Instruct: Given a question, retrieve passages that answer the question.
Query: What is blight in tomatoes?
Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. Accordingly, many diseases that primarily exhibit this symptom are called blights. Several notable examples are:
To continue, the symptoms of this bacterial blight include spots and lesions on leaves, and rot of floral buds and flowers. The floral symptoms undergo changes throughout the seasons that ultimately end in the floral bud dying and falling off. These symptoms are found initially as brown and sunken spots on the green sepals of the vine that enclose the flower buds. The result is the flower buds begin to rot when unopened. If the buds do open and yield a yellow-orange color, rather than white, the flower turns brown rather quickly and dies. In addition, the anthers or male sexual parts of the flower can be destroyed in this disease causing an incomplete retraction of sepals. Regarding the leaves, symptoms are visible in later spring and are found on the lower leaves first. The lesions created are angular and gray on the lower leaves, and the lesions are surrounded with a yellow halo on the upper leaves. These lesions turn brown and can be a site for a secondary infection by a fungus or some other pathogen. All of this leads to abnormal fruit development on diseased plants which can create an economic problem for the grower. Fruit development is the largest economical concern when referring to this pathogen. Yield loss can become very high, reaching over 90% in orchards that have symptoms of this pathogen. When no symptoms are present, however, the plant is healthy and fruit development is normal. It is stated that it is very rare to find normal fruit development on plants with symptoms of bacterial blight showing how detrimental this disease and pathogen is.
Bacterial blight of soybeans can enter leaves through wounds or natural openings such as stomata. After gaining entrance to the host leaves, "Pseudomonas syringae pv. glycinea" multiplies in the leaf intercellular fluid. The pathogen must then overcome the plants defenses. "Pseudomonas syringae pv. glycinea" accomplishes this by using the type three secretion system to inject a variety of pathogenicity effector proteins (Hrp proteins) into the plant cell cytoplasm. These proteins act by interfering with effector-triggered immunity and producing phytohormones/toxins that suppress plant defenses. The expression of these virulence factors depends on the environmental conditions at the time of infection (see "environment section). Furthermore, expression of virulence factors will only take place when a sufficiently large population of bacteria is present, which is determined through quorum sensing. When successful, the common symptoms of bacterial blight will be seen, with the main effect on the plant being a reduction in photosynthetic leaf area. Generally, the amount of photosynthetic area lost is not enough to impede plant growth. As the plant continues to grow it overcomes the loss of photosynthetic area and reduction in yield, if there is any, is negligible.
Although insects can be a problem, by far the biggest killer of carnivorous plants (besides human maltreatment) is grey mold ("Botrytis cinerea"). This thrives under warm, humid conditions and can be a real problem in winter. To some extent, temperate carnivorous plants can be protected from this pathogen by ensuring that they are kept cool and well ventilated in winter and that any dead leaves are removed promptly. If this fails, a fungicide is in order.
Group C
The spores remain viable for five years in fallen boxwood leaves, and are dispersed by wind and rain over short distances. Since they are sticky the spores may also be spread by birds, animals, and contaminated clothing and footwear. The most common mode of transmitting the blight is by the introduction of asymptomatic plants, or plants treated with fungicide (which can mask the disease) to unaffected areas. Warm and humid conditions facilitate its spread. The fungus does not need a wound to infect a plant, but it does require high humidity or free water.
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A few strains from organisms genetically identified as other "Clostridium" species have caused human botulism: "C. butyricum" has produced type E toxin and "C. baratii" had produced type F toxin. The ability of "C. botulinum" to naturally transfer neurotoxin genes to other clostridia is concerning, especially in the food industry, where preservation systems are designed to destroy or inhibit only "C. botulinum" but not other "Clostridium" species.
Striga hermonthica, commonly known as purple witchweed or giant witchweed, is a hemiparasitic plant that belongs to the family Orobanchaceae. It is devastating to major crops such as sorghum ("Sorghum bicolor") and rice ("Oryza sativa"). In sub-Saharan Africa, apart from sorghum and rice, it also infests maize ("Zea mays"), pearl millet ("Pennisetum glaucum"), and sugar cane ("Saccharum officinarum").
The first genetically modified crop, an antibiotic-resistant tobacco plant, was produced in 1982. China was the first country to commercialize transgenic plants, introducing a virus-resistant tobacco in 1992. In 1994 Calgene attained approval to commercially release the Flavr Savr tomato, the first genetically modified food. Also in 1994, the European Union approved tobacco engineered to be resistant to the herbicide bromoxynil, making it the first genetically engineered crop commercialised in Europe. An insect resistant Potato was approved for release in the US in 1995, and by 1996 approval had been granted to commercially grow 8 transgenic crops and one flower crop (carnation) in 6 countries plus the EU.
Group D
Early detection of "P. ramorum" is essential for its control. On an individual-tree basis, preventive treatments, which are more effective than therapeutic treatments, depend on knowledge of the pathogen’s movement through the landscape to know when it is nearing prized trees. On the landscape level, "P. ramorum’s" fast and often undetectable movement means that any treatment hoping to slow its spread must happen very early in the development of an infestation. Since "P. ramorum’s" discovery, researchers have been working on the development of early detection methods on scales ranging from diagnosis in individual infected plants to landscape-level detection efforts involving large numbers of people.
Soybean is one of the most important commercial crops around the world and in the United States. Asian soybean rust is the major disease that affects soybeans. It causes lesions on the leaves of soybean plants and eventually kills the plants. The disease has caused serious yield loss of soybeans. In the areas where this disease is common, the yield losses can be up to 80%. In 2002, USDA reported 10-60% of yield losses in South America and Africa.
Food-borne botulism results, indirectly, from ingestion of food contaminated with Clostridium spores, where exposure to an anaerobic environment allows the spores to germinate, after which the bacteria can multiply and produce toxin. Critically, "it is ingestion of toxin rather than spores or vegetative bacteria" that causes botulism. Botulism is nevertheless known to be transmitted through canned foods not cooked correctly before canning or after can opening, and so is preventable. Infant botulism cases arise chiefly as a result of environmental exposure and are therefore more difficult to prevent. Infant botulism arising from consumption of honey can be prevented by eliminating honey from diets of children less than 12 months old.
Fungi, bacteria and viruses attack cacti, the first two particularly when plants are over-watered. Fusarium rot can gain entry through a wound and cause rotting accompanied by red-violet mold. ""Helminosporium" rot" is caused by "Bipolaris cactivora" ( "Helminosporium cactivorum"); "Phytophthora" species also cause similar rotting in cacti. Fungicides may be of limited value in combating these diseases. Several viruses have been found in cacti, including cactus virus X. These appear to cause only limited visible symptoms, such as chlorotic (pale green) spots and mosaic effects (streaks and patches of paler color). However, in an "Agave" species, cactus virus X has been shown to reduce growth, particularly when the roots are dry. There are no treatments for virus diseases.
In South America, a phenomenon known as the El Nino Oscillation Cycle, between floods and drought on the Pacific Coast has made as much as a 35% difference in Global yields of wheat and grain.
Research and development in managing "P. ramorum" in nursery settings extends from "P. ramorum" in the individual plant, to "P. ramorum" in the nursery environment, to the pathogen’s movement across state and national borders in infected plants.
The pomelo ("Citrus maxima"), a second of the core species from which most citrus hybrids have derived, is native to southeast Asia. Among the hybrids deriving from mandarin/pomelo crosses, there is a direct correlation between the proportion of pomelo DNA in the hybrid and fruit size, while the more palatable mandarins are those that have received specific genes from pomelos that alter their acidity. Some of the more common pomelos are genetically pure, while a number have a single small region of introgressed mandarin DNA on one chromosome, the result of a cross followed by extensive backcrossing with pomelo.
Pomelo (the Asian fruit that was crossed with an orange to produce grapefruit) contains high amounts of furanocoumarin derivatives. Grapefruit relatives and other varieties of pomelo have variable amounts of furanocoumarin.
Wheat diseases such as wheat bunt and stinking smut can be successfully treated with a fungicide. 
Disease of plants and animals can break an agricultural producer. Tuberculosis in animals was an early threat, and cattle needed to be tested, and areas accredited in 1956. The newer disease such as chronic wasting disease or transmissible spongiform encephalopathy (TSE) affects both elk and deer. Elk and deer raising is a pioneer field of domestication, has had a setback with this disease. Mad cow disease in cattle and scrapie of sheep are monitored by the Canadian Food Inspection Agency. The poultry sector was plagued by Pullorum disease, and by controlling the flock via poultry husbandry, this disease has been brought under control.
Organophosphate pesticides are one of the top causes of poisoning worldwide, with an annual incidence of poisonings among agricultural workers varying from 3-10% per country.
Stemphylium solani is a plant pathogen fungus in the phylum Ascomycota. It is the causal pathogen for grey leaf spot in tomatoes and leaf blight in alliums and cotton, though a wide range of additional species can serve as hosts. Symptoms include white spots on leaves and stems that progress to sunken red or purple lesions and finally leaf necrosis. "S. solani" reproduces and spreads through the formation of conidia on conidiophores. The teleomorph name of "Stemphyllium" is Pleospora though there are no naturally known occurrences of sexual reproduction. Resistant varieties of tomato and cotton are common, though the pathogen remains an important disease in Chinese garlic cultivation.
Early blight caused by "A. solani" is the most destructive disease of tomatoes in the tropical and subtropical regions. Each 1% increase in intensity can reduce yield by 1.36%, and complete crop failure can occur when the disease is most severe. Yield losses of up to 79% have been reported in the U.S., of which 20-40% is due to seedling losses (i.e., collar rot) in the field.
Alternaria solani is a fungal pathogen, that produces a disease in tomato and potato plants called early blight. The pathogen produces distinctive "bullseye" patterned leaf spots and can also cause stem lesions and fruit rot on tomato and tuber blight on potato. Despite the name "early," foliar symptoms usually occur on older leaves. If uncontrolled, early blight can cause significant yield reductions. Primary methods of controlling this disease include preventing long periods of wetness on leaf surfaces and applying fungicides.
AAL’s main symptom is cankers in the stem. It resides in seeds and seedlings, and is often spread by spores as they become airborne and land on plants. It can also spread throughout other plants. Under severe infection, lesions enlarge and become coalesced causing blighting of the leaves. This symptom progression occurred in research done in Pakistan: the symptoms on affected tomatoes started with yellowing and browning of the lower leaves, then began developing on the leaf tips and along the margins of the leaf petiole. This progression continued until the entire leaves were covered in diseased tissue and then fell off. In addition under to necrotic leaves and petioles, plants are found to have severe defoliation, with considerable yield losses when it occurs before flowering. The tomato fruit can also be infected as well, with brown cankers dotting them and making them inedible. Once the disease has spread to a certain point, little can be done to save the tomato plant.