RT @Britishhops: @Jimthebrewer @CharlesFaram For more info about Hop Stunt Viroid and its impact see: http://t.co/Im9nLTDYb1
Hop plants may be cropped for over 20 years, so it important that the original planting is free from debilitating virus and viroid disease (some of them symptomless). Specialist hop propagators, located outside the main hop growing regions, supply certified disease free stock under an official approval scheme.
All species continuously evolve to adapt to changing environments. The genetic variation that fosters such adaptation is caused by a plethora of mechanisms, including meiotic recombination that generates novel allelic combinations in the progeny of two parental lineages. However, a considerable number of eukaryotic species, including many fungi, do not have an apparent sexual cycle and are consequently thought to be limited in their evolutionary potential. As such organisms are expected to have reduced capability to eliminate deleterious mutations, they are often considered as evolutionary dead ends. However, inspired by recent reports we argue that such organisms can be as persistent as organisms with conventional sexual cycles through the use of other mechanisms, such as genomic rearrangements, to foster adaptation.
Verticillium dahliae is among 20% of fungal species lacking sexual cycle of reproduction. However, the authors suggest that its genome contains a high amount of transposable elements (TE) which may drive genome evolution in this pathogen. TEs are DNA sequences that can change their position within genome and can impact the genome by inducing gene knockouts, modulating gene regulation or causing double-stranded DNA breaks. These sources of variability enable evolution: selection and adaptaion to plant hosts and evolution of fungal aggressiveness.
Similar asexual mechanisms facilitate genome evolution in other eukaryotes, known to be plant pathogens: Phytophthora infestans causing potato blight, Leptosphaeria maculans causing stem canker on Brassica, Blumeria graminis causing powdery mildew, Alternaria spp., Fusarium spp., Mycosphaerella graminicola...
- COUTINHO - 2009 - Molecular Plant Pathology - Wiley Online Library: Pantoea ananatis causes disease symptoms in a wide range of economically important agricultural crops and forest tree species worldwide. It is regarded as an emerging pathogen based on the increasing number of reports of diseases occurring on previously unrecorded hosts in different parts of the world. Its unconventional nature lies in the fact that, unlike the majority of plant pathogenic microbes, P. ananatis is capable of infecting humans and occurs in diverse ecological niches, such as part of a bacterial community contaminating aviation jet fuel tanks and contributing to growth promotion in potato and pepper.
Pantoea ananatis is a ubiquitous bacterium which is associated with plants as an epiphyte, endophyte, pathogen or symbiont, it also occupies diverse and unusual ecological niches, where it may function as a saprophyte. BUT: It can infect also humans! P. ananatis has also been reported to cause bacteraemia (De Baere et al., 2004). With the exception of perhaps only Pantoea agglomerans, no other plant pathogen behaves in such an unconventional manner.
Mango (Mangifera indica L.) is an economically important fruit crop in many tropical and subtropical regions. Recently, the wilt disease caused by Ceratocystis fimbriata has limited mango production in Brazil and other countries (3). There are reports that Hypocryphalus mangifera (Coleoptera: Curculionidae) is a vector of Ceratocystis spp. and that other beetles, such as Xyleborus affinis (Coleoptera: Curculionidae), may attack mango trees and excavate gallery burrows, thereby producing sawdust.
In Europe, Ceratocystis fimbriata (alias Ophiostoma fimbriata) is known as fungal pathogen of Prunus species. But according to its common names it can cause several diseases: Black rot of sweet potato; Blight of mango; Canker of cocoa; Canker of coffee; Mouldy rot of Hevea; Wilt of cocoa...
EPPO has listed Ceratocystis fimbriata f.sp. platani as A2 qurantine pest, since plane tree show advanced dieback after 2-3 years after infection by C. fimbriata. See an update of pest record by C.J. Baker and T. C. Harrington and by T. Harrington in 2004:
Elixothrips brevisetis (Bagnall), a species exotic to Brazil, is first recorded in the country. Individuals were collected on banana fruits (Musa sp.) (Musaceae) in July 2010 in the municipality of Luís Alves, state of Santa Catarina, causing rusting on the fruit peel in several bunches of bananas
A species of whitefly that transmits cassava mosaic virus has been detected in South Africa for the first time. The whitefly, Bemisia tabaci is a cryptic species complex containing some important agricultural pests and virus vectors.
The researchers discovered two non-native types of Bemisia tabaci, one that originates in the Mediterranean (known as the “Q” type) and one that originate in Middle East-Asia (known as the “B” type). Both the “Q” and “B” type Bemisia tabaci are known worldwide as invasive species and have been observed attacking a wide range of crop plants as well as showing the ability to develop insecticide resistance, making them a major agricultural pest.
Elkhart, Indiana (January 5, 2013)--A leading provider of agricultural diagnostic test kits and services has implemented a new, novel, testing method for diagnosing Potato spindle tuber viroid (PSTVd) in tomato seed.
Of the many diseases caused by viroids, the spindle tuber disease of potatoes was the first to be recognized and studied by plant pathologists. Nearly 50 years were to elapse between initial description of this disease in the early 1920's and the identification of its causal agent, a small, highly-structured, covalently closed circular RNA molecule known as Potato spindle tuber viroid (PSTVd). PSTVd remains an important pathogen of potato and tomato, and a recent increase in the number of reported latent infections of ornamental species is creating new challenges for current disease management strategies.
Phytoplasmas are pathogens of important plants, including coconut, sugarcane, sandal wood, causing a wide variety of symptoms that range from mild yellowing to death of infected plants. They are most prevalent in tropical and sub-tropical regions of the world. Phytoplasmas require a vector to be transmitted from plant to plant, and this normally takes the form of sap sucking insects such as leaf hoppers in which they are also able to replicate.
Wikipedia has a nice gallery of plants diseased with phytoplasma infections.
Phytoplasma are specialised bacteria that are obligate parasites of plant phloem tissue and transmitting insects (vectors). They were first discovered by scientists in 1967 and were named mycoplasma-like organisms or MLOs. They cannot be cultured in vitro in cell-free media. They are characterised by their lack of a cell wall, a pleiomorphic or filamentous shape, normally with a diameter less than 1 micrometer, and their very small genomes.
Hybridization and Biological Indexing Results showed that the 2 Jujube tree samples which were collected from the same field of “Jujube tree-pear” intercroping in Qiqiao,Cangzhou were positive for Hop stunt viroid (HSVd). This is the first report of HSVd in Jujube trees in the world.
Both of the 2 samples were selected for cloning, sequence analysis of HSVd and then comparing withthe first HSVd sequence (X00009,1983) from the Hop and also the HSVd sequences in GenBank.
The Mt. Rainier variety is a fine hop that hasn’t taken off yet. Mt. Rainier was released right after this huge oversupply of hops occurred and there was very little demand for hops--new or old. The production and distribution of Mt. Rainier was also hampered by the appearance of hop stunt viroid in 2008. To make a long story short, it was entered into the Clean Plant Network as soon as possible and if I’m not mistaken, will become available this year for limited distribution of cuttings.
MyJournals.org. Analysis of Sequence Polymorphism and Population Structure of Tomato chlorotic dwarf viroid and Potato spindle tuber viroid in Viroid-Infected Tomato Plants is presented. The results demonstrated for the first time that TCDVd, like many other viroids including PSTVd, exists in host plants as a collective group comprised of various sequence variants. However, in comparison to PSTVd, TCDVd is less polymorphic in tomato plants as fewer variants and lower haplotype/nucleotide diversities were observed.
Today (4/25) is national DNA day. Digital World Biology™ is celebrating by sharing some of our favorite structures of DNA. We created these photos with Molecule World™ a new iPad app for viewing molecular structures.
As reported by group of specialists from Bari, "Quick decline syndrome of olive” appeared suddenly a couple of years ago in the vicinity of Gallipoli, in the province of Lecce (Salento peninsula, Apulia, south-east Italy). It soon exploded in epidemic form, so as to affect an estimated surface area of about 8,000 hectares.
Symptoms consist in the apperance of withering and dessication of terminal shoots distributed at random which expand to the rest of the canopy, thus resulting in the collapse and death of the trees. In the affected groves all plants show symptoms.
Olive trees are new hosts of Xylella fastidiosa, which has never been found in a number of grapevines and citrus plants growing next to or within contaminated olive groves; the olive strain of Xf is close to the subspecies pauca. It is transmitted by xylem-sap-feeding leafhoppers
(Hemiptera:Cicadellidae) and spittlebugs (Hemiptera: Cercopidae).
There are strong indications that OQDS of aged (centenary) olive trees is a complex disorder, in which also a leopard moth (Zeuzera pyrina) and xylem inhabiting fungi Phaeoacremonium parasiticum are involved.
EU plant health measures are under the preparation while in Italy emergency measures have been already in place: ban on movement of host plants (olive, almond, oleander and oak), treatments of vectors and elimination of spontaneous host plant in the vicinity of nurseries.
CLEWISTON, Fla. — The call Ricke Kress and every other citrus grower in Florida dreaded came while he was driving. “It’s here” was all his grove manager needed to say to force him over to the side of the road. The disease that sours oranges and leaves them half green, already ravaging citrus crops across the world, had reached the state’s storied groves. Mr. Kress, the president of Southern Gardens Citrus, in charge of two and a half million orange trees and a factory that squeezes juice for Tropicana and Florida’s Natural, sat in silence for several long moments. “O.K.,” he said finally on that fall day in 2005, “let’s make a plan.” In the years that followed, he and the 8,000 other Florida growers who supply most of the nation’s orange juice poured everything they had into fighting the disease they call citrus greening. To slow the spread of the bacterium that causes the scourge, they chopped down hundreds of thousands of infected trees and sprayed an expanding array of pesticides on the winged insect that carries it. But the contagion could not be contained.
They scoured Central Florida’s half-million acres of emerald groves and sent search parties around the world to find a naturally immune tree that could serve as a new progenitor for a crop that has thrived in the state since its arrival, it is said, with Ponce de León. But such a tree did not exist. “In all of cultivated citrus, there is no evidence of immunity,” the plant pathologist heading a National Research Council task force on the disease said. In all of citrus, but perhaps not in all of nature. With a precipitous decline in Florida’s harvest predicted within the decade, the only chance left to save it, Mr. Kress believed, was one that his industry and others had long avoided for fear of consumer rejection. They would have to alter the orange’s DNA — with a gene from a different species.
The article well addresses a dilemma of the nowadays world: Do we dare to use the top scientific results and high-tech knowledge such as genetic engineering? How much is still ethically to interfere with basic genetic code of species? Is it right to mix genes of organisms belonging to different kingdoms? Mankind has always feared of anything that was not understood. And we are still far from understanding firstly, how related we are with plants and animals and secondly, how often we consume mixed genes/proteins with infected crops.
A global code of ethics for genetic engineering of plants would be needed, which would support the GMO technology to maintain the plant health, while limiting the use of GMOs for commercial purposes – to achieve better taste and color of the crop…
The Second European Congress on Chestnut 9 – 12 October 2013, Debrecen, Hungary - will consider the joint topic of this ISHS meeting 2013 as the opportunity to group together the specialists from different fields of plant biology, plant protection, ecology and improving technologies, who may go deeper into the research methodology and techniques of nut and timber production under a changing environment and be inspired in searching for new conceptional approaches of solving problems.
Over the past 50 years of intensive chestnut production and apperance of new plant protection problems lead to a dramatic change in farmland productivity and decline of biodiversity and health status in many chestnut growing regions of the World.
A whole day Symposium will be held on October 11, Friday and will cover the next topics: a) Dryocosmus kuriphilus: pest biology, early detection, pest control, economic harm b) natural enemies and their role in the control of D. kuriphilus c) biological methods of pest control, Torymus sinensis.
European chestnut growers should be aware of the threat from Asian chestnut gall wasp attack (Dryocosmus kuriphilus). The most serious pest of chestnut is spread by plants for planting and naturally by flying. This invasive species was introduced unintentionally into Europe most probably by planting material. It has already been spread in Italy, France, Slovenia and it is spreading further into neighbouring countries. D. kuriphilus has one generation per year, but female populations are reproducing by parthenogenesis. In infested areas all nursery production in open air is banned, which has caused problems to many producers (for example in Piemonte, Italy). D. kuriphilus is considered as the most serious pest of chestnut worldwide, since no effective measures are available even for fruit production.
Population of adult periodical Cicadae will occure from mid-to-late May 2013 (they occured in 1979 and 1996 & the next occurence will be in 2030). Staten Islanders will start to notice the noisy critters as millions dig their way out from a depth of about 18 inches. Once they emerge, the cicadas split their nymphal skins after feeding on tree-root sap for 17 years to become mature, winged adults.
The males waste no time looking for romance; their distinctive "singing" will continue throughout June. Waiting females hang back and listen for a male's song that particularly impresses them before choosing a mate.
"Please pass the earplugs: Cicadas set to announce their first arrival since 1996 ..."
Periodical Cicadae are smaller and narrower-bodied as annual cicada. Their bright red eyes contrast in their black bodies.Magicicadas are found only in eastern part of US. They have long life cycle: 13 years in the south and 17 years in the north. There are 3 different species of periodical cicadas in Staten Island, all on a 17 year cycle.
Only young broadleaf trees need net or other physical protection against massive occurence of cicadas. The pest netting needs to be wrapped completely around the tree and tied, or sealed off, to keep any insects from finding an entryway. Even if the Cicadas have already emerged, one has 5-10 days to cover young trees before the female begins to cause damage, as she lays her eggs.
Viroids are important pathogens of many plants. In citrus trees Citrus exocortis viroid (CEVd) and Citrus viroidⅡ(CVd-Ⅱ,known as Hop stunt viroid, HSVd) can cause the dwarf of citrus trees, decrease growth vigor and fruit production. These two viroids also can infect grapevine. However, they usually do not induce any visible symptoms. In this study, the viroids in citrus and grapevine trees grown in China were detected and their molecular characteristics were analysized.
The results showed that 2 samples were infected with CEVd and this was the first report of CEVd from grapevine in China. The infection rate by HSVd was 35%.
At present two kinds viroids were reported infected peach. Hop stunt viroid (HSVd) and Peach latent mosaic viroid (PLMVd). PLMVd had been already reported on peach tree of China, but for HSVd this is the first report in peach in China. Photo: PLMVd infected peach.
Virus classification is the process of naming viruses and placing them into a taxonomic system. Species names generally take the form of [Disease] virus. Similar to the classification systems used for cellular organisms, virus classification is the subject of taxonomists. The International Committee on Taxonomy of Viruses (ICTV) is the only body charged by the International Union of Microbiological Societies with the task of developing, refining, and maintaining a universal virus taxonomy - see ICTV classification.
Baltimore classification (se picture) is a classification system that places viruses into one of seven groups depending on a combination of their nucleic acid (DNA or RNA). In the original @ Virus Classification - Wiki Article also subviral agents like viroids, satellits and prions are described. They are smaller than viruses but have some of their properties.