First report of bacterial leaf blight on cosmos (Cosmos bipinnatus Cav.) caused by Pseudomonas cichorii in Japan

Since 2006, a commercial grower in Japan has noted a leaf blight symptom on potted cosmos plants grown in a field. In August 2012, a Pseudomonas-like bacterium was isolated from the symptomatic leaves and found to cause the same symptom on cosmos seedlings after inoculation. On the basis of bacteriological and phylogenetic analyses, the causative bacterium was identified as Pseudomonas cichorii. This is the first report of bacterial leaf blight on cosmos caused by P. cichorii in Japan.     

Anthracnose of sweet pepper caused by Colletotrichum scovillei in Japan

Severe fruit rot of sweet pepper was found in Shimane, Hyogo, Chiba, Toyama, and Nagano prefectures, Japan from 2005 to 2011. Dark, sunken spots with concentric rings of orange conidial masses appeared on fruits. Pathogenic isolates from diseased fruits in the prefectures were identified as Colletotrichum scovillei. This species was added to the pathogens of sweet pepper anthracnose in Japan. The representative isolate was pathogenic to sweet pepper, tomato and chili pepper fruits, kidney bean pod, azuki bean, pea and strawberry leaves, but a caused no symptoms on cucumber or carrot in inoculation tests.     

Growth of bell pepper plants (Capsicum annuum) affected by coloured covers

While a plant utilizes the full spectrum of visible light, some colours of light have more important applications than others. The aim of this study was to evaluate the responses of bell pepper plants grown under coloured covers. Bell pepper plants (Capsicum annuum) were grown hydroponically in a greenhouse in Tunja, Colombia, under different light quality regimes that were obtained with polypropylene films (yellow, green, blue, transparent, red, and a control without a plastic film cover). Conventional growth indices were calculated or measured as response variables. All of the evaluated parameters were influenced in a different ways by the colour of the covers, e.g. the leaf area was higher under the green and blue covers. The highest water uptake was found in the plants grown under the blue film. Plants under the yellow cover presented higher water use efficiency than the other treatments. The chlorophyll content index was higher under the blue, green and transparent covers. Based on these results, a coloured cover that favors most of the growth indices of plants cannot be selected; however, according to the needs of growers, the supplemental light quality can be used to achieve a specific effect.     

The effectiveness of postharvest hot water dipping on the control of grey and black moulds in sweet red pepper (Capsicum annuum)

The effectiveness of hot water dipping on the control of grey mould, caused by Botrytis cinerea , and black mould, caused by Alternaria alternata on sweet red pepper quality was investigated. Dipping naturally infected or artificially inoculated fruit at 508C for 3 min completely inhibited, or significantly reduced, decay development caused by B. cinerea and A. alternata , respectively. Heat damage was observed on fruit dipped for 5 min at 50°C, or at 55°C for 1 min or longer. Damage appeared as cracks and pitting on the fruit surface. Spore germination and germ tube elongation in vitro was inversely related to the duration of exposure or to the range of temperature used. The ET₅₀ for spore germination for B. cinerea was 3.2, 1.5 and 0.8 min, and for A. alternata 8.8, 4.2 and 1.4 min, at 45, 50 and 55°C, respectively. The ET₅₀ for germ tube elongation for Botrytis was 2.6, 0.9 and 0.5 min, and for Alternaria , 7.2, 2.5 and 1.6 min, at 45, 50 and 55°C. The mode of action of hot water dips on decay of pepper appears to be by direct interaction with the fungi.     

Two Hungarian isolates of cucumber mosaic virus from sweet pepper (Capsicum annuum) and melon (Cucumis melo): Identification and antiserum preparation

Two Hungarian virus isolates from sweet pepper (K8) and melon (S4) were identified as cucumber mosaic virus (CMV) on the basis of host plant reactions and serology. The isolates were purified and antisera prepared. Homologous antiserum titers in double-diffusion tests were 256 (K8) and 512 (S4). They were serologically closely related to each other and to other CMV isolates. On the basis of symptoms they belong to different symptomatological groups of CMV; this was supported by serological properties. Sedimentation coefficients were c. 93 S, at 2 mg ml^–1. Purified preparations, stained with 2% uranyl acetate, showed spherical particles. In ELISA purified preparations reacted with each other's antisera.Samenvatting Twee hongaarse virusisolaten uit paprika (K8) en meloen (S4) werden geïdentificeerd als komkommermozaïekvirus (CMV) met behulp van toetsplanten en serologie. Beide isolaten werden gezuiverd en er werden antisera tegen bereid. De homologe titers van de antisera in de agar-geldiffusietoets bedroegen 256 (K8) en 512 (S4). K8 en S4 waren serologisch nauw verwant aan elkaar, evenals aan andere CMV-isolaten. Op grond van hun symptomen op toetsplanten behoren ze tot verschillende symptomatologische groepen van CMV. Dit laatste werd gesteund door de serologische eigenschappen. Beide isolaten hebben een sedimentatiecoëfficiënt van ca 93 S, bij een concentratie van 2 mg ml^–1. Gezuiverde preparaten, gekleurd met 2% uranylacetaat, bleken bolvormige deeltjes te bevatten. In ELISA reageerden gezuiverde preparaten van K8 en S4 met elkaars antisera.     

Bacterial leaf spot and blight of crucifer plants (Brassicaceae) caused by Pseudomonas syringae pv. maculicola and P. cannabina pv. alisalensis

Bacterial leaf spot and blight diseases caused by Pseudomonas syringae pv. maculicola (Psm) and P. cannabina pv. alisalensis (Pcal) are becoming a significant concern for producers of crucifer crops worldwide. Since Psm was first described in 1911, many have reported on its diverse phenotypic, genetic and pathogenic characteristics. Japanese isolates of Psm are also heterogeneous and differ in their host preferences. Pcal was first described in 2002 and has quickly spread globally. Recent work demonstrated that some isolates that had been identified as Psm are actually Pcal. Pcal was also shown to be split into two groups, A and B, based on bacteriological properties, genetic traits and pathogenicity. Group A of Pcal consists mostly of isolates from Japanese radish and radish, isolated before 1990s, that are more aggressive on radish leaves but less aggressive on other Brassica plants compared with group B. Group B of Pcal consists of recent isolates from various crucifer plants including the pathotype of Pcal. In this review, we suggest that group A of Pcal may have existed since the 1950s and survived as a relatively minor pathogen on radish or Japanese radish, whereas group B emerged in the late 1990s, causing global epidemics because of its stronger virulence on various Brassica crops. We also suggest that emergence of a new group of a pathogenic bacterium may cause a re-emergence or new epidemics of a disease that previously was of minor importance.     

Bacterial leaf spot of bougainvillea caused by Pseudomonas andropogonis in Brunei Darussalam

A leaf spot disease was found widespread on Bougainvillea in Brunei Darussalam. Leaf spots were characterized by circular to irregular brown necrotic areas with yellow haloes. A non-fluorescent bacterium was isolated consistently from the lesions and confirmed as the causal agent by Koch's postulates. On the basis of biochemical characterization and inoculation tests, the bacterium was identified as Pseudomonas andropogonis. This is the first report of a bacterial disease on bougainvillea in Brunei Darussalam.     

A garlic (Allium sativum) leaf blight caused by Stemphylium vesicarium in Brazil

The causal agent of a fohar disease of garlic ( Allium sutivum ) was identified as Stemphylium resicarium (Wallr) Simm Disease symptoms were reproduced on garlic leases 8 to 10 days after inoculation in a greenhouse (temperature range 22-26 C) Onion and tomato, two previously reported hosts of S, testcarnon. were also artificially infected with the isolate from garlic. This is believed to be the first report of S. testcarnom causing a severe leaf blight of garlic in the New World area.     

Epidemiology of Northern leaf blight on sweet corn

The epidemiology of northern leaf blight of corn, caused byExserohilum turcicum (Pass.) Leonard and Suggs, is reviewed. The minimal dew period required for infection is temperature-dependent. At 25°C, 1 h of dew is sufficient to cause infection and at this temperature the minimal dew period for sporulation is 14 h. Under natural conditions when one dew night is not long enough for conidia to develop, the dew period on the following night enables the completion of conidial formation. The amount of conidia formed is dependent on temperature, light, plant age, leaf position and plant susceptibility. Both qualitative and quantitative types of resistance were identified in several hybrids. Subsequently, there developed additional biotypes ofE. turcicum which are aggressive to plants containing qualitative monogenic resistance. Within the same physiological race, a significant variation in aggressiveness between isolates from various locations is observed. The pathogen overwinters as mycelia and conidia in infected leaves, husks and other plant parts, or onSorghum halepense L. Reduction in yield due to northern leaf blight is associated with the level of resistance of the host plant, with disease severity, plant age during infection, and position of infected leaves.     

First report of bacterial blight of crucifers caused by Pseudomonas cannabina pv. alisalensis in Japan

In October 2010, a bacterial disease produced flecks and spots on leaves of Chinese cabbage, cabbage and Japanese radish in Nagano Prefecture, Japan. The symptoms started on the abaxial surface of leaves as angular, water-soaked flecks of 1–2 mm in diameter with a yellow halo of 3–4 mm width. These flecks then became visible on both leaf surfaces, enlarged and coalesced into large blight lesions. The symptoms were similar to bacterial leaf spot caused by Pseudomonas syringae pv. maculicola. The bacterium isolated from leaf lesions formed a white colony and produced polysaccharides on YP agar. The isolates were identified as P. syringae group by LOPAT tests and the 16S rDNA sequence. Moreover, the results of pathogenicity on cruciferous plants, bacteriological characteristics, rep-PCR and the sequences of rpoD and gyrB showed that the isolates should be identified as P. cannabina pv. alisalensis (recently transferred from P. syringae pv. alisalensis). This is the first report of P. cannabina pv. alisalensis isolated from diseased crucifers in Japan.     

Bacterial leaf spot of hemp caused by Xanthomonas campestris pv. cannabis in Japan

Bacterial leaf spot disease of hemp was observed in Tochigi Prefecture, Japan in 1982 and characterized by necrotic lesions ca. 1–2 mm diameter on leaves with a yellow halo 2–3 mm wide. In this report, we describe the pathological, physiological and genetic properties of the causal bacterium. Our results indicated that this bacterium is identical with Xanthomonas campestris pv. cannabis reported in Romania.     

Valdensia leaf blight of highbush blueberry caused by Valdensinia heterodoxa, a new fungal disease in Japan

In July 2003, a new disease occurred on leaves of highbush blueberry (Vaccinium corymbossum L.) in Iwate, Japan. Leaves initially had brownish spots, which subsequently developed into large lesions with concentric rings, resulting in premature defoliation. Teardrop-shaped conidia infecting leaves were visible by the naked eye as small protuberances in the center of lesions. Star-shaped conidia were sporadically produced on large lesions. The causal fungus was identified as Valdensinia heterodoxa, based on cultural, morphological and genetic studies. Inoculation tests showed that the fungus reproduced lesions on detached young leaves of highbush blueberry. A field survey in 2009 indicated that symptoms initially appeared on the lower leaves of basal shoots in late May, and the disease rapidly progressed on leaves of basal shoots, eventually spreading to lateral shoots from late June to late July. Removal of all basal shoots in late June significantly reduced disease incidence on lateral shoots in late July.     

Serratia marcescens associated with bell pepper (Capsicum annuum L.) soft-rot disease under greenhouse conditions

Soft-rotting bacteria affecting bell peppers crops represent an economically destructive disease of growing importance worldwide. In Venezuela since 2006, soft-rot symptoms have been occasionally observed in bell pepper fruits grown under greenhouse conditions. Affected fruits presented water-soaked lesions that progressed to complete fruit maceration. Bacteria were isolated from water-soaked lesions in order to identify the causal agent of this disease. Of 13 bacterial isolates recovered from affected fruits, only isolate AGPim1A was able to produce a hypersensitive reaction in tobacco plants and to reproduce soft-rot symptoms in bell peppers fruits. Several methods, including classical bacteriological tests and carbon utilization profiling, alongside with sequence analysis of 16S rRNA and housekeeping genes gyrB and groES-groEL, allowed identification of the soft-rotting bacterium as Serratia marcescens. To our knowledge, this is the first report showing a S. marcescens strain associated with soft-rot disease in bell pepper fruits.     

Internal fruit rot of sweet pepper caused by Fusarium lactis in Japan and fungal pathogenicity on tomato and eggplant fruits

Journal of General Plant Pathology - A postharvest rot of ripe sweet pepper fruits was found in Kagawa Prefecture in western Japan in October 2002. A fungus, isolated repeatedly from the diseased...     

Identification and development of molecular markers linked to Phytophthora root rot resistance in pepper (Capsicum annuum L.)

Phytopthora root rot in pepper (C. annuum) is caused by Phytophthora capsici L., which exhibits a high level of pathogenic diversity. Resistance to this disease is conditioned by a number of quantitative trait loci. Pyramiding resistance alleles is desirable and could be simplified by the use of molecular markers tightly linked to the resistance genes. The purpose of this study was development of molecular markers linked to Phytophthora root rot resistance. An F₈ recombinant inbred line (RIL) population derived from a cross between YCM334 and a susceptible cultivar ‘Tean’ was used in combination with bulk segregant analysis utilizing RAPD and conversion of AFLP markers linked to Phytophtora root rot resistance into sequence-characterized amplified region (SCAR) markers. In conversion: one marker was successfully converted into a co-dominant SCAR marker SA133_4 linked to the trait. In bulked segregant analysis (BSA): three RAPD primers (UBC484, 504, and 553) produced polymorphisms between DNA pools among 400 primers screened. Genetic linkage analysis showed that the SCAR and RAPD markers were located on chromosome 5 of pepper. Quantitative trait locus (QTL) analysis showed that the SA133_4 and UBC553 were linked to Phytophtora root rot resistance. These markers were correctly identified as resistant or susceptible in nine promising commercial pepper varieties. These markers will be beneficial for marker-assisted selection in pepper breeding.