Bacterial rot of witloof chicory roots caused by Erwinia chrysanthemi

Erwinia chrysanthemi (biovars 5 and 6) was isolated from unusual symptoms on witloof chicory, both in the field and in hydroponic culture, in Brittany in 1989 and 1990. Symptoms included a greyish-brown soft rot on the lower part of the root and the destruction of the cortical tissues. The cribrovascular and the medullary part of the bottom of the root sometimes became slimy. A few cases of vascular transmission were observed, which resulted in a red coloration of the infected vessels and a soft rot of the leaves.     

Bacterial soft rot of myoga (Zingiber mioga) caused by Erwinia chrysanthemi

In 2010, a bacterial soft rot was found on myoga [Zingiber mioga (Thunb.) Rosc.] in Japan. Initial small spots on flower buds rapidly enlarged while changing from light brown to brown. Diseased flower buds became completely rotten. Several bacteria isolated from the diseased tissues caused the same symptoms as those observed in the fields and were reisolated from the tissue. These bacteria were identified as Erwinia chrysanthemi and were classified into subdivision IV and biovar 3. This is the first report of bacterial soft rot of myoga in the world.     

香蕉品种对香蕉细菌性软腐病的抗性鉴定

由菊欧文氏杆菌香蕉致病变种[Dickeya paradisiaca(原名Pectobacterium chrysanthemi pv.paradisiaca)]引起的香蕉细菌性软腐病是我国新入侵的毁灭性香蕉病害,应用抗病品种将是防治该病害的有效方法.采用离体叶片法和盆栽法相结合的筛选方法对39个香蕉品种进行抗性鉴定,结果表明,供试品种对香蕉细菌性软腐病菌的抗性存在明显差异,其中表现高抗(HR)的品种为‘皇帝蕉’,抗病(R)品种为‘红河矮’,中抗(MR)品种为‘矮脚遁地蕾’和‘龙州中把’.离体和盆栽鉴定结果与品种田间抗病性一致,可有效、快速、准确地筛选出抗病品种.     

Infection of roots of Dieffenbachia maculata by the foliar blight and soft rot pathogen, Erwinia chrysanthemi

Erwinia chrysanthemi, the organism causing foliage blight, leaf spotting, basal stem rot and root rot of Dieffenbachia maculata, was shown to be capable of infecting via roots. Inoculated plants were sectioned and internal spread of the pathogen determined by 'sandwich' plating between two layers of Miller's selective medium. Light microscopy and SEM confirmed that the pathogen was present throughout the plant in the xylem. Resin ducts, previously claimed as being the route for systemic infection, were not found. Initially confined to the xylem, the pathogen spread intercellularly to the neighbouring parenchyma and, after about 8 days, pockets of infection, often surrounded by periderm–like tissues, were seen.     

117个玉米品种对禾谷镰孢根腐病的抗性鉴定及根腐病对苗势与产量的影响

为评价东北地区玉米主推品种对禾谷镰孢根腐病的抗性水平,探究根腐病发生与苗势、产量损失间的关系,采用人工接种方法鉴定东北地区117个玉米主推品种对禾谷镰孢根腐病的抗性水平,应用室内盆栽试验分析自交系LN810在施用氮、磷、钾及复合肥后对禾谷镰孢根腐病发生和苗势的影响,在田间对先玉335接种禾谷镰孢菌Fusarium graminearum后探究根腐病发生程度对其苗势及产量的影响。结果显示,117个玉米品种对禾谷镰孢根腐病的抗性差异明显,鉴定出高抗品种14个,抗病品种44个,中抗品种47个,感病品种12个,其中表现中抗以上的品种占89.74%,且中早熟材料均表现为抗性。与未施肥相比,施用磷钾肥后玉米禾谷镰孢根腐病发生率最低,为22.03%。按照禾谷镰孢根腐病发生程度从轻到重将先玉335群体划分为一、二、三类苗,级别越高苗势越弱,产量测定发现二、三类苗的平均产量较一类苗的平均产量分别下降了39.97%和76.39%。表明东北地区主推玉米品种大部分对禾谷镰孢根腐病表现出抗性,但仍有部分品种存在较大感病风险,且该病害的发生程度与幼苗长势和产量呈负相关,施用磷钾肥可降低该病害的发生率。     

Dry rot of potatoes caused by Gliocladium roseum

The pathogenicity of Gliocladium roseum, isolated in a previous study as the sole organism from potato tubers with typical Fusarium dry-rot lesions, was investigated. Although usually considered to be a saprophyte, G. roseum was pathogenic to potato tubers (cv. Up-to-date) after artificial inoculation. It caused raised dry-rot lesions from which it was consistently reisolated. This is the first report that dry rot of potato tubers is caused by G. roseum .     

Root rot of lavender caused by Phytophthora nicotianae

Lavender (Lavandula angustifolia) plants with rotted roots and discoloured vascular systems consistently yielded cultures of fungi that were identified as Phytophthora nicotianae van Breda de Haan (= P. parasitica). Inoculation experiments using either zoospore suspensions or mycelial fragments were successful in reproducing symptoms originally observed on wilting and dying plants. Lavender is a new host for P. nicotianae.     

Root rot of cabbage caused by Phytophthora drechsleri

A root rot of cabbage is reported from South Africa. The causal pathogen was identified as Phytophthora drechsleri , based on morphological characters and electrophoretic patterns of soluble proteins.     

Studies on the chemical control of chrysanthemum white rust caused by Puccinia horiana

Experiments evaluating the curative and protective effect of sprays of benodanil, bitertanol, oxycarboxin, triadimefon, triforine and propiconazole, and intensive oxycarboxin fog and triforine spray regimes, against chrysanthemum white rust are described. All treatments reduced the disease when applied before symptoms developed but only propiconazole completely prevented disease development. A single spray of propiconazole applied 4–8 days after inoculation was sufficient to eradicate infection. This fungicide was also found to eliminate symptomless infection from cuttings when used as a dip prior to planting, or as two sprays after planting. When sporulation had occurred, three sprays of propiconazole or benodanil killed the telia, but viable telia were still present after three sprays of oxycarboxin, triadimefon or triforine. When applied as single protective sprays none of these fungicides consistently prevented infection, although levels were considerably reduced when application was made 2–3 days before exposure to the disease. Observational trials indicate that although propiconazole has some growth retardant effect it does not appear to present any significant phytotoxicity problems, either as a spray or as soil residue. As a result of this work propiconazole has been successfully used in a statutory eradication campaign against this rust. To avoid the possible development of resistance, it is suggested that its use should be confined to actual outbreaks, or when it is suspected that plants or cuttings may have become infected.     

Root rot of hyacinths caused by species of Pythium

The root rot widely seen in hyacinth was found to be caused byPythium spp. instead of byFusarium culmorum. Of sixPythium species isolated, three, includedP. ultimum andP. violae, were investigated in glasshouse experiments and their pathogenicity demonstrated. In these experiments plants were successfully grown in containers in which an aqueous mist was maintained, or in water cultures. In experimental plots on infected soil, Dexon, a fungicide selective for Pythiaceae, distinctly reduced the number of dead plants and increased yield and bulb size, thus confirming the role ofPythium in causing root rot. Practical application of Dexon deserves further attention.     

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 tree lucerne caused by Phytophthora nicotianae

Phytophthora nicotianae Breda de Haan was consistently isolated from rotted roots and discoloured vascular tissues of tree lucerne ( Chamaecytisus palmensis ). It was identified with the aid of total DNA restriction fragment length polymorphisms and morphological characters. Pathogenicity was demonstrated by inoculation. This is the first record of P. nicotianae on tree lucerne in South Africa.     

Bacterial rot of Chinese yam caused by Pseudomonas allii

Tuber rot is a major problem for the commercialization of the under-utilized Chinese yam (Dioscorea polystachya ‘Nagaimo’), a tuber rich in nutrients and bioactive, health-promoting metabolites. Black to dark brown discoloration or indistinct lesions form on the surface of the tubers, and the discoloration spreads to internal tissues. Pseudomonas-like bacteria were isolated from lesions, caused the same symptoms in tubers after inoculation, and were identified as Pseudomonas allii based on phenotypic characteristics and phylogenetic features. This is the first report of bacterial rot caused by P. allii in Chinese yam.

     

Storage rot of swede caused by Phytophthora sp.

During long-term storage trials of swedes ( Brassica napus ) carried out during five seasons between 1982 and 1987, storage rots caused by a Phytophthora sp. were observed, the first report of the disease in the UK.     

Chemical control of the olive rot caused by Glomerella cingulata1

The effect of various fungicides on Glomerella cingulata, the causal agent of a serious rot of olive fruits, was evaluated both in vitro and in the field. The following fungicides were tested: copper oxychloride, Bordeaux mixture, ziram, myclobutanil, hexaconazole, metiram, bitertanol and benomyl. Field trials were carried out in Calabria (southern Italy) for 2 years on two olive cultivars, Ottobratica (susceptible) and Sinopolese (resistant). The minimum effective concentrations of bitertanol, hexaconazole, myclobutanil, benomyl, metiram, ziram, and copper oxychloride on mycelial growth in vitro were < 5, < 50, < 50, < 1000, < 1000, < 1000, < 1000 μg ml^?1, respectively. The ED90 values for conidial germination were 0.01, 0.02, 50, 50, 1000, 1000, and 1000 μg ml^?1 of benomyl, ziram, myclobutanil, copper oxychloride, bitertanol, hexaconazole and metiram, respectively. In field trials, Bordeaux mixture and copper oxychloride proved to be the most effective products; however ziram, myclobutanil, bitertanol, metiram, and hexaconazole reduced the incidence of fruit rot significantly.