Viroids are small infectious pathogens. They are composed solely of a short strand of circular, single-stranded RNA. Unlike viruses, they have no protein coating. All known viroids are inhabitants of angiosperms, and most cause diseases, whose respective economic importance to humans varies widely.
Citrus is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus Citrus is native to South Asia, East Asia, Southeast Asia, Melanesia, and Australia. Various citrus species have been used and domesticated by indigenous cultures in these areas since ancient times. From there its cultivation spread into Micronesia and Polynesia by the Austronesian expansion ; and to the Middle East and the Mediterranean via the incense trade route, and onwards to Europe.
A clementine is a tangor, a citrus fruit hybrid between a willowleaf mandarin orange and a sweet orange, named for its late 19th-century discoverer. The exterior is a deep orange colour with a smooth, glossy appearance. Clementines can be separated into 7 to 14 segments. Similar to tangerines, they tend to be easy to peel. They are typically juicy and sweet, with less acid than oranges. Their oils, like other citrus fruits, contain mostly limonene as well as myrcene, linalool, α-pinene and many complex aromatics.
Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen, red, and may bleed. In its more serious form, called periodontitis, the gums can pull away from the tooth, bone can be lost, and the teeth may loosen or fall out. Bad breath may also occur.
Corymbia ficifolia, commonly known as the red flowering gum, is a species of small tree that is endemic to the south-west of Western Australia. It has rough, fibrous bark on the trunk and branches, egg-shaped to broadly lance-shape adult leaves, flower buds in groups of seven, bright red, pink or orange flowers and urn-shaped fruit. It has a restricted distribution in the wild but is one of the most commonly planted ornamental eucalypts.
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:
American sweetgum, also known as American storax, hazel pine, bilsted, redgum, satin-walnut, star-leaved gum, alligatorwood, or simply sweetgum, is a deciduous tree in the genus Liquidambar native to warm temperate areas of eastern North America and tropical montane regions of Mexico and Central America. Sweet gum is one of the main valuable forest trees in the southeastern United States, and is a popular ornamental tree in temperate climates. It is recognizable by the combination of its five-pointed star-shaped leaves and its hard, spiked fruits. It is currently classified in the plant family Altingiaceae, but was formerly considered a member of the Hamamelidaceae.
Citrus greening disease is a disease of citrus caused by a vector-transmitted pathogen. The causative agents are motile bacteria, Candidatus Liberibacter spp. The disease is vectored and 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 also been shown to be graft-transmissible. Three different types of HLB are currently known: The heat-tolerant Asian form, and the heat-sensitive African and American forms. The disease was first described in 1929 and first reported in China in 1943. The African variation was first reported in 1947 in South Africa, where it is still widespread. Eventually, it affected the United States, reaching Florida in 2005. Within three years, it had spread to the majority of citrus farms. The rapid increase in this disease has threatened the citrus industry not only in Florida, but the entire US. As of 2009, 33 countries have reported HLB infection in their citrus crop.
The blood orange is a variety of orange with crimson, almost blood-colored flesh.
The orange is the fruit of various citrus species in the family Rutaceae ; it primarily refers to Citrus × sinensis, which is also called sweet orange, to distinguish it from the related Citrus × aurantium, referred to as bitter orange. The sweet orange reproduces asexually ; varieties of sweet orange arise through mutations.
The citrange is a citrus hybrid of the sweet orange and the trifoliate orange.
Citrus tristeza virus (CTV) is a viral species of the genus Closterovirus that causes the most economically damaging disease to its namesake plant genus, Citrus. The disease has led to the death of millions of Citrus trees all over the world and has rendered millions of others useless for production. Farmers in Brazil and other South American countries gave it the name "tristeza", meaning sadness in Portuguese and Spanish, referring to the devastation produced by the disease in the 1930s. The virus is transmitted most efficiently by the brown citrus aphid.
Phanerochaete salmonicolor is a fungal plant pathogen which has become a serious problem, especially in Brazil. P. salmonicolor is a member of the Corticiaceae family, which is a paraphyletic group classified based on their basidiocarps. This pathogen causes Pink Disease, most commonly in citrus, although P. salmonicolor has a wide host range including rubber and cacao trees. Pink Disease causes branch and stem die-back due to canker formation. The cankers are recognizable by gum exudation and longitudinal splitting of the bark.
Citrus australis, the Dooja, round lime, Australian lime or Australian round lime, is a large shrub or small tree producing an edible fruit. It grows in forest margins in the Beenleigh area and northwards, in Queensland, Australia.
Grafting or graftage is a horticultural technique whereby tissues of plants are joined so as to continue their growth together. The upper part of the combined plant is called the scion while the lower part is called the rootstock. The success of this joining requires that the vascular tissues grow together and such joining is called inosculation. The technique is most commonly used in asexual propagation of commercially grown plants for the horticultural and agricultural trades.
Gingivitis is a non-destructive disease that causes inflammation of the gums. The most common form of gingivitis, and the most common form of periodontal disease overall, is in response to bacterial biofilms that is attached to tooth surfaces, termed plaque-induced gingivitis. Most forms of gingivitis are plaque-induced.
The hop stunt viroid is a viroid species that infects the common hop plant, citrus plants and grapevines, among others. It is a member of the Pospiviroidae family and the Hostuviroid genus. There are quite a few different sub-species of the hop stunt viroid.
Citrus exocortis is a disease of citrus plants, caused by the Citrus exocortis viroid (CEVd). It can cause stunted growth and reduced yields in affected plants. The disease is also sometimes called "scalybutt". CEVd can also infect tomato plants. The resulting disease is sometimes called "tomato bunchy top disease."
Cadang-cadang is a disease caused by Coconut cadang-cadang viroid (CCCVd), a lethal viroid of coconut, African oil palm, anahaw, and buri palms. The name cadang-cadang comes from the word gadang-gadang that means dying in Bicol. It was originally reported on San Miguel Island in the Philippines in 1927/1928. "By 1962, all but 100 of 250,000 palms on this island had died from the disease," indicating an epidemic. Every year one million coconut palms are killed by CCCVd and over 30 million coconut palms have been killed since Cadang-cadang was discovered. CCCVd directly affects the production of copra, a raw material for coconut oil and animal feed. Total losses of about 30 million palms and annual yield losses of about 22,000 tons of copra have been attributed to Cadang-cadang disease in the Philippines.
