General Details of Chili
Food and medical usages of chili: Capsicum is a genus of flowering plants in the nightshade family Solanaceae. Its species are native to the Americas. Chili fruit was consumed as food and medicine. Capsicum contains capsaicin (methyl vanillyl nonenamide), named capsaicin. Pungency is caused by the presence of capsaicinoids. Bell pepper and other chilies are excellent sources of carotenoids, vitamins and many elements.
Production area of chili & import and export of chili in Thailand: In 2012, China was the first among all nations in harvested area of chili and fresh chili production. Thailand ranked 63th in harvested area of chili and ranked 60th in fresh chili production. Thailand imports a large amount of chili which is much higher than exported amount. Hybrid and open-pollinated chili seeds are produced in Thailand. The seeds are exported at higher amount compared to import.
Classification of chilies: Phylogenetical relationships and plant morphologies are used in the botanical classification of the Genus Capsicum while fruit size, fruit shape, fruit color, and pungency are used in horticultural classification. Thirty eight species are currently recognized, 5 of which are domesticated: C. annuum L., C. chinense Jacquin, C. frutescens L., C. baccatum L. and C. pubescens Ruiz & Pavon.
C. annuum has very large, bright white flowers, C. chinense has a calyx constriction and generally more than two dull white flowers per axil, C. frutescens shows an unmistakably greenish-white, stiffly erect solitary flower, C. baccatum displays distinctive yellow-green corolla throat spots and C. pubescens displays purple flowers with white throat spots.
Alkaloids of chili fruit: The fruit of most species of Capsicum contains capsaicin. They have been found to be an effective pain reducer for muscle soreness, skin irritations, and rheumatism. Their consumption has been found to help reduce the risk of cardiovascular disease and cancer.
Changes in phytochemical and antioxidant activity of chilies: The effect of fruit maturation on changes in carotenoids, flavonoids, phenolic acid, capxanthin, zeaxanthin, ascorbic acid, and antioxidant activity in different chili species (Capsicum annuum, Capsicum frutescens, and Capsicum chinense) has been demonstrated. Generally, the concentration of these chemicals increased as the chilies reached maturity. Ascorbate is one of the best natural anti-oxidant substances, and chili (C. annuum L.) has the highest ascorbate content among plants.
Controls of pungency: Chili pungency levels of the fruit depend on genetic and environmental factors. The capsaicinoid content is affected by the genetic make-up of the cultivar, weather conditions, growing conditions, and fruit age. It was reported that pungency characteristics were generally controlled by at least two pairs of genes. However, when transcriptional levels of enzymes on the capsaicinoid pathway were monitored in C. annuum and C. chinense fruit, three genes were positively correlated with degree of pungency in placental tissue. Additionally, other studies have shown that only a single locus controlled the capsaicinoids synthesis. The presence of capsaicinoids is controlled by the Pun1 locus.
Pungency: The nature of pungency results from a mixture of seven homologous branded-chain alkyl vanillylamides. They often are called capsaicin after the most prevalent one, the amide of 3-hydroxy-2-methoxy-benzylamine with 8-methyl-6-noneneoic acid, (C18H27NO3). Examination of the placenta of hot and sweet cultivars of red chili with light microscopy has shown that both types have glandular areas. The placenta of the pungent type has a more conspicuous blisterlike surface emerging from the glandular area where the cell wall is detached. The placental surface of the non-pungent type is smooth.
Pungency evaluation methods: Levels of capsaicinoids in chili can be determined by using chemical, instrumental, or sensorial methods. Chili pungency is expressed in Scoville Heat Units (SHU). The Scoville Organoleptic Test has been replaced with instrumental methods. The most common instrumental method is high-performance liquid chromatography (HPLC). This provides accurate and efficient analysis of content and type of capsaicinoids present in a chili sample.
Pungency levels of chili fruit: Bhut Jolokia (sometime called Naga Jolokia, or Bih Jolokio, or ghost chili) was officially proclaimed by the Guinness World Record as the new World’s hottest chili. The pungency showed 1,001,304 SHU (Scoville heat units). However, it was later found that the Trinidad Moruga scorpion was the hottest chili in the World with a heat level of 1,200,000- 2,009,231 SHU.
Genetics and male sterility in chili: There are two types of male sterilities: cytoplasmic male-sterility and genic male sterility. Production of F1 hybrids requires emasculation of the female parent and pollination by pollen from the male plant. Cytoplasmic male sterility eliminates the need for emasculation of the female plants and reduces the cost of production of F1 hybrid seeds. Today, several internationally known seed companies use the genic male sterility (msms) on a large scale for producing hybrids, whereas the cytoplasmic male sterility is used mainly for breeding pungent (S) Rf rf hybrids.
Genetic and interspecific hybridization of chilies: Five cultivated species, C. annuum L., C. frutescens L., C. chinense Jacq., C. baccatum L., and C. pubescens R. & P. were reported. The first three domesticated species, considered part of the same gene complex, can intercross, while the other two are generally considered reproductively isolated, although some hybridization is possible with difficulties. Natural interspecific hybridization was found in ‘Bhut Jolokia’ which is a Capsicum chinense Jacq. cultivar. However, molecular analysis with randomly amplified polymorphic DNA markers confirmed the species identification and, interestingly, revealed that there may have been genetic introgression from Capsicum frutescens L. into ‘Bhut Jolokia’.
Genic male sterility: The genic male sterility of (GMS) in chili (C. annuum) is controlled by a recessive nuclear gene, ms. The pollen sterility is caused by nuclear genes. The GMS has been used in commercial F1 hybrid seed production of sweet peppers.
Cytoplasmic male sterility: Cytoplasmic male sterility is a maternally inherited trait in which a plant fails to produce functional anthers, pollen grains, or male gametes. The CMS system requires nuclear genes that restore male fertility in the F1 hybrids produced. These restorers of fertility are called Rf genes and are distinct from genetic male sterility genes. The Rf genes have no expression except to restore sterile cytoplasm. Rf genes are required to restore fertility in the CMS cytoplasms that causes sterility. Molecular markers are used to speed up the process of CMS selection. Rflinked molecular markers in chili (C. annuum L.) are detected by using bulked segregant analysis to identify amplified fragment length polymorphism markers (AFLPs).
Cytoplasmic genic male sterility in the genetic diversity of chilies (Capsicum annuum L.): Six experiments were carried out to evaluate the chili germplasm sources of cytoplasmic male sterility (CMS) at Chiang Mai University. Seventy-five accessions of chilies (Capsicum annuum L.) were evaluated for ability to be sterilized by CMS. Some of the male sterile and partially sterile lines showed excellent horticultural characteristics. They could be used as C lines and maintainers in F1 hybrid seed production.
Levels of capsaicin in chili fruit: Five experiments of long green chili, long white chili, and big fruit chili (Capsicum annuum) were tested in the rainy and winter seasons of 2006-2010 at Chiang Mai University. Chiang Mai, Thailand. It was found that the capsaicin levels in mature green fruits of the experiments varied significantly according to genetics and environment. The ranges of capsaicin levels of green mature fruits of the varieties tested were 2,760-12,030, 4,230-6,710, 530-6,450, 0-2,332, 50-5,720 Scoville units from the first to the fifth experiments, respectively.
Levels of vitamin C in chili fruit: Levels of vitamin C in chili fruit were observed in the five experiments of long green chili, long white chili, and big fruit chili in the rainy and winter seasons of 2006-2010 at Chiang Mai University. Chiang Mai, Thailand. It was found that the vitamin C levels in mature green fruits of the experiments varied significantly. The ranges of vitamin C levels of the varieties tested were 3.80-142.86, 114.74-158.98, 6.25-81.94, 31.79-154.97, and 3.85-7.69 mg./ 100 g. fruit fresh wt. from the first to the fifth experiments, respectively.
The Faculty of Agriculture, Chiang Mai University, announced the release of open-pollinated cultivars of chilies (Capsicum annuum L.) that are either restorers or maintainers of cytoplasmic male sterility. An outstanding contract was entered into in the agreement between Chiang Mai University and the Horticultural Research Institute, Yunnan Academy of Agricultural Science in China. Two commercial F1 hybrids were developed for the Chinese market.
Breeding methods for chili improvement: Improvement of chili varieties aims to improve yield, disease resistance, insect resistance, and various unique characteristics. Researchers have identified varieties of chili resistant to bacteria, fungal, and viruses. Traditional methods of breeding for self-pollinating crops are used in the improvements. There are several methods used: pedigree method, single seed descent, mass or bulk selection method, backcross method, recurrent selection, and the F1 hybrid development. Single seed descent, mass selection, and recurrent selection are rarely used for chili. On the other hand, pedigree method, backcross method, and F1 hybrid are commonly used.
F1 hybrids: Five experiments of long green chili, long white chili, and big fruit chili (Capsicum annuum) were tested in the rainy and winter seasons of 2006-2010 at Chiang Mai University. Chiang Mai, Thailand. The general combining abilities of the lines in all experiments were significantly different for horticultural characteristics. However, the specific combining abilities of these characteristics of the F1 hybrids were not significantly different. The significance of the specific combining abilities was noted for some of the physio-chemical properties. Some F1 hybrids of showed heterosis and heterobeltiosis of some horticultural characteristics and physio-chemical properties. Fruit characteristics of these varieties were more or less the same as the commercial varieties. They are potential varieties for commercial markets.
Improvement of chili varieties in Thailand: Major improvements of chili varieties in Thailand have been carried out by the private sector. Most commercial chili cultivars sold in Thailand have been developed by seed companies. Very few government sectors participate in chili research, especially in varietal improvement. The National Center for Genetics and Engineering and Biotechnology and the National Research Council of Thailand have supported other government sectors financially in carrying out research and development of chili. Kasetsart University, Kamphaeng Saen Campus has collected chili germplasm and evaluated the germplasm for disease and insect resistance, resistance to anthracnose, resistance to viruses and resistance to the fruit fly. Routine breeding techniques were used to identify cytoplasmic male sterilities of chili germplasm at Chiang Mai University and Ubon Ratchathani Unirversity Stabilities of cytoplasmic male sterility, combining abilities, heterosis and heterobeltiosis of horticultural characteristics, and physio-chemical properties of chili maintainers were also evaluated were observed at Chiang Mai University. Identifying chili cultivars with stable amounts of capsaicinoids have been studied at Khon Kaen University. Kasetsart University, Kamphaeng Saen Campus has reported on the resistance mechanisms, genetic controls for resistance, inheritance of the resistant genes, and breeding of chili for resistance to Colletotrichum spp.
Improvement of chili varieties outside Thailand: Major improvements in chili varieties have been carried out by the World Vegetable Center. Multiple disease resistant (Tobamovirus and Phytophthora blight) sweet pepper hybrid, resistant to PVY, resistant to pepper mottle virus (PepMoV), resistant to CMV, resistant to insects, resistant to bacterial wilt, and resistant to anthracnose have been released by the Center. The Center initiated the development of hot pepper CMS lines, more than a dozen pairs (with different genetic backgrounds) of CMS (Peterson’s cytoplasm), maintainer and restorer inbred lines have been developed and made available to public and private sector partners.
Dr. Maneechat Nikornpun (Associate Professor)
Faculty of Agriculture, Chiang Mai University, Chiang Mai, Thailand.
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