A recent development is the use of "somaclones" in banana cultivation. Micropropagation involves growing plants from very small amounts of source tissue, sometimes even a single cell, under sterile conditions using artificial techniques to induce growth. The purpose of micropropagation is often to produce a large number of genetically identical offspring. However, by inducing mutations through various means, it is possible to produce plants which differ slightly from the "parent" plant and from each other ("somaclonal variations"). By growing on these somaclones and selecting those with desirable features, new cultivars can be produced which are very similar to an existing cultivar, but differ in one or two features, such as disease resistance. Somaclones may only be distinguishable by genetic analysis.
The species and varieties include many economically important cultivars with different shapes, colors, and flavors that are grown for different purposes, such as spices, vegetables, and herbal medicines. Some confusion has resulted from the legal term "plant variety", which is used interchangeably with "cultivar" (not with "taxonomic variety"). The terminology around a cultivar also includes terms such as heirloom, open-pollinated, self-pollinating, and hybrid.
The total number of cultivars of bananas and plantains has been estimated to be anything from around 300 to more than 1000. Names are highly confused, even within a single country. Many common names do not refer to a single cultivar or clone; for example 'Lady's Finger' or 'Lady Finger' has been used as the name for members of different genome groups, including AA and AAB. Many other names are synonyms of cultivars grown in the same or different countries. Attempts have been made to create lists of synonyms. In 2000, Valmayor et al. listed equivalent local names for 68 cultivars across five Southeast Asian countries (the Philippines, Malaysia, Indonesia, Thailand and Vietnam), together with their internationally used names. They considered a further 81 cultivars to be unique to one country. In 2007, Ploetz et al. listed more cultivar names and synonyms, with an emphasis on those grown in the islands of the Pacific, but including some grown in areas such as India, Africa and South America. As an example, for the widely grown cultivar 'Dwarf Cavendish', they gave 58 synonyms from 29 different countries or geographical areas. ProMusa has created a checklist of banana cultivar names based on available literature.
Hybrid varieties take advantage of a phenomenon called heterosis or hybrid vigor, which occurs in pepper. To generate a hybrid variety, two self-pollinated varieties are intentionally crossed, and all seed from this cross are collected. The new hybrid variety typically is more vigorous than either of the two parents contributing to traits such as higher yield. Hybrid seed if saved will not produce a homogeneous set of plants the next generation, meaning that the two parents will need to be crossed again to generate more hybrid seed. This method is used to produce hybrid Capsicum cultivars such as the blocky-types Double-Up and Orange Blaze. Much of the commercial pepper production uses hybrid varieties for their improved traits.
Selection of rootstock cultivars can be difficult: vigorous roots tend to give trees that are healthy but grow too tall to be harvested easily without careful pruning, while dwarfing rootstocks result in small trees that are easy to harvest from, but are often shorter-lived and sometimes less healthy. Most modern commercial orchards use one of the "Malling series" (aka 'M' series), introduced or developed by the East Malling Research Station from the early 20th century onward. However, a great deal of work has been done recently introducing new rootstocks in Poland, the U.S. (Geneva), and other nations. The Polish rootstocks are often used where cold hardiness is needed. The Geneva series of rootstocks has been developed to resist important diseases such as fireblight and collar rot, as well as for high fruit productivity.
In 1955, researchers Norman Simmonds and Ken Shepherd proposed abandoning traditional Latin-based botanical names for cultivated bananas. This approach foreshadowed the International Code of Nomenclature for Cultivated Plants which, in addition to using Latin names based on the International Code of Nomenclature for algae, fungi, and plants, gives cultivars names in a currently spoken language, enclosed in single quotes, and organizes them into "cultivar groups", also not given Latin names.
In practice, the scoring system and the associated grouping is not as straightforward as the Simmonds and Shepherd naming system implies. For example, a member of the AAB Group should have a score about one third of the way between ''M. acuminata and M. balbisiana (i.e. about 35) if one third of its chromosomes come from M. balbisiana''. However, the cultivars 'Silk' and 'Pome', both classified in the AAB Group, scored 26 and 46 respectively. The cultivar 'Pelipita' is placed in the ABB group, so should have 11 of its 33 chromosomes derived from ''M. acuminata''. However, a technique called "genomic in situ hybridization" (GISH) showed that actually only 8 chromosomes were of this origin. Other lines of evidence suggest a more complex genome structure is present in other banana cultivars, so the group names should not be taken at face value.
Banana cultivars derived from ''M. acuminata and M. balbisiana'' can be classified into cultivar groups using two criteria. The first is the number of chromosomes: whether the plant is diploid, triploid or tetraploid. The second is relationship to the two ancestral species, which may be determined by genetic analysis or by a scoring system devised by Simmonds and Shepherd. A cultivar is scored on 15 characters, chosen because they differ between the two species. Each character is given a score between one and five according to whether it is typical of ''M. acuminata or of M. babisiana'' or is in between. Thus the total score for a cultivar will range from 15 if all characters agree with ''M. acuminata to 75 if all characters agree with M. balbisiana''. Intermediate scores suggest mixed ancestry: for example, 45 would be expected for diploids with equal genetic contributions from both species.
Groups are then named using a combination of the letters "A" and "B". The number of letters shows the ploidy; the proportion of As and Bs the contributions of the ancestral species. The AAB Group, for example, comprises triploid cultivars with more genetic inheritance from ''M. acuminata than M. balbisiana''. A character score of around 35 is expected for members of this group. Within groups, cultivars may be divided into subgroups and then given a cultivar name, e.g. Musa AAA Group (Cavendish Subgroup) 'Robusta'.
Many of the sweet potato cultivars below were bred at agricultural experiment stations. An agricultural experiment station (AES) is a research center where scientists work to increase the quality and quantity of food production. Agricultural experiment stations are usually operated by a government agency and/or a university.
Over 80 varieties and cultivars have gained the Royal Horticultural Society’s Award of Garden Merit.
Notable cultivars include 'Donald Waterer' and 'Superba'. The latter has gained the Royal Horticultural Society's Award of Garden Merit. It bears fragrant cream-coloured flowers, which age to yellow.
Cultivars are classified in two groups. Most of the cultivars belong to the Akanashi ('Russet pears') group, and have yellowish-brown rinds. The Aonashi ('Green pears') have yellow-green rinds.
Heirloom tomato cultivars can be found in a wide variety of colors, shapes, flavors and sizes. Some heirloom cultivars can be prone to cracking or lack of disease resistance. As with most garden plants, cultivars can be acclimated over several gardening seasons to thrive in a geographical location through careful selection and seed saving.
Other cultivars he developed include many Yucca hybrids in the years from 1897 to 1907.
Numerous cultivars of ''C. australis'' are sold within New Zealand and around the world. Like other Cordyline species, ''C. australis'' can produce sports which have very attractive colouration, including pink stripes and leaves in various shades of green, yellow or red. An early cultivar was published in France and England in 1870: Cordyline australis 'Lentiginosa' was described as having tinted leaves with brownish red spots. Other early cultivars included 'Veitchii' (1871) with crimson midribs, 'Atrosanguinea' (1882) with bronze leaves infused with red, 'Atropurpurea' (1886) and 'Purpurea' (1890) with purple leaves, and a range of variegated forms: 'Doucetiana' (1878), 'Argento-striata' (1888) and 'Dalleriana' (1890). In New Zealand and overseas, hybrids with other Cordyline species feature prominently in the range of cultivars available. New Plymouth plant breeders Duncan and Davies included hybrids of ''C. australis and C. banksii'' in their 1925 catalogue, and have produced many new cultivars since. In New Zealand, some of the coloured forms and hybrids seem to be more susceptible to attacks from the cabbage tree moth.
The two cultivars that comprise d'Anjou pears are the 'Green Anjou' pear and the 'Red Anjou' pear. The 'Green Anjou' pear has a pale green skin that does not change color as the pear ripens, unlike most other cultivars of green pears, which turn yellow as they ripen. The 'Red Anjou' pear originated as naturally occurring bud sport found on 'Green Anjou' trees. 'Red Anjou' pears are very similar to the original Anjou other than color.
Garden cultivars are sold under the names ‘Black Pearl’, ‘Thelma's Giant’, ‘Lambrook Gold’, ‘Silver Swan’ and ‘Tasmanian Tiger’, among others. They come in a variety of colors, from silvery grey and bluish green to greenish yellow. These garden varieties are valued in Mediterranean or desert landscaping for not being highly demanding and for looking good despite lack of watering in sunny areas.
Different cultivars of the plant produce fruit of different size, shape, and color, though typically purple. The less common white varieties of eggplant are also known as Easter white eggplants, garden eggs, Casper or white eggplant. The most widely cultivated varieties—cultivars—in Europe and North America today are elongated ovoid, 12–25 cm long and 6–9 cm broad with a dark purple skin.
Hundreds of cultivars of the olive tree are known. An olive's cultivar has a significant impact on its colour, size, shape, and growth characteristics, as well as the qualities of olive oil. Olive cultivars may be used primarily for oil, eating, or both. Olives cultivated for consumption are generally referred to as table olives.