| Xanthomonas fragariae | |
|---|---|
Scientific classification  | |
| Domain: | Bacteria |
| Phylum: | Pseudomonadota |
| Class: | Gammaproteobacteria |
| Order: | Xanthomonadales |
| Family: | Xanthomonadaceae |
| Genus: | Xanthomonas |
| Species: | X. fragariae |
| Binomial name | |
| Xanthomonas fragariae Kennedy and King 1962 | |
| Type strain | |
| NCPPB 1469 | |
Xanthomonas fragariae is a species of bacteria. It causes a leaf spot disease found in strawberries (Fragaria spp.). [1] The type strain is NCPPB1469 from Fragaria chiloensis var. ananassa.
Favorable environmental factors for Xanthomonas fragariae are not fully understood and need to be studied more. It has been noticed, however, that X. fragariae thrive in humid climates. [2] Xanthomonas fragariae are also most prevalent in climates with cool to moderate temperatures. [3]
Infection caused by the angular leaf spot pathogen first appears as water-soaked lesions found on the lower surface of strawberry leaves. These water-soaked lesions are the result of bacterial colonization within the plant leaf tissue. Lesions typically get larger as the infection worsens, and the enlarged lesions then form translucent spots. These angular spots typically exude an ooze of bacteria that appears as a white and flakey film once dry.[2] Lesions on the upper surface of leaves will also become visible with time. As the disease worsens, the angular spots grow larger and begin to combine. Severely affected leaves can tear away and become jagged, with a dry and reddish-brown appearance. Prolonged wetness on strawberry leaves can exacerbate this disease, so air circulation and sunlight exposure are important to protecting the host plants. These symptoms are similar to leaf scorch and common leaf spot so be careful when examining symptoms of diseased plants.[3] Dark purple spots scattered on the leaf surface are symptoms of leaf scorch and common leaf spot, but not angular leaf spot. [4]
X. fragariae was first reported on strawberries in 1960 in Minnesota. [3] It is now found throughout many American states, Europe, South America, Africa, Australia, and New Zealand. [5] X. fragariae does not have a large host range, it infects different strawberry varieties, including Fragaria virginiana and F. vesca , along with Potentilla fruticosa, and P. glandulosa. [6] Even though X. fragariae has a small host range, it is capable of causing major damage. Angular Leaf Spot, caused by X. fragariae, can cause up to 75% yield reduction of strawberries. [2] Angular Leaf Spot is currently an issue in strawberry nursery production, leading to problems in transporting strawberry plants throughout the U.S and over to Europe. [5] Xanthomonas fragariae is not only an issue transporting young plants, but infected fruits can lead to a symptom known as “black cap” that can reduce the quality and marketability of the fruit. [5]
Place suspected diseased leaves up against a bright light to see the translucent spots associated with Xanthomonas fragariae.[4] By looking from the backside of infected leaves, light should pass through the angular shaped lesions and appear as lighter colored patches.
X. fragariae is a gram-negative bacterium, that is rod shaped ranging from 0.4-1.0 μm wide and 0.7-2.0 μm long (Louws). [7] The primary host of X. fragariae are strawberry plants (F. virginiana and F. vesca). [6] X. fragariae are classified as an A2 level quarantine pathogen by the European Plant Protection Organization, meaning that this bacteria can be spread easily through the movement of strawberry plants. [5] X. fragariae will attack both the stock and the fruit of strawberries plants. [8] X. fragariae is often spread by infected transplants or systemically infected overwintered plants and dead leaves. [3] It can also be spread plant to plant through water droplets from rain or irrigation. [3] Once X. fragariae lands on a new host, it will enter into the strawberry plant through its open stomata. [8] X. fragariae produces many toxins that are key factors in pathogenesis, including hemolytic and cytolytic RTX-toxins. [8] X. fragariae also uses a T3SS to secrete T3E genes: xopN, xopR, xopV to suppress the innate immune response in strawberries. [8]
The primary source of inoculum is previously infected debris and necrotic plant tissue, as the pathogen itself cannot freely survive in the soil.[5] Strawberry plants that suffer from systemic infection unfortunately have the bacteria in their vascular system. In spring, after the crowns of infected live plants overwinter, the vascularized bacteria become active and begin inducing symptoms. Bacteria oozes out of the leaf lesions, causing the disease to spread when rain splashes the bacteria onto other susceptible plants and enters through natural openings or wounds. [6]
Chemical controls are ineffective against this disease, and the use of copper containing compounds can cause phytotoxicity in the plants. It is best to destroy infected leaves, plants, and debris immediately by burning or burying it. [9] Cultural controls can include choosing a growing site with adequate air circulation, low humidity, and moderate daytime temperatures to promote the drying of plant leaves. Also try to limit the surrounding weeds so that air circulation is not compromised, and use overhead irrigation if available. Avoid harvesting or moving equipment when fields are wet to limit wounding on susceptible plants. Although there are no completely resistant cultivars, using less susceptible cultivars can be a helpful preventative measure. Allstar, Annapolis, Cavendish, Honeoye, and Kent are the least resistant to the disease and should be planted with high caution. [10] Relatively recent studies by Turecheck et al. [5] have shown heat treatments to be successful in dealing with angular leaf spot. They found that the number of living Xanthomonas fragariae were reduced by a minimum of 105-106 CFU/ml after exposing infected plants to heat treatments of 44-48o C for 2–4 hours. [11] At temperatures this high, this bacterial pathogen can be killed on infected plants. It is still unclear how these treatments would be conducted on commercial scales however, so other modes of control are being investigated.
A leaf spot is a limited, discoloured, diseased area of a leaf that is caused by fungal, bacterial or viral plant diseases, or by injuries from nematodes, insects, environmental factors, toxicity or herbicides. These discoloured spots or lesions often have a centre of necrosis. Symptoms can overlap across causal agents, however differing signs and symptoms of certain pathogens can lead to the diagnosis of the type of leaf spot disease. Prolonged wet and humid conditions promote leaf spot disease and most pathogens are spread by wind, splashing rain or irrigation that carry the disease to other leaves.
Citrus canker is a disease affecting Citrus species caused by the bacterium Xanthomonas. Infection causes lesions on the leaves, stems, and fruit of citrus trees, including lime, oranges, and grapefruit. While not harmful to humans, canker significantly affects the vitality of citrus trees, causing leaves and fruit to drop prematurely; a fruit infected with canker is safe to eat, but too unsightly to be sold. Citrus canker is mainly a leaf-spotting and rind-blemishing disease, but when conditions are highly favorable, it can cause defoliation, shoot dieback, and fruit drop.
Xanthomonas campestris is a gram-negative, obligate aerobic bacterium that is a member of the Xanthomonas genus, which is a group of bacteria that are commonly known for their association with plant disease. This species includes Xanthomonas campestris pv. campestris the cause of black rot of brassicas, one of the most important diseases of brasicas worldwide.
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.
Xanthomonas arboricola is a species of bacteria. This phytopathogenic bacterium can cause disease in trees like Prunus, hazelnut and walnut.
Xanthomonas vasicola pv. vasculorum (Xvv) is a gram-negative rod-shaped bacterium which has a single polar flagellum. It is a plant pathogen, causing both bacterial leaf streak of maize (corn) and sugarcane gumming disease. One outbreak in eucalyptus has been reported. Under experimental conditions it can infect sorghum, oats and some grass species. It is not currently a quarantine pathogen in any country, but it has already spread outside its native range and is highly adaptable to different environments.
Diplocarpon earlianum is a species of fungus that causes disease in strawberry plants called strawberry leaf scorch. The disease overwinters in plant debris and infects strawberry plants during the spring season when it is wet. The five main methods to reduce strawberry leaf scorch include: irrigation techniques, crop rotation, planting resistant and disease-free seeds, fungicide use, and sanitation measures. Control of strawberry leaf scorch is important because it is responsible for the majority of disease in strawberries. Diplocarpon earliana affects the fruit quality and yield of the strawberry crop. Losses range from negligible to severe depending on numerous epidemiological factors including cultivar susceptibility, type of cropping system, and weather conditions
Phomopsis obscurans is a common fungus found in strawberry plants, which causes the disease of leaf blight. Common symptoms caused by the pathogen begin as small circular reddish-purple spots and enlarge to form V-shaped lesions that follow the vasculature of the plant's leaves. Although the fungus infects leaves early in the growing season when the plants are beginning to develop, leaf blight symptoms are most apparent on older plants towards the end of the growing season. The disease can weaken strawberry plants through the destruction of foliage, which results in reduced yields. In years highly favorable for disease development, leaf blight can ultimately lead to the death of the strawberry plants. A favorable environment for the growth and development of the Phomopsis obscurans pathogen is that of high temperature, high inoculum density, a long period of exposure to moisture, and immature host tissue. In the case of disease management, a conjunction of cultural practices is the most effective way of reducing the infection.
Xylophilus ampelinus is a species of bacteria that can cause plant disease. It is available from the NCPPB in the United Kingdom and other international culture collections such as ICMP in New Zealand, and LMG/BCCM in Belgium.
Strawberry foliar nematode, or strawberry crimp nematode, is a disease caused by Aphelenchoides fragariae, a plant pathogenic nematode. It is common in strawberries and ornamental plants and can greatly affect plant yield and appearance, resulting in a loss of millions of dollars of revenue. Symptoms used to diagnose the disease are angular, water soaked lesions and necrotic blotches. Aphelenchoides fragariae is the nematode pathogen that causes the disease. Its biological cycle includes four life stages, three of which are juvenile. The nematode can undergo multiple life cycles in one growing season when favorable conditions are present. The crowns, runners, foliage, and new buds of the plant via stylet penetration or through the stomata can be infected. The best management practices for this disease are sanitation, prevention of induction of the pathogen to the environment, and planting clean seed or starter plants.
Bacterial leaf scorch is a disease state affecting many crops, caused mainly by the xylem-plugging bacterium Xylella fastidiosa. It can be mistaken for ordinary leaf scorch caused by cultural practices such as over-fertilization.
Black rot, caused by the bacterium Xanthomonas campestris pv. campestris (Xcc), is considered the most important and most destructive disease of crucifers, infecting all cultivated varieties of brassicas worldwide. This disease was first described by botanist and entomologist Harrison Garman in Lexington, Kentucky, US in 1889. Since then, it has been found in nearly every country in which vegetable brassicas are commercially cultivated.
Xanthomonas campestris pv. vesicatoria is a bacterium that causes bacterial leaf spot (BLS) on peppers and tomatoes. It is a gram-negative and rod-shaped. It causes symptoms throughout the above-ground portion of the plant including leaf spots, fruit spots and stem cankers. Since this bacterium cannot live in soil for more than a few weeks and survives as inoculum on plant debris, removal of dead plant material and chemical applications to living plants are considered effective control mechanisms.
Bacterial blight of cotton is a disease affecting the cotton plant resulting from infection by Xanthomonas axonopodis pathovar malvacearum (Xcm) a Gram negative, motile rod-shaped, non spore-forming bacterium with a single polar flagellum
Common spot of strawberry is one of the most common and widespread diseases afflicting the strawberry. Common spot of strawberry is caused by the fungus Mycosphaerella fragariae. Symptoms of this disease first appear as circular, dark purple spots on the leaf surface. Mycosphaerella fragariae is very host-specific and only infects strawberry.
Xanthomonas axonopodis pv. manihotis is the pathogen that causes bacterial blight of cassava. Originally discovered in Brazil in 1912, the disease has followed the cultivation of cassava across the world. Among diseases which afflict cassava worldwide, bacterial blight causes the largest losses in terms of yield.
Bacterial wilt of turfgrass is the only known bacterial disease of turf. The causal agent is the Gram negative bacterium Xanthomonas translucens pv. graminis. The first case of bacterial wilt of turf was reported in a cultivar of creeping bentgrass known as Toronto or C-15, which is found throughout the midwestern United States. Until the causal agent was identified in 1984, the disease was referred to simply as C-15 decline. This disease is almost exclusively found on putting greens at golf courses where extensive mowing creates wounds in the grass which the pathogen uses in order to enter the host and cause disease.
Xanthomonas oryzae pv. oryzae is a bacterial pathovar that causes a serious blight of rice, other grasses, and sedges.
Bacterial leaf streak (BLS), also known as black chaff, is a common bacterial disease of wheat. The disease is caused by the bacterial species Xanthomonas translucens pv. undulosa. The pathogen is found globally, but is a primary problem in the US in the lower mid-south and can reduce yields by up to 40 percent.[6] BLS is primarily seed-borne and survives in and on the seed, but may also survive in crop residue in the soil in the off-season. During the growing season, the bacteria may transfer from plant to plant by contact, but it is primarily spread by rain, wind and insect contact. The bacteria thrives in moist environments, and produces a cream to yellow bacterial ooze, which, when dry, appears light colored and scale-like, resulting in a streak on the leaves. The invasion of the head of wheat causes bands of necrotic tissue on the awns, which is called Black Chaff.[14] The disease is not easily managed, as there are no pesticides on the market for treatment of the infection. There are some resistant cultivars available, but no seed treatment exists. Some integrated pest management (IPM) techniques may be used to assist with preventing infection although, none will completely prevent the disease.[2]
Xanthomonas campestris pv. juglandis is an anaerobic, Gram negative, rod-shaped bacteria that can affect walnut trees though the flowers, buds, shoots, branches, trunk, and fruit. It can have devastating effects including premature fruit drop and lesions on the plant. This pathogen was first isolated by Newton B. Pierce in California in 1896 and was then named Pseudomonas juglandis. In 1905 it was reclassified as Bacterium juglandis, in 1930 it became Phytomas juglandis, and in 1939 it was named Xanthomas juglandis. The International Standards for Naming Pathovars declared it to be named Xanthomonas campestris pv. juglandis in 1980. There have been recent proposals to change the name once again to Xanthomonas arboricola pv. juglandis, but this has not yet been universally accepted.