Galls or cecidia are a kind of swelling growth on the external tissues of plants. Plant galls are abnormal outgrowths of plant tissues, similar to benign tumors or warts in animals. They can be caused by various parasites, from viruses, fungi and bacteria, to other plants, insects and mites. Plant galls are often highly organized structures so that the cause of the gall can often be determined without the actual agent being identified. This applies particularly to insect and mite plant galls. The study of plant galls is known as cecidology.
Agrobacterium radiobacter is the causal agent of crown gall disease in over 140 species of eudicots. It is a rod-shaped, Gram-negative soil bacterium. Symptoms are caused by the insertion of a small segment of DNA, from a plasmid into the plant cell, which is incorporated at a semi-random location into the plant genome. Plant genomes can be engineered by use of Agrobacterium for the delivery of sequences hosted in T-DNA binary vectors.
A plant canker is a small area of dead tissue, which grows slowly, often over years. Some cankers are of only minor consequence, but others are ultimately lethal and therefore can have major economic implications for agriculture and horticulture. Their causes include a wide range of organisms as fungi, bacteria, mycoplasmas and viruses. The majority of canker-causing organisms are bound to a unique host species or genus, but a few will attack other plants. Weather and animal damage can also cause stress to the plant resulting in cankers. Other causes of cankers is pruning when the bark is wet or using un-sterilized tools.
Phytotoxins are substances that are poisonous or toxic to the growth of plants. Phytotoxic substances may result from human activity, as with herbicides, or they may be produced by plants, by microorganisms, or by naturally occurring chemical reactions.
Pseudomonas syringae is a rod-shaped, Gram-negative bacterium with polar flagella. As a plant pathogen, it can infect a wide range of species, and exists as over 50 different pathovars, all of which are available to researchers from international culture collections such as the NCPPB, ICMP, and others.
Pseudomonas avellanae is a Gram-negative plant pathogenic bacterium. It is the causal agent of bacterial canker of hazelnut. Based on 16S rRNA analysis, P. avellanae has been placed in the P. syringae group. This species was once included as a pathovar of Pseudomonas syringae, but following DNA-DNA hybridization, it was instated as a separate species. Following ribotypical analysis Pseudomonas syringae pv. theae was incorporated into this species.
Pseudomonas viridiflava is a fluorescent, Gram-negative, soil bacterium that is pathogenic to plants. It was originally isolated from the dwarf or runner bean, in Switzerland. Based on 16S rRNA analysis, P. viridiflava has been placed in the P. syringae group. Following ribotypical analysis misidentified strains of Pseudomonas syringae pv. ribicola and Pseudomonas syringae pv. primulae were incorporated into this species. This pathogen causes bacterial blight of Kiwifruit.
Pseudomonas amygdali is a Gram-negative plant pathogenic bacterium. It is named after its ability to cause disease on almond trees. Different analyses, including 16S rRNA analysis, DNA-DNA hybridization, and MLST clearly placed P. amygdali in the P. syringae group together with the species Pseudomonas ficuserectae and Pseudomonas meliae, and 27 pathovars of Pseudomonas syringae/Pseudomonas savastanoi, constituting a single, well-defined phylogenetic group which should be considered as a single species. This phylogenetic group has not been formally named because of the lack of reliable means to differentiate it phenotypically from closely related species, and it is currently known as either genomospecies 2 or phylogroup 3. When it is formally named, the correct name for this new species should be Pseudomonas amygdali, which takes precedence over all the other names of taxa from this group, including Pseudomonas savastanoi, which is and inadequate and confusing name whose use is not recommended.
Pseudomonas cannabina is a gray, Gram-negative, fluorescent, motile, flagellated, aerobic bacterium that causes leaf and stem rot of hemp, from which it derives its name. It was formerly classified as a pathovar of Pseudomonas syringae, but following ribotypical analysis, it was reinstated as a species. The type strain is CFBP 2341.
Pseudomonas coronafaciens is a Gram-negative bacterium that is pathogenic to several plant species. Following ribotypical analysis several pathovars of P. syringae were incorporated into this species.
Pantoea agglomerans is a Gram-negative bacterium that belongs to the family Erwiniaceae.
Halo blight of bean is a bacterial disease caused by Pseudomonas syringae pv. phaseolicola. Halo blight’s pathogen is a gram-negative, aerobic, polar-flagellated and non-spore forming bacteria. This bacterial disease was first discovered in the early 1920s, and rapidly became the major disease of beans throughout the world. The disease favors the places where temperatures are moderate and plentiful inoculum is available.
"Pseudomonas tomato" is a Gram-negative plant pathogenic bacterium that infects a variety of plants. It was once considered a pathovar of Pseudomonas syringae, but following DNA-relatedness studies, it was recognized as a separate species and several other former P. syringae pathovars were incorporated into it. Since no official name has yet been given, it is referred to by the epithet 'Pseudomonas tomato' .
"Pseudomonas helianthi" is a Gram-negative plant pathogenic bacterium that infects a variety of plants. It was once considered a pathovar of Pseudomonas syringae, but following DNA-relatedness studies, it was recognized as a separate species and P. syringae pv. tagetis was incorporated into it, as well. Since no official name has yet been given, it is referred to by the epithet 'Pseudomonas helianthi' .
Autoinducers are signaling molecules that are produced in response to changes in cell-population density. As the density of quorum sensing bacterial cells increases so does the concentration of the autoinducer. Detection of signal molecules by bacteria acts as stimulation which leads to altered gene expression once the minimal threshold is reached. Quorum sensing is a phenomenon that allows both Gram-negative and Gram-positive bacteria to sense one another and to regulate a wide variety of physiological activities. Such activities include symbiosis, virulence, motility, antibiotic production, and biofilm formation. Autoinducers come in a number of different forms depending on the species, but the effect that they have is similar in many cases. Autoinducers allow bacteria to communicate both within and between different species. This communication alters gene expression and allows bacteria to mount coordinated responses to their environments, in a manner that is comparable to behavior and signaling in higher organisms. Not surprisingly, it has been suggested that quorum sensing may have been an important evolutionary milestone that ultimately gave rise to multicellular life forms.
Bleeding canker of horse chestnut is a common canker of horse chestnut trees that is known to be caused by infection with several different pathogens.
Bacterial blight of soybean is a widespread disease of soybeans caused by Pseudomonas syringaepv. glycinea.
Giuseppe Maria Giovene was an Italian archpriest, naturalist, agronomist, geologist, meteorologist, entomologist and ichthyologist. He is best known for his studies on the "nitrosity" of Pulo di Molfetta, which made him famous abroad, so as to be cited and appreciated by many Italian and foreign scholars, including Eberhard August Wilhelm von Zimmermann in a French publication.
Tsune Kosuge was an American plant pathologist and plant biochemist who researched plant–microbe interactions. He was particularly known for his work on bacterial-synthesized plant hormones in plant tumors. He was a professor in the department of plant pathology at the University of California, Davis, from 1971 until his death, serving as departmental chair (1974–80).
Since the colonization of land by ancestral plant lineages 450 million years ago, plants and their associated microbes have been interacting with each other, forming an assemblage of species that is often referred to as a holobiont. Selective pressure acting on holobiont components has likely shaped plant-associated microbial communities and selected for host-adapted microorganisms that impact plant fitness. However, the high microbial densities detected on plant tissues, together with the fast generation time of microbes and their more ancient origin compared to their host, suggest that microbe-microbe interactions are also important selective forces sculpting complex microbial assemblages in the phyllosphere, rhizosphere, and plant endosphere compartments.
