Current situation of sharka disease in Ankara,Turkey

Sharka disease has a limited distribution in Turkey and does not present a problem for stone fruit production. However, sharka is the most common virus disease of apricots, plums and peaches in Ankara, although it is not a common disease in other cities in Turkey. In different parts of Ankara, 212 private gardens in 21 locations were surveyed forPlum pox virus (PPV) incidence. All together 935 trees of apricot, plum, peach, sweet cherry and sour cherry were sampled and tested for the presence ofPPV by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA).PPV was identified in numerous trees,viz. 286 apricots, 172 plums and 65 peaches. Strain differentiation ofPPV was accomplished using double-antibody sandwich indirect enzyme-linked immunosorbent assay (DASI-ELISA). These assays confirmed the presence of isolates belonging toPPV-M, PPV-D and mixed infections ofPPV-M+D. This is the first report of the presence ofPPV-D and mixed infections ofPPV-M+D in Turkey. http://www.phytoparasitica.org posting July 14, 2004.     

Three<Emphasis Type="Italic">Orobanche</Emphasis> species newly found on crops in israel

Orobanche amethystea Thuill.,O. loricata Reichenb. andO. pubescens D’Urv. were found to parasitize the roots of cultivated plants in Israel.Orobanche pubescens is known from the local flora, and was now found to cause damage in parsley fields and toTropaeolum majus L. (nasturtium) in ornamental gardens.Orobanche amethystea andO. loricata are known as occasional weeds in Europe and were recently found for the first time in Israel.Orobanche amethystea densely populated vetch fields in Israel, andO. loricata was found in ornamental gardens. A key for the identification ofOrobanche species in cultivated areas in Israel is given, based on morphological features. http://www.phytoparasitica.org posting Jan. 13, 2002.     

New mite-borne virus isolates from rakkyo,shallot and wild leek species

Flexuous viruses were transmitted from rakkyo (Allium chinense) and wild leek species (especiallyA. commutatum) to plants of crow garlic (A. vineale), by transfer of dry bulb mites. By electron microscope decoration tests using three antisera and by inoculations onto test plants, it was concluded that from each of the two natural host species at least two viruses were isolated. The viruses from wild leeks are both pathogenic onAllium spp. and may be of economic importance. Decoration tests on a virus mixture from shallot obtained earlier, revealed another new mite-borne virus in this species. The mite-borne viruses ofAllium spp. appear to be very common; they are largely diverse and their identification remains difficult.     

Acidified peel of litchi fruits selects for postharvestPenicillium decay

Litchi fruits are fumigated after harvest with sulfur dioxide (SO₂) to prevent their rapid browning. SO₂ blocks enzymatic activity but bleaches the fruits and, if this process is followed by dipping the fruit in dilute hydrochloric acid, the appealing red color is regained. Hot water brushing (HWB) is among the alternative methods that were developed to replace the use of SO₂. HWB reduced fungal population size on the surface of the fruit peel after treatment but did not eliminate fruit infection after storage. Whereas untreated fruits were infected with a variety of fungal species,Penicillium sp. was the only fungus that developed on the pericarp after storage in fruits that had been dipped in 1.5M HCl. Fruit treated by HWB followed by handling and storage under sterile conditions suffered greater decay than fruit stored under non-sterile conditions but with more ventilation. APenicillium sp. isolated from litchi grew well in liquid medium acidified to the pH range reported for SO₂ and HCl-treated litchi fruits. Morphological analysis identified fungal isolates asP. aurantiogriseum. Internal transcribed spacer sequence analysis of five isolates suggested a sequence similarity toP. commune. Our data support the hypothesis that dipping litchi fruit in hydrochloric acid eliminates infection by common opportunistic fungi and selects forPenicillium species that tolerate low pH. http://www.phytoparasitica.org posting April 30, 2004.     

Vegetative compatibility among isolates ofColletotrichum gloeosporioides from almond in Israel

Anthracnose, caused byColletotrichum gloeosporioides, is the major disease of almond in Israel. Pathogen attack of young fruit results in fruit rot and leaf wilting. Seventy isolates ofC. gloeosporioides were obtained from affected almond fruits collected at 11 sites during 1991–2 and 1994. Chlorate-resistant nitrate-nonutilizing (nit) mutants were generated from each isolate and used in complementation (heterokaryon) tests. The formation of complementary stable heterokaryons between mutants from different isolates showed that all the isolates belonged to a single vegetative compatibility group. Representative isolates ofC. gloeosporioides from almond did not form heterokaryons with local isolates ofColletotrichum from anemone and avocado, indicating that the almond isolates constitute a distinct subspecific group withinC. gloeosporioides.     

Physiological, Biochemical and Molecular Analyses of an Italian Collection of Agrobacterium tumefaciens strains

Physiological, biochemical and molecular characteristics of Agrobacterium tumefaciens strains isolated in Italy from different host plants were analysed. Diseased plants were collected from several nurseries located in nine different regions. Out of 1293 strains isolated from 12 fruit tree and six ornamental plant species, a group of 120 strains was chosen as representative of the whole collection. The majority of the strains were biovar 2 (82.5%), agrocin 84 sensitive, and were isolated from stone fruit trees. Most of the strains identified as biovar 1 were isolated from ornamental plants and were insensitive to A. radiobacter antagonistic strain K84. Some strains that were isolated from Euonymus spp, Prunus GF 677 and Pyrus communis (pear) OHF tumours could not be allocated to any of the three Agrobacterium biovars. PCR-restriction fragment length polymorphism of the rrs gene plus the intergenic spacer was used for strain fingerprinting and characterisation. Results showed a wide genetic variability within the biovar 1 strains and homogeneity within the biovar 2 group. Biovar 2 strains from Sardinia were highly variable and differed from the biovar 2 strains isolated from the other regions of Italy.     

Host‐range studies,genetic diversity and evolutionary relationships of ACLSV isolates from ornamental,wild and cultivated Rosaceous species

A large‐scale survey was carried out to study the host range and genetic diversity of Apple chlorotic leaf spot virus (ACLSV) in various Rosaceae species, with a special emphasis on ornamentals and wild shrubs. Samples were tested by DAS‐ELISA using two different antisera, and RT‐PCR amplification of part of the CP gene. There was generally a poor correlation between the results obtained with the two sets of serological reagents and between serological and molecular detection assays. Using a nested RT‐PCR assay developed here, ACLSV was found to be widespread among cultivated, ornamental and wild species of the Rosaceae. The virus was detected for the first time in plum, wild cherry, Crataegus monogyna, Prunus spinosa and Prunus cerasifera in Greece. Sequences of a part of the CP encoding gene and the 3′ untranslated region from ACLSV isolates originating from various wild species and ornamentals were compared to those of isolates from cultivated hosts, showing similar divergence levels. Further phylogenetic analysis using the sequenced region indicated that the isolates from wild or ornamental hosts were not more closely related to each other than to isolates from cultivated hosts. The possible role of different factors in the spread of ACLSV on cultivated, ornamental and wild species is discussed.     

山东省樱桃主产区果蝇的调查与鉴定

为了解山东省樱桃主产区果蝇的发生情况,本研究选择了山东省主要樱桃产区的7个地点进行调查,并通过形态学特征和分子鉴定法对果蝇的种类进行鉴定。结果发现,山东省樱桃主产区有4种果蝇,通过形态特征与分子鉴定法最终确定4种果蝇,分别为斑翅果蝇Drosophila suzukii、黑腹果蝇D.melanogaster、海德果蝇D.hydei和伊米果蝇D.immigrans。这4种果蝇对樱桃的为害程度与种植地区、果实腐烂程度和樱桃的品种均有关系;莱芜和泰安地区果蝇分别有4种和3种;烟台和威海地区则只有斑翅果蝇和黑腹果蝇2种。烟台地区果蝇为害率最高,且数量最多,其中烟台丁家夼村樱桃为害率高达45.16%,在第2次采集中烟台薛家村每100粒樱桃中斑翅果蝇和黑腹果蝇的数量最多。美早和先锋2个品种樱桃对果蝇的吸引力较强;采摘后期腐烂的果实可吸引大量的果蝇产卵。因此,应对烟台地区进行重点预防、早期防治,并减少美早和先锋品种樱桃在山东省的种植。     

Phytophthora root and crown rot of raspberry in Bulgaria

Root and crown rot of raspberry (Rubus idaeus L.) was observed in a plantation at the experimental station of small fruits in Kostinbrod, Bulgaria. Isolates ofPhytophthora spp. were obtained from diseased plants. Colony morphology, growth rates, features of asexual and sexual structures were studied and as a result twoPhytophthora species were identified:Phytophthora citricola Saw. andPhytophora citrophthora (R.E. Sm. & E.H. Sm.) Leonian. Their pathogenicity was confirmed in artificial inoculation experiments. The isozyme (-esterase) patterns ofP. citrophthora andP. citricola isolates from raspberry and from the collection of the CBS, Baarn the Netherlands were compared, using micro-gel electrophoresis. Both species are reported for the first time as pathogens of raspberry in Bulgaria. This is only the second report in phytopathological literature ofP. citrophthora on raspberry, the first being from Chile [Latorre and Munoz, 1993].     

Correlation of ethylene synthesis in Citrus fruits and their susceptibility to Alternaria alternata pv. citri

The susceptibility of Fortune (Citrus clementina × Citrus reticulata), Citrus paradisi and Citrus limon fruits to Alternaria alternata pv. citri was investigated using different artificial inoculation methods. The results obtained reveal that the C. paradisi and C. limon fruits are less susceptible to A. alternata pv. citri than Fortune fruits, although all showed symptoms of Alternaria brown spot when the cuticle was broken and the flavedo or flavedo + albedo was removed. Furthermore, it was seen that susceptibility to the fungus decreased as the age of the fruit increased. There was a positive correlation between the susceptibility of the different Citrus fruits to A. alternata pv. citri and their “in vivo” ethylene levels, the most susceptible fruit (Fortune) producing more ethylene during growth than the less susceptible C. limon and C. paradisi. This suggests that ethylene may well be considered as a possible marker of Citrus fruit susceptibility to A. alternata pv. citri. Disease development increased when the Fortune fruits were treated with 1 mM ACC (a precursor of ethylene biosynthesis) or 1 mM Ethephon (an ethylene-releasing compound) prior to inoculation with A. alternata pv. citri. The role of ethylene as a factor involved in disease development is discussed.     

An important new apricot disease in Spain is associated with <Emphasis Type="Italic">Hop stunt viroid</Emphasis> infection

The province of Murcia (Murcia Region) is the one of the most important apricot growing regions in Europe. In recent years a fruit disorder named by growers as “degeneración” has been detected in apricot commercial orchards of this region, mainly in the variety Velázquez Fino. Affected fruits are characterized by changes in their external appearance involving rugosity and a loss of organoleptic characteristics, which leads to an unmarketable product. In order to identify the causal agent of this disorder, the presence of the most important viruses affecting stone fruit trees and Hop stunt viroid (HSVd) was tested. While negative results were obtained for all viruses analysed, the viroid was detected in all the symptomatic trees. Within a single tree, the viroid was restricted to branches bearing fruits with the characteristic symptoms but was usually absent from the rest of the tree. Sequence analysis of several isolates of HSVd obtained from these affected trees revealed the presence of two variants previously detected in other apricot cultivars. Taken together, these results suggest that degeneration is associated with HSVd.     

Untersuchungen zur Europäischen Steinobstvergilbung (ESFY) in Deutschland

From 2003 to 2007 surveys have been conducted in different stone fruit growing regions in southwest Germany to detect European stone fruit yellows (ESFY) disease in Germany. Samplings have been done regularly in selected reference orchards in the regions Neuwieder Becken, Rheinhessen, Vorderpfalz and Südpfalz in summer on trees showing ESFY typical symptoms as well as on branches of trees with unspecific symptoms. All samples have been analysed by PCR for infection with Candidatus Phytoplasma prunorum. The phytoplasma could be detected in all investigated regions on the cultivated Prunus species P. armeniaca, P. persica and P. domestica. No infection was found in wild Prunus species. The main spread of the disease appeared on apricot while peach and European plum were less affected. A good correlation between symptoms and molecular detection of the pathogen could be shown for the typical symptoms in summer and winter for apricot as well as for peach. During regular psyllid captures in the reference orchards the population dynamics of Cacopsylla pruni could be described in southwest Germany for several years. By PCR-testing all collected insects individually a yearly natural infection rate of about 1–2% of all individuals of C. pruni could be calculated.     

Identifying resistance in wild and ornamental cherry towards bacterial canker caused by Pseudomonas syringae

Bacterial canker is a major disease of stone fruits and is a critical limiting factor to sweet cherry (Prunus avium) production worldwide. One important strategy for disease control is the development of resistant varieties. Partial varietal resistance in sweet cherry is discernible using shoot or whole tree inoculations; however, these quantitative differences in resistance are not evident in detached leaf assays. To identify novel sources of resistance to canker, we used a rapid leaf pathogenicity test to screen a range of wild cherry, ornamental Prunus species and sweet cherry × ornamental cherry hybrids with the canker pathogens, Pseudomonas syringae pvs syringae, morsprunorum races 1 and 2, and avii. Several Prunus accessions exhibited limited symptom development following inoculation with each of the pathogens, and this resistance extended to 16 P. syringae strains pathogenic on sweet cherry and plum. Resistance was associated with reduced bacterial multiplication after inoculation, a phenotype similar to that of commercial sweet cherry towards nonhost strains of P. syringae. Progeny resulting from a cross of a resistant ornamental species Prunus incisa with susceptible sweet cherry (P. avium) exhibited resistance indicating it is an inherited trait. Identification of accessions with resistance to the major bacterial canker pathogens is the first step towards characterizing the underlying genetic mechanisms of resistance and introducing these traits into commercial germplasm.     

Composition,abundance and phytoplasma infection in the hawthorn psyllid fauna of northwestern Italy

Hawthorn (Crataegus monogyna) is one of the natural hosts of Cacopsylla melanoneura, the acknowledged vector of ‘Candidatus Phytoplasma mali’, the causal agent of Apple Proliferation disease, a serious and growing problem for apple production in Europe, particularly in northern Italy. Wild plants could be important sources of both insects and phytoplasmas, but their role in the epidemiology of phytoplasma diseases and their insect vectors has never been thoroughly examined. Cacopsylla melanoneura’s primary host is hawthorn, a plant closely related to apple which often grows wild near orchards. Other psyllid species feed on hawthorn, but no data are available on their possible role as phytoplasma vectors. We investigated the hawthorn’s psyllid fauna in northwestern Italy using yellow sticky traps, beat trays, and molecular analyses from 2003–2005, to study the relationship between hawthorn, the phytoplasma and the insect vector. Population dynamics were monitored, and insects and hawthorn samples were analysed by polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP), and DNA sequencing for the presence of phytoplasmas. Cacopsylla melanoneura was the dominant psyllid species, followed by C. peregrina, C. affinis and C. crataegi. PCR and RFLP analyses revealed the presence of different fruit tree phytoplasmas in hawthorn plants, and in all four psyllid species.     

Control of postharvest diseases of rambutan using controlled atmosphere storage and potassium metabisulphite or<Emphasis Type="Italic">Trichoderma harzianum</Emphasis>

Botryodiplodia theobromae, Colletotrichum gloeosporioides andGliocephalotrichum microchlamydosporum are the causal fungi of three rambutan postharvest diseases, stemend rot, anthracnose and brown spot, respectively. Two different treatments of rambutan fruits to control the diseases were investigated: application of potassium metabisulphite (250 ppm) or culture filtrate ofTrichoderma harzianum (TrH 40) followed by controlled atmosphere storage (CA) at 13.5°C and 95% r.h. Potassium metabisulphite at 250 ppm under CA effectively controlled the incidence and severity of the three postharvest diseases and maintained the eating quality and color of the fruit for 21 days. The greatest effect of this treatment was on brown spot disease, caused byG. microchlamydosporum. Application of TrH 40 was less effective than potassium metabisuphite. http://www.phytoparasitica.org posting July 8, 2002.     

Testing variability in pathogenicity ofPhytophthora cactorum, P. citrophthora andP. syringae to apple, pear, peach, cherry and plum rootstocks

The relative virulence ofPhytophthora cactorum andP. syringae originating from almond trees, and ofP. citrophthora originating from citrus, to apple, pear, peach, cherry and plum rootstocks, was studiedin vivo andin vitro. Results of the different experiments were in good agreement. All testedPhytophthora isolates showed little virulence to pear rootstocks-causing only minor crown rot symptoms - and no virulence at all to apple rootstocks. In contrast, they were highly virulent to stone fruit rootstocks, causing crown rot disease. The non-pathogenicity of these isolates to pome rootstocks could be interpreted as strict host specificity.     

Effect ofMelia azedarach fruit extract on juvenile hormone titer and protein content in the hemolymph of two species of noctuid lepidopteran larvae [insecta: Lepidoptera: Noctuidae]

The effect of an enriched methanolic extract ofMelia azedarach L. (Meliaceae) fruits on the size of the corpora allata (CA), the juvenile hormone (JH) titer and the protein content in the hemolymph of two lepidopteran pests in Egypt,Spodoptera littoralis (Boisd.) andAgrotis ipsilon (Hufn.), was studied. Different concentrations of the extract were incorporated into an artificial diet on which the larvae were allowed to feed. InS. littoralis, a significant reduction in the CA volume of larvae treated at the 1000 ppm extract levelvs that of control larvae was observed. In A.ipsilon, a reduction was found in the right CA gland only. Larvae of both species that had fed on a diet withMelia extract had a higher mean JH-II titer in the hemolymph than did control larvae. In both species, the content of hemolymph protein was decreased significantly after feeding for 6 days on a diet treated with concentrations above 50 ppm extract, followed by 6 days on a normal diet. The results show that aM. azedarach fruit extract has an effect on the neuroendocrine control in the insects. The effect on the hemolymph protein levels is discussed in connection with changes in the morphology/physiology of the gut.     

Alternaria Brown Spot of Minneola in Greece; Evaluation of Citrus Species Susceptibility

During the last three years, a new disease was observed in northwestern Greece on Minneola trees, hybrid of mandarin and grapefruit. On May small brown necrotic leaf spots surrounded by yellow halo areas of various sizes appeared and covered a major portion of the leaves with extension of necrosis into the veins. On young fruits small, slightly depressed black spots were the first symptoms, which later became 2–7 mm in diameter. Brown spots were observed on the leaves and fruits in several orchards in the same area, causing leaves and fruits to drop. In some orchards over 50% of the fruits were affected. From the fruit and leaf spots the typical small-spore species Alternaria alternata was isolated. Pathogenicity tests were performed by artificially inoculating fruits of Minneola, common mandarin and Clementine. The symptoms of the disease were reproduced only on fruits of Minneola hybrids by the specific strain of the fungus Alternaria alternata pv. citri. Different citrus susceptibility tests indicated that mandarins Minneola, Nova and Page were very susceptible to tested isolates while Clementine SRA and Poros Clementine were not. All lemons and lime Seedless were not susceptible. Grapefruit New Hall was not susceptible, while the Star Ruby was. Orange Lane Late, Navel Late, Oval Poros, Olinda, Navel Athos were not susceptible and only Moro showed reaction being slightly susceptible only to one isolate.     

Infection of<Emphasis Type="Italic">Ceratitis capitata</Emphasis> by two species of the<Emphasis Type="Italic">Entomophthora muscae</Emphasis> species complex (Zygomycetes: Entomophthorales) in the field

Adult Mediterranean fruit flies (Ceratitis capitata), collected in the field, were infected with entomophthoralean fungi. The fungi sporulated poorly on the cadavers, and resting spores, rhizoids and cystidia were not observed. Measurements of conidia and nuclei and counts of nuclei per conidium from different specimens suggest that the causative agents wereEntomophthora muscae sensu stricto andEntomophthora schizophorae, species recently separated from theEntomophthora muscae species complex. This is the first report ofC. capitata as a host for entomopathogenic fungi. http://www.phytoparasitica.org posting Jan. 29, 2003.     

Parasitoid community of the loreyi leaf wormMythimna (Acantholeucania) loreyi: Novel host-parasitoid associations and their efficiency in the eastern mediterranean region of Turkey

The loreyi leaf worm,Mythimna (Acantholeucania) loreyi Duponchel (Lepidoptera, Noctuidae), is a pest of gramineous crops and causes significant economic damage to maize. In field surveys on maize to determine the parasitoid community and its impact on the pest in the eastern Mediterranean region of Turkey, nine parasitoid species were found associated with immature stages ofM. loreyi: The hymenopteran (Braconidae and Ichneumonidae) parasitoidsCotesia (=Apanteles) ruficrus (Haliday),Chelonus oculator Panzer,Meteorus ictericus Nees,Hyposoter didymator (Thunberg),Sinophorus sp.; and the dipteran (Tachinidae) parasitoidsPseudogonia rufifrons Wiedeman,Exorista rossica Mesnil,Gonia picea (Robineau-Desvoidy) andLinnaemya vulpina (Fallen) — the last three recorded for the first time as parasitoids ofM. loreyi in Turkey.C. ruficrus was the dominant parasitoid species, being recovered from 38.5% of the larvae collected and was also the most prevalent species, existing in 91.0% of the fields in whichM. loreyi was found. Total parasitism levels achieved by braconid species was 41.4%, by ichneumonid parasitoids 4.8%, and by tachinid parasitoids 1.9%. In a separate field experiment, seasonal population fluctuations and natural efficiency ofC. ruficrus onM. loreyi were found to be 35.1% and 42.4%, respectively. Population levels ofC. ruficrus were closely related to fluctuations in the population ofM. loreyi, with parasitism ranging between 0 and 77.3% during the study. http://www.phytoparasitica.org posting Aug. 28, 2005.