Phoma macrostoma var. incolorata and P. exigua var. exigua were isolated from leaf spots of artichoke in Mie Prefecture, Japan in June 1997. Colonies of P. macrostoma var. incolorata grew fast, pigmented the medium vinous without staining the mycelium, and changed blue with NaOH. Conidial size in culture was 3 to 10 μm × 2 to 4.5 μm. Colonies of P. exigua var. exigua grew fast without pigmentation and changed yellow-green with NaOH. The conidia were sometimes septate, and size of aseptate conidia was 4 to 9.5 μm × 2 to 3.5 μm. These fungi produced gray, round spots on artichoke leaves. This report is the first on the occurrence of artichoke black rot caused by P. macrostoma var. incolorata and P. exigua var. exigua in Japan. Received 5 July 2001/ Accepted in revised form 12 March 2002     

摩西球囊霉对紫花苜蓿烟色织孢霉根腐病的影响

紫花苜蓿Medicago sativa是一种优质的多年生豆科牧草,素有"牧草之王"的美称。根腐病是紫花苜蓿生产中的主要限制因素,可抑制植物生长,严重时导致植物死亡,造成巨大的经济损失。丛枝菌根真菌（Arbuscular mycorrhizal fungi,AM）广泛存在于农业系统中,可与植物根系形成内生菌根,提高宿主植物对营养元素和水分的吸收,增加植物产量和抗逆性。本研究以紫花苜蓿为试验材料,探究接种AM真菌摩西球囊霉Glomus mosseae对紫花苜蓿根腐病烟色织孢霉Microdochium tabacinum的影响。结果表明,摩西球囊霉可抑制烟色织孢霉的侵染,植株发病率降低了20.78%;病原菌的侵染显著抑制紫花苜蓿根系生长和养分吸收,植物地下生物量降低12.87%,根长降低20.52%,根系P含量降低了18.29%,丙二醛（MDA）含量提高了12.78%;AM真菌可以缓解病原菌的危害,促进紫花苜蓿生长,与不接种AM真菌的处理相比,地上生物量、地下生物量、根长分别提高了47.77%,38.67%和20.67%;防御酶超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性分别提高了42.25%、26.05%和33.62%;地上部分和地下部分P含量分别提高了58.63%和75.38%。     

芽孢杆菌BH_1防治大豆根腐病的效果及机制

芽孢杆菌BH1分离于大豆根际,在温室试验中表现出较好的防治效果。田间试验对尖孢镰刀菌引起的大豆根腐病防效达56.1%,增产7.6%。该菌株发酵无菌滤液对尖孢镰刀菌F3、茄孢镰刀菌W1和镰刀菌S1孢子萌发和菌丝生长有抑制作用;对热处理较稳定。对其抗利福平标记株B R+ 4与大豆根系的亲和性研究表明,BH1可定殖于无菌土和病土中生长的大豆根际,且动态变化趋势相似,但在无菌土中数量略高于病土。组织印记法表明:B R+ 4可在整个大豆根系生长。扫描电镜观察发现,BH1主要存在于根表凹陷处,在根尖或侧根处则很少。透射电镜观察,根细胞间隙内未检测到BH1。在大豆根际的定殖试验说明,B R+ 4与大豆根系有很好的亲和性,对营养和空间位点的竞争是其拮抗病原菌的主要机制。     

芽孢杆菌BH1防治大豆根腐病的效果及机制

芽孢杆菌BH1分离于大豆根际，在温室试验中表现出较好的防治效果。田间试验对尖孢镰刀菌引起的大豆根腐病防效达56．1％，增产7．6％。该菌株发酵无菌滤液对尖孢镰刀菌F3、茄孢镰刀菌W1和镰刀菌Sl孢子萌发和菌丝生长有抑制作用；对热处理较稳定。对其抗利福平标记株B-R^ -4与大豆根系的亲和性研究表明，BH1可定殖于无菌土和病土中生长的大豆根际，且动态变化趋势相似，但在无菌土中数量略高于病土。组织印记法表明：B-R^ -4可在整个大豆根系生长。扫描电镜观察发现，BH1主要存在于根表凹陷处，在根尖或侧根处则很少。透射电镜观察，根细胞间隙内未检测到BH1。在大豆根际的定殖试验说明，B-R^ -4与大豆根系有很好的亲和性，对营养和空间位点的竞争是其拈抗病原菌的主要机制。     

Alternaria Leaf Spot on Three Species of Pelargonium Caused by Alternaria alternata in Japan

A new disease of pelargonium (Pelargonium domesticum Bailey), ivy geranium (P. peltatum (L.) L'Hér. ex Ait.) and scented geranium (P. graveolens L'Hér.), primarily causing brown spots on leaves, was found in Kawasaki-shi in Kanagawa Prefecture and Tachikawa-shi in Tokyo. An Alternaria sp. was consistently isolated from these diseased leaves, and the isolates were pathogenic to their host leaves. Based on morphological characteristics, the causal fungus in all three cases was identified as Alternaria alternata (Fr.) Keissler. Because Alternaria leaf spot of geranium by A. alternata has already been reported, the pathogenicity of isolates from four groups of genus Pelargonium was investigated. The isolates from scented geranium were pathogenic only to their original host, but the isolates from pelargonium, ivy geranium and geranium were pathogenic to all groups of pelargonium. This is the first report of this disease on pelargonium, ivy geranium and scented geranium caused by A. alternata in Japan. We propose the names for these diseases as Alternaria leaf spot of pelargonium (kappan-byo), Alternaria leaf spot of ivy geranium (kappan-byo) and Alternaria leaf spot of scented geranium (kappan-byo). Received 11 December 2000/ Accepted in revised form 19 July 2001     

New Leaf Spot Disease of Cymbidium Species Caused by Fusarium subglutinans and Fusarium proliferatum

Fusarium species were consistently isolated from yellow, swollen spots with reddishbrown centers and small black spots on leaves of Cymbidium plants in the greenhouse. Fusarium subglutinans caused the yellow spots and Fusarium proliferatum caused either the yellow or the black spots. We propose the name “yellow spot” for the new disease. To denote differences in their pathogenicity to orchid plants, we designate the population causing yellow spot as race Y and that causing black spot as race B of F. proliferatum. Received 29 October 1999/ Accepted in revised form 10 March 2000     

Rhizoctonia Blight of Yacon Caused by Rhizoctonia solani AG-1 (IB)

Severe blight of stems and leaves caused by Rhizoctonia solani AG-1 (IB) was found on yacon (Smallanthus sonchifolius), a Compositae tuber crop, grown in Ehime Prefecture, Japan, from August to September 1996 and 1999. We named it “Rhizoctonia blight of yacon” as a new disease. Received 15 October 2001/ Accepted in revised form 25 November 2001     

Simulation of Epidemics Caused by Venturia inaequalis (Cooke) Aderh.1

We discuss simulation of apple scab epidemics based on analog computer models, multivariate regression analyses, and systems analyses. Details of underlying models and their scope for applications are emphasized. Monomolecular growth functions by Bertalanffy and Gompertz in analog computers permit fast simulation of disease progress curves. The models derived from multivariate analyses of field experiments on apple scab epidemics simulate closely the changes in infection rates. EPIVEN, our comprehensive and self–generating simulator of apple scab epidemics is reviewed and compared to a reduced model, also based on elements of the system “apple scab epidemic”.     

我国莲藕主产区莲藕田间杂草组成及群落特征

采用倒置“W”形9点取样法,对湖南益阳、湖北蔡甸、江苏吴江、浙江金华、四川都江堰5个地区的莲藕田间杂草进行调查统计,结果表明：莲藕田间杂草共25种（含变种）,隶属于19科、24属,其中禾本科、莎草科和雨久花科的杂草种类较多,共占杂草种类的36％;发生优势度较大的杂草为空心莲子草（ Alternanthera philoxe-roides）和浮萍（ Herba spirodelae）。基于物种优势度进行群落相似性聚类分析发现,湖南益阳与湖北蔡甸的莲藕田间杂草群落相似性最高,四川都江堰地区的莲藕田间杂草群落组成与其他4个地区的差异较大。     

Knot Formation Caused by Pseudomonas syringae subsp. savastanoi on Olive Plants Is hrp-Dependent

ABSTRACT The virulence of Pseudomonas syringae subsp. savastanoi, which causes hyperplastic symptoms (knots) on olive plants, is associated with secreted phytohormones. We identified a Tn5-induced mutant of P. syringae subsp. savastanoi that did not cause disease symptoms on olive plants although it was still able to produce phytohormones. In addition, the mutant failed to elicit a hypersensitive response in a nonhost plant. Molecular characterization of the mutant revealed that a single Tn5 insertion occurred within an open reading frame encoding a protein 92% identical to the HrcC protein of P. syringae pv. syringae. Moreover, sequence analysis revealed that the gene encoding the HrcC protein in P. syringae subsp. savastanoi was part of an operon that included five genes arranged as in other phytopathogenic bacteria. These results imply that hrp/hrc genes are functional in P. syringae subsp. savastanoi and that they play a key role in the pathogenicity of this plant pathogen.     

Experience of Brown Rot Caused by Pseudomonas solanacearum (Smith) Smith in Sweden1

Brown rot (Pseudomonas solanacearum [Smith] Smith) infection of 5% or less was found in potatoes from some fields in Southern Sweden at about 56° N in the years 1972 and 1973²⁾. The fields were irrigated with water from small streams. The pathogen has been isolated from a wild host, Solanum dulcamara, growing at the water's edge in one of the streams. The wild host is perennial and bacteria can overwinter in this host. Overwintering also occurred in artificially infected S. dulcamara at 59° N. No overwintering in soil has hitherto been demonstrated, in spite of experiments with artificially infested soil. Infections have probably originated from imported potatoes.     

四种重要实蝇类害虫对福建省造成的经济损失评估

实蝇类害虫是世界性检疫害虫,对福建省农作物造成为害的主要包含橘小实蝇、南亚寡鬃实蝇、瓜实蝇、具条实蝇4种。这4种实蝇类害虫给福建省水果、蔬菜带来较为严重的经济损失,并且由于防治过程中农药的使用,造成生态环境问题。本研究选取实蝇类害虫为害较为严重的福建省主要水果和蔬菜作为研究对象,从直接经济损失、防治费用和间接经济损失3个层面建立评估模型,并对2016年4种实蝇类害虫造成的经济损失进行评估,旨在通过评估经济损失情况,为今后防治政策的制定提供思路。研究结果显示,这4种实蝇类害虫对福建省造成的经济损失约为313.48亿元,其中直接经济损失约为221.74亿元,防治费用约为84.24亿元,间接经济损失约为7.5亿元。最后,本研究提出了重视有害生物灾情评估、完善经济损失评价方法,开展农户专业培训、提升防控技术水平,加强环境规制力度、发展绿色生态农业等政策建议。     

Green Mold Diseases of Agaricus and Pleurotus spp. Are Caused by Related but Phylogenetically Different Trichoderma Species

ABSTRACT Producers of champignon (Agaricus bisporus) and oyster mushroom (Pleurotus ostreatus) are facing recent incidents of green mold epidemics in Hungary. We examined 66 Trichoderma strains isolated from Agaricus compost and Pleurotus substrate samples from three Hungarian mushroom producing companies by a polymerase chain reaction-based diagnostic test for T. aggressivum, sequence analysis of the internal transcribed spacer region 1 (ITS1) and ITS2 and (selectively) of the fourth and fifth intron of translation elongation factor 1alpha (tef1alpha), and restriction fragment length polymorphism of mitochondrial DNA. Seven Trichoderma species were identified: T. aggressivum f. europaeum (17 isolates), T. harzianum (three isolates), T. longibrachiatum (four isolates), T. ghanense (one isolate), T. asperellum (four isolates), T. atroviride (nine isolates), and a still undescribed phylogenetic species, Trichoderma sp. DAOM 175924 (28 isolates). T. aggressivum f. europaeum was exclusively derived from A. bisporus compost, whereas Trichoderma sp. DAOM 175924 exclusively occurred in the substrate for Pleurotus cultivation. Sequences of the latter strains were co-specific with those for Trichoderma pathogens of P. ostreatus in Korea. The widespread occurrence of this new species raises questions as to why infections by it have just only recently been observed. Our data document that (i) green mold disease by T. aggressivum f. europaeum has geographically expanded to Central Europe; (ii) the green mold disease of P. ostreatus in Hungary is due to the same Trichoderma species as in Korea and the worldwide distribution of the new species indicates the possibility of spreading epidemics; and (iii) on mushroom farms, the two species are specialized on their different substrates.     

Red Stripe of Rice Is Caused by a Bacterium <Emphasis Type="Italic">Microbacterium</Emphasis> sp.

In an etiological study to identify the causal agent of red stripe of rice, white bacterial colonies were consistently isolated from all diseased leaf samples collected in Indonesia. All the bacterial isolates were pathogenic to rice and caused symptoms similar to red stripe. The bacterial infection in rice leaves was confirmed histologically. Bacterial masses were observed in the lumina of xylem vessels in the lesion area, especially in those of connecting strands. Analysis of the 16S rDNA of the causal bacterium gave best matches to the 16S rDNA sequence of Microbacterium spp. of Microbacteriaceae which includes Clavibacter. Received 9 September 1999/ Accepted in revised form 16 November 1999     

An Experiment to Assess Losses Caused by Frit-fly (Oscinella frit L) Shoot Attack and the Application of Phorate in a Crop of Sweet Corn (Zea mays L)

Wilt caused by the fungus Fusarium oxysporum f. sp. ciceris adversely affects the productivity of cultivated chickpea. For the management of this disease, seed and soil application formulations developed from another fungus, Trichoderma species, were evaluated. In pot experiments, T. harzianum-based formulations Pusa 5SD for seed dressing and Pusa Biopellet (PBP) 10G and Pusa Biogranule (PBG) 5 for soil application, and T. viride-based formulations Pusa 5SD for seed dressing and PBP 4G and PBG 4 for soil application, were found to be highly effective against the disease. A combination of PBP 4G (T. viride) for soil application and Pusa 5SD (T. harzianum) for seed treatment together with a fungicide, carboxin, provided the highest seed germination, shoot and root lengths and grain yield with the lowest incidence of wilt in chickpea under field conditions. Individually, soil application of PBP 4G, and seed treatment with Pusa 5SD were effective in reducing the incidence of wilt and increasing the grain yield of chickpea, but their effectiveness was greater when applied as a combination. Thus, combined application of the formulations of two different species of Trichoderma in two modes of application is recommended for the management of chickpea wilt.