Chile is historically associated with the voyage of Columbus (Heiser 1976). Columbus is given credit for introducing chile to Europe, and subsequently to Africa and to Asia. On his first voyage, he encountered a plant whose fruit mimicked the pungency of the black pepper, Piper nigrum L. Columbus called it red pepper because the pods were red. The plant was not the black pepper, but a heretofore unknown plant that was later classified as Capsicum. Capsicum is not related to the Piper genus. In 1493, Peter Martyr (Anghiera 1493) wrote that Columbus brought home "pepper more pungent than that from the Caucasus." Chile spread rapidly across Europe into India, China, and Japan. The new spice, unlike most of the solanums from the Western Hemisphere, was incorporated into the cuisines instantaneously. Probably for the first time, pepper was no longer a luxury spice only the rich could afford. Since its discovery by Columbus, chile has been incorporated into most of the world's cuisines. It has been commercially grown in the United States since at least 1600, when Spanish colonists planted seeds and grew chile using irrigation from the Rio Chama in northern New Mexico (DeWitt and Gerlach 1990).
Capsicum terminology is confusing. Pepper, chili, chile, chilli, aji, paprika, and Capsicum are used interchangeably for plants in the genus Capsicum. Capsicum investigators use chile, pepper, or aji, as vernacular terms. Capsicum is reserved for taxonomic discussion. The word "chile" is a variation of "chil" derived from the Nahuatl (Aztec) dialect which referred to plants now known as Capsicum, whereas "aji" is a variation of "axi" from the extinct Arawak dialect of the Caribbean. This brings up the point of the correct way to spell "chile" (Domenici 1983). The "e" ending in chile is the authentic Hispanic spelling of the word, whereas English linguists have changed the e to an i. Chile pepper has come to mean pungent chile cultivars. However, chile means pepper (Capsicum) whether the fruits are pungent or not. Generally, chili is used to identify the state dish of Texas, which is a combination of pungent chile cultivars and meat (Domenici 1983). Bell pepper generally refers to non-pungent blocky chile types. Additional confusion is present within species designation, because C. annuum was sometimes called C. frutescens in the scientific literature (Heiser and Smith 1953).
By the time the Spanish arrived in Mexico, Aztec plant breeders had already developed dozens of pod-types. According to historian Bernardino de Sahagún, who lived in Mexico in 1529, "hot green chiles, smoked chiles, water chiles, tree chiles, beetle chiles, and sharp-pointed red chiles" existed (DeWitt and Gerlach 1990). Undoubtedly, these chiles were the precursors to the large number of pod-types found in Mexico today. Even though many pod-types exist, improvement continues today because of specific needs in the industry. Improvement in quality and yields are occurring, along with refinement of the pod-types to fit special niches of the industry.
Fresh market types such as bell peppers, cuban, and squash, are usually non-pungent, and eaten raw, stir-fried, or prepared in some fashion to season a culinary dish. Bell apparently refers to the fruit's blocky shape, with four lobes preferred in the United States. Bell types were first mentioned in 1699 by the English pirate, Wafer, who found them growing in Panama (Wafer 1699). The conventional green bell pepper has given way to innovative colored pods that can ripen to shades of red, orange, yellow, and brown. A survey in the 1992 issue of Fresh Trends stated that 95% of the people who tried a colored bell liked them and 5 out of 6 preferred them over the green bell. More people are trying colored bell peppers than any other produce category. There has been an increase of 75% in the consumption of colored bells in the United States. In 1992, colored bells were tried by as many consumers as leaf lettuce, fresh asparagus, peas, squash, and red potatoes. Consumers bought more colored bells than yellow beans, artichokes, or romaine lettuce. The innovative fruit colors have brought increased consumption and sales.
Chile processing pod-types can be grouped into two main categories. The first consists of a fresh product that is frozen, canned, or pickled Some of the pod-types included in this group are the pimento, jalapeño, serrano, pepperoncini, yellow wax, and the New Mexican. The second category consists of those used as a dehydrated product. Dehydrated pod-types are New Mexican, cayenne, ancho, pasilla, mirasol, piquin, and de arbol (Bosland 1992).
A relatively recent pod-type is the New Mexican, also called long green or 'Anaheim' type. Actually, the pod-type is New Mexican, and 'NuMex Big Jim' and 'Anaheim' are cultivars within this type. The New Mexican pod-type was developed in 1894 when Fabian Garcia at New Mexico State University began improving the local chiles grown by the Hispanic gardeners around Las Cruces, New Mexico. This type, characterized by long green pods that turn red, is the chile of choice for Mexican-style cooked sauces in the United States. Green and red chile represent two developmental states of the same fruit. 'Anaheim' seed originated in New Mexico and was brought to Anaheim, California, where it was widely cultivated. Thus, until Dr. Garcia released the New Mexican pod-type, it did not exist. If pods are left on the plant to be harvested at the red stage, they are usually dried and ground into chile powder (paprika if non-pungent). A green, New Mexican chile pod contains three times the vitamin C of a 'Valencia' orange and provides the minimum daily requirement. As green pods turn red, pro-vitamin A content increases until they contain twice the pro-vitamin A of a carrot (Lantz 1943). A one half tablespoon of red chile powder furnishes the minimum daily requirement of vitamin A.
A peculiar chile category is paprika. It is not a pod-type in the United States, but it is a product. In Europe, there are chile pod-types that are paprikas. This is because in the Hungarian language "paprika" means Capsicum (Somos 1984). Paprika is defined in the United States as a sweet, dried, red powder. This mild powder can be made from any type of C. annuum that is non-pungent and has brilliant red color. Paprika may be pungent in Hungary, but paprika is always non-pungent in international trade.
A small group of chiles can be classified as ornamental. Although edible, ornamentals are grown primarily for their unusual pod shapes or for their dense foliage and colorful fruits. Ornamental chiles can have all the colors of the rainbow, often displaying pods in four or five colors on the same plant at the same time (Bosland et al. 1994). In the past, they have been called Christmas peppers because of the bright red fruits during the holiday season. Decorations, such as wreaths, made with chile that can be dehydrated are popular in the southwestern United States, and are a major tourist product. A tradition in New Mexico is to harvest mature red chiles and string them into colorful strings (ristras). The ristra is hung near the entrance of the house as a symbol of hospitality. Ornamental chiles have become an innovative way for small farmers to produce a high-value alternative crop.
The C. chinense species, like all Capsicum species, originated in the New World. However, the French taxonomist who named this species in 1776 got his seed from China (Smith and Heiser 1957). Habanero, or Scotch Bonnet, is the best known chile of this species. One accession of Habanero has the distinction of being the world's hottest chile (in excess of 200,000 scoville heat units). Fruit shape can vary from long and slender to short and obtuse. Fruit can be extremely pungent and aromatic, with persistent pungency when eaten. C. chinense is popular in all tropical regions.
The C. frutescens species is represented by two cultivars, tabasco and malagueta. Tabasco is the most common cultivar of C. frutescens. The red fruit is the ingredient in Tabasco sauce. The malagueta is a popular cultivar in Brazil. It is not related to Aframomum melegueta, the melegueta or Guinea pepper, from Africa which is related to ginger.
In South America, C. baccatum is the most commonly grown species, where it is called aji, not chile. Three botanical varieties of C. baccatum are recognized: C. baccatum var. baccatum, C. baccatum var. pendulum, and C. baccatum var. microcarpum. C. baccatum flowers have yellow, brown, or dark green spots on the corolla. As many different pod-types of chiles (in relation to shape, color, and size) exist within C. baccatum as in C. annuum. Fruits vary in pungency from non-pungent to very hot. They embody unique aromatics and flavors that can be overpowering to some people. C. baccatum is the chile of choice when making ceviche (marinated fish).
Another of the five species, C. pubescens, is a relatively unknown chile. It is found from Mexico to Peru, growing in the Andean South America and the Central American highlands. Common names include rocoto or locoto in South America. Other common names are manzano and peron because the fruits can be apple- or pear-shaped. Instead of white flowers, it has purple flowers with large nectaries. The presence of conspicuous leaf pubescence and black seeds readily distinguish this chile from any of the other species. This chile is adapted to cooler temperatures, 4.4° to 21.1°C (40° to 70°F), but does not tolerate frost.
The other approximately 20 Capsicum species lack extensive study on their biology. It is interesting to note that all wild chiles have small fruits which are eaten with ease by birds, the natural dispersal agent for Capsicum. Many of the known wild species have restricted distribution. These species may contain genes for adaptation to unusual environmental conditions as well as disease resistance.
Exotic germplasm will continue to be an important asset for breeding improved commercial chiles. Not only will it be useful in breeding for disease resistance, but it will be used to increase the nutritional quality, yield, and efficiency for machine harvesting of the crop. The enhancement of commercial cultivars by exotic germplasm is dependent on the availability of living material. This may be impossible because the natural habitat for these species is in dire straits. Collection may never be accomplished before their extinction. Tropical deforestation is among the most massive and urgent environmental problems facing Capsicum germplasm resources.
The United States National Plant Germplasm System houses an extensive Capsicum germplasm collection at the Southern Plant Introduction Station located in Experiment, Georgia. This collection contains approximately 3000 Capsicum accessions that includes lines from all over the world. Passport data are recorded upon arrival of the seed at the facility and a USDA Plant Introduction (PI#) Number is assigned. Evaluation data is subsequently entered in the Germplasm Resources Information Network (GRIN) after it has been received. The material held in the USDA collection is the source of germplasm for breeding and research programs throughout the world. Many have been evaluated for descriptors. Preserving genetic diversity in germplasm is of paramount importance.
The genetic diversity of Capsicum can be saved only through the use of several strategies. The genetic resources of Capsicum need to be enlarged and conserved in base and active genebanks. The improvement of appropriate storage facilities for germplasm and the financial support of those operations is very urgent. It is especially imperative to aid the active collections of Latin America, because Capsicum is native to this region. When possible it is desirable to set up Capsicum genetic resources reserves in conjunction with relevant biosphere resources and other protected areas.
Chile plants are considered a self-pollinating crop (Allard 1960). However, the rates of out-crossing (7% to 91%) recorded by several investigators argue that Capsicum should be considered to be facultative cross-pollinating species in field research (Odland and Porter 1941; Franceschetti 1971; Tanksley 1984). The out-crossing is associated with natural insect pollinators. The amount of cross-pollination has an effect not only on the precautions needed for seed production, but also on the breeding methodologies used by the plant breeder (Bosland 1993). Natural pollinators such as insects must be excluded to insure self-pollination.
The commercial production of hybrid chiles has been successful accomplished using hand-emasculation, genic male-sterility, and cytoplasmic male-sterility. Male-sterile chile plants are found as spontaneous mutants in commercial fields. Cytoplasmic male sterility (CMS) in chiles was first discovered by Peterson (1958) in C. annuum PI 164835 from India. Unfortunately, Peterson's CMS line is unstable in fluctuating environments, producing pollen at cool temperatures. Some commercial seed companies use the CMS system to produce F1 hybrids.
Other genetic systems that may assist the chile breeder are the use of trisomic and chromosome mapping. Most Capsicum species have 2n = 24 chromosomes. Meiosis is surprisingly regular within interspecific crosses. The similarity in karyotype of the species was illustrated by Ohta (1962). However, cryptic structural hybridity as defined by Stebbins (1971) appears to be functioning in Capsicum.
Pochard (1970) identified primary trisomics that could be distinguished from secondary and tertiary trisomics by their phenotype, frequency, and fertility and by their chromosome configurations in meiosis. Eleven of the 12 possible trisomics could be identified by foliage color, anther/stamen color, and fruit characteristics. Cytologically, only three of the 12 chromosomes in C. annuum differ significantly in length. The other nine are metacentric and have lengths too close to permit identification.
The recent development of molecular marker-assisted selection techniques may provide new tools in the breeding of chiles. Isozyme and molecular markers have been applied to chiles. Usefulness of isozyme markers is restricted to the insufficient polymorphic bands and a limited number of detectable loci. Molecular based DNA markers such as Restriction Fragment Length Polymorphism (RFLP) and Random Amplified Polymorphic DNA (RAPD) are unlimited in numbers. A saturated isozyme and RFLP map of chile has been reported (Prince et al. 1993). The map contains 192 chile and tomato genomic cDNA clones with 19 linkage groups with a total coverage of 720 cM. However, specific map positions of 26 RFLP markers in seven linkage groups were not determined and vast regions of the chile genome remain unmapped. This area of research is rapidly adding to our knowledge of chiles and will undoubtedly be important in the future.
A peculiar aspect of chiles is the inability to be regenerated from protoplasts. This limits the technique of genetic transformation. Within other solonaceous crops such as tomato, tobacco, and petunia, excellent progress has been made regenerating plants using genetic transformation to introduce novel genes into the genome. For unexplained reasons, chile has been recalcitrant to being regenerated but many laboratories are addressing this issue. Once this perplexing problem is solved, genetic transformation will be available to introduce novel genes into chiles.
Pungency is produced by the capsaicinoids, alkaloid compounds, that are found only in the plant genus, Capsicum. The nature of the pungency has been established as a mixture of seven homologous branded-chain alkyl vanillylamides (Hoffman et al. 1983). They often are called capsaicin after the most prevalent one. Dihydrocapsaicin is usually the second most prevalent capsaicinoid, while the other five compounds, norcapsaicin, nordihydrocapsaicin, nornordihydrocapsaicin, homocapsaicin, homodihydrocapsaicin, are considered minor capsaicinoids because of their relative low abundance in most natural products. Capsaicin is a powerful and stable alkaloid that can be detected by human taste buds in solutions of ten parts per million. Capsaicin's composition (C18H27NO3) is similar to peperin (C17H19NO3), that gives black pepper its bite.
The capsaicinoids are produced in glands on the placenta of the fruit. While seeds are not the source of pungency, they occasionally absorb capsaicin because of their proximity to the placenta. No other plant part produces capsaicinoids.
Chile pungency is expressed in Scoville Heat Units (Scoville 1912). The Scoville Organoleptic Test was the first reliable measurement of the pungency of chiles. This test used a panel of five human representatives, who tasted a chile sample and then recorded the heat level. A sample was diluted until pungency could no longer be detected. The organoleptic method or taste test has been the standard method for pungency analysis. Although this method is widely used, it has limitations. Tasters must be trained and their ability to test many samples is restricted by the heat of the test solution. Taster fatigue is a real phenomenon and tasters are also not able to distinguish between the different capsaicinoids. Therefore, the Scoville Organoleptic Test has been replaced with instrumental methods.
The most common instrumental method is high-performance liquid chromatography (HPLC). It provides accurate and efficient analysis of content and type of capsaicinoids present in a chile sample (Woodbury 1980; Collins et al. 1995). HPLC analysis has become the standard method for routine analysis by the processing industry. The method is rapid and can handle a larger number of samples. A common practice today is to multiply capsaicinoid ppm by 15 to convert to SHU.
The chile pungency level has genetic and environmental components. The capsaicinoid content is affected by the genetic make-up of the cultivar, weather conditions, growing conditions, and fruit age. Plant breeders can selectively develop cultivars with varying degrees of pungency. Also, growers can somewhat control pungency by the amount of stress to which they subject their plants. Pungency is increased with increased environmental stress (Lindsay and Bosland 1995). More specifically, any stress to the chile plant will increase the amount of capsaicinoid level in the pods. A few hot days can increase the capsaicinoid content significantly. In New Mexico, it has been observed that even after a furrow irrigation, the heat level will increase in the pods. Anthropopathically, the plant has sensed the flooding of its root zone as a stress, and has increased the capsaicinoid level in its pods. If the same cultivar was grown in both a hot semi-arid region and a cool coastal region, the fruit harvested from the hot semi-arid region would be higher in capsaicinoids than that the fruits harvested in the cool coastal climate.
The medicinal applications of capsaicinoids have brought innovative ideas for their use. Medicinal use of Capsicums has a long history, dating back to the Mayas who used them to treat asthma, coughs, and sore throats. The Aztecs used chile pungency to relieve toothaches. The pharmaceutical industry uses capsaicin as a counter-irritant balm for external application (Carmichael 1991). It is the active ingredient in Heet and Sloan's Liniment, two rubdown liniments used for sore muscles. The capsaicin is being used to alleviate pain. Its mode of action is thought to be from nerve endings releasing a neurotransmitter called substance P. Substance P informs the brain that something painful is occurring. Capsaicin causes an increase in the amount of substance P released. Eventually, the substance P is depleted and further releases from the nerve ending are reduced. Creams containing capsaicin have reduced pain associated with post-operative pain for mastectomy patients and for amputees suffering from phantom limb pain. Prolonged use of the cream has also been found to help reduce the itching of dialysis patients, the pain from shingles (Herpes zoster), and cluster headaches. Further research has indicated that capsaicin cream reduces pain associated with arthritis. The repeated use of the cream apparently counters the production of substance P in the joint, hence less pain. Reducing substance P also helps by reducing long-term inflammation, which can cause cartilage break down.
The chile industry has grown from a regional food for tourists to an industry competing on the international market. At present, there is an expanding chile market for dietary consumption. At the same time, chile is also becoming more important in manufacturing other commodities. Chile will become more important as a food coloring agent and this may be the leading use of chile in the future. The most innovative use of chile by humankind may yet be discovered.
The College of Agriculture and Home Economics at New Mexico State University has founded the Chile Institute. The Chile Institute is a non-profit, international organization devoted to the study of Capsicum. Some of the goals of The Chile Institute are to assist in preserving Capsicum germplasm, provide an international information clearinghouse and be an archive of chile publications. It has already published a bibliography containing more than 6,000 references (Bosland 1995). For further information on The Chile Institute write: The Chile Institute, Box 30003, Dept. 3Q, NMSU, Las Cruces, NM 88003 or phone: (505) 646-3028.
Fig. 1. Diversity in Capsicum.