Biological and genetic characterization of carrot red leaf virus and its associated virus/RNA isolated from carrots in Hokkaido,Japan

Carrot motley dwarf (CMD) is caused by mixed infection of carrot red leaf virus (CtRLV) with either carrot mottle virus (CMoV) or carrot mottle mimic virus, and additional infection with CtRLV-associated RNA (CtRLVaRNA). Here, the author investigated the viruses or virus-like RNA isolated from carrots with reddening symptoms in Hokkaido, the northern island of Japan. Three types of infections were mainly detected: single infection with CtRLV, which was most prevalent; double infection with CtRLV and CMoV; and triple infection with CtRLV, CMoV, and CtRLVaRNA. Fields with the three agents were severely affected, with diseased plants showing mottling, whereas in fields where disease incidence was low and sporadic, CtRLV was often found alone in plants with mild symptoms. Inoculation tests using carrot plants showed that CMoV enhanced disease severity, and the RNA accumulation of CtRLV. However, in the presence of CtRLVaRNA (+ CMoV), distinct symptoms such as systemic mottling and stunting developed, while the enhancement of CtRLV accumulation was abolished. These results imply that CtRLVaRNA (+ CMoV) antagonizes CtRLV despite its dependence on CtRLV for aphid transmission, and that mixed infection with CtRLVaRNA is involved in the development of the conspicuous mottling. All agents detected in Hokkaido were very similar to European and American isolates in terms of their genomic sequences and host range. This represents the first report of CMD in Japan, and provides further information on the genetic and biological properties of CMD-associated agents, as well as the aetiology of the disease.     

Distribution of Typhula spp. and Typhula ishikariensis Varieties in Wisconsin, Utah, Michigan, and Minnesota

ABSTRACT Snow molds are psychrophilic fungi that grow under snow cover by taking advantage of carbohydrate-depleted, dormant plants. Typhula snow molds caused by Typhula incarnata, T. phacorrhiza, and T. ishikariensis are the most important winter diseases of perennial grasses and winter cereals in the United States. Colonized turfgrass samples with sclerotia were collected from 135 golf courses in Wisconsin, Utah, Michigan, and Minnesota in spring 2001 and 2002. Species and varieties from a total of 2,864 samples were identified using Typhula spp.-specific polymerase chain reaction markers. All three species were found throughout the states sampled, except T. phacorrhiza, which was not found in Minnesota. T. incarnata was distributed in areas of shorter snow cover duration and higher mean temperature than T. ishikariensis. Canonical correspondence analysis indicated that snow cover days and mean temperature were significantly correlated with frequency of Typhula spp. and T. ishikariensis varieties infecting turfgrasses on golf courses in Wisconsin, and that T. incarnata, T. phacorrhiza, and T. ishikariensis were ecologically distinct based on the 2001 data. However, because these two variables accounted for a relatively small proportion of total variation, other environmental variables also may be important in characterizing the distribution of these pathogens and require further study.     

向日葵镰刀菌病害研究进展及其综合防治

美国、印度、突尼斯等国已有由镰刀菌引起的向日葵病害的相关报道,但我国尚未见系统研究和报道。本文综述了向日葵镰刀菌病害的病原、症状和危害、国外种传镰刀菌的检测、种传镰刀菌的致病性和对种子发芽的影响以及综合防治方法。     

Genetic relationships between the dominant genotypes of Phytophthora infestans in Hokkaido, Japan

The genetic characteristics of the dominant genotypes of Phytophthora infestans in Japan (US-1, JP-1, Japanese A1-A, A1-B) were compared. Differences were evident in the peptidase genotype, amplified fragment length polymorphism, and RG57 DNA fingerprints. Almost all of the fingerprint bands for the Japanese genotype A1-B were also present in JP-1 and Japanese A1-A, and few bands were unique to Japanese A1-B. These results suggest that the Japanese A1-B genotype was generated from sexual reproduction involving Japanese A1-A and JP-1 or related genotypes.     

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     

Viral dieback of carrot and other umbelliferae caused by the Anthriscus strain of parsnip yellow fleck virus,and its distinction from carrot motley dwarf

Viral dieback of carrot, chervil, coriander, dill and wild Umbelliferae is described. Disease incidence in carrot crops grown for seed is often high but low in ware carrot. There is no secondary spread in carrot crops.The causal virus was identified as theAnthriscus strain of parsnip yellow fleck virus (PYFV) transmitted byCavariella aegopodii from cow parsley(Anthriscus sylvestris). Nicotiana benthamiana was practically indespensable for isolation of PYFV by sap transmission from plants with viral dieback.No immunity was found in 12 carrot cultivars or in wild carrot. Disease control with a systemic insecticide had limited effect.Carrot red leaf virus and carrot mottle virus were commonly found in carrot, but they did not cause dieback symptoms. Cucumber mosaic virus, parsnip mosaic virus and a virus resembling that of carrot yellow leaf were occasionally isolated from carrot. Symptoms due to mycoplasma were also observed.Samenvatting Bij de zaadteelt van peen is in ons land reeds lang een schadelijke, vroeg in het seizoen optredende instervingsziekte bekend als voorjaarsziekte of het zwart. Planten vallen op door necrose van jonge spruiten (insterving). Soms gaat meer dan de helft van het gewas verloren. Voor consumptie geteelde peen wordt echter nauwelijks aangetast. De ziekte is nu ook gevonden bij dille, kervel, koriander en wilde schermbloemigen.Uit zieke planten en ook vaak uit symptoomloze fluitekruidplanten werd een virus geïsoleerd waarmee de insterving kon worden gereproduceerd. Het werd herkend als de fluitekruid-(ofAnthriscus-)stam van pastinakegeelvlekvirus (PYFV) op grond van waardplanten, symptomen, serologie en overdracht doorCavariella aegopodii met als onmisbare helper hetAnthriscus-vergelingsvirus (AYV), dat ook in fluitekruid voorkomt. Het gebruik vanNicotiana benthamiana als toetsplant maakte isolatie uit planten met virusinsterving mogelijk. Voor de ziekte wordt nu de naam virusinsterving van schermbloemigen voorgesteld.Peenroodbladigheid veroorzaakt door peenroodbladvirus, dat meestal samengaat met peenvlekkenvirus, bleek ook algemeen voor te komen. Deze twee virussen spelen geen rol bij het veroorzaken van virusinsterving, zoals wel werd aangenomen. Beide ziekten zijn geheel verschillend in symptomatologie en epidemiologie. Incidenteel werden komkommermozaïekvirus, pastinakemozaïekvirus en een virus gelijkend op peengeelbladvirus in aangetroffen. Ook werd eenmaal een aan een mycoplasma toe te schrijven ziekte geconstateerd.Virusinsterving bleek epidemiologisch te kunnen worden verklaard door de massale jaarlijkse migratie vanC. aegopodii in het voorjaar, waarbij PYFV van fluitekruid naar peen en andere schermbloemigen wordt verspreid. Door onvatbaarheid van peen voor het helpervirus (AYV) treedt in dit gewas geen secundaire verspreiding op.In geen van 12 peenrassen en wilde peen werd resistentie aangetroffen. Toepassing van een systemisch insekticide bleek in eerder onderzoek slechts een beperkt effect te hebben. Peenzaadteelt in gebieden met minder bladluizen, zoals het noorden des lands, lijkt aan te bevelen, maar verder lijkt de ziekte niet te bestrijden.Work in partial fulfillment of requirements for master's training at Agricultural University, Wageningen     

Detection and prediction of post harvest carrot diseases

Specific PCR primers were developed for identifying two post harvest pathogens, Mycocentrospora acerina and Fibularhizoctonia carotae, which cause liquorice rot and crater rot respectively, during prolonged low temperature storage of carrots. The methods allow routine detection of less than 0.3 pg of M. acerina DNA and less than 0.03 pg F. carotae DNA, even in the presence of large excess of plant or soil DNA. Standard PCR and quantitative PCR gave similar results and either method could be used in a practical situation. Experiments were carried out testing these methods on different types of carrot tissue- and soil- samples. Soil was sampled before sowing, and soil adhering to the roots or root tissue was sampled at different times during the growing season or at harvest. Soil adhering to the carrots at harvest had the best predictive ability for liquorice rot development during storage (R² predicted 74.9% using standard PCR), but samples taken during the growing season also gave reasonably good predictive ability values. PCR data from soil samples taken in the spring were not as good as a predictor for this disease. A dense sampling strategy using 20 m between sampling points generally gave better correlation between PCR data and disease data than using 40 m between the sampling points. Use of the developed methods in an IPM strategy for liquorice rot is discussed. For crater rot the correlation between PCR data and disease data was generally poor for all types of samples. These results are discussed in relation to the biology of F. carotae.     

First report of black scurf on carrot caused by binucleate Rhizoctonia AG-U

Black scurf on carrot roots was found in Hokkaido, Japan, in 2010. An isolate of a binucleate Rhizoctonia was obtained from sclerotia on the root surface. This isolate was identified as anastomosis group (AG)-U based on cultural characteristics, hyphal fusions and the sequence of ribosomal DNA-internal transcribed spacer region. The AG-U isolate caused black scurf symptoms on carrot roots in an inoculation test. The reference isolate of Rhizoctonia solani AG-2-2 IV, which causes carrot root rot, a disease with symptoms that differ from the black scurf symptom. This is the first report of carrot black scurf caused by binucleate Rhizoctonia AG-U.     

Losses caused by diseases in Irish grassland

The pathogens causing diseases of grassland are reviewed with particular reference to Ireland. Herbage losses, and decrease in quality are considered. Recent work on ten common diseases of grasses and forage legumes in Ireland is described.     

Damping-off of soybean caused by Pythium myriotylum in Japan

Severe rotting and blight of seedlings of soybean, Glycine max (L.) Merr., were found in Hiroshima Prefecture in the southwest region of Japan in July 2009. A filamentous microorganism, isolated repeatedly from the diseased seedlings and identified as Pythium myriotylum, was demonstrated to be pathogenic to seedlings of soybean. The disease was new in Japan, and we propose to include this oomycete as one of the pathogens causing damping-off of soybean.