Characterization of Botryosphaeriaceae species associated with diseased loquat (Eriobotrya japonica) in Spain

Loquat (Eriobotrya japonica) is an important subtropical fruit crop in Spain and other Mediterranean countries. In recent years, characteristic symptoms of branch canker and dieback have been observed in the main cultivated areas of loquat in Spain. The goal of this study was to identify and characterize the species of Botryosphaeriaceae associated with these symptoms. For this, 36 affected orchards were surveyed between 2010 and 2011 in six provinces of southeastern Spain. Eighty‐four isolates belonging to the family Botryosphaeriaceae were recovered from samples with symptoms. These isolates were characterized by means of phenotypical studies, DNA sequence analyses of the internal transcribed spacer (ITS) and part of the translation elongation factor 1‐α regions, and pathogenicity tests. Ten fungal species were identified: Diplodia malorum, Diplodia olivarum, Diplodia seriata, Diplodia pseudoseriata/Diplodia alatafructa, Diplodia sp., Dothiorella sarmentorum, Neofusicoccum mediterraneum, N. parvum, Spencermartinsia plurivora and S. viticola. In addition, Diplodia eriobotryicola and Dothiorella eriobotryae are newly described. The most frequent species isolated from cankers was D. seriata and, as far as is known, this is the first report of D. malorum, and species belonging to the complex D. pseudoseriata/D. alatafructa, in Spain. All species were pathogenic to 1‐year‐old loquat plants cv. Algerie, with Diplodia sp. and S. viticola as the most virulent.     

Comparison of conventional and molecular methods for the detection of Rosellinia necatrix in avocado orchards in southern Spain

White root rot, caused by Rosellinia necatrix , is one of the most important diseases in avocado orchards and is particularly widespread on the Mediterranean seaboard of southern Spain. In this study, the presence of the pathogen in soil samples collected from the base of 47 plants showing different symptoms of canopy decline was assessed with a molecular detection method based on real-time Scorpion PCR. Results were compared with symptoms in the canopy and with the traditional method of isolation of R. necatrix from roots and/or bark. The fungus was isolated from 24 samples by the traditional method and from 37 soil samples by the molecular method (cycle threshold values 25·8 to 47·1), demonstrating the higher sensitivity and reliability of the molecular method. A single real-time PCR amplification was sufficient to detect R. necatrix in naturally infested soils. The avoidance of nested PCR has important practical implications because of the reduced costs and risk of cross contamination. Also, it enables faster sample analysis and is more appropriate for quantitative detection. A modified molecular method was also developed to detect R. necatrix in roots and in soils with very low populations of the pathogen.     

Characteristics and distribution of Colletotrichum species in coffee plantations in Hainan,China

Anthracnose caused by Colletotrichum species is a serious disease on a range of economically important hosts. To determine the Colletotrichum species in coffee plantations in Hainan, China, 55 isolates were obtained from Coffea arabica (arabica) and C. canephora var. robusta (robusta) in five counties. Initially, partial sequences of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were used to measure fungal genetic diversity. Then a subset of 23 isolates was selected to represent the range of genetic diversity, varieties and geographic origin for further multilocus phylogenetic analyses. These isolates belong to eight known Colletotrichum species from three Colletotrichum species complexes, including gloeosporioides (C. endophytica, C. fructicola, C. ledongense, C. siamense and C. tropicale), boninense (C. karstii), gigasporum (C. gigasporum), and one singleton species (C. brevisporum). Of these, C. siamense was isolated in all sampled counties and C. fructicola was identified in three counties. The other six species were isolated only in one or two counties. Only C. siamense and C. fructicola were isolated from arabica, whereas all eight species were isolated from robusta. Occurrence of C. brevisporum, C. endophytica, C. ledongense and C. tropicale in coffee has not been reported previously. Pathogenicity tests showed that all eight species were pathogenic to coffee leaves and fruit. In vitro tests showed that Colletotrichum isolates from coffee in Hainan were most sensitive to prochloraz, less sensitive to carbendazim, propiconazole and difenoconazole, and least sensitive to myclobutanil.     

出芽短梗霉菌株YW1防治储藏期草莓灰霉病的研究

本文研究了出芽短梗霉Aureobasidium pullulans菌株Yw1防治储藏期草莓果实灰霉病Botrytiscinerea的效果,并对其防病机制进行了初步探索。结果表明,菌株Ywl可以有效的控制储藏期草莓灰霉病的发生,发病率可由95．1％降至30．5％-55．6％,菌株Ywl产生的挥发性物质可以抑制灰葡萄孢菌丝生长,抑制率达到52．1％。去除菌体的上清液对灰霉菌无明显抑制活性,说明其抗菌作用机制可能是活菌的竞争作用。由此可见,菌株Ywl是1株有应用潜力的生防菌。     

Characterization of Colletotrichum truncatum from papaya,pepper and physic nut based on phylogeny,morphology and pathogenicity

Colletotrichum truncatum (syn. C. capsici) has been identified as the causal agent of anthracnose on various hosts, predominantly pepper (Capsicum spp.) plants. The aim of this study was to determine whether C. truncatum isolates infecting papaya, pepper and physic nut in southeastern Mexico are morphologically, genetically and pathogenically different, in order to improve disease management strategies. A total of 113 C. truncatum isolates collected from five producer states were subjected to phenotypic characterization and divided into six different morphological groups. These morphological traits and the location of the isolates were used to select a subset of 20 isolates for further studies. Differences in the pathogenicity of the isolates were tested with a cross‐inoculation assay using pepper, papaya and physic nut. The pathogenicity tests revealed that all isolates could infect the three hosts and produce typical anthracnose symptoms, indicating a lack of host specificity for this species and therefore its pathogenic potential on other plants. Phylogenetic analysis using internal transcribed spacer (ITS) and glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) sequences of the C.   truncatum isolates from this study and reference strains was performed, grouping the isolates into a monophyletic clade. This study reports for the first time the characterization of C. truncatum causing anthracnose disease on three different hosts in Mexico.     

Genetic diversity and pathogenicity of Pseudomonas syringae pv. aptata isolated from sugar beet

Pseudomonas syringae pv. aptata is the causal agent of bacterial leaf spot disease of sugar beet (Beta vulgaris). During 2013, 250 samples were collected from leaf lesions with typical symptoms of bacterial leaf spot in commercial fields of sugar beet in Serbia, and 104 isolates of P. syringae pv. aptata were obtained. Identification and characterization was performed using biochemical, molecular and pathogenicity tests. Identification included LOPAT tests and positive reactions using primers Papt2F and Papt1R specific for P. syringae pv. aptata. Repetitive (rep) sequence‐based PCR typing with ERIC, REP and BOX primers revealed high genetic variability among isolates and distinguished 25 groups of different fingerprinting profiles. Pulse‐field gel electrophoresis (PFGE) and multilocus sequence analysis (MLSA) of representative isolates showed higher genetic variability than in rep‐PCR analysis and distinguished three and four major genetic clusters, respectively. A pathogenicity test performed with 25 representative isolates on four cultivars of sugar beet confirmed the occurrence of leaf spot disease and showed correlation between the most aggressive isolates and the genetic clusters obtained in MLSA. All these findings point to the existence of several lines of P. syringae pv. aptata infection in Serbia that are genetically and pathologically different.     

Evaluation of neonicotinoid, organophosphate and avermectin trunk injections for the management of avocado thrips in California avocado groves

BACKGROUND: Trunk injections of systemic insecticides were evaluated for the management of avocado thrips. Insecticide residues were quantified in leaves to determine when after treatment, and for how long, toxic concentrations of the insecticides were present. Residues in fruit were quantified to determine whether trunk injection of insecticides might present a greater risk than traditional application methods for contaminating fruit. RESULTS: Residues of imidacloprid and dinotefuran were at least tenfold higher in leaves when trees were treated via trunk injection compared with soil application. Dinotefuran uptake was more rapid than imidacloprid, and no residues were detected within fruit. Acephate was also mobilized very rapidly and gave good control of thrips in bioassays; however, residues of acephate and its insecticidal metabolite methamidophos were detected in the fruit for up to 4 weeks after injection. Avermectin uptake was very slow, and it was ineffective against avocado thrips. CONCLUSIONS: Trunk injections of acephate and dinotefuran permitted rapid uptake into avocados, and they are strong candidates as control methods for avocado thrips. However, residues of organophosphates in fruit could necessitate increased preharvest intervals. Residues of neonicotinoids were below detection limits in fruit, suggesting that neonicotinoids may be the more suitable control option of the two chemical classes. Copyright © 2012 Society of Chemical Industry     

Field evaluation of systemic imidacloprid for the management of avocado thrips and avocado lace bug in California avocado groves

BACKGROUND: The efficacy of systemic applications of imidacloprid for the management of avocado thrips and avocado lace bug was determined in field trials. Following insecticide treatment by chemigation, leaves of appropriate age for each insect were sampled over a 6 month period and used for bioassays. Imidacloprid residues were measured by ELISA in leaves used for bioassays to determine concentrations of insecticide that were toxic to both pests. RESULTS: The uptake of imidacloprid into treated trees was extremely slow, peaking in the current year's leaf flush at only 8 ng cm^?2 leaf tissue after 15 weeks. Avocado thrips mortality in bioassays with young flush leaves, the preferred feeding substrate for this insect, was minimal, indicating that imidacloprid concentrations were below threshold levels needed for effective control. Residues present in older leaves, which are preferred by the avocado lace bug, were higher than in young flush leaves, and provided good control of this pest. Probit analysis of bioassay data showed that the avocado lace bug (LC₅₀ = 6.1 ng imidacloprid cm^?2 leaf tissue) was more susceptible to imidacloprid than the avocado thrips (LC₅₀ = 73 ng imidacloprid cm^?2 leaf tissue). CONCLUSIONS: In spite of the slow uptake of imidacloprid into avocado trees, the levels of imidacloprid would be sufficient to control avocado lace bug infestations. In contrast, the slow uptake would be problematic for avocado thrips control because inadequate levels of insecticide accumulate in new flush foliage and would allow avocado thrips populations to build to levels that would subsequently damage developing avocado fruit. Copyright © 2010 Society of Chemical Industry     

Volatile Metabolite Profiling for the Discrimination of Onion Bulbs Infected by Erwinia carotovora ssp. carotovora, Fusarium oxysporum and Botrytis allii

The volatile metabolites of the headspace gas of onion bulbs inoculated with three different pathogens, Erwinia carotovora ssp. carotovora, Fusarium oxysporum and Botrytis allii, were profiled using gas chromatography/mass spectrometry. Differences in the number and amount of volatile metabolites were observed. Two hundred and fifty three volatile metabolites were detected in bulbs inoculated with three pathogens or sterile distilled water. On day three, 202 volatile metabolites were observed, compared to 166 on day six. Of the 253 compounds, however, only 59 occurred relatively consistently over replications, of which 25 compounds were specific to one or more pathogens, including 10 that were unique to a pathogen. Metabolites such as 1-Oxa-4,6-diazacyclooctane-5-thione and 4-mercapto-3-(methylthio)--(thio-lactone)-crotonic acid were exclusive to onions inoculated with F. oxysporum. Acetone, acetic acid-hydrazide, propylcarbamate, 1-bromo-1-propene, thiirane, 1-(methylthio)-E-1-propene and 1-ethenyl-4-ethyl-benzene were specific to B. allii. 3-bromo-furan was specific to E. carotovora ssp. carotovora. Sterile water-inoculated bulbs produced 3,3-dioxy-1,2-propanediol-tetranitrate. Highest amount of sulfurs was found in pathogen-inoculated, while highest amounts of terpenes, aromatics and aliphatics were found in sterile distilled water-inoculated bulbs. The possible use of these differences in the volatile metabolites for detecting and discriminating diseases of onion in storage is discussed.     

Genetic,biochemical and pathogenic diversity of Pseudomonas syringae pv. pisi strains

Pseudomonas syringae pv. pisi is a seedborne pathogen distributed worldwide that causes pea bacterial blight. Previous characterization of this pathogen has been carried out with relatively small and/or geographically limited samples. Here, a collection of 91 strains are examined that include strains from recent outbreaks in Spain (53 strains) and from 14 other countries, and that represent all races and the new race 8, including the type race strains. This collection was characterized on the basis of 55 nutritional tests, genetic analysis (rep‐PCR, amplification of AN3 and AN7 specific markers, and multilocus sequence typing (MLST)) and pathogenicity on the differential pea cultivars to identify races. Principal component analysis and distance dendrograms confirm the existence of two genetic lineages within this pathovar, which are clearly discriminated by the AN3/AN7 markers, rep‐PCR and MLST. Strains from races 1 and 7 amplified the AN3 marker; those from races 2, 6 and 8 amplified AN7, while strains of races 3, 4 and 5 amplified either AN3 or AN7. Nevertheless, strains were not grouped by race type by any of the genetic or biochemical tests. Likewise, there was no significant association between metabolic and/or genetic profiling and the geographical origin of the strains. The Spanish collection diversity reflects the variability found in the worldwide collection, suggesting multiple introductions of the bacteria into Spain by contaminated seed lots.     

柑橘根霉软腐病的病原菌分离与鉴定

采后腐烂给柑橘产业带来巨大的经济损失。本研究对2018年从陕西城固采集的温州蜜柑发病果实样品进行了病原菌的分离、柯赫氏法则验证和病原菌鉴定,证实获得的菌株CBS1可以通过伤口侵染温州蜜柑、椪柑、沃柑和伦晚脐橙果实,引起果实腐烂。基于形态学鉴定和ITS序列分析,将菌株CBS1鉴定为Rhizopus stolonifer,并对其生物学特性进行了初步研究。这是我国R.stolonifer侵染柑橘果实的首次报道。