Citrus production encompasses the production of citrus fruit, which are the highest-value fruit crop in terms of international trade. There are two main markets for citrus fruit:
Psyllidae, the jumping plant lice or psyllids, are a family of small plant-feeding insects that tend to be very host-specific, i.e. each plant-louse species only feeds on one plant species (monophagous) or feeds on a few closely related plants (oligophagous). Together with aphids, phylloxerans, scale insects and whiteflies, they form the group called Sternorrhyncha, which is considered to be the most "primitive" group within the true bugs (Hemiptera). They have traditionally been considered a single family, Psyllidae, but recent classifications divide the group into a total of seven families; the present restricted definition still includes more than 70 genera in the Psyllidae. Psyllid fossils have been found from the Early Permian before the flowering plants evolved. The explosive diversification of the flowering plants in the Cretaceous was paralleled by a massive diversification of associated insects, and many of the morphological and metabolic characters that the flowering plants exhibit may have evolved as defenses against herbivorous insects.
Phytoplasmas are obligate intracellular parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission. Phytoplasmas were discovered in 1967 by Japanese scientists who termed them mycoplasma-like organisms. Since their discovery, phytoplasmas have resisted all attempts at in vitro culture in any cell-free medium; routine cultivation in an artificial medium thus remains a major challenge. Phytoplasmas are characterized by the lack of a cell wall, a pleiomorphic or filamentous shape, a diameter normally less than 1 μm, and a very small genome.
Citrus greening disease or yellow dragon disease is a disease of citrus caused by a vector-transmitted pathogen. The causative agents are motile bacteria, Liberibacter spp. The disease is transmitted by the Asian citrus psyllid, Diaphorina citri, and the African citrus psyllid, Trioza erytreae, also known as the two-spotted citrus psyllid. It has no known cure. It has also been shown to be graft-transmissible.
Acholeplasmataceae is a family of bacteria. It is the only family in the order Acholeplasmatales, placed in the class Mollicutes. The family comprises the genera Acholeplasma and Phytoplasma. Phytoplasma has the candidatus status, because members still could not be cultured.
Spiroplasma is a genus of Mollicutes, a group of small bacteria without cell walls. Spiroplasma shares the simple metabolism, parasitic lifestyle, fried-egg colony morphology and small genome of other Mollicutes, but has a distinctive helical morphology, unlike Mycoplasma. It has a spiral shape and moves in a corkscrew motion. Many Spiroplasma are found either in the gut or haemolymph of insects where they can act to manipulate host reproduction, or defend the host as endosymbionts. Spiroplasma are also disease-causing agents in the phloem of plants. Spiroplasmas are fastidious organisms, which require a rich culture medium. Typically they grow well at 30 °C, but not at 37 °C. A few species, notably Spiroplasma mirum, grow well at 37 °C, and cause cataracts and neurological damage in suckling mice. The best studied species of spiroplasmas are Spiroplasma poulsonii, a reproductive manipulator and defensive insect symbiont, Spiroplasma citri, the causative agent of citrus stubborn disease, and Spiroplasma kunkelii, the causative agent of corn stunt disease.
Xylella fastidiosa is an aerobic, Gram-negative bacterium of the genus Xylella. It is a plant pathogen, that grows in the water transport tissues of plants and is transmitted exclusively by xylem sap-feeding insects such as sharpshooters and spittlebugs. Many plant diseases are due to infections of X. fastidiosa, including bacterial leaf scorch, oleander leaf scorch, coffee leaf scorch (CLS), alfalfa dwarf, phony peach disease, and the economically important Pierce's disease of grapes (PD), olive quick decline syndrome (OQDS), and citrus variegated chlorosis (CVC). While the largest outbreaks of X. fastidiosa–related diseases have occurred in the Americas and Europe, this pathogen has also been found in Taiwan, Israel, and a few other countries worldwide.
"Candidatus Carsonella ruddii" is an obligate endosymbiotic Gammaproteobacterium with one of the smallest genomes of any characterised bacteria.
Ralstonia solanacearum is an aerobic non-spore-forming, Gram-negative, plant pathogenic bacterium. R. solanacearum is soil-borne and motile with a polar flagellar tuft. It colonises the xylem, causing bacterial wilt in a very wide range of potential host plants. It is known as Granville wilt when it occurs in tobacco. Bacterial wilts of tomato, pepper, eggplant, and Irish potato caused by R. solanacearum were among the first diseases that Erwin Frink Smith proved to be caused by a bacterial pathogen. Because of its devastating lethality, R. solanacearum is now one of the more intensively studied phytopathogenic bacteria, and bacterial wilt of tomato is a model system for investigating mechanisms of pathogenesis. Ralstonia was until recently classified as Pseudomonas, with similarity in most aspects, except that it does not produce fluorescent pigment like Pseudomonas. The genomes from different strains vary from 5.5 Mb up to 6 Mb, roughly being 3.5 Mb of a chromosome and 2 Mb of a megaplasmid. While the strain GMI1000 was one of the first phytopathogenic bacteria to have its genome completed, the strain UY031 was the first R. solanacearum to have its methylome reported. Within the R. solanacearum species complex, the four major monophyletic clusters of strains are termed phylotypes, that are geographically distinct: phylotypes I-IV are found in Asia, the Americas, Africa, and Oceania, respectively.
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.
Pantoea agglomerans is a Gram-negative bacterium that belongs to the family Erwiniaceae.
Bactericera cockerelli, also known as the potato psyllid, is a species of psyllid native to southern North America. Its range extends from Central America north to the American Pacific Northwest and parts of Manitoba, in Canada. It is restricted to the western part of the continent. As its name suggests, it is commonly found on potato and tomato crops, but has a species range that encompasses over 40 species of solanaceous plants and as many as 20 genera. Breeding hosts are generally recognised as being restricted primarily to Solanaceae, including important crop and common weed species, and a few species of Convolvulaceae, including bindweed and sweet potato. On some plants, especially potato, feeding of the nymphs causes a condition called psyllid yellows, presumed to be the result of a toxin. Both nymphs and adults can transmit the bacterium Candidatus Liberibacter.
Psyllid yellows is a disease of potatoes infested by the potato/tomato psyllid, Bactericera cockerelli. The symptoms are a marked yellowing of the leaves, an upright appearance to the leaves, with severe cases resulting in early death of the plant. Tuber initiation and growth is affected. Many small tubers are formed, frequently misshaped. In some cases, the tubers seem to have lost sprouting inhibition and have begun sprouting before harvest. At later stages, the tubers sprout weakly, if at all.
Zebra chip, also known as papa manchada and papa rayada, is a disease in potatoes putatively caused by an alphaproteobacterium "Candidatus Liberibacter solanacearum", which is vectored by the potato psyllid. When fried, potato tubers from infected plants develop unsightly black lines resembling the stripes of zebras that render the chips unsellable. Additionally, striped sections of chips frequently burn and caramelize, resulting in a bitter flavor. No health risks have been connected with consumption of infected potato chips.
Diaphorina citri, the Asian citrus psyllid, is a sap-sucking, hemipteran bug now in the taxonomic family Psyllidae. It is one of two confirmed vectors of citrus greening disease. It has a wide distribution in southern Asia and has spread to other citrus growing regions.
Trioza erytreae, the African citrus psyllid, is a sap-sucking insect, a hemipteran bug in the family Triozidae. It is an important pest of citrus, being one of only two known vectors of the serious citrus disease, huanglongbing or citrus greening disease. It is widely distributed in Africa. The other vector is the Asian citrus psyllid, Diaphorina citri.
Spiroplasma citri is a bacterium species and the causative agent of Citrus stubborn disease.
Tamarixia radiata, the Asian citrus cyllid parasitoid, is an hymenopteran wasp from the family Eulophidae which was discovered in the 1920s in the area of northwestern India (Punjab), now Pakistan. It is a parasitoid of the Asian citrus psyllid, an economically important pest of citrus crops around the world and a vector for Citrus greening disease.
Xanthoferrin is an α-hydroxycarboxylate-type of siderophore produced by xanthomonads. Xanthomonas spp. secrete xanthoferrin to chelate iron under low-iron conditions. The xanthoferrin siderophore mediated iron uptake supports bacterial growth under iron-restricted environment.
Spiroplasma kunkelii is a species of Mollicutes, which are small bacteria that all share a common cell wall-less feature. They are characterized by helical and spherical morphology, they actually have the ability to be spherical or helical depending on the circumstances. The cells movement is bound by a membrane. The cell size ranges from 0.15 to 0.20 micrometers.
