Dieback Disease Research Articles

Multigene phylogeny and morphology reveal Cytospora spiraeae sp. nov. (Diaporthales, Ascomycota) in China

Members of Cytospora encompass important plant-associated pathogens, endophytes and saprobes, commonly isolated from a wide range of hosts with a worldwide distribution. Two specimens were collected associated with symptomatic canker and dieback disease of Spiraea salicifolia in Gansu, China. These isolates are characterized by its hyaline, biseriate, aseptate, elongate-allantoid ascospores and allantoid conidia. Cytospora spiraeae sp. nov. is introduced based on its holomorphic morphology plus support from phylogenetic analysis (ITS, LSU, ACT and RPB2), and differs from similar species in its host association.

First Report of Die-back Disease of Onion (Allium cepa L.) Induced by Fusarium equiseti (Mart) Sacc in Nigeria

First Report of Die-back Disease of Onion (Allium cepa L.) Induced by Fusarium equiseti (Mart) Sacc in Nigeria

Effectiveness of several dosage formula of oil and nano emulsion of citronella against vascular streak dieback (VSD) disease on cocoa

The disease of Vascular streak dieback (VSD) is a deadly disease of cocoa plants, because it attacks the vascular tissue of cocoa at growing point of the plant. In West Sumatra the disease was first reported in 2015 with an incidence of disease range 58.82% - 100% and an intensity of disease range 24.29% - 44.7%. The purpose of this study was to examine the effectiveness of dosage application of oil formula and nano emulsion of citronella formula against Vascular streak dieback (VSD) disease on cocoa plants in West Sumatra (in Padang Pariaman District and Limapuluh Kota District). The results showed that the percentage of VSD disease attacks in both testing sites was 100%. The oil and nano emulsion of citronella formulas can reduce the intensity of VSD disease on cocoa plants in West Sumatra, particularly in Padang Pariaman District and Limapuluh Kota District. The reduction of VSD intensity in Padang Pariaman district ranged from 8.32 to 21.13%; while in Limapuluh Kota district ranged from 4.33 to 11.80%. The nano emulsion of citronella formulation is effective to suppress the intensity of VSD disease on cocoa plants at doses 0.1% (≥ 30% of effectiveness level).

Genetic evaluation of damage caused by ash dieback with emphasis on selection stability over time

Abstract Damage caused by Hymenoscyphus fraxineus, the causal agent of ash dieback, was genetically evaluated based on scorings made on five occasions during the years 2006–2016 at two seed orchards of ash (Fraxinus excelsior L.) established in southern Sweden in 1992 and 1995, respectively. The studied population included grafts originating from 106 plus-tree clones selected from 27 stands in southern Sweden. The study verified previous results of (1) high genetic control of damage traits, (2) high genotypic variation in disease susceptibility and (3) that only a small proportion of the natural population are at least partly resistant. The clonal response for dieback damage was stable over the 10-year period, i.e. the least susceptible clones selected in 2006 still belong to the healthiest ones after several years of heavy infection pressure. There were no clear trends in the development of damage over time for trees being alive at each assessment. However, the proportion of trees that died was substantial (7–8% per year), but this estimation was influenced by other factors than the disease, such as wild game and sanitary cuttings. Altogether, the results are promising for initiating breeding programs to improve the dieback resistance. However, this is a heavy and costly task, since only a very small proportion of the ash trees are partially resistant to the dieback disease. Thus, a joint breeding program involving all the northern European countries is justified.

Identification and Pathogenicity of Fungal Dieback Disease on Sengon (Paraserianthes falcataria (L.) Nielsen) Seedling and Rice (Oryza sativa).

Sengon (Paraserienthes falcataria (L.) Nielsen) is a plant species in forestry plantation while rice (Oryza sativa) is an agricultural crop which potentially used in the agroforestry system. Both species are susceptible to dieback disease. This study aimed to isolate and identify the dieback disease on sengon seedlings to understand the pathogenicity of fungal dieback disease on the seedlings of both sengon and rice and to observe the symptom of dieback disease both macroscopically and microscopically. Pathogenicity test was conducted in a factorial completely randomized design (CRD). The treatments were control, wounded by carborundum, inoculated with pathogen as well as inoculated with pathogen and wounded by carborundum. Results revealed that the greatest percentage of dieback disease on sengon and rice was occurred on the treatment of inoculation with wound both100%. While, the greatest percentage of dieback disease intensity of sengon and rice was obtained on the treatment of inoculation with wound by 98.2 and 40.6%, respectively. The PCR result identified that the pathogen was Ceratobasidium ramicola that form imperfect state as Rhizoctonia sp. This species of fungal pathogen is the major cause of dieback disease on sengon and rice seedlings due to seedlings death.

Morphological Character Analysis and Signal Cryptic Speciation in Lasiodiplodia theobromae on Cashew (Anacardium occidentale L.)

Lasiodiplodia theobromae (Pat) Griffon & Maubl. is a pathogen causing inflorescence dieback disease of cashew in Nigeria and also a common pathogen with a wide host range in the tropics and sub-tropics. The character variations in this pathogen necessitate better understanding of it towards development of management strategies. Isolates identified as L. theobromae were cultured from inflorescence dieback disease of cashew across growing ecologies of Nigeria and studied base on morphological characters. Variability in mycelial texture and colour, conidia and septa sizes and pycnidia production were recorded in this study. The Principal Component Analysis (PCA) and WARD clustering analysis identified four well-supported traits within the isolate group. Isolates within each cluster was: 2, 2, 4 and 1 respectively and isolate CDA1416 (Obollo-Afor) and CDA2924 (Idi-Ayunre) in cluster III were the most similar. Members within clusters I and II united at the semi-partial R-Square distance of 0.0294 and 0.0278 respectively. Isolate CDA2308 (Oro) was distinguished among others and signal a potential cryptic specie, differences in these isolates were supported by conidial morphology and textural variations. This understanding will form the bases for development of diseases management strategy against the pathogen.

Potential of Trichoderma spp. Secondary Metabolite in Controlling Vascular Streak Dieback (VSD) on Cacao Seedlings

<p class="Default">Trichoderma<em> spp. is a beneficial microbe that produces bioactive molecules (secondary metabolites) containing antibiotics, enzymes, hormones, as well as toxins, which play an important role in plant diseases biocontrol. The research aimed to determine the potential of secondary metabolite </em>Trichoderma<em> spp. to control vascular streak dieback disease in cacao seedlings. The research was conducted in Plant Protection Laboratory of Indonesian Industrial and Beverage Crops Research Institute (IIBCRI) and farmers' garden in Balubus village, Lima Puluh Kota, West Sumatera, from April to August 2016. The research used a complete randomized design of 7 treatments using 5 replications, each treatment with 5 plants. The treatment was a secondary metabolite of </em>T. virens<em> LP1, </em>T. hamatum<em> LP2, </em>T. amazonicum<em> LP3, </em>T. atroviride<em> JB2, and </em>T. viride<em> PRD, control (no secondary metabolite), and chemical fungicide as comparison. The 3 months old cacao seedlings were treated with secondary metabolite of </em>Trichoderma<em> spp. by spraying the metabolite suspension throughout the leaf surface. The secondary metabolite applied once a week for 6 times. </em>C. theobromae <em>inoculation was conducted naturally by placing cacao seedlings under a cacao tree infected with VSD. Observations were incubation period, VSD intensity, and growth of cacao seedlings. The results showed that secondary metabolites potentially utilized for controlling VSD in cacao seedlings. The most potential secondary metabolites are </em>T. amazonicum<em> LP3 and </em>T. virens<em> LP1 with respective disease suppression up to 81.8% and 63.2% or higher than and equivalent chemical fungicide (63.6%), and can increase plants height, number of leaves, and girth diameter.</em></p>

Ash leaf metabolomes reveal differences between trees tolerant and susceptible to ash dieback disease

European common ash, Fraxinus excelsior, is currently threatened by Ash dieback (ADB) caused by the fungus, Hymenoscyphus fraxineus. To detect and identify metabolites that may be products of pathways important in contributing to resistance against H. fraxineus, we performed untargeted metabolomic profiling on leaves from five high-susceptibility and five low-susceptibility F. excelsior individuals identified during Danish field trials. We describe in this study, two datasets. The first is untargeted LC-MS metabolomics raw data from ash leaves with high-susceptibility and low-susceptibility to ADB in positive and negative mode. These data allow the application of peak picking, alignment, gap-filling and retention-time correlation analyses to be performed in alternative ways. The second, a processed dataset containing abundances of aligned features across all samples enables further mining of the data. Here we illustrate the utility of this dataset which has previously been used to identify putative iridoid glycosides, well known anti-herbivory terpenoid derivatives, and show differential abundance in tolerant and susceptible ash samples.

Effect of Fungicides and Plant Extracts in the Management of Foliar, Twig and Fruit Diseases of Citrus (Citrus limon)

A research work was conducted on citrus plants raised at GPC, of Fruit Tree Improvement Project (FTIP) at Horticulture Farm, Bangladesh Agricultural University, Mymensingh, to investigate the effect of fungicides and plant extracts in controlling the scab, die-back and canker. Three fungicides viz. Cupravit 50 wp (0.4%), Dithane M-45 (0.3%), Rovral 50 WP (0.2%) and extracts of 3 plants viz. Neem {Azadirachta indica), Ginger {Zingiber officinale) and Garlic {Allium sativum) were applied for controlling the citrus (C. limon) diseases (scab, die-back and canker). All the fungicides showed significant effect in the control of the above mentioned citrus diseases. The highest reduction of the scab, die-back and canker diseases was recorded applying Rovral 50 WP. Neem leaf extract was the most effective in controlling canker of leaf and fruit. Garlic extract and Neem leaf extract were the most effective in controlling die-back of twig and branches of citrus, respectively. From the above results it can be concluded that Rovral 50 WP is the most effective chemical for controlling all citrus (C. limon) diseases and citrus canker can successfully be controlled specially by Neem leaf and garlic extract.J. Environ. Sci. & Natural Resources, 10(1): 93-100 2017

Allophoma hayatii sp. nov., an undescribed pathogenic fungus causing dieback of Lantana camara in Iran

Dieback and canker diseases are a major problem in ornamental shrubs and trees of Ahvaz, southwestern Iran. Symptomatic stems and branches were collected from two urban parks in the downtown regions of Ahvaz to identify the dieback-causing agents of Lantana camara. Accordingly, two isolates of a new species, Allophoma hayatii sp. nov., were obtained, which are described and illustrated. This species is identified based on morphological characters and analyses of nucleotide sequences of four regions, including internal transcribed spacer 1 and 2 and 5.8S nrDNA (ITS), partial large subunit 28S nrDNA (LSU-D1/D2), a partial sequence of the β-tubulin (tub2) and part of the RNA polymerase II (rpb2). The isolates of A. hayatii generated a well-supported clade in the trees constructed from multi-locus phylogenetic analysis, distinct from other previously known species of Allophoma. Pathogenicity of both isolates was verified by the inoculation of stem fragments of L. camara. These findings confirm A. hayatii as the causal agents of dieback and canker of L. camara in Ahvaz.

Fraxitoxin, a New Isochromanone Isolated from Diplodia fraxini.

A new isochromanone, named fraxitoxin, was isolated together with (-)-mellein and tyrosol from liquid cultures of Diplodia fraxini, a pathogen involved in the etiology of canker and dieback disease of Fraxinus spp. in Europe. It was characterized as 5-methoxy-3-methylisochroman-1-one using spectroscopic methods (essentially NMR and HR-EI-MS). Its absolute configuration (R) at C(3) was assigned by electronic circular dichroism (ECD) measurements and calculations. Phytotoxic activity of the compound was evaluated on ash, cork and holm oak leaves at concentration of 1 mg/ml by the leaf-puncture assay. Interestingly, fraxitoxin caused necrotic lesions only on ash leaves.

Emerging citrus diseases in Europe caused by species of Diaporthe

Species of Diaporthe are considered important plant pathogens, saprobes, and endophytes on a wide range of plant hosts. Several species are well-known on citrus, either as agents of pre- or post-harvest infections, such as dieback, melanose and stem-end rot on fruit. In this study we explored the occurrence, diversity and pathogenicity of Diaporthe species associated with Citrus and allied genera in European orchards, nurseries, and gardens. Surveys were carried out during 2015 and 2016 in Greece, Italy, Malta, Portugal, and Spain. A total of 79 Diaporthe strains were isolated from symptomatic twigs, branches and trunks. A multi-locus phylogeny was established based on five genomic loci (ITS, tef1, cal, his3 and tub2), and the morphological characters of the isolates determined. Preliminary pathogenicity tests were performed on lemon, lime, and orange plants with representative isolates. The most commonly isolated species were D. foeniculina and D. baccae, while only four isolates of D. novem were collected. Two new Diaporthe species, described here as D. limonicola and D. melitensis spp. nov. were found associated with a new devastating dieback disease of lemon plants. Furthermore, one cluster of sterile Diaporthe isolates was renamed as D. infertilis. Pathogenicity tests revealed most of the Citrus species as susceptible to D. baccae, D. foeniculina, and D. novem. Moreover, D. limonicola and D. melitensis caused serious cankers affecting all the Citrus species tested. This study is the first report of D. baccae and D. novem on citrus in Europe, and the first detection of a new Diaporthe canker disease of citrus in Europe. However, no isolates of D. citri were found. The study improves our understanding of the species associated with several disease symptoms on citrus plants, and provides useful information for effective disease management.

Detection and Management of Mango Dieback Disease in the United Arab Emirates.

Mango is affected by different decline disorders causing significant losses to mango growers. In the United Arab Emirates (UAE), the pathogen was isolated from all tissues sampled from diseased trees affected by Lasiodiplodia theobromae. Symptoms at early stages of the disease included general wilting appearance of mango trees, and dieback of twigs. In advanced stages, the disease symptoms were also characterized by the curling and drying of leaves, leading to complete defoliation of the tree and discolouration of vascular regions of the stems and branches. To substantially reduce the devastating impact of dieback disease on mango, the fungus was first identified based on its morphological and cultural characteristics. Target regions of 5.8S rRNA (ITS) and elongation factor 1-α (EF1-α) genes of the pathogen were amplified and sequenced. We also found that the systemic chemical fungicides, Score®, Cidely® Top, and Penthiopyrad®, significantly inhibited the mycelial growth of L. theobromae both in vitro and in the greenhouse. Cidely® Top proved to be a highly effective fungicide against L. theobromae dieback disease also under field conditions. Altogether, the morphology of the fruiting structures, molecular identification and pathogenicity tests confirm that the causal agent of the mango dieback disease in the UAE is L. theobromae.

Recent incidence of collar canker and dieback of tea (Camellia sinensis) caused by Fusarium solani species complex in Sri Lanka

A collar canker and dieback disease of tea has recently emerged in Sri Lanka. Isolation from cankers consistently yielded fusaria. Morphological characters and ITS and tef1 combined sequence analysis identified the selected isolates as members of Fusarium solani Species Complex Clade 3. Artificial inoculation to young and mature tea plants confirmed pathogenicity.

High-Throughput Chemical Screening Identifies Compounds that Inhibit Different Stages of the Phytophthora agathidicida and Phytophthora cinnamomi Life Cycles.

Oomycetes in the genus Phytophthora are among the most damaging plant pathogens worldwide. Two important species are Phytophthora cinnamomi, which causes root rot in thousands of native and agricultural plants, and Phytophthora agathidicida, which causes kauri dieback disease in New Zealand. As is the case for other Phytophthora species, management options for these two pathogens are limited. Here, we have screened over 100 compounds for their anti-oomycete activity, as a potential first step toward identifying new control strategies. Our screening identified eight compounds that showed activity against both Phytophthora species. These included five antibiotics, two copper compounds and a quaternary ammonium cation. These compounds were tested for their inhibitory action against three stages of the Phytophthora life cycle: mycelial growth, zoospore germination, and zoospore motility. The inhibitory effects of the compounds were broadly similar between the two Phytophthora species, but their effectiveness varied widely among life cycle stages. Mycelial growth was most successfully inhibited by the antibiotics chlortetracycline and paromomycin, and the quaternary ammonium salt benzethonium chloride. Copper chloride and copper sulfate were most effective at inhibiting zoospore germination and motility, whereas the five antibiotics showed relatively poor zoospore inhibition. Benzethonium chloride was identified as a promising antimicrobial, as it is effective across all three life cycle stages. While further testing is required to determine their efficacy and potential phytotoxicity in planta, we have provided new data on those agents that are, and those that are not, effective against P. agathidicida and P. cinnamomi. Additionally, we present here the first published protocol for producing zoospores from P. agathidicida, which will aid in the further study of this emerging pathogen.

A New Cane Dieback Disease of Northern Highbush Blueberry in the United States Caused by Lasiodiplodia mediterranea

A New Cane Dieback Disease of Northern Highbush Blueberry in the United States Caused by <i>Lasiodiplodia mediterranea</i>

Temporal development of collar necroses and butt rot in association with ash dieback

Abstract: In recent years collar necroses and butt rot associated with the ash dieback disease occurred with alarming frequency in Fraxinus excelsior. We analysed tree ring structures to identify the year of necrosis initiation on a set of 507 necroses on 155 stem discs from nine severely diseased south-western German stands. The number of first-time infections of trees was highest from 2010 to 2012 and slightly decreased in 2013 and 2014, whereas the total number of newly emerging individual necroses remained high. Logistic modelling of disease progression suggests that collar rot infection has almost reached its maximum incidence and that a fraction of trees will remain healthy at the root collar. On average, Hymenoscyphus fraxineus was isolated more frequently from younger collar necroses, whereas older necroses were more often colonized by Armillaria spp. Advanced stages of rot that may pose a risk to forest workers, visitors and traffic were observed already in two years-old necroses infected by Armillaria spp.

α-Copaene is an attractant, synergistic with quercivorol, for improved detection of Euwallacea nr. fornicatus (Coleoptera: Curculionidae: Scolytinae).

The tea shot-hole borer, Euwallacea fornicatus Eichhoff, is an ambrosia beetle endemic to Asia and a pest of commercial tea, Camellia sinensis (L.) Kuntze. Recently, a complex of species morphologically similar to E. fornicatus has been recognized, which includes new pests established in Israel and the USA, both in California and Florida. Collectively termed E. nr. fornicatus, these cryptic species carry symbiotic Fusarium spp. fungi, some of which cause dieback disease in susceptible hosts, which include avocado, Persea americana Miller. Due to the threat to this economically important crop, research was initiated to evaluate efficacy of kairomone-based lures for detection of the beetle in Florida (termed the Florida tea shot hole borer, FL-TSHB). A series of field tests were conducted in 2016 in commercial avocado groves known to have FL-TSHB at various population levels. All tests evaluated lures containing quercivorol (p-menth-2-en-1-ol) and α-copaene, presented separately and in combination; and one test evaluated effect of trap type on beetle captures. In addition, electroantennography (EAG) was used to quantify female olfactory responses to lure emissions. This study identified (-)-α-copaene as a new attractant for FL-TSHB, equivalent in efficacy to quercivorol (the standard lure for Euwallacea detection in the USA); however, the combination of lures captured significantly more FL-TSHB than either lure alone. This combination resulted in synergistic attraction at two field sites and additive attraction at a third site. Sticky panel traps captured more FL-TSHB than comparably-baited Lindgren funnel traps. Females engaged in host-seeking flight from 11:00 to 16:00 hr (EST), with peak numbers observed between 12:00 and 13:00 hr. EAG analyses confirmed olfactory chemoreception of both kairomones, with a higher response elicited with the combination of volatiles. Results indicate that detection of pest E. nr. fornicatus in Florida can be improved by using a two-component lure consisting of p-menth-2-en-1-ol and (-)-α-copaene.

Diversity, phylogeny and pathogenicity of Botryosphaeriaceae on non-native Eucalyptus grown in an urban environment: A case study

The Botryosphaeriaceae are opportunistic pathogens mostly of woody plants, including Eucalyptus. These fungi can cause cankers and die-back diseases on non-native Eucalyptus trees in South African plantations. Botryosphaeriaceae were isolated from diseased and asymptomatic twigs and leaves from 20 Eucalyptus spp. grown in a Pretoria, South Africa arboretum and its surroundings. The isolates were initially grouped based on conidial morphology and Internal Transcribed Spacer (ITS) rDNA PCR-RFLP profiles. They were further identified using DNA sequence data for the ITS rDNA and translation elongation factor 1-α (TEF-1α) gene regions and tested for pathogenicity. Five species were identified including Botryosphaeria dothidea and four Neofusicoccum species namely Neofusicoccum parvum; N. cryptoaustrale and N. ursorum that were recently described from plant tissues collected as a part of the current study; and Neofusicoccum eucalypti (Winter) Maleme, Pavlic & Slippers comb. nov. The latter species is recorded for the first time on Eucalyptus in South Africa. Most of the identified species were collected from the leaves of 17 different Eucalyptus spp. Neofusicoccum parvum was most commonly isolated (72% of all isolates) followed by B. dothidea species complex (17%). With exception of N. parvum which was isolated from majority of Eucalyptus spp. the other species were isolated from limited number of Eucalyptus species indicating host-preferences. All the isolated Botryosphaeriaceae species produced lesions on inoculated Eucalyptus grandis plants that were significantly larger than those associated with the controls.

Ingestion of infected roots by feral pigs provides a minor vector pathway for kauri dieback disease Phytophthora agathidicida

Ingestion of infected roots by feral pigs provides a minor vector pathway for kauri dieback disease Phytophthora agathidicida