| Xanthomonas oryzae pv. oryzae | |
|---|---|
 | |
| Xanthomonas oryzae pv. oryzae, bacterial blight of rice | |
Scientific classification  | |
| Domain: | Bacteria |
| Phylum: | Pseudomonadota |
| Class: | Gammaproteobacteria |
| Order: | Xanthomonadales |
| Family: | Xanthomonadaceae |
| Genus: | Xanthomonas |
| Species: | X. oryzae |
| Pathovar: | X. o. pv. oryzae |
| Trionomial name | |
| Xanthomonas oryzae pv. oryzae | |
Xanthomonas oryzae pv. oryzae is a bacterial pathovar that causes a serious blight of rice, other grasses, and sedges. [1]
The genus Xanthomonas , which mostly comprises phytopathogenic bacteria, is a member of the family Xanthomonadaceae. Among xanthomonads, X. o. pv. oryzae causes bacterial blight (BB) of rice which is one of the most important diseases of rice in most of the rice growing countries. [2]
Bacterial blight of rice has high epidemic potential and is destructive to high-yielding cultivars in both temperate and tropical regions especially in Asia. Its occurrence in the 70s in Africa and the Americas has led to concerns about its transmission and dissemination. [3]
Research on bacterial blight of rice was begun in Japan as early as in 1901, and those efforts were focused mainly on ecological studies and chemical control. Since then, significant gains have been made in understanding BB through analysis of the interactions between X. oryzae pv. oryzae and rice at many levels, including studies focused on the epidemiology, population biology, physiology, cell biology, biochemistry, and molecular genetics of the host pathogen interaction. It is very notable that BB became the first case where the genome sequencing of both host plant and pathogen was completed. [4]
There is a very large host range for Xanthomonas oryzae pv. oryzaa. [5]
Among the grasses, hosts include:
Among the Cyperaceae (Sedges), hosts include:
In its advanced stages, the disease is difficult to distinguish from leaf blight caused by X. o. pv. oryzicola, but lesion margins are wavy rather than linear as for the former. Damage is often associated with lepidopteran leaf rollers, leaf-folders and hispa beetles, since bacteria readily enter the damaged tissue caused by insect infestation. [6]
Rice plants become infected with Xanthomonas oryzae through rice seed, stem and roots that are left behind at harvest, as well as alternative weed hosts. X. oryzae lives on dead plants and seeds and probably moves plant-to-plant best through pattywater from irrigation or storms. Upon introduction to the host plant, the bacterium infiltrates the plant through natural openings (water pores and growth cracks on roots) and/or leaf and root wounds. X. oryzae grows in the plant and infects the plant's leaf veins as well as the xylem causing blockage and plant wilting. Bacteria oozes from leaf lesions and is spread by wind or rain, especially when strong storms occur and cause wounds to plants. X. oryzae has a wide host range that includes Leersia sayanuka which acts as alternative host for the bacterium and are considered the most important source of primary inoculums, as well as a great mechanism for bacterium survival. [7]
Xanthomonas oryzae is endemic to Japan, but can also be found throughout the tropical rice producing countries of Asia. In the tropics the pathogen has the highest level of incidence during the rainy season when rain and wind wound crops. Rain and infected pattywater are the main dispersers of the disease therefore fields found in low, wet areas with poor drainage and susceptibility to flooding are areas of high incidence. The presence of Leersia sayanuka is also key to the spread of disease because it is a naturally growing weed usually found around patties and has the ability to be infected by the bacterium and spread the bacterium through a rice patty.
The use of nitrogenous fertilizer has shown an increase in incidence but mainly because there is more plant growth and conditions stay more humid, [8] but does not have an effect on lesion size. During drier weather bacterial ooze will secrete from leaf lesions in hopes of finding a new host. Ideal temperatures for X. oryzae growth are 26–30 °C (79–86 °F); 20 °C (68 °F) being the best temperature for initial growth. X. oryzae can live in soil with pH range from 4–8.8; optimum pH being 6-6.50.
Xanthomonas oryzae causes a potentially devastating disease. Found worldwide in temperate and tropical regions, it can destroy up to 80 percent of a crop if the disease develops early. Even if it develops late, it can nonetheless severely diminish the quality and yield of the grain.
Bacterial leaf blight is a prevalent and destructive disease which affects millions of hectares/acres throughout Asia. [9] In Japan alone, annual losses are estimated to be between 22,000 and 110,000 tons[ clarification needed ]. In the Philippines, susceptible varieties lose up to 22.5% of the total harvest during wet seasons and up to 7.2% in the dry season. In resistant crops, these numbers are, respectively, 9.5% and 1.8%. [10]
Management of bacterial leaf blight is most commonly done by planting disease resistant rice plants. PSB Rc82 is the standard variety of rice used in Southeast Asia, and the use of this cultivar enables the harvest of an estimated 0.8 million metric tons of rice per cropping season that would have otherwise been lost to bacterial leaf blight. Macassane, a new variety released in 2011, has been shown to have improved resistance to bacterial leaf blight and is being used currently in Mozambique. [11]
Traditional treatments, such as the applications of copper compounds or antibiotics, are largely ineffective in the control of bacterial leaf blight. Increasingly, rice is being genetically engineered for resistance to the disease, as treatment proves difficult. More than 30 genes have been identified as being associated with resistance to bacterial leaf blight, and have been given names Xa1 to Xa33. [12]
Biological control methods are relatively recent developments which are not currently in common use. They may be used in the future to reduce damage done by bacterial leaf blight, with experimental data showing up to a 64% reduction in damage. [13] Including the use of metabolic products isolated from fungus Paraphaeosphaeria minitans (syn.Coniothyrium minitans). [14]
The first definite evidence of cost of virulence in any plant pathogen was discovered in this bacterium. [15] Vera Cruz et al., 2000 find it is possible to find and quantify this subtype of evolutionary trade-off in Xoo. [15] They do this by trialling Xoo isolates against rice isogenic lines with clones of avirulence genes to obtain the necessary precision. [15]
In 2019, genes that enable host resistance to bacterial blight were engineered into rice, leading to more than ten resistant cultivars. They rely on resistance genes Xa4, xa5, xa13, Xa21, Xa33 and Xa38, and were released for commercial cultivation. [16]
The OsSWEET13 transcription promoter is related to resistance in an unusual way. [17] Zhou et al., 2015 knocks out OsSWEET13 using PthXo2– a transcription activator-like effector nuclease (TALEN). [17] Knockout produces a rice with resistance to Xoo. [17]
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.
Magnaporthe grisea, also known as rice blast fungus, rice rotten neck, rice seedling blight, blast of rice, oval leaf spot of graminea, pitting disease, ryegrass blast, Johnson spot, neck blast, wheat blast and Imochi (稲熱), is a plant-pathogenic fungus and model organism that causes a serious disease affecting rice. It is now known that M. grisea consists of a cryptic species complex containing at least two biological species that have clear genetic differences and do not interbreed. Complex members isolated from Digitaria have been more narrowly defined as M. grisea. The remaining members of the complex isolated from rice and a variety of other hosts have been renamed Magnaporthe oryzae, within the same M. grisea complex. Confusion on which of these two names to use for the rice blast pathogen remains, as both are now used by different authors.
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.
Bacterial blight is a disease of barley caused by the bacterial pathogen Xanthomonas campestris pv. translucens. It has been known as a disease since the late 19th century. It has a worldwide distribution.
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.
Xanthomonas is a genus of bacteria, many of which cause plant diseases. There are at least 27 plant associated Xanthomonas spp., that all together infect at least 400 plant species. Different species typically have specific host and/or tissue range and colonization strategies.
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.
Xanthomonas arboricola is a species of bacteria. This phytopathogenic bacterium can cause disease in trees like Prunus, hazelnut and walnut.
Xanthomonas fragariae is a species of bacteria. It causes a leaf spot disease found in strawberries. The type strain is NCPPB1469 from Fragaria chiloensis var. ananassa.
Xanthomonas oryzae is a species of bacteria. The major host of the bacterium is rice.
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.
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.
Banana Xanthomonas Wilt (BXW), or banana bacterial wilt (BBW) or enset wilt is a bacterial disease caused by Xanthomonas campestris pv. musacearum. After being originally identified on a close relative of banana, Ensete ventricosum, in Ethiopia in the 1960s, BXW emanated in Uganda in 2001 affecting all types of banana cultivars. Since then BXW has been diagnosed in Central and East Africa including banana growing regions of: Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Burundi, and Uganda.
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
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.
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]
Bacterial blight of soybean is a widespread disease of soybeans caused by Pseudomonas syringaepv. glycinea.
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.